Method for storing and releasing energy and obtaining geothermal energy through formation fractures

Abstract

The invention discloses a method for storing and releasing energy and obtaining geothermal energy through stratum fractures. The method comprises the steps that an energy storage geothermal layer which contains geothermal resources and does not contain oil gas is recognized; high-pressure fluid is injected into a target shaft, so that a target artificial stratum fracture is generated, or a target original stratum fracture in a closed state in the target shaft in the energy storage geothermal layer is opened; normal-temperature high-pressure fluid is injected into the target wellbore, so that the width of the stratum fracture is increased, stratum rock is elastically deformed to store energy, and the fluid in the stratum fracture exchanges heat with the energy storage geothermal layer; when the width of the ground layer crack reaches the target width, the reverse exhaust pipeline is closed to enable the fluid to continuously exchange heat with the energy storage geothermal layer so that the fluid can store heat; and high-temperature and high-pressure fluid reversely discharged in the stratum fracture closing process is used for driving hydroelectric power generation equipment and geothermal power generation equipment to generate power, so that the obtained geothermal energy and the stratum rock elastic deformation energy are converted into electric energy to be released.

Description

[0001] Priority application

[0002] This application claims priority to Chinese invention patent applications [Application No.: 202410721967 2] [Title: A method and system for storing and releasing energy and obtaining geothermal energy through formation cracks] filed on June 5, 2024, and [Application No.: 2024112086187] [Title: A method and system for storing and releasing energy and obtaining geothermal energy through existing original formation cracks in the formation], and the two priority invention patent applications are incorporated by reference in their entirety. Technical Field

[0003] The present invention relates to the field of underground energy storage, and in particular to a method for storing and releasing energy through stratum fractures and obtaining geothermal energy. Background Art

[0004] Renewable energy sources such as wind and solar power often exhibit significant intermittent, volatile, and random characteristics. With the large-scale development of renewable energy and their high proportion of grid integration, power balance, safe and stable control, and other issues will face unprecedented challenges. Therefore, the energy storage industry is essential for balancing the volatility of renewable energy generation and meeting peak electricity demand. Existing energy storage technologies primarily include mechanical energy storage and electrochemical energy storage. Electrochemical energy storage includes lead-acid batteries, lithium-ion batteries, and hydrogen fuel cells. Due to high investment and maintenance costs, as well as significant environmental and safety concerns, it has not been widely adopted. Mechanical energy storage primarily includes pumped hydro energy storage and compressed air energy storage. Pumped hydro energy storage involves pumping water from lower elevations to higher elevations, converting electrical energy into the water's gravitational potential energy. Therefore, pumped hydro energy storage often has high requirements for topography and cannot be applied in relatively flat plains or hilly areas. It also has corresponding requirements for the climate and rainfall in the application area. Compressed air energy storage is a mature energy storage technology, but it requires abandoned mines or underground caverns as a gas storage medium, limiting its application to specific areas. Geothermal energy is also a major development direction for new energy sources. Traditional geothermal energy extraction involves two methods with completely contradictory technical approaches: one is to extract geothermal energy through hydraulic fracturing, and the other is to avoid the generation of fractures in the bottom layer by hydraulic fracturing and only target faults in the formation where natural fractures are well developed. Among them, the method of extracting geothermal energy through hydraulic fracturing is generally called an enhanced geothermal system. It requires at least two wellbores (one for injection fluid and one for extraction fluid) connected by formation fractures to work together. During geothermal extraction, the formation fractures are in a closed state, and the fracture gaps are only supported by rough surfaces or proppants. The disadvantages of this method include: because the fractures are closed, the fracture gaps are small, and the friction within the fractures is large, resulting in large energy losses of the injected fluid (large parasitic load); because the injection well and the extraction well are connected by multiple formation fractures, the injected fluid tends to flow rapidly through the formation fractures with larger fracture gaps, failing to effectively exchange heat with the surrounding rock, causing a "thermal short circuit" and causing the temperature at the extraction well outlet to drop sharply.

[0005] For example, the invention patent application with publication number CN117150591A discloses a method for constructing a multi-well enhanced geothermal system, which includes: (1) drilling a vertical well into the heat reservoir as the injection well of the multi-well enhanced geothermal system, and at the same time arranging microseismic monitoring shallow well stations around the wellhead; (2) carrying out large-scale hydraulic fracturing on the vertical well, and performing moment tensor inversion on the stress waves received by the microseismic monitoring shallow well stations to obtain source mechanism information and determine the important parameters of the main hydraulic fracture; (3) establishing a continuous fracture network model, and displaying the fracture permeability distribution in the heat reservoir calculated according to the fracture network model in a geological honeycomb volume image; (4) drilling multiple target directional wells as the production wells of the multi-well enhanced geothermal system, and then carrying out sub-scale hydraulic fracturing on the directional wells to form a connection with the hydraulic fractures of the vertical wells, and finally circulating heat extraction. In the above-mentioned prior art, the fractured wells after hydraulic fracturing are only used to obtain geothermal energy, resulting in low power generation efficiency and energy conversion efficiency. Moreover, since the injection well and the production well are connected by multiple formation fractures, and the fluid circulates continuously between the injection well and the production well, the injected fluid tends to flow quickly through the formation fractures with larger gaps during the circulation process, failing to effectively exchange heat with the surrounding rocks, causing a "thermal short circuit" and causing the outlet temperature of the production well to drop sharply. In addition, this method has problems such as high investment and maintenance costs, easy flow short circuiting, and low utilization rate of geothermal extraction. Among them, the faults with more developed natural fractures in the formation are found as targets. Since it is difficult to meet today's geothermal extraction needs by relying solely on natural fractures, it is only applicable to specific areas with a very large number of natural fractures.

[0006] For example, the Chinese invention patent application with publication number CN114413494A discloses a hot dry rock thermal energy utilization and collection device. In order to avoid the problems of high fracturing pressure and uncontrollable extension of fracturing cracks in hot dry rock formations due to hydraulic fracturing, it directly utilizes large faults to construct hot dry rocks, which are natural faults and fracture zones, as artificial heat reservoirs between well groups. Appropriate artificial heat reservoirs have strong permeability, developed cracks, and large heat exchange areas. A well group is arranged in the fault, which includes multiple energy storage and release units, each energy storage and release unit includes an injection well and a production well connected by cracks or hydraulics. Then, a double-circuit collection system connected to each other is set near the wellhead of the production well to collect heat, thereby realizing uninterrupted heat collection. However, when one collection channel fails, the heat of the hot dry rock can also be collected and utilized through another channel, making the overall device more flexible, convenient and easy to use. In this prior art, although natural fractures in the fault are used instead of artificial fractures as channels for the fluid to circulate continuously between the injection well and the production well, it still uses connected injection wells and production wells to collect heat, that is, it still uses an enhanced geothermal system to obtain heat; and an additional flash tower is set up to collect geothermal heat and use the collected geothermal heat to heat the fluid circulating out of the production well. It also faces problems such as high investment and maintenance costs, easy flow short-circuiting, and low geothermal mining utilization rate. Moreover, excessive development of faults will also lead to geological safety issues. In addition, as mentioned above, since it relies solely on natural fractures, if it is to meet today's geothermal mining needs, it is only applicable to specific areas with a very large number of natural fractures.

[0007] In view of this, there is an urgent need for a new method that has low investment and maintenance costs, adapts to storage requirements of various terrains, and can effectively exploit geothermal resources. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for storing and releasing energy through formation fractures and obtaining geothermal energy, which can solve or alleviate the above-mentioned problems to a certain extent. While utilizing the elastic deformation of formation fractures in an independent wellbore that is not connected to other wellbores to store and release energy, it also obtains geothermal resources and utilizes geothermal resources to generate electricity and / or provide heating. That is, a single wellbore that is not connected to other wellbores is used as an independent unit for storing, releasing and obtaining thermal energy. Compared with the traditional method of obtaining thermal energy by continuously injecting fluid between connected injection wells and generation wells, it is not only less expensive, but also more resource-efficient.

[0009] In order to solve the above-mentioned technical problems, the present invention specifically adopts the following technical solutions:

[0010] The present invention provides a method for storing and releasing energy and obtaining geothermal energy through formation fractures, which comprises: identifying an energy storage geothermal layer containing geothermal resources but not oil and gas; injecting high-pressure fluid into a target wellbore in the energy storage geothermal layer, so that the energy storage geothermal layer generates at least one target artificial formation fracture, or opens at least one target original formation fracture in a closed state in the target wellbore in the energy storage geothermal layer; wherein the target wellbore is not connected to any other wellbore through the formation fracture; injecting normal temperature high-pressure fluid into the target wellbore, so that the width of the target artificial formation fracture or the target original formation fracture in the target wellbore increases, thereby causing the formation rock to undergo elastic deformation. Energy storage is converted, and the fluid in the target artificial formation fracture or the target original formation fracture exchanges heat with the energy storage geothermal layer, so that the temperature of the fluid increases; when the width of at least one target artificial formation fracture or at least one target original formation fracture in the target wellbore reaches the target width, the reverse flow pipeline is closed so that the fluid in the formation fracture continuously exchanges heat with the energy storage geothermal layer, so that the temperature of the fluid continuously increases, so as to store heat; the high-temperature and high-pressure fluid reversed during the closing process of the target artificial formation fracture or the target original formation fracture is used to drive the preset hydroelectric power generation equipment and geothermal power generation equipment to generate electricity, thereby converting the acquired geothermal energy and the elastic deformation energy of the formation rock into electrical energy for energy release.

[0011] In some embodiments, the high-temperature and high-pressure fluid discharged during the closing process of the target artificial formation fracture or the target original formation fracture is used to drive preset hydroelectric power generation equipment and geothermal power generation equipment to generate electricity, thereby converting the acquired geothermal energy and the elastic deformation energy of the formation rock into electrical energy for energy release. The steps specifically include: when there is a demand for power generation, using the fluid discharged during the closing process of the target formation fracture to drive the hydroelectric power generation equipment to generate electricity; the target formation fracture includes the target artificial formation fracture or the target original formation fracture; and / or, when the heat storage time of the target wellbore is greater than or equal to the pre-calculated target closed heat storage time, using the fluid to drive the geothermal power generation equipment to generate electricity; and / or, when there is a demand for heating, judging whether the fluid temperature meets the heating demand, and using the fluid for heating if the fluid temperature meets the heating demand. In some embodiments, the method for storing and releasing energy and obtaining geothermal energy through formation fractures further includes the steps of: injecting high-pressure fluid into the target wellbore to generate at least one target artificial formation fracture in the energy storage geothermal layer, and monitoring the actual three-dimensional size of the target artificial formation fracture in the target wellbore in real time; judging whether the actual three-dimensional size reaches a pre-configured preset threshold, and when the real-time monitoring shows that the actual three-dimensional size reaches the set threshold, stopping the injection of high-pressure fluid into the target wellbore to ensure that the target wellbore does not connect to other adjacent wellbores through the target artificial formation fracture; wherein the preset threshold is the minimum value of the preset energy storage three-dimensional size and the preset safety three-dimensional size. In some embodiments, the actual three-dimensional size includes an actual expansion radius and / or an actual expansion height, and the step of configuring the preset threshold specifically includes the steps of: obtaining the distance L0 between the target wellbore and its nearest adjacent wellbore, and the actual expansion radius R of the formation fracture in the nearest adjacent wellbore. 邻 Or actual extended height H 邻 Based on the spacing L0, and the actual expansion radius R of the formation fracture in the nearest adjacent wellbore 邻 Determine the safe expansion radius R0 of the target artificial formation fracture in the target wellbore, and the safe expansion radius R0 satisfies the condition: R0<L0-R 邻; Determine whether the preset target expansion radius R0' of the target artificial formation fracture is greater than or equal to the preset safety expansion radius R0; if the target expansion radius R0' ≥ the safety expansion radius R0, use the safety expansion radius R0 as the set threshold of the target artificial formation fracture in the target wellbore; if the target expansion radius R0' < the safety expansion radius R0, use the target expansion radius R0' as the set threshold of the target artificial formation fracture in the target wellbore. In some embodiments, the actual three-dimensional size includes an actual expansion radius and / or an actual expansion height, and the step of configuring the preset threshold specifically includes the steps of: obtaining the height difference V0 between the initiation point of the target artificial formation fracture in the target wellbore and the initiation point of the nearest formation fracture on its nearest adjacent wellbore, and the actual expansion height H of the nearest formation fracture on the nearest adjacent wellbore. 邻 Based on the height difference V0, and the actual extension height H of the nearest formation fracture on the nearest adjacent wellbore 邻 Determine the safe expansion height H0 of the target wellbore, and the safe expansion height H0 satisfies the condition: H0<V0-H 邻; Determine whether the preset target expansion height H0' of the target artificial formation fracture is greater than or equal to the preset safe expansion height H0; if the target expansion height H0' ≥ the safe expansion height H0, use the safe expansion height H0 as the set threshold for the target formation fracture in the wellbore; if the target expansion height H0' < the safe expansion height H0, use the target expansion height H0 as the set threshold for the target formation fracture in the wellbore. In some embodiments, if the safe expansion radius R0 is used as the set threshold for the target formation fracture in the target wellbore, the step of injecting high-pressure fluid into the target wellbore to generate at least one target artificial formation fracture in the energy storage geothermal layer specifically includes: recalculating the target expansion height of the target formation fracture based on the preset target energy storage capacity and the safe expansion radius R0; adjusting the construction parameters according to the recalculated target expansion height and the safe expansion radius R0, so that the final actual expansion radius of the target formation fracture is less than or equal to the safe expansion radius, and the final actual expansion height is greater than or equal to the recalculated target expansion height. In some embodiments, if the safe expansion height H0 is used as a threshold for the target formation fracture in the target wellbore, the step of injecting high-pressure fluid into the target wellbore to generate at least one target artificial formation fracture in the energy storage geothermal layer specifically includes: recalculating the target expansion radius of the target formation fracture based on a preset target energy storage amount and the safe expansion height H0; adjusting construction parameters based on the recalculated target expansion radius and the safe expansion height H0 so that the final actual expansion radius of the target formation fracture is greater than or equal to the recalculated target expansion radius, and the final actual expansion height is less than or equal to the safe expansion height. In some embodiments, the method for storing and releasing energy through formation fractures and obtaining geothermal energy further includes: if there are multiple target wellbores, if there is a power generation demand, determining whether the outlet temperature of the target wellbores meets the requirements of the geothermal power generation equipment; if no target wellbores have an outlet temperature that meets the requirements of the geothermal power generation equipment, randomly selecting at least one target wellbores to discharge fluid for power generation; and when the outlet temperature of any target wellbores meets the requirements of the geothermal power generation equipment, utilizing the discharged fluid from any target wellbores for synergistic power generation. Among them, the method for judging whether the wellbore outlet temperature meets the requirements of geothermal power generation equipment includes: simulating the changing relationship between the wellbore closed heat storage time and the wellbore outlet temperature based on the fluid-solid-heat coupling numerical model; according to the wellbore outlet temperature required for power generation and / or heating needs, using the fluid-solid-heat coupling numerical model to calculate the required closed heat storage time; if the closed heat storage time is reached, the wellbore outlet temperature meets the requirements of geothermal power generation equipment.In some embodiments, the method for storing and releasing energy and obtaining geothermal energy through formation fractures further includes the steps of: before discharging the fluid, calculating in advance based on a preset energy storage cycle efficiency and a hydraulic fracturing model the minimum volume threshold of the high-temperature and high-pressure fluid that needs to be retained in the target artificial formation fracture or the target original formation fracture at the end of energy release; accordingly, controlling the discharge process of the high-temperature and high-pressure fluid in the target artificial formation fracture or the target original formation fracture based on the minimum volume threshold, so that at the end of energy release, the volume of the high-temperature and high-pressure fluid retained in the target artificial formation fracture or the target original formation fracture is greater than or equal to the minimum volume threshold, thereby ensuring that the fracture width of the formation fracture during the energy storage and release cycle is greater than or equal to the preset width threshold (the preset width threshold is also calculated in advance based on the preset energy storage cycle efficiency and the hydraulic fracturing model). In some embodiments, the method for storing and releasing energy through formation fractures and obtaining geothermal energy further includes the steps of: determining whether the distance between the target wellbore and at least one of its nearest adjacent wellbore is less than or equal to a preset distance threshold; or determining whether the height difference between the initiation point of the target artificial formation fracture or the target original formation fracture in the target wellbore and the initiation point of the nearest formation fracture in the nearest adjacent wellbore is less than or equal to a preset height difference threshold; if so, during the energy storage process, real-time monitoring is performed to determine whether the formation fractures between adjacent wellbores are connected; if so, high-pressure fluid is simultaneously injected into all connected wellbores; during energy release, the high-pressure fluid is simultaneously discharged through all connected wellbores, and the kinetic energy of the high-pressure fluid and the obtained thermal energy are converted into electrical energy. In other words, all connected wellbores are treated as an energy storage and release unit that can independently store and release energy and has a large storage capacity.In some embodiments, before the step of injecting high-pressure fluid into the target wellbore in the energy storage geothermal layer to open at least one target original formation fracture in a closed state in the energy storage geothermal layer, the steps specifically include: identifying at least one original formation fracture in the energy storage geothermal layer, and screening out at least one original formation fracture in a closed state from the at least one original formation fracture, and screening out at least one target original formation fracture therefrom; wherein, the step of screening out at least one target original formation fracture therefrom specifically includes: the original formation fractures include original artificial fractures in a closed state, and the step of screening out at least one target formation fracture therefrom specifically includes the steps of: obtaining first monitoring data of the original artificial fractures in the energy storage formation using a preset monitoring device; calculating the original length and original height of the original artificial fracture in the energy storage formation through a numerical model of fracture extension combined with the first monitoring data and the first construction parameters of the original artificial fracture obtained in advance; and judging whether the original length and original height of the original artificial fracture are whether the preset target length threshold and target height threshold are reached, and if so, the original artificial fracture is marked as the target original formation fracture; and / or the original formation fracture includes a natural fracture in a closed state, and the step of screening out at least one target original formation fracture therefrom specifically comprises the steps of: obtaining second monitoring data of the natural fracture in the energy storage geothermal layer through a preset monitoring device, and performing inversion based on the second monitoring data to obtain the distribution of the at least one natural fracture; the second monitoring data includes: well logging data and seismic data; obtaining the three-dimensional stress distribution of the energy storage geothermal layer through tectonic stress analysis; using a three-dimensional fracture-stress coupling model, simulating the opening of the at least one natural fracture during the process of injecting normal temperature and high pressure fluid into the at least one natural fracture, and calculating the energy storage amount when the width of the at least one natural fracture expands to the target width under the action of the normal temperature and high pressure fluid; judging whether the energy storage reaches the preset target energy storage, and if so, marking the at least one natural fracture as the target original formation fracture.

[0012] In some embodiments, it is determined whether the number of the target original formation cracks screened out reaches a preset number threshold; if not, the original artificial cracks whose original length and original height do not reach the preset target length threshold and target height threshold are subjected to secondary transformation, and / or the natural cracks whose original length and original height do not reach the preset target length threshold and target height threshold are transformed; wherein the step of secondary transformation of the original artificial cracks specifically includes: according to a preset third construction parameter, injecting fluid into the original formation cracks through the wellbore, so that the crack pressure in the original formation cracks is greater than the crack expansion pressure, thereby causing the original formation cracks to expand along their original height and original length; obtaining third monitoring data of the original formation crack expansion process through monitoring equipment; calculating the original formation crack expansion along the original height and original length according to the third construction parameter and the third monitoring data in combination with the crack expansion numerical model. the latest length and the latest height after the length extension; judging whether the latest length and the latest height reach the preset target length threshold and the target height threshold, and if so, stopping the injection of the high-pressure fluid to obtain the target original formation fracture; wherein, the step of transforming the natural fracture specifically includes: injecting fluid into the natural fracture through the wellbore according to the preset fourth construction parameter, so that the fracture pressure in the natural fracture is greater than the fracture expansion pressure, thereby causing the natural fracture to expand along the original height and original length direction; obtaining the fourth monitoring data during the expansion of the natural fracture through the monitoring equipment; calculating the latest length and the latest height of the natural fracture after extension using the fracture expansion numerical model according to the fourth construction parameter and the fourth monitoring data; judging whether the latest length and the latest height of the natural fracture after extension reach the preset target length threshold and the target height threshold, and if so, stopping the injection of fluid to obtain the target original formation fracture.

[0013] In some embodiments, during the secondary modification of the original artificial fracture or the modification of the natural fracture, the actual three-dimensional size of the modified original artificial fracture or the modified natural fracture is monitored in real time to determine whether the actual three-dimensional size reaches a pre-configured threshold. When the real-time monitoring shows that the actual three-dimensional size reaches the pre-configured threshold, injection of high-pressure fluid into the wellbore is stopped to ensure that the target wellbore does not connect to other adjacent wellbores through the modified artificial formation fracture or the modified natural formation fracture. The pre-configured threshold is the minimum of a pre-set energy storage three-dimensional size and a pre-set safety three-dimensional size.

[0014] Beneficial Effects: Both CN114016988A and CN118654399A disclose a method for storing and releasing energy through formation fractures, but neither discloses how to obtain thermal energy. As previously mentioned, conventional geothermal extraction through hydraulic fracturing is often referred to as an enhanced geothermal system (EDS), which requires at least two wellbores (one for injecting fluid and one for extracting fluid) connected by formation fractures to work together. The fractures must be closed, with the gaps between the fractures supported by a rough surface or proppant. The disadvantages of enhanced geothermal systems include: since the fractures are in a closed state, the fracture gaps are small, and the friction within the fractures is large, resulting in large energy losses of the injected fluid (large parasitic load); since the injection wells and the production wells are connected by multiple formation fractures, the injected fluid can easily flow quickly through the formation fractures with larger gaps, failing to effectively exchange heat with the surrounding rocks, causing a "thermal short circuit" and a sudden drop in the temperature at the outlet of the production well; for the use of medium and low temperature geothermal resources (150℃-250℃), the power generation cost of the enhanced geothermal system is relatively high, and it has no cost advantage compared with other renewable energy sources (such as photovoltaic and wind power). The method disclosed in the present invention can overcome the above-mentioned disadvantages of the enhanced geothermal system and has the following advantages: (1) The independent energy storage and release unit only needs one wellbore to complete the injection-shutdown-mining (reverse discharge) process of the heat exchange medium, effectively avoiding the "thermal short circuit" caused by the connection of multiple wells through formation cracks; (2) During the energy storage and release process, the cracks are always in an open state, the crack width is much larger than the closed crack gap, and the friction resistance in the cracks is small, which greatly reduces the energy loss of the injected fluid (small parasitic load); (3) During the energy storage process, the high-pressure fluid as the heat exchange medium is always maintained in the formation cracks, and there is enough time to fully exchange heat with the formation, so that the outlet fluid temperature during the energy release process can be controlled, so that the target width and number of the required formation cracks can be reversely calculated based on the required storage energy. Moreover, for a single wellbore, it is only necessary to inject the corresponding fluid once and then control its heat storage time. In contrast, conventional enhanced geothermal systems require fluid to circulate continuously between injection wells and production wells in order to obtain heat. This means that there is no heat storage process, and it is naturally impossible to quickly and accurately determine whether the collected heat meets the demand. (4) Energy storage and geothermal energy extraction are carried out simultaneously, which greatly improves the economic value of the utilization of medium and low temperature geothermal resources.

[0015] Furthermore, in order to ensure that the wellbore is not connected to other wellbores, the formation of formation fractures is controlled in advance based on the minimum value of the target expansion radius / target expansion height and the preset safe expansion radius / safety expansion height as a standard, so that in response to different power supply requirements, multiple energy storage and release units that cannot store energy (that is, a single target wellbore as an energy storage and release unit has the ability to independently store and release energy and obtain thermal energy) are grouped, and multiple groups are used for cross-circulation power supply, thereby achieving continuous power supply (or continuous power supply).

[0016] Ideally, after the energy storage of at least some wellbores reaches a predetermined maximum energy storage (for example, reaches the target expansion radius or target expansion height) and its heat storage time reaches the target heat storage time, these wellbores that meet the standards are used to collaboratively supply power. This not only ensures continuous power supply, but also improves the efficiency and utilization of heat energy acquisition to a certain extent. However, in actual applications, the power supply demand may be sudden. In this case, when there is a power supply demand, the heat storage time of no wellbores reaches the target heat storage time, and the width of the formation fracture of no target wellbores may not even reach the target width. At this time, it is still necessary to enable one of the target wellbores that do not meet the standards or multiple target wellbores for power supply (of course, the specific number of target wellbores to be activated can be determined according to the actual power supply demand). When the width of any other target wellbores reaches the target width, or the width reaches the target width and the heat storage time reaches the target heat storage time, switch to any target wellbores for power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0018] Figure 1 This is a flow chart of an embodiment of a method for storing and releasing energy through formation fractures and obtaining geothermal energy according to the present invention; Figure 2 It is a schematic diagram of the system for hydraulic fracturing vertical wells and horizontal wells; Figure 3A is a schematic diagram of an example embodiment of the present invention wherein an electric injection device injects fluid from a reservoir into a formation fracture in a shale formation; Figure 3B It is a schematic diagram of discharging high-pressure fluid in a formation fracture back into a water reservoir and driving a power generation device to generate electricity in an exemplary embodiment of the present invention; Figure 4A is a schematic diagram of an electric injection device injecting fluid from a water reservoir into a formation fracture in a shale formation in another exemplary embodiment of the present invention; Figure 4B is a schematic diagram of discharging high-pressure fluid in a formation fracture back into a water reservoir and driving a power generation device to generate electricity in another exemplary embodiment of the present invention; Figure 5 It is a schematic diagram of a system for realizing continuous energy storage and release by hydraulic fracturing of multiple vertical wells and multiple horizontal wells; Figure 6A A schematic flow chart of another embodiment of a method for storing and releasing energy through formation fractures and obtaining geothermal energy according to the present invention; Figure 6BSchematic diagram of a flow chart of another embodiment of a method for storing and releasing energy through formation fractures and obtaining geothermal energy according to the present invention; Figure 7 Schematic diagram of the process of screening at least one target artificial fracture from original formation fractures in the present invention; Figure 8 Schematic diagram of the process of secondary transformation of artificial cracks in the present invention; Figure 9 This is a functional module diagram of a system for storing and releasing energy and obtaining geothermal energy through existing original formation fractures in an exemplary embodiment of the present invention; Figure 10A is a schematic diagram of an example embodiment of the present invention wherein an electric injection device injects fluid from a reservoir into a formation fracture in a shale formation; Figure 10B It is a schematic diagram of discharging high-temperature and high-pressure fluid in a formation fracture back into a water reservoir and driving a power generation device to generate electricity in an exemplary embodiment of the present invention; Figure 11A is a schematic diagram of an electric injection device injecting fluid from a water reservoir into a formation fracture in a shale formation in another exemplary embodiment of the present invention; Figure 11B is a schematic diagram of another exemplary embodiment of the present invention, in which high-temperature and high-pressure fluid in a formation fracture is discharged back into a water reservoir to drive a power generation device to generate electricity; Figure 12 It is a schematic diagram of a system for utilizing multiple vertical wells and multiple horizontal wells for hydraulic fracturing to achieve continuous energy storage and release and obtain geothermal energy; Figure 13 Schematic diagram of a flow chart of yet another embodiment of a method for storing and releasing energy through formation fractures and obtaining geothermal energy according to the present invention; Figure 14 This is a schematic diagram showing that the formation fractures in two adjacent wellbores are located at the same height; Figure 15 This is a schematic diagram showing that the formation fractures in two adjacent wellbores are located at different heights. DETAILED DESCRIPTION

[0019] As used herein, "and / or" includes any and all combinations of one or more of the listed items. As used herein, "plurality" means two or more, i.e., it includes two, three, four, five, etc. "Fluid" herein may include, but is not limited to, gases, liquids, emulsions, slurries, and solid particle flows with flow characteristics similar to those of liquid flow. For example, a fluid may include a water-based liquid with chemical additives. Furthermore, chemical additives may include, but are not limited to, acids, gels, potassium chloride, surfactants, etc. A "formation" or "reservoir" herein refers to a porous and permeable underground rock formation (e.g., shale formations, sandstone formations, carbonate formations, etc.) that can serve as a storage space for fluids. Typically, these fluids can be water, hydrocarbons, or gases. Such porous and permeable rock formations that can store high-pressure fluids are collectively referred to herein as "energy storage formations." Shale formations are used as a preferred embodiment to illustrate the energy storage and release methods and systems of this application because they can store fluids in their internal fractures for long periods of time. As used herein, "hydraulic fracturing," "fracture," or "fracturing" refers to the formation and propagation of cracks in formation rock under the action of external forces (such as high-pressure fluids). "Hydraulic fractures," "formation fractures," or "fractures" are open gaps in the rock created by hydraulic fracturing. The terms "hydraulic fractures," "formation fractures," or "fractures" are used interchangeably. "Bottomhole pressure" refers to the pressure at or near the initiation depth of a hydraulic fracture (formation fracture) within a wellbore. When frictional losses are negligible, the bottomhole pressure is equal to the fracture pressure of the hydraulic fracture. "Wellbore" refers to the hole drilled or inserted into a formation by conduit. Typically, a wellbore is cylindrical and may have a circular cross-section. However, a wellbore may have any other cross-section. A wellbore may be open-hole, or cased, with cemented casing attached to the inner wall. The "width of a formation fracture" in this article refers to the relative displacement distance between the two walls perpendicular to the fracture plane. The width of a formation fracture is related to the fracture pressure. The current width of the formation fracture can be calculated using a mathematical model by monitoring the fluid pressure at the wellhead or bottomhole in real time. When the formation fracture reaches the "target width," it is equivalent to the formation fracture pressure reaching the "target pressure." Whether the formation fracture has reached the "target pressure" can be determined by monitoring the fluid pressure at the wellhead or bottomhole in real time. In this article, the "target width" or "target pressure" of the formation fracture can be dynamically changed based on actual conditions during different energy storage and release cycles (one cycle refers to the completion of one energy storage and release process). For example, when the energy storage power supply is insufficient, the "target width" or "target pressure" of the formation fracture can be smaller than the corresponding "target width" or "target pressure" of the formation fracture when the energy storage power supply is sufficient.For example, insufficient solar or wind energy may limit the amount of high-pressure fluid injected into a formation fracture by an injection device, resulting in a smaller target width or target pressure for the fracture. Conversely, sufficient solar or wind energy may allow the injection device to inject more high-pressure fluid into the fracture, resulting in a larger target width or target pressure for the fracture. In this document, when a formation fracture is assumed to be circular (or, in engineering practice, considered circular or approximately circular), the "propagation radius" of the fracture refers to the radius of the circle. When a formation fracture is assumed to be non-circular (such as an ellipse), the "propagation radius" of the fracture refers to the half-length of the fracture. The "propagation height" of a formation fracture refers to the vertical distance the fracture extends upward or downward from the initiation point (e.g., the perforation location). The terms "constant" or "unchanged" in this document do not mean that the absolute change in the specified item is zero, but rather that the change in the specified item is very small, and in engineering practice, the item can be considered constant. For example, the term "bottom hole pressure remains constant" in this document also means "approximately constant bottom hole pressure", or, the term "expansion radius remains constant" in this document actually means that the "expansion radius" of the formation fracture remains "substantially constant" or "approximately constant" under the action of high-pressure fluid, or, the term "width of the formation fracture remains constant" in this document actually means that the "width of the formation fracture remains "substantially constant" or "approximately constant" under the action of high-pressure fluid. It should also be recognized that the term "equal / equal" used in this disclosure does not mean that the specified items are exactly the same, but is used to specify two items with negligible differences in engineering practice. For example, the term "equal / equal" in this disclosure can also mean "approximately equal / equal". The "geothermal layer" in this document is a layer with a relatively high temperature that meets the needs of geothermal power supply and / or heating. For example, to achieve economical and continuous heating, the layer temperature of the geothermal layer generally needs to be higher than 60°C, and to achieve economical and continuous power supply, the layer temperature of the geothermal layer generally needs to be higher than 120°C. Low geothermal gradients are mainly distributed in mountainous areas such as the Liaodong hills, the southern part of the Greater Khingan Range, and the Wuyi Mountains, and their geothermal gradients are generally as low as 20°C / km; high geothermal gradients are mainly distributed in the Northeast Plain, the North China Plain, and the southeast coastal areas, and the geothermal gradients are mostly in the range of 40-50°C / km; the geothermal gradients in the central region are mostly in the range of 20-26°C / km, and can reach more than 30°C / km locally. It can be seen that in areas with low geothermal gradients, the ground temperature at 500 meters in winter does not exceed 20°C. Generally, the ground temperature above 1km cannot achieve the economy of geothermal power generation, and due to the low temperature, it is necessary to use a heat pump (consuming electricity) to further increase the return water temperature to meet the heating requirements. Therefore, preferably, the geothermal layer in this article is mainly a layer below 1km and with a temperature above 60°C.The "original formation fractures" in this article refer to the open cracks in the rock that have been transformed by hydraulic fracturing (i.e., artificial formation fractures), or the naturally existing fractures in the energy storage formation that contain geothermal resources but do not contain oil and gas (i.e., natural formation fractures), and these original formation fractures are in a closed state. The "transformation" or "secondary transformation" in this article refers to the extension and expansion of the original formation fractures in the energy storage formation along their original height and / or length under the action of external forces (such as normal temperature and high-pressure fluid), but their width, fracture spacing and number remain unchanged. The "normal temperature" in this article refers to the temperature under local outdoor natural conditions (affected by latitude and season). "Normal temperature fluid" refers to a fluid that is maintained at a certain temperature in an outdoor storage facility (such as a reservoir or water tank) without artificial heating or cooling measures. The "closed state" in this article refers to the state where the fracture pressure of the formation fracture is less than the "fracture closure pressure" or "closing pressure". For example, when exploiting artificial fractures / natural fractures in depleted crude oil and gas reservoirs, since there is no fluid or crude oil in the fractures, the artificial fractures / natural fractures are in a state of neither continuing to close, nor expanding, nor extending. For another example, during the backflow process, as the fluid is discharged, the formation fractures gradually close. The "open" or "open state" herein refers to the state in which the fracture pressure of a formation fracture that was originally in a "closed state" is greater than the "fracture closure pressure" or "closing pressure" under the action of an external force (such as a high-pressure fluid). For example, the process in which the fracture pressure of a formation fracture that was originally in a closed state gradually increases under the action of an external force (such as a high-pressure fluid), and the state in which the fracture pressure is greater than the expansion pressure, causing the fracture to expand along the original length and / or height direction.

[0020] The core concept of this invention is to utilize target artificial formation fractures within the energy storage geothermal layer, or target original formation fractures selected from existing original formation fractures within the geothermal layer, to store energy (specifically, high-pressure fluid is injected into the target artificial formation fractures or target original formation fractures to increase their width), and then seal them to ensure that the formation fractures can store heat for a sufficient period of time to meet power supply requirements. Furthermore, during the heat storage process, if there is a power supply demand, the reversed fluid is used to drive hydroelectric power generation equipment to generate electricity; and / or, when the heat storage time of the target wellbore is greater than or equal to the pre-calculated target closed heat storage time and there is a power supply demand, the fluid is used to drive the geothermal power generation equipment to generate electricity. Furthermore, during the process of creating fractures, or during the process of modifying or re-modifying original formation fractures, it is necessary to monitor in real time the actual three-dimensional size changes of the fractures and / or the distribution of existing original formation fractures in the formation, so as to control the injection pressure, flow rate and other construction parameters of the injected fluid according to the actual three-dimensional size changes and / or distribution, thereby preventing the target wellbore formed in the geothermal reservoir from being connected to other wellbores through the formation fractures, resulting in capacity loss and inter-well interference in the energy storage process, thereby reducing power generation efficiency and other problems.

[0021] Example 1: Shale is widely distributed and has extremely low permeability. In the oil and gas sector, shale formations are often considered the overlying seal of conventional oil and gas reservoirs, preventing oil and gas from migrating upward and evaporating to the surface. Furthermore, shale formations themselves can also serve as fluid storage media. Due to their extremely low permeability, shale formations can store high-pressure fluids in internal formation fractures for extended periods of time, with only minimal fluid loss into the pores of the formation rock. Therefore, the present invention preferably achieves the goal of long-term energy storage by storing high-pressure fluids in artificial fractures (i.e., fractures created by hydraulic fracturing) within porous and permeable shale formations, thereby utilizing shale formations as energy storage formations. Of course, the present invention can also be applied to other porous and permeable rock formations. Of course, the purpose of the present invention is not merely to convert energy through formation fractures; more importantly, it is also used to capture geothermal energy. Therefore, the aforementioned low-permeability rock formations also need to store abundant geothermal energy. Based on the above concept, the present invention provides a system for storing and releasing energy through formation fractures and obtaining geothermal energy, specifically including: a fracturing device for pumping fracturing fluid into a wellbore through a wellbore that reaches the energy storage geothermal layer to generate formation fractures in the energy storage geothermal layer.

[0022] like Figure 2 As shown, the fracturing fluid is pumped into the vertical wellbore 230 and the horizontal wellbore 232 respectively through the fracturing devices 210 and 212 arranged on the ground. Once the bottom hole pressure of the vertical wellbore 230 and the horizontal wellbore 232 reaches the fracture pressure of the underground rock formation 220 (i.e., the energy storage formation) (i.e., the bottom hole pressure is greater than or equal to the fracture pressure), the formation fractures 240, 242, 244 in the vertical wellbore 230 will fracture from around the vertical wellbore 230 and expand into the underground rock formation 220 until the pumping stops (i.e., the hydraulic fracturing operation stops). Correspondingly, the formation fractures 246, 248, 250 in the horizontal wellbore 232 will fracture from around the horizontal wellbore 232 and expand into the underground rock formation 220 until the pumping stops. Figure 2 As shown, formation fractures (e.g., Figure 2 The formation fractures 240, 242, 246, 248 in the shale formation can form a planar geometry and extend in a direction perpendicular to the minimum principal stress of the shale formation. However, under certain geological conditions, the formation fractures (e.g., Figure 2 The formation fractures 244, 250) in the stratum can interact with pre-existing natural fractures to form complex fracture geometries.

[0023] The system also includes an injection pipeline connected to an injection device that pressurizes and injects ambient temperature fluid into the wellbore, increasing the width of the formation fractures, thereby causing elastic deformation of the formation rock to store energy and allowing the fluid in the formation fractures to exchange heat with the energy storage geothermal layer, raising the fluid temperature. The system also includes a backflow pipeline connected to hydroelectric power generation equipment, geothermal power generation equipment, and a heating system, so that when the fluid in the formation fractures is reversed through the backflow pipeline, it can drive the hydroelectric power generation equipment and geothermal power generation equipment to generate electricity and provide heating through the heating system. The system also includes a plugging device for closing the backflow pipeline, allowing the fluid in the formation fractures to continuously exchange heat with the energy storage geothermal layer, raising the fluid temperature. The plugging device can preferably be a control valve installed on the backflow pipeline. Of course, to prevent fluid backflow from the injection pipeline, the plugging device can also include a control valve installed on the injection pipeline. To ensure fluid recycling, a water reservoir for storing the fluid can also be included, with both the injection pipeline and the backflow pipeline connected to the water reservoir. It is understandable that in order to avoid heat loss and improve the efficiency of geothermal power generation, the wellbore, backflow pipe, hydropower equipment and water reservoir are all insulated.

[0024] See also Figure 3A and Figure 3B The injection pipe 330 and the backflow pipe 380 connecting the water reservoir 320 and the wellbore 340 are both provided with control valves for controlling the flow and closure of the surface pipes. When it is detected that power generation is required (for example, the corresponding control system, or the first power generation equipment, or the corresponding staff receives a power supply request from an external source, such as the power grid or other control system), the control system connected to the control valve, or the hydroelectric power generation equipment 360 and the geothermal power generation equipment 370, opens the corresponding control valve of the backflow pipe 380 between the wellbore and the water reservoir (of course, it can also be opened manually by the staff). This allows the wellbore 340 to communicate with the reservoir 320. Consequently, under the action of rock compression, the high-temperature, high-pressure fluid within the formation fractures 390 within the shale formation 350 is reversed into the reservoir 320. During this process, the high-temperature, high-pressure fluid first drives the impeller of the hydroelectric power generation equipment 360 to rotate to generate electricity. When passing through the geothermal power generation equipment 370, it is determined whether the high-temperature, high-pressure fluid meets the geothermal power generation requirements. If so, the geothermal power generation equipment 370 is activated to generate electricity. If not, the geothermal power generation equipment 370 is not activated, and the fluid is instead introduced into the heating system for heating (if necessary). Of course, if no power supply request is received, the reverse flow pipe 380 between the wellbore and the reservoir will remain closed, i.e., the control valve on the reverse flow pipe 380 is in a normally closed state. At this point, monitoring for power supply demand is continued. It is understood that even if there is a power supply demand and / or heating demand, it is still necessary to determine whether the fluid in the formation fractures can meet the power generation and / or heating requirements.

[0025] Example 2: In order to simplify the equipment, unlike Example 1, the injection pipeline and the reverse flow pipeline in this embodiment are the same pipeline; the hydroelectric generator and the injection equipment are an integrated power generation and water injection machine. When energy storage is required, the integrated power generation and water injection machine can pressurize the normal temperature fluid and input it into the wellbore to increase the width of the formation fracture. When power generation is required, the integrated power generation and water injection machine can convert the kinetic energy of the reverse flow fluid into electrical energy. The so-called integrated power generation and water injection machine is a device with water pump function and power generation function. It can pump water or convert the kinetic energy of water into electrical energy by forward and reverse rotation. Specifically, it can be an electric generator, a motor that has both the functions of a generator and an electric motor. It can be used as a generator driven by a turbine to generate electricity, and it can also be converted into an electric motor to drive a water pump to pump water. For details, see Figure 4A and Figure 4B After the integrated power generation and water injection unit 410 stops injecting normal-temperature, high-pressure fluid into at least one formation fracture, the valve in the pipeline 440 between the wellbore 450 and the reservoir 430 is also closed. When power generation is detected, the corresponding control valve in the pipeline 440 between the wellbore 450 and the reservoir 430 is opened. At this time, under the action of rock compression, the high-temperature, high-pressure fluid heated by the formation in the formation fractures 470 within the shale formation 460 is discharged back into the reservoir 430 through the pipeline 440. In this process, the impeller of the integrated power generation and water injection unit 410 is first driven to rotate to generate electricity. Then, the fluid passes through the geothermal power generation device 420. If the geothermal power generation conditions are met, the geothermal power generation device 420 is driven to generate electricity. Otherwise, the geothermal power generation device 420 remains closed. The system then determines whether there is a heating demand. If so, the fluid is introduced into the heating system. Otherwise, the fluid is returned to the reservoir. If no power supply demand is detected, the pipeline 440 between the wellbore 450 and the reservoir 430 remains closed.

[0026] Example 3: Different from Example 1, there are multiple wellbores in this embodiment, and each wellbores is connected to the energy storage geothermal layer and the formation fractures; it also includes a number of water inlet pipes and backflow pipes respectively matched with each wellbores, the water inlet pipes are connected to injection equipment, and the backflow pipes are connected to hydroelectric power generation equipment, geothermal power generation equipment and heating systems. At the same time, some of the multiple wellbores are performing the water injection process, some are performing the energy storage process, and some are performing the energy release process. Of course, it is also possible that the injection pipe and the backflow pipe in Example 2 are the same pipe, and the principle is the same, so it will not be repeated here. This embodiment provides a system for realizing continuous energy storage and release by hydraulic fracturing using multiple vertical wellbores and multiple horizontal wellbores, see Figure 5During the hydraulic fracturing construction, the construction of the vertical wellbore 510, the vertical well 520, the vertical well 530 and the horizontal wellbore 540, the horizontal wellbore 550, and the horizontal wellbore 560 is completed (in this case, three horizontal wellbores or vertical wellbores are taken as an example, but the number of multiple vertical wellbores and horizontal wellbores described in the present invention includes all cases where the number is greater than 1), so that at least one formation fracture is generated in each vertical wellbore and horizontal wellbore. During the period of utilizing the formation for energy storage and release, the vertical wellbore 510, the vertical wellbore 520, the vertical wellbore 530 and the horizontal wellbore 540, the horizontal wellbore 550, and the horizontal wellbore 560 cooperate with each other to achieve continuous energy storage and release. For example, when the vertical wellbore 510 and the horizontal wellbore 540 are performing the injection process and converting the electrical energy into the elastic deformation energy of the formation, the vertical wellbore 520 and the horizontal wellbore 550 have completed the injection and converted the electrical energy into the elastic deformation energy of the formation for storage, and at the same time obtained geothermal energy. The vertical wellbore 530 and the horizontal wellbore 560 are performing the reverse discharge process due to the power generation demand, converting the stored elastic deformation energy of the formation and the obtained geothermal energy into electrical energy and putting it into the power grid for use, and then completing the energy release of the vertical wellbore 530 and the horizontal wellbore 560 performs the injection process. After the injection is completed, the vertical wellbore 520 and the horizontal wellbore 550 in the storage process perform the back discharge process to release energy, while the vertical wellbore 510 and the horizontal wellbore 540 are in the energy storage process after the injection is completed and obtain geothermal energy. Taking this as an example, the vertical wellbore 510, the vertical wellbore 520, the vertical wellbore 530 and the horizontal wellbore 540, the horizontal wellbore 550, and the horizontal wellbore 560 are coordinated through circulation to ensure that they can provide electricity to the power grid at any time to meet the electricity demand.

[0027] Example 4: This example provides a method for storing and releasing energy through formation fractures and obtaining geothermal energy. This method is applicable to the aforementioned system for storing and releasing energy through formation fractures and obtaining geothermal energy, and includes the following steps: S101 identifies a geothermal energy storage layer containing geothermal resources but devoid of oil and gas. In some embodiments, the energy storage layer devoid of oil and gas includes depleted oil and gas formations. In some embodiments, intuitive methods can be used to identify relevant information about the energy storage layer (preferably a shale formation) (e.g., burial depth and thickness), such as by obtaining core drilling data. In other embodiments, indirect methods can be used to identify relevant information about the formation, such as by interpreting well logging data and seismic data inversion. Furthermore, by analyzing factors such as the thermal conductivity, temperature gradient, and groundwater circulation of the subsurface rock, a coupled fluid-solid-thermal numerical model of the "wellbore-fracture-formation" is established to simulate the dynamic changes in wellbore outlet temperature and formation temperature during long-term operation. If the wellbore outlet temperature can be maintained above the power generation temperature for a long period of time (the power generation temperature depends on the geothermal power generation technology used, for example, dry steam power generation and flash evaporation power generation require a wellbore outlet temperature above 150 degrees Celsius, and binary cycle power generation requires a wellbore outlet temperature above 50 degrees Celsius), then the geothermal energy storage formation can directly provide electricity or heating. If the wellbore outlet temperature cannot be maintained above the power generation temperature for a long period of time, but can be maintained above the heating temperature (usually above 35 degrees Celsius), then the geothermal energy storage formation can only be used for heating.

[0028] S102 performs hydraulic fracturing on the energy storage geothermal layer, so that the energy storage geothermal layer generates formation cracks. During the hydraulic fracturing, the injected fracturing fluid is pumped into the wellbore through the surface facilities, such as Figure 2 The fracturing fluid is pumped into the vertical wellbore 230 and the horizontal wellbore 232 respectively through the fracturing devices 210 and 212. Once the bottom hole pressure of the vertical wellbore 230 and the horizontal wellbore 232 reaches the fracture pressure of the underground rock formation 220 (i.e., the energy storage formation) (i.e., the bottom hole pressure is greater than or equal to the fracture pressure), the formation fractures 240, 242, 244 in the vertical wellbore 230 will fracture from around the vertical wellbore 230 and expand into the underground rock formation 220 until the pumping stops (i.e., the hydraulic fracturing operation stops). Correspondingly, the formation fractures 246, 248, 250 in the horizontal wellbore 232 will fracture from around the horizontal wellbore 232 and expand into the underground rock formation 220 until the pumping stops. Figure 2 As shown, formation fractures (e.g., Figure 2 The formation fractures 240, 242, 246, 248 in the shale formation can form a planar geometry and extend in a direction perpendicular to the minimum principal stress of the shale formation. However, under certain geological conditions, some formation fractures (e.g., Figure 2The formation fractures 244 and 250 in the structure can interact with pre-existing natural fractures to form complex fracture geometries. In practical applications, the extent of formation fracture expansion can be determined based on different energy storage requirements and the mechanical properties of the energy storage formation. For example, if more energy needs to be stored, a longer formation fracture needs to be designed, and more geothermal energy can be obtained. If relatively less energy needs to be stored, a shorter formation fracture needs to be designed, and less geothermal energy can be obtained. Therefore, the design parameters of the formation fracture, such as the expansion radius (or expansion length), can be set in advance according to actual needs. When it is determined that the expansion radius of the formation fracture has reached the design requirements, the pumping of the fracturing fluid (i.e., the hydraulic fracturing construction is stopped), so that the formation fracture gradually stops expanding. In addition, before hydraulic fracturing construction, the required fluid kinetic energy and thermal energy carried by the fluid can be obtained based on the power of the hydroelectric power generation equipment and geothermal power generation equipment; then, the target expansion radius of the formation fracture can be inferred based on the required fluid kinetic energy and thermal energy carried by the fluid. During hydraulic fracturing, a determination is made as to whether the expansion radius of a formation fracture is equal to or greater than a target expansion radius. Specifically, a three-dimensional shape of the formation fracture is calculated based on a pre-established hydraulic fracturing model, rock mechanical properties, and a first construction parameter, and the expansion radius of the formation fracture is determined based on the three-dimensional shape. In some embodiments, the hydraulic fracturing model may employ a two-dimensional PKN model, a KGD model, a RADIAL model, a pseudo-three-dimensional model, or a full three-dimensional model. The first construction parameter is the construction parameter of the surface facility (i.e., the injection equipment in the hydraulic fracturing construction apparatus), including: injection rate, total injection volume, and viscosity of the fracturing fluid. When a formation fracture is detected with an expansion radius equal to or greater than the target radius, hydraulic fracturing is terminated. Of course, in other embodiments, the timing for terminating hydraulic fracturing may be determined by the staff based on relevant work experience. For example, the staff may determine or calculate the time to terminate hydraulic fracturing based on their work experience and the injection rate, total injection volume, and viscosity of the fracturing fluid. Preferably, in some embodiments, the preset target radius is set by professional technicians based on the mechanical properties of the energy storage formation, ensuring that the formation fractures have a certain storage capacity while avoiding the formation fractures from causing damage to the energy storage formation due to an excessive expansion radius. In some embodiments, multiple formation fractures will be created during the hydraulic fracturing construction process. During the specific implementation, in order to avoid the formation fractures from causing damage to the energy storage formation due to an excessive expansion radius, preferably, when it is detected that there is a formation fracture with an expansion radius equal to or greater than the preset target expansion radius, the hydraulic fracturing construction is stopped. Of course, in other embodiments, the hydraulic fracturing construction can also be stopped when it is determined that the average expansion radius of all formation fractures is equal to or equal to the preset target expansion radius.It is understood that when hydraulic fracturing is stopped, the formation fractures do not stop expanding immediately. Only when the fluid pressure in the formation fractures tends to balance with the fracture pressure, that is, when the fluid pressure is less than the fracture pressure, do the formation fractures stop expanding. Therefore, to avoid excessive expansion radius of the formation fractures, preferably, in some embodiments, hydraulic fracturing is stopped when the expansion radius of the formation fractures is approximately equal to (or close to) the target radius (for example, expansion radius = target radius × 0.90-0.95). Preferably, to reduce the rate of filtration of the fracturing fluid in the formation fractures into the surrounding rock, so that the formation fractures in the energy storage formation have the ability to store fracturing fluid or high-pressure fluid for a long time, in some embodiments, a fluid loss control agent is added to the fracturing fluid in the hydraulic fracturing in this step.

[0029] S103 injects a normal temperature and high pressure fluid into the formation fracture, so that the width of the formation fracture increases, thereby causing the formation rock to undergo elastic deformation and store energy, and the fluid in the formation fracture exchanges heat with the energy storage geothermal layer, causing the fluid temperature to increase. Furthermore, in some embodiments, the pressure of the fluid injected into the formation fracture is greater than the minimum principal stress of the energy storage formation and less than the expansion pressure of the formation fracture, so that the fracture width of the formation fracture gradually increases, and the expansion radius remains unchanged or constant (because the fluid pressure is less than the expansion pressure of the formation fracture, the formation fracture will not expand, that is, the fracture radius remains unchanged or constant). Of course, in other embodiments, the expansion radius of the formation fracture remains unchanged or constant, which can be understood as remaining unchanged or constant for a period of time. For example, when the width of a formation fracture changes due to the action of a high-pressure fluid, its expansion radius will also gradually change (i.e., continue to expand), but within a certain period of time (e.g., one hour), the change in the expansion radius can be ignored in engineering practice; or, when a formation fracture expands due to the action of a high-pressure fluid, after a certain period of time, the granular objects added to the high-pressure fluid will fill or partially fill the fracture that continues to expand. Preferably, in some embodiments, the minimum principal stress of the energy storage formation can be obtained by a small-scale fracturing (Diagnostic Fracturing Injection Test) or a reflux-assisted small-scale fracturing (Rapid Injection-Flowback Test) test. The expansion pressure of the formation fracture can be obtained by analyzing the instantaneous shut-in pressure (Instantaneous Shut-In Pressure) of the pressure drop curve after the pump is stopped during hydraulic fracturing construction.

[0030] In some embodiments, this step further includes: real-time monitoring of the injected fluid pressure and determining whether the injected fluid pressure is greater than the minimum principal stress of the formation and less than the expansion pressure of the formation fracture; if so, maintaining the second operation parameter for injecting the normal temperature, high pressure fluid into the formation fracture; otherwise, adjusting the second operation parameter (i.e., the operation parameter of the injection equipment) for injecting the normal temperature, high pressure fluid into the formation fracture so that the current fluid pressure remains between the expansion pressure and the minimum principal stress of the energy storage formation. In some embodiments, the second operation parameter includes the fluid injection rate and the total injection volume. Specifically, the fluid pressure can be adjusted by adjusting the injection rate or the amount of high pressure fluid injected by the injection equipment, and the fluid pressure can be monitored by a pre-installed pressure monitoring device.

[0031] In some implementations, the width of the formation fracture is inferred based on the required fluid kinetic energy and the thermal energy carried by the fluid; when injecting normal temperature and high pressure fluid into the formation fracture, it is determined whether the width of the formation fracture is equal to or greater than the target width; when it is detected that the width of a formation fracture is equal to or greater than the target width, or / and when the average width of all formation fractures is equal to or greater than the target width, the injection of normal temperature and high pressure fluid into the formation fracture is stopped. Specifically, it is determined whether the width of at least one formation fracture is equal to or greater than the preset target width. If so, the injection equipment stops injecting normal temperature and high pressure fluid into the at least one formation fracture, thereby maintaining the bottom hole pressure unchanged and making the width of the formation fracture unchanged (at this time, since the pipelines between the wellbore and the water reservoir and the injection equipment are all in a closed state, the bottom hole pressure remains unchanged after the injection of normal temperature and high pressure fluid is stopped); otherwise, the injection of normal temperature and high pressure fluid into the formation fracture continues. The width of the formation fracture is calculated based on the height of the formation fracture, the expansion radius of the formation fracture, and the bottom hole pressure. It is understandable that the widths at different locations in the formation fracture are not equal. Preferably, in some embodiments, the "width of the formation fracture" in step S106 refers to the average width of all formation fractures; of course, in other embodiments, the "width of the formation fracture" in step S106 may also refer to the width of any formation fracture. For example, in some embodiments, during the process of injecting normal temperature and high pressure fluid into the formation fracture, the width data of all formation fractures are obtained, and the widths of all formation fractures are averaged to obtain the average width of all formation fractures. When the average width is equal to or greater than a preset target width, power is stopped to the injection device, so that the injection device stops injecting high pressure fluid into the formation fracture.

[0032] In some embodiments, the target width of the formation fracture is pre-set by professionals based on the mechanical properties of the energy storage formation and different energy storage requirements. This ensures that the formation fracture has a certain storage capacity while preventing damage to the energy storage formation caused by excessive width of the formation fracture. It is understood that, due to the presence of multiple formation fractures, to prevent damage to the energy storage formation caused by excessive width of the formation fracture, preferably, when it is detected (or determined) that the width of a formation fracture is equal to or greater than the preset target width, step S108 is executed to stop supplying power to the injection device, so that the injection device stops injecting the normal temperature high pressure fluid into the at least one formation fracture, thereby maintaining the bottom hole pressure and the fracture width unchanged. Of course, in other embodiments, when it is detected that the power supply to the injection device is insufficient (for example, due to weather changes causing insufficient solar or wind power generation, specifically, when all or most of the solar or wind power generation is consumed by the end users, leaving no excess power for the injection device), the power supply to the injection device is stopped, so that the injection device stops injecting the normal temperature high pressure fluid into the at least one formation fracture, thereby maintaining the bottom hole pressure and the fracture width unchanged. Preferably, in some embodiments, one or more additives may be added to the fluid in the reservoir in advance (i.e., one or more additives may be added to the fluid injected into the formation fracture), such as fungicides, descaling agents, mineral salts (e.g., KCl, NaCl, CaCl2, NaSiO4, etc.) and fluid loss control agents, wherein the mineral salts are used to balance the electrolytes in the energy storage formation. As a specific example, Figure 3A As shown, the grid-powered injection device 310 injects the fluid from the reservoir 320 through the injection pipe 330 to the wellbore 340 and then into the hydraulic fracture 390 in the shale formation 350, causing the width of the formation fracture to expand. The rocks around the fracture undergo elastic deformation to store energy. At the same time, the surrounding rocks heat the fluid in the fracture to obtain geothermal energy. Figure 3A As shown by the double-headed arrow R), the average Young's modulus of the rock is 20 GPa at a height of 500 meters from the ground. The fluid pressure in the fracture is 3 MPa higher than the minimum principal stress of the shale formation. The formation temperature is 50°C. According to fracture mechanics, the energy stored in the elastic deformation of the shale formation around the fracture is 2.8×10 11 J, which is 78530kw·h. According to heat transfer theory, the available geothermal energy is 7.2×10 12 J, that is, 2019343kw·h.

[0033] S104 When there is a demand for power generation, the fluid discharged during the closing process of the formation fracture is used to drive the hydroelectric power generation equipment to generate electricity. The water reservoir and the wellbore corresponding to the formation fracture are connected by a pipe and a reverse discharge pipe, and when the injection of high-pressure fluid into the formation fracture is stopped, the reverse discharge pipe and the injection pipe are both in a closed state. Specifically, the control valves in the reverse discharge pipe and the injection pipe are in a closed state. Therefore, when it is detected that there is a demand for power generation, the control valve corresponding to the reverse discharge pipe is opened to allow the reverse discharge pipe to circulate, so that the high-pressure fluid in the formation fracture can be discharged back into the water reservoir through the reverse discharge pipe under the action of rock squeezing, and the hydroelectric power generation equipment is driven during the reverse discharge process, converting the kinetic energy of the fluid into electrical energy. For example, see Figure 3A and Figure 3B The injection pipe 330 and the backflow pipe 380 connecting the water reservoir to the wellbore are both provided with control valves for controlling the circulation and closure of the surface pipes. When it is detected that power generation is required (for example, the corresponding control system, or hydroelectric power generation equipment, or the corresponding staff receives a power supply request from the outside, such as the power grid or other control systems), the control valve corresponding to the backflow pipe 380 between the wellbore and the water reservoir is opened (of course, it can also be opened manually by the staff), thereby connecting the wellbore and the water reservoir. Then, under the action of rock squeezing, the high-temperature and high-pressure fluid in the formation cracks is backflowed into the water reservoir. In this process, the high-temperature and high-pressure fluid drives the impeller of the hydroelectric power generation equipment in front to rotate to generate electricity.

[0034] S105: When the temperature of the fluid meets the requirements of the geothermal power generation equipment, the fluid is used to drive the geothermal power generation equipment to generate electricity. When passing through the geothermal power generation equipment 370, the judgment device determines whether the high-temperature and high-pressure fluid meets the requirements of geothermal power generation. If so, the geothermal power generation equipment 370 is turned on to generate electricity, thereby converting geothermal energy into electrical energy, realizing the acquisition and application of geothermal heat. If not, the geothermal power generation equipment 370 is not turned on. Of course, if no power supply request is received, the backflow pipe 380 between the wellbore and the water reservoir will always remain closed, that is, the control valve in the backflow pipe 380 is in a normally closed state. At this time, it is sufficient to continue to monitor whether there is a power supply demand.

[0035] S106 determines whether the fluid temperature meets the heating requirement if there is a heating demand. If so, the fluid is used for heating. After the fluid passes through the geothermal power generation equipment 370, whether or not the fluid is being used for power generation, a determination is first made as to whether there is still a heating demand. If there is a heating demand, it is further determined whether the fluid temperature meets the heating requirement. Only if the fluid temperature meets the heating requirement is the fluid discharged into the heating system for heating, thus achieving another aspect of geothermal heat acquisition and application. Of course, it is understood that the heated fluid can also be ultimately discharged into a reservoir, thereby achieving fluid recycling and reuse.

[0036] Example 5: Referring to Example 3, if there are multiple target wellbores, and there is a power generation demand, it is also possible to determine whether the wellbores' outlet temperature meets the requirements of the geothermal power generation equipment. Then, the wellbores with outlet temperatures that meet the requirements are selected for backflow and power generation. The purpose of this step is to determine whether the fluid has accumulated sufficient geothermal heat to generate electricity for the geothermal generator. If it does not meet the power generation demand, the geothermal heat will be wasted in the absence of heating demand. Of course, if there is only one wellbore, since power generation takes precedence, this step can be omitted. Specifically, the method for determining whether the wellbores' outlet temperature meets the requirements of the geothermal power generation equipment includes: simulating the relationship between the wellbores' closed thermal storage time and the wellbores' outlet temperature based on a fluid-solid thermal coupling numerical model; calculating the required closed thermal storage time based on the wellbores' outlet temperatures required for power generation and / or heating using the fluid-solid thermal coupling numerical model; and if the closed thermal storage time is met, the wellbores' outlet temperature meets the requirements of the geothermal power generation equipment. In this example, since the stratum energy storage depth is greater than 1000 meters, heat pump heating is not required. Instead, the thermal storage time is controlled to meet varying power generation demands. In addition, this step can also be applied to the collaborative work of multiple wellbores. When the power generation demand is higher than the power that a single wellbores can provide, this step can be used to select multiple wellbores to work collaboratively to meet the power generation demand.

[0037] Example 6: As mentioned above, traditional geothermal energy is often extracted by looking for faults with relatively developed natural fractures in the formation as a target, or by using multiple wells through multi-stage hydraulic fracturing technology. However, it is difficult to meet the current geothermal extraction needs by relying solely on natural fractures. At the same time, excessive development of faults will also lead to geological safety problems. The extraction of geothermal energy through multi-stage hydraulic fracturing faces the problems of high investment and maintenance costs, easy flow short circuits, and low geothermal extraction utilization. Preferably, the present invention achieves the purpose of long-term energy storage by storing high-pressure fluid in artificial fractures (i.e., fractures in the formation formed by hydraulic fracturing construction) in porous and permeable shale formations, that is, using shale formations as energy storage formations. Of course, the present invention can also be applied to other porous and permeable rock formations.

[0038] See also Figure 6A , is a flow chart of a method for storing and releasing energy and obtaining geothermal energy through formation fractures according to an exemplary embodiment of the present invention. Specifically, the method includes the following steps: in step S100, at least one energy storage geothermal layer (i.e., reservoir) with rich geothermal resources, no oil and gas, and at least one original formation fracture is identified.

[0039] In some embodiments, the energy storage formation that does not contain oil and gas includes: depleted oil and gas formations that have been hydraulically fractured and depleted. That is, there is at least one artificial fracture (for example, a formation fracture formed by hydraulic fracturing) in the energy storage formation, and because it has been depleted, the artificial fracture is currently in a closed state. In other embodiments, the energy storage formation that does not contain oil and gas may also include: an energy storage formation that already has at least one natural fracture. Of course, there may be both at least one artificial fracture (i.e., the original artificial fracture) and at least one natural fracture (i.e., the original natural fracture) in the energy storage formation that does not contain oil and gas.

[0040] In some embodiments, the method for identifying energy storage formations (preferably shale formations) is the same as in the above-mentioned embodiments and will not be described in detail here. Preferably, if it is obtained through simulation that the wellbore outlet temperature can be maintained above the power generation temperature for a long time (the power generation temperature depends on the geothermal power generation technology adopted, such as dry steam power generation and flash evaporation power generation require the wellbore outlet temperature to be above 150 degrees Celsius, and binary cycle power generation requires the wellbore outlet temperature to be above 50 degrees Celsius), then the geothermal energy storage formation can directly provide electricity or heating and be marked. If the wellbore outlet temperature cannot be maintained above the power generation temperature for a long time, but can be maintained above the heating temperature (usually above 35 degrees Celsius), then the geothermal energy storage formation can only be used for heating and be marked. That is, the geothermal energy storage formation is classified and marked by simulation through the above-mentioned fluid-solid heat coupling numerical model.

[0041] In some embodiments, well logging methods and seismic information can be used to identify and predict natural and artificial fractures within formations. For example, electromagnetic direction finders, CT scanners, micro-Lambda logging, annular acoustic logging, imaging logging (FMI), full-bore formation microresistivity imaging (FMI), DSI dipole shear wave imagers, microseismic monitoring, and downhole television (BHTV) can measure the inclination, strike, width, apparent porosity, and filling and opening of reservoir fractures, and can even identify microfractures and submicroscopic fractures. Of course, nonlinear theoretical methods can also detect and identify natural and artificial fractures in formations, such as fractal theory and neural networks. These methods can describe the distribution patterns and fractal dimension characteristics of fractures, as well as the connectivity of fracture networks. Based on the analysis of tectonic stress, natural and artificial fractures in the formation can also be predicted. For example, the main curvature of the structural surface is used to study the fracture problems in oil and gas reservoirs, the mechanical model of buckling thin plates is used to simulate longitudinal bending folds, the analytical calculation method of fault paleostress field is established, and the influence of tectonic stress field on fracture development is studied using numerical simulation methods.

[0042] In step S102P, at least one target artificial fracture (i.e., target original formation fracture) is screened out from at least one original formation fracture in step S100. In some embodiments, various parameters of the formation fractures for energy storage are planned in advance according to energy storage requirements, such as the amount of stored energy (including fluid kinetic energy and thermal energy) and economic costs, such as target width, target length threshold, target height threshold, and target number of fractures. Among them, the target length threshold and target height threshold can also be obtained by reverse deduction based on the required fluid kinetic energy and thermal energy carried by the fluid, and the target width of the existing formation fractures. Therefore, when the corresponding parameters of the identified artificial fracture reach the above-mentioned target values, it means that it meets the energy storage requirements. Therefore, high-pressure fluid can be directly injected into it to change its width (i.e., deform it) to store energy. Otherwise, it does not meet the energy storage requirements. Specifically, see Figure 7 Step S102P includes the following steps: obtaining first monitoring data of the artificial fractures identified in step S100 from a monitoring device; calculating the number of closed artificial fractures in the energy storage formation, as well as the original length and original height of each artificial fracture, by combining the first monitoring data and pre-acquired first construction parameters (e.g., injection rate, wellhead and bottomhole pressure, etc.) with a numerical model of fracture propagation; and determining whether the original length and original height of each artificial fracture meet a preset target length threshold and target height threshold. If so, mark it as a target artificial fracture; otherwise, continue screening until all target artificial fractures are screened out.

[0043] In some embodiments, as described above, the first monitoring data is obtained using various monitoring equipment, including electromagnetic direction finders, CT scanners, micro-Lambda logging, annular sonic logging, Fullbore Formation Microresistivity Imaging (FMI), DSI dipole shear wave imagers, microseismic monitoring, and downhole television (BHTV). Specifically, the first monitoring data includes the dip, strike, width, and apparent porosity of artificial fractures in the formation, as well as the filling and opening degree of the fractures.

[0044] In some embodiments, the first construction parameter includes injection rate and wellhead and bottomhole pressure. Generally, the first construction parameters of each artificial fracture in the formation can be obtained in advance.

[0045] In other embodiments, if the number of target artificial cracks finally screened out is less than a preset target artificial crack number threshold (usually, the target number of artificial cracks required to store the corresponding energy storage is pre-calculated based on the current energy storage demand, such as energy storage and economic cost, to obtain the target artificial crack number threshold, that is, the preset number threshold), artificial cracks that do not meet the preset target values ​​(for example, artificial cracks whose original length and / or original height do not meet the corresponding target length threshold and / or target height threshold), that is, the remaining artificial cracks that are not marked as target artificial cracks, can also be subjected to secondary transformation. Specifically, the number of artificial cracks that are secondary transformed can be the difference between the current target number of artificial cracks and the target number threshold, or it can be set according to the current target energy storage. Specifically, see Figure 8 The steps of performing secondary transformation on the artificial fracture specifically include: injecting high-pressure fluid into the artificial fracture through a wellbore according to a preset third construction parameter, so that the fracture pressure in the artificial fracture is greater than the fracture expansion pressure, thereby causing the artificial fracture to expand along its original height and original length; calculating the latest length and latest height of the artificial fracture after extending along the original height and original length according to the preset third construction parameter and third monitoring data obtained by real-time monitoring, combined with a numerical model of fracture expansion; then determining whether the latest length and latest height reach a preset target length threshold and a target height threshold; if so, stopping the injection of high-pressure fluid to obtain a target artificial fracture; otherwise, continuing to inject high-pressure fluid to extend the artificial fracture along the original height and original length, so that the artificial fracture is secondary transformed into a target artificial fracture until the height and length of the target artificial fracture reach the preset target threshold.

[0046] In step S104P, electric energy is used to drive the injection equipment to inject normal temperature and high pressure fluid into at least one target artificial fracture, so that the fracture width of at least one target artificial fracture increases to the target width, thereby converting the electric energy into elastic deformation energy of the formation rock for storage, and obtaining geothermal energy at the same time.

[0047] In some embodiments, the injection equipment uses an integrated power generation and water injection machine. When energy storage is required, the integrated power generation and water injection machine can pressurize the normal temperature fluid and input it into the wellbore to increase the width of the target formation fracture. When power generation is required, the integrated power generation and water injection machine can convert the kinetic energy of the backflow fluid into electrical energy.

[0048] In some embodiments, step S104P specifically includes: injecting high-pressure fluid into the target artificial fracture according to a preset second construction parameter, so that the fracture pressure gradually increases; monitoring the fracture pressure in the target artificial fracture in real time, and determining whether the fracture pressure is greater than the closure stress (that is, the minimum principal stress or closure pressure of the formation); if so, adjusting the second construction parameter so that the pressure of the fluid injected into the target artificial fracture is greater than the closure pressure and less than the expansion pressure of the formation fracture; otherwise, continuing monitoring.

[0049] In some embodiments, since the target artificial fracture (i.e., the target original formation fracture) is originally in a closed state, the pressure of the fluid initially injected into the closed target artificial fracture is less than the closure stress. However, with continued fluid injection, the fracture pressure within the target artificial fracture gradually increases and eventually exceeds the closure stress, causing the closed target artificial fracture to become open, i.e., opening the artificial fracture.

[0050] In some embodiments, the second construction parameter includes: the injection rate and the total injection volume of the fluid. Specifically, the fluid pressure can be adjusted by adjusting the injection rate of the high-pressure fluid or the amount of fluid injected by the injection device, and the fluid pressure can be monitored by a pre-installed pressure monitoring device. In some embodiments, the fracture pressure can be monitored by a pre-installed pressure monitoring device, such as a pressure sensor. In some embodiments, by adjusting the second construction parameter (for example, the injection rate and volume of the fluid, etc.), the injected fluid pressure is greater than the closing pressure of the formation and less than the expansion pressure of the target artificial fracture, so that the fracture width of the target artificial fracture gradually increases, and the expansion radius remains unchanged or constant (because the fluid pressure is less than the expansion pressure of the formation fracture, the target artificial fracture will not expand, that is, the fracture radius remains unchanged or constant, and its length and height will not change), thereby converting electrical energy into elastic deformation energy of the formation rock for storage.

[0051] Of course, in other embodiments, the expansion radius of the formation fracture / target artificial fracture remaining unchanged or constant can be understood as remaining unchanged or constant over a period of time. For example, when the width of the target formation fracture changes due to the action of high-pressure fluid, its expansion radius will also gradually change (i.e., continue to expand), but within a certain period of time (e.g., one hour), the change in expansion radius can be negligible in engineering practice; or, when the formation fracture expands due to the action of high-pressure fluid, after a certain period of time, the particles added to the high-pressure fluid will fill or partially fill the continuously expanding fracture.

[0052] Preferably, in some embodiments, the minimum principal stress of the energy storage formation can be obtained through a diagnostic fracturing injection test or a rapid injection flowback test. The propagation pressure of the formation fracture can be obtained by analyzing the instantaneous shut-in pressure (ISP) of the pressure drop curve after pump shutdown during hydraulic fracturing.

[0053] Specifically, in some embodiments, before injecting the normal temperature, high pressure fluid into the at least one target artificial fracture (i.e., before executing step S104P), the method further includes the step of providing at least one reservoir underground or on the surface for storing the fluid, wherein the reservoir is connected to the wellbore via a pipeline (e.g., a surface pipeline).

[0054] Preferably, in some embodiments, one or more additives may be added to the fluid in the reservoir in advance (that is, one or more additives may be added to the fluid injected into the formation fractures), for example, bactericides, descaling agents, mineral salts (such as KCl, NaCl, CaCl2, NaSiO4, etc.) and fluid loss preventers, wherein the mineral salts are used to balance the electrolytes in the energy storage formation.

[0055] When the water reservoir is set on the ground, preferably, in order to reduce the loss of fluid, in some embodiments, the water reservoir is provided with a shielding structure for preventing the evaporation of the fluid, for example, a plastic or metal film is covered above the water reservoir.

[0056] S106P: Determine whether the width of at least one target artificial fracture is equal to or greater than a preset target width. If so, execute step S108; otherwise, execute step S110. S108: Stop injecting the normal temperature, high pressure fluid into the at least one target formation fracture, i.e., the at least one target artificial fracture, to maintain the bottomhole pressure constant or negligibly small, so that the width of the target formation fracture remains constant or negligibly small. S110: Continue injecting the normal temperature, high pressure fluid into the at least one target artificial fracture and execute step S106P. In some embodiments, the width of the target artificial fracture is calculated based on the height of the target artificial fracture, the expansion radius of the target artificial fracture, and the bottomhole pressure. It is understood that the width of the target artificial fracture may not be equal at different locations within the target artificial fracture. Preferably, in some embodiments, the "width of the target artificial fracture" in step S106P refers to the average width of all target artificial fractures. Of course, in other embodiments, the "width of the target artificial fracture" in step S106P may also refer to the width of any target artificial fracture. For example, in some embodiments, for the same wellbore, during the process of injecting a normal temperature, high pressure fluid into each target artificial fracture, the width data of all target artificial fractures is obtained, and the widths of all target artificial fractures are averaged to obtain the average width of all target artificial fractures. When the average width is equal to or greater than a preset target width, power is stopped to the injection device, causing the injection device to stop injecting the normal temperature, high pressure fluid into each target artificial fracture. In some embodiments, the target width of the target artificial fracture is pre-set by professionals based on the mechanical properties of the energy storage formation and different energy storage requirements. While ensuring that the target artificial fracture has a certain storage capacity, it is avoided that the width of the target artificial fracture is too large and causes damage to the energy storage formation. It is understandable that since there are multiple target artificial fractures, in order to avoid the width of the target artificial fracture being too large and causing damage to the energy storage formation, preferably, when it is monitored (or determined) that the width of a target artificial fracture is equal to or greater than the preset target width, the injection of the normal temperature, high pressure fluid into at least one target artificial fracture is stopped, thereby keeping the bottom hole pressure unchanged or the change small enough to be negligible, so that the fracture width remains unchanged or the change small enough to be negligible. As a specific example, Figure 10A As shown, the grid-powered injection device 500 drives the fluid in the water reservoir 510 through the injection pipe 5200 to the wellbore 530 and then injects it into the hydraulic fracturing crack 590 (i.e., the target artificial crack) in the shale formation 540, so that the width of the formation crack expands, and the rock around the crack undergoes elastic deformation to store energy. At the same time, the surrounding rock heats the fluid in the crack to obtain geothermal energy.

[0057] S114: Utilize the high-temperature, high-pressure fluid discharged during the closure of at least one target artificial fracture to drive a pre-set hydroelectric power generation device to generate electricity, thereby converting the elastic deformation energy of the formation rock into electrical energy for energy release. In some embodiments, before executing step S114, the system further includes step S112: monitoring for power generation demand. If power generation demand is detected, step S114 is executed; otherwise, monitoring for power generation demand continues. Of course, in other embodiments, when insufficient power is detected to the injection device 500 (e.g., due to weather changes causing insufficient solar or wind power generation, specifically, when all or most of the solar or wind power generated is consumed by end users, leaving no excess power available for the injection device), step S108 is executed to cease power supply to the injection device 500, thereby causing the injection device 500 to cease injecting the normal-temperature, high-pressure fluid into the at least one target artificial fracture, thereby maintaining a constant bottomhole pressure and a constant fracture width. Furthermore, connecting the power generation device to the power grid can provide stable power to the power-consuming devices.

[0058] S118: Utilize the high-temperature, high-pressure fluid discharged during the closure of at least one target artificial fracture to drive a predetermined geothermal power generation device to generate electricity. In some embodiments, before executing step S118, the process further includes step S116: Determining whether the high-temperature, high-pressure fluid meets geothermal power generation requirements. If so, step S118 is executed; otherwise, monitoring continues for power generation demand. If the high-temperature, high-pressure fluid discharged during the closure of the target formation fracture still meets geothermal power generation requirements after driving the hydroelectric power generation device (e.g., the wellbore outlet temperature is greater than or equal to the required power generation temperature of the geothermal power generation device), the control valve connected to the discharge pipe connected to the geothermal power generation device is opened, allowing the high-temperature, high-pressure fluid discharged during the closure of the target formation fracture to drive the geothermal power generation device to generate electricity. In other embodiments, if it is determined in step S116 that the high-temperature, high-pressure fluid does not meet geothermal power generation requirements, the process further includes step S120: Determining whether the high-temperature, high-pressure fluid meets heating requirements. If so, step S122 is executed; otherwise, the high-temperature, high-pressure fluid is discharged into a water reservoir. S122: Connect the high-temperature, high-pressure fluid to an external heating system for heating. The water reservoir is connected to the wellbore corresponding to the formation fracture through a pipe and a reverse discharge pipe. When the injection of normal temperature and high pressure fluid into the formation fracture stops, the reverse discharge pipe and the injection pipe are both in a closed state. Specifically, the control valves in the reverse discharge pipe and the injection pipe are in a closed state. Therefore, when it is detected that there is a demand for power generation, the control valve corresponding to the reverse discharge pipe is opened to allow the reverse discharge pipe to circulate, so that the high temperature and high pressure fluid in the formation fracture can be reversed into the water reservoir through the reverse discharge pipe under the action of rock compression, and the hydropower generation equipment is driven during the reverse discharge process, converting the kinetic energy of the fluid into electrical energy. Specifically, see Figure 10A and Figure 10B, the injection pipe 520S and the backflow pipe 570S connecting the water reservoir 510S and the wellbore 530S are both provided with control valves for controlling the circulation and closure of the ground pipes. When it is detected that power generation is required (for example, the corresponding control system, or the first power generation equipment, or the corresponding staff will receive a power supply request from the outside, such as the power grid or other control systems), the control system connected to the control valve, or the hydroelectric power generation equipment 550S and the geothermal power generation equipment 560S opens the control valve corresponding to the backflow pipe 570S between the wellbore and the water reservoir (of course, it can also be opened manually by the staff), so that the wellbore 530S and the water reservoir are connected. The pools 510S are connected, and then under the action of rock squeezing, the high-temperature and high-pressure fluid in the formation fractures 590S in the shale formation 540S is discharged back into the water storage tank 510S. In this process, the high-temperature and high-pressure fluid first drives the impeller of the hydroelectric power generation equipment 550S to rotate to generate electricity. When passing through the geothermal power generation equipment 560S, it is judged whether the high-temperature and high-pressure fluid meets the geothermal power generation requirements. If so, the geothermal power generation equipment 560S is turned on to generate electricity. If not, the geothermal power generation equipment 560S is not turned on, but the fluid is introduced into the heating system 580S for heating (for example, when it is detected that there is a heating demand and the fluid temperature reaches the heating demand).

[0059] Through the reciprocating cycle of steps S104P-S118, the cyclic storage and release of electrical energy and the acquisition of geothermal energy for power generation can be achieved. For example, during the day, excess solar power is stored as the elastic deformation energy of the rock around at least one target artificial fracture, while geothermal energy is obtained. At night, when solar power generation is not possible, the elastic deformation energy of the stored formation and the acquired geothermal energy are converted back into electrical energy and released to the power grid for power supply. Of course, this electrical energy can also be generated by wind power generation or other methods. Of course, in other embodiments, if the high-temperature and high-pressure fluid discharged during the closure of the target formation fracture drives the hydroelectric power generation equipment to generate electricity but does not meet the geothermal power generation requirements, but meets the heating requirements, if the heating requirements are monitored, it is determined whether the fluid temperature meets the heating requirements. Only when the fluid temperature meets the heating requirements is the fluid sent to the heating system through the discharge pipe for heating. Of course, it is understandable that the heated fluid can also be discharged into the reservoir to achieve fluid recycling.

[0060] Example 7: See Figure 6B, is a flow chart of a method for storing and releasing energy and obtaining thermal energy through formation fractures according to another exemplary embodiment of the present invention. Specifically, the method includes the steps of the sixth embodiment, except that, in step S102P of the method in this embodiment, at least one target natural fracture is screened from the energy storage formation. Accordingly, in step S104P, a normal temperature and high pressure fluid is injected into the target natural fracture to increase the fracture width of the at least one target natural fracture, thereby converting electrical energy into elastic deformation energy of the formation rock for storage and simultaneously obtaining geothermal energy. In step S106P, it is determined whether the width of the target natural fracture has reached a preset target width. If so, the injection of normal temperature and high pressure fluid into the natural fracture is stopped in step S108, thereby maintaining the bottomhole pressure constant or causing negligible changes, thereby maintaining the width of the target formation fracture constant or causing negligible changes. In steps S114 and S118, the high temperature and high pressure fluid discharged during the closure of the natural fracture is used to drive preset hydroelectric power generation equipment and geothermal power generation equipment to generate electricity, thereby converting the elastic deformation energy of the formation rock and the obtained geothermal energy into electrical energy for release.

[0061] In other embodiments, when it is determined that the high-temperature and high-pressure fluid discharged back does not meet the geothermal power generation requirements after driving the preset hydropower generation equipment, it is determined whether it meets the heating requirements. If so, the high-temperature and high-pressure fluid is connected to the heating system for heating; otherwise, the high-temperature and high-pressure fluid is discharged into the water reservoir.

[0062] In some embodiments, the step of screening out at least one target natural fracture from at least one in situ formation fracture in the energy storage formation specifically includes: obtaining the distribution of the at least one natural fracture through well logging and seismic data inversion; obtaining the three-dimensional stress distribution of the energy storage formation through tectonic stress analysis; using a three-dimensional fracture-stress coupling model to simulate the opening of the at least one natural fracture during the injection of fluid into the at least one natural fracture, and calculating the energy storage capacity of the at least one natural fracture; judging whether the energy storage capacity reaches the target energy storage capacity, and if so, marking the corresponding natural fracture as a target natural fracture.

[0063] Furthermore, when it is determined that the energy storage capacity of the at least one natural fracture has not reached the target energy storage capacity, the natural fracture may be modified. Specifically, the step of modifying the natural fracture includes: injecting a normal temperature and high pressure fluid into the natural fracture through the wellbore according to a preset fourth construction parameter, so that the fracture pressure in the natural fracture is greater than the fracture expansion pressure, thereby causing the natural fracture to expand along the original height and original length direction; calculating the latest length and latest height of the natural fracture after extension using a fracture expansion numerical model according to the fourth construction parameter and real-time monitoring data; and determining whether the latest extended length and latest height of the natural fracture reach a preset target length threshold and target height threshold; if so, stopping the injection of the normal temperature and high pressure fluid; otherwise, continuing the injection of the normal temperature and high pressure fluid.

[0064] In practical applications, the degree of expansion of the natural fracture can be determined according to different energy storage requirements and the mechanical properties of the energy storage formation. For example, if more energy needs to be stored, a longer formation fracture needs to be designed. If relatively less energy needs to be stored, a shorter formation fracture needs to be designed. Therefore, the parameters of the target formation fracture, such as the target width, target length threshold, target height threshold, and target fracture number threshold, can be set in advance according to actual needs. When it is determined that the identified natural fracture reaches the desired target threshold: the target length threshold and the target height threshold, normal temperature and high pressure fluid is directly injected into it to increase its width to the target width, thereby storing energy. Of course, if the identified natural fracture does not reach the desired target threshold, normal temperature and high pressure fluid can be injected into it for transformation, that is, to expand it in the height or length direction until it meets the corresponding target threshold (including the target length threshold, the target height threshold, and the target fracture number threshold).

[0065] In some embodiments, the step of using electric energy to drive an injection device to inject a room-temperature, high-pressure fluid into at least one target natural fracture specifically includes: injecting a room-temperature, high-pressure fluid into the target natural fracture according to a preset second construction parameter, so that the fracture pressure in the target natural fracture gradually increases; monitoring the fracture pressure in the target natural fracture in real time, and determining whether the fracture pressure is greater than the closing pressure, so that the closed target natural fracture becomes open; if the fracture pressure is greater than the closing pressure, adjusting the second construction parameter so that the pressure of the fluid injected into the target natural fracture is greater than the closing pressure and less than the expansion pressure of the target natural fracture, thereby gradually increasing the fracture width of the target natural fracture to the target width.

[0066] Of course, if the target natural fracture is obtained through modification, since the natural fracture is currently in an open state, accordingly, when injecting room temperature and high pressure fluid into the target natural fracture through the injection device, it is only necessary to make the pressure of the injected room temperature and high pressure fluid greater than the closing pressure and less than the expansion pressure of the target natural fracture, so that the crack width of the target natural fracture gradually increases to the target width.

[0067] Typically, during the injection of normal-temperature, high-pressure fluid, the energy storage process, and even the reverse flow process, due to fluid loss, the electrical energy ultimately obtained from reverse flow may only be a portion of the target energy storage capacity, for example, only 70%-80% of the target energy storage capacity. Therefore, in order to minimize the potential for lower electrical energy ultimately obtained from reverse flow due to loss, the target length, width, and / or number of target natural fractures / target artificial fractures can be increased. For example, while simulating and calculating the energy storage capacity of a natural fracture, the fluid loss capacity of the natural fracture can also be calculated, thereby calculating the number of target natural fractures, the target length threshold, and the target height threshold based on the fluid loss capacity, energy storage capacity, and the target energy storage capacity.

[0068] Of course, in other embodiments, at least one target artificial fracture and at least one target natural fracture can be simultaneously selected from the existing original formation fractures in the formation for energy storage (and the order of identifying the target artificial fractures and the target natural fractures can be adjusted according to actual needs), and the number of target artificial fractures and target natural fractures, as well as the corresponding target threshold (for example, target width) are set according to the current energy storage demand; of course, if the data of the corresponding target artificial fractures and / or target natural fractures do not reach the respective preset target number thresholds, the existing artificial fractures can be modified for a second time, and / or the natural fractures can be modified. The specific modification method is the same as the corresponding modification method in the above-mentioned embodiments six and seven, and will not be repeated here.

[0069] Embodiment 8: Different from embodiment 6 or 7, there are multiple wellbores in this embodiment, and each wellbores is connected to the energy storage geothermal layer and the target formation fracture; it also includes a number of injection pipes and return pipes respectively matched with each wellbores, the injection pipes are connected to injection equipment, and the return pipes are connected to hydroelectric power generation equipment, geothermal power generation equipment and heating systems. However, the multiple wellbores are not connected through the formation fractures. At the same time, some of the multiple wellbores are performing the process of injecting fluid for secondary transformation, some are performing the process of energy storage, and some are performing the process of energy release. Of course, the injection pipe and the return pipe in the process of injecting normal temperature and high-pressure fluid can also be the same pipe. The principle is the same and will not be repeated here.

[0070] In the case of multiple wellbores, if there is a demand for power generation, it is also possible to determine whether the wellbore outlet temperature meets the requirements of the geothermal power generation equipment; and then select at least one wellbore whose outlet temperature meets the requirements of the geothermal power generation equipment to discharge fluid for power generation. The purpose of this step is to determine whether the fluid has accumulated sufficient geothermal heat to be used by the geothermal generator for power generation. Of course, in the case of a single wellbore, since power generation has the highest priority, this step can be ignored. Specifically, the method for determining whether the wellbore outlet temperature meets the requirements of the geothermal power generation equipment includes: simulating the relationship between the wellbore closed heat storage time and the wellbore outlet temperature based on a fluid-solid thermal coupling numerical model; calculating the required target closed heat storage time based on the wellbore outlet temperature required for power generation (including hydropower generation and geothermal power generation) and / or heating needs using the fluid-solid thermal coupling numerical model; if the actual closed heat storage time of any wellbore reaches the corresponding target closed heat storage time, then the outlet temperature of the corresponding wellbore is determined to meet the requirements of the geothermal power generation equipment. In addition, this step can also be applied to the coordinated operation of multiple wellbores. When the power generation demand exceeds the power that a single wellbore can provide, this step can be used to select multiple wellbores that can work together to meet the power generation demand. Specifically, the required number of wellbores is calculated based on the desired power generation demand.

[0071] See also Figure 12This embodiment provides a system for continuously storing and releasing energy and obtaining geothermal energy by utilizing existing formation fractures in an energy storage formation. Specifically, the energy storage formation includes depleted oil and gas wells that have completed production, such as vertical wells 710, 720, and 730, and horizontal wells 740, 750, and 760 (three horizontal wells or vertical wells are used as an example in this case, but the number of multiple vertical wells and horizontal wells described in the present invention includes all cases where the number is greater than 1), and each vertical well and horizontal well has at least one formation fracture in a closed state. During the period of utilizing the formation for energy storage and release, vertical wells 710, vertical well 720, and vertical well 730 and horizontal wells 740, horizontal well 750, and horizontal well 760 cooperate with each other to achieve continuous energy storage and release and obtain geothermal energy. For example, when vertical well 710 and horizontal well 740 are performing the injection process and converting electrical energy into formation elastic deformation energy, vertical well 720 and horizontal well 750 have already completed injection, and thus can convert electrical energy into formation elastic deformation energy for storage while obtaining geothermal energy. Vertical well 730 and horizontal well 760, due to power generation needs, are performing the reverse discharge process, converting the stored formation elastic deformation energy and the obtained geothermal energy into electrical energy and putting it into the grid for use. Then, vertical well 730 and horizontal well 760, which have completed energy release, perform the injection process. After completing the injection, vertical well 720 and horizontal well 750, which are in the storage process, perform the reverse discharge process to release energy. After completing the injection, vertical well 710 and horizontal well 740 are in the energy storage process and obtain geothermal energy. Taking this as an example, vertical well 710, vertical well 720, vertical well 730 and horizontal well 740, horizontal well 750, and horizontal well 760 are cyclically coordinated to ensure that electrical energy can be provided to the grid at any time to meet electricity demand.

[0072] Example 9: The present invention also provides a system for storing and releasing energy through formation fractures and obtaining geothermal energy, see Figure 9The system specifically includes: a formation identification device 02, which is used to identify at least one energy storage geothermal layer with rich geothermal resources, no oil and gas, and at least one original formation fracture; wherein the original formation fracture includes a natural fracture, and / or an artificial fracture in a closed state; a formation fracture screening device 04, which is used to screen out at least one target formation fracture from the at least one original formation fracture identified by the formation identification device 02; wherein the at least one target formation fracture includes at least one target artificial fracture, and / or at least one target natural fracture; an injection device 06, which is used to inject a normal temperature and high pressure fluid into the at least one target formation fracture, so that the fracture width of the at least one target formation fracture increases to a target width, thereby converting electrical energy into elastic deformation energy of the formation rock for storage and obtaining geothermal energy; a power generation device 12, which includes a hydroelectric power generation device and a geothermal power generation device, which is used to generate electricity when the high temperature and high pressure fluid in the target formation fracture squeezes the rock during the closing process of the target formation fracture. When reverse discharge is carried out under the action of the high-temperature and high-pressure fluid, the elastic deformation energy of the formation rock and the obtained geothermal energy are converted into electrical energy reverse discharge pipes under the drive of the high-temperature and high-pressure fluid, which are connected to the above-mentioned hydroelectric power generation equipment and geothermal power generation equipment. The fluid in the formation fracture is reversed through the reverse discharge pipe and drives the hydroelectric power generation equipment and / or geothermal power generation equipment to generate electricity. Preferably, the hydroelectric power generation equipment is driven to generate electricity first. After driving the hydroelectric power generation equipment to generate electricity, if the geothermal power generation demand is still met (for example, by detecting the temperature of the high-temperature and high-pressure fluid through a temperature detection device, or whether the temperature at the wellbore outlet meets the heating temperature required by the geothermal power generation equipment), the geothermal power generation equipment is driven to generate electricity. If the geothermal power generation demand is not met, it is determined whether it meets the heating demand. If so, the high-temperature and high-pressure fluid is connected to the heating system for heating. If not, it is directly reversed into the water storage tank. The plugging device is used to close the reverse discharge pipe so that the fluid in the formation fracture continues to exchange heat with the energy storage geothermal layer, so that the fluid temperature continues to rise. Preferably, the plugging device is a control valve provided on the reverse discharge pipe. Of course, in order to prevent the fluid from flowing back from the injection pipe, the plugging device may further include a control valve provided on the injection pipe. In some embodiments, the system further includes: a water reservoir 14, connected to the injection device 06, for storing fluid. Further, in some embodiments, the water reservoir is connected to the wellbore corresponding to the original formation fracture through a reverse flow pipe, and a control valve for controlling the wellbore or reverse flow pipe to be opened (i.e., circulated) or closed (i.e., not circulated) is provided in the wellbore or reverse flow pipe. Accordingly, the system further includes: a (power generation demand) monitoring device, connected to the control valve, for monitoring whether there is a power generation demand. When a power generation demand is detected, a first control instruction for opening the control valve of the reverse flow pipe is generated and sent to the control valve to control the control valve to open, i.e., the water reservoir and the wellbore are connected. Otherwise, the system continues to monitor whether there is a power generation demand.

[0073] Specifically, in some embodiments, the reverse flow pipe between the water reservoir and the wellbore is normally in a closed state / non-circulating state (specifically, the valve in the reverse flow pipe is normally in a closed state). When the power generation device 12 receives a first control instruction sent by the monitoring device indicating to open the control valve corresponding to the reverse flow pipe (for example, a control instruction from the power grid or other control system connected to the power generation device 12, or a control instruction issued by a staff member), the power generation device 12 will open the reverse flow pipe between the wellbore and the water reservoir (specifically, open the control valve corresponding to the reverse flow pipe), so that under the action of rock squeezing, the high-temperature and high-pressure fluid in the formation fracture is reversed into the water reservoir through the reverse flow pipe, and drives the hydraulic generator in the power generation device 12. The impeller of the electric device rotates to generate electricity. Subsequently, the determination device determines whether the high-temperature, high-pressure fluid discharged back into the hydroelectric power generation device meets the geothermal power generation demand. If the geothermal power generation demand is met, a second control instruction indicating the start of the geothermal power generation device is generated and sent to the geothermal power generation device, causing the geothermal power generation device in the power generation device 12 to generate electricity. If the power generation device 12 does not receive the first control instruction indicating the opening of the control valve of the backflow pipe, the power generation device 12 will always keep the backflow pipe closed. At this time, the monitoring device continues to monitor whether there is a power supply demand. Of course, in other embodiments, the determination of whether there is a power supply demand can be made by the staff and the staff can control the opening and closing of the valve in the injection / backflow pipe. In other embodiments, if it is determined that the geothermal power generation conditions are not met, the geothermal power generation device is shut down, and further determination is made whether the heating demand is met. If the heating demand is determined to be met, the high-temperature, high-pressure fluid discharged back into the heating system is allowed to flow into the heating system for heating.

[0074] Specifically, see Figure 10A and Figure 10B, the injection pipe 520 and the backflow pipe 570 connecting the water reservoir 510 and the wellbore 530 are both provided with control valves for controlling the circulation and closure of the ground pipes. When it is detected that power generation is required (for example, the corresponding control system, or the first power generation equipment, or the corresponding staff will receive a power supply request from the outside, such as the power grid or other control systems), the control system connected to the control valve, or the hydroelectric power generation equipment 550 and the geothermal power generation equipment 560 will open the control valve corresponding to the backflow pipe 570 between the wellbore and the water reservoir (of course, it can also be opened manually by the staff), so that the wellbore 530 and the water reservoir are connected. The pools 510 are connected, and then under the action of rock squeezing, the high-temperature and high-pressure fluid in the formation cracks 590 in the shale formation 540 is discharged back into the water storage tank 510. In this process, the high-temperature and high-pressure fluid first drives the impeller of the hydroelectric power generation equipment 550 to rotate to generate electricity. When passing through the geothermal power generation equipment 560, it is judged whether the high-temperature and high-pressure fluid meets the geothermal power generation requirements. If so, the geothermal power generation equipment 560 is turned on to generate electricity. If not, the geothermal power generation equipment 560 is not turned on, but the fluid is introduced into the heating system 580 for heating (for example, when it is detected that there is a heating demand and the fluid temperature reaches the heating demand).

[0075] Of course, if no power request is received, the backflow pipe 570 between the wellbore and the reservoir will remain closed, that is, the control valve on the backflow pipe 570 will be in a normally closed state. In this case, it is sufficient to continue monitoring whether there is a power demand. It will be understood that even if there is a power demand and / or heating demand, it is still necessary to determine whether the fluid in the formation fracture can meet the power generation and / or heating requirements.

[0076] In some embodiments, the formation fracture screening device 04 specifically includes: a monitoring device for monitoring the energy storage formation to obtain monitoring data of at least one original formation fracture in the energy storage formation; specifically, the monitoring data includes first monitoring data of the artificial fracture and / or second monitoring data of the natural fracture; a data storage module for storing the first construction parameters of the artificial fracture in the energy storage formation obtained in advance; a first calculation module, connected to the monitoring device and the data storage module, for calculating the original length and original height of the artificial fracture based on the fracture extension numerical model combined with the above-mentioned first monitoring data and the first construction parameters; a first control module, connected to the first calculation module and the injection device 06, for determining whether the original length and original height of the artificial fracture meet the preset target length threshold and target height threshold, and if so, marking the corresponding artificial fracture as a target artificial fracture and triggering the injection device to inject high-pressure fluid into the target artificial fracture; or, when it is determined that the original length and original height of the artificial fracture reach the preset target length threshold and target height threshold, triggering the injection device to inject high-pressure fluid into the target artificial fracture to perform secondary transformation on the artificial fracture. Of course, when the target artificial fracture is obtained through transformation, the first control module is further used to trigger the injection device to inject high-pressure fluid into the target artificial fracture for energy storage;

[0077] In some embodiments, the formation fracture screening device also includes: a second calculation module, which is used to invert the logging data and the seismic data to obtain the distribution of the at least one natural fracture; a third calculation module, which is used to obtain the three-dimensional stress distribution of the energy storage formation through structural stress analysis; a fourth calculation module, which is used to use a three-dimensional fracture-stress coupling model to simulate the opening of the natural fracture during the process of injecting fluid into the natural fracture, and calculate the energy storage capacity of the natural fracture; a second control module, which is used to determine whether the energy storage capacity has reached the preset target energy storage capacity. If so, the corresponding natural fracture is marked as a target natural fracture, and the injection device is triggered to inject high-pressure fluid into the target natural fracture; or, when it is determined that the energy storage capacity has not reached the preset target energy storage capacity, the injection device is triggered to transform the natural fracture. Of course, when the target natural fracture is obtained by transformation, the second control module is also used to trigger the injection device to inject normal temperature and high-pressure fluid into the target natural fracture to store energy and obtain geothermal energy;

[0078] In some embodiments, the formation fracture screening device also includes: a second control device 10, connected to the injection device 06, for determining whether the width of at least one target formation fracture is equal to or greater than a preset target width. If so, a third control instruction indicating to stop injecting normal temperature and high pressure fluid is generated and sent to the injection device 06, so that the injection device 06 stops injecting normal temperature and high pressure fluid into at least one target formation fracture, so that the width of the target formation fracture remains unchanged.

[0079] In some embodiments, the second control device 10 is also used to monitor whether the power supply of the injection device 06 is sufficient. If not, a third control instruction indicating to stop injecting normal temperature and high pressure fluid is generated and sent to the injection device 06, so that the injection device 06 stops injecting normal temperature and high pressure fluid into at least one target formation fracture, so that the width of the target formation fracture remains unchanged.

[0080] Specifically, in some embodiments, the injection device 06 is installed in an injection pipeline (i.e., a pipeline connecting the water reservoir and the wellbore and for fluid injection). When the injection device 06 stops injecting normal temperature and high-pressure fluid into at least one formation fracture, the injection device 06 puts the injection pipeline into a closed state / non-circulating state. Specifically, the injection device 06 closes the valve in the injection pipeline.

[0081] In some embodiments, the injection device 06 includes: a fluid injection module 062, used to inject high-pressure fluid at room temperature into at least one formation fracture; a pressure monitoring module 064, used to monitor the pressure of the injected fluid in real time; a pressure judgment module 066, connected to the fluid injection module 062 and the pressure monitoring module 064, used to judge whether the pressure of the injected fluid is greater than the closing pressure of the energy storage formation and less than the expansion pressure of the formation fracture. If so, the pressure judgment module 066 does nothing; otherwise, the pressure judgment module 066 generates a fourth control instruction indicating adjustment of the second construction parameter (i.e., the working parameter of the fluid injection module 062), and sends it to the fluid injection module 062 to control the fluid injection module 062 to adjust the second construction parameter so that the current fluid pressure is always maintained between the fracture expansion pressure and the closing pressure of the energy storage formation.

[0082] In some embodiments, the pressure judgment module 066 is also used to determine whether the internal crack pressure of the natural crack / artificial crack is greater than the crack expansion pressure during the modification of the natural crack / artificial crack. If so, the pressure judgment module 066 does nothing. Otherwise, the pressure judgment module 066 generates a fifth control instruction indicating the adjustment of the third construction parameter / fourth construction parameter (i.e., the working parameter of the fluid injection module 062) and sends it to the fluid injection module 062 to control the fluid injection module 062 to adjust the third construction parameter / fourth construction parameter so that the internal crack pressure of the natural crack / artificial crack is greater than the crack expansion pressure, thereby achieving the expansion of the natural crack / artificial crack along the original height and original length.

[0083] In some embodiments, the second control device 10 is also used to monitor the injection device according to the fourth construction parameter and the fourth monitoring data monitored in real time by the monitoring equipment, and use the numerical model of crack extension to calculate the latest length and the latest height of the natural crack after extension, or use the numerical model of crack extension to calculate the latest length and the latest height of the artificial crack after extension according to the third construction parameter and the third monitoring data monitored in real time by the monitoring equipment; and to determine whether the latest length and the latest height of the natural crack / artificial crack reach the preset target length threshold and the target height threshold, and when it is determined that the latest length and the latest height reach the preset target length threshold and the target height threshold, the injection module is controlled to stop injecting fluid.

[0084] In other embodiments, in order to simplify the equipment, the difference is that the injection pipeline and the reverse flow pipeline in this embodiment are the same pipeline; the hydraulic generator and the injection equipment are an integrated power generation and water injection machine. When energy storage is required, the integrated power generation and water injection machine can pressurize the normal temperature fluid and input it into the wellbore to increase the width of the formation fracture. When power generation is required, the integrated power generation and water injection machine can convert the kinetic energy of the reverse flow fluid into electrical energy.

[0085] A so-called integrated power generation and water injection unit is a device that combines both water pumping and power generation functions. It can pump water or convert the kinetic energy of water into electricity through forward and reverse rotation. Specifically, it can be a motor-generator, a machine that combines both generator and motor functions. It can function as a generator driven by a turbine to generate electricity, or as a motor to drive a water pump to pump water.

[0086] See Figure 11A and Figure 11BAfter the integrated power generation and water injection unit 610 stops injecting normal temperature, high pressure fluid into at least one formation fracture, the valve in the pipeline 640 between the wellbore 650 and the water reservoir 630 is also closed. When power generation is detected, the corresponding control valve in the pipeline 640 between the wellbore 650 and the water reservoir 630 is opened. At this time, under the action of rock compression, the high temperature, high pressure fluid heated by the formation in the formation fracture 670 within the shale formation 660 is reversed through the pipeline 640 into the water reservoir 630. In this process, the impeller of the integrated power generation and water injection unit 610 is first driven to rotate to generate electricity, and then the fluid passes through the geothermal power generation equipment 620. At this time, if it is determined that the high temperature, high pressure fluid meets the geothermal power generation conditions, the geothermal power generation equipment 620 is driven to generate electricity. Otherwise, the geothermal power generation equipment 620 remains closed and determines whether there is a heating demand. If so, the fluid is introduced into the heating system 680; otherwise, it is returned to the water reservoir. If no power demand is detected, the pipeline 640 between the wellbore 650 and the water reservoir 630 remains closed at all times.

[0087] Example 10: Based on the same inventive concept, the present invention also provides another method for storing and releasing energy through formation fractures and obtaining geothermal energy, see Figure 13 The method of this embodiment specifically includes the following steps: S1301 identifying an energy storage geothermal layer containing geothermal resources but not containing oil and gas; S1302 injecting high-pressure fluid into a target wellbore in the energy storage geothermal layer, so as to generate at least one target artificial formation crack in the energy storage geothermal layer, or open at least one target original formation crack in a closed state in the target wellbore; wherein, the target wellbore is not connected to other wellbores in the energy storage geothermal layer through formation cracks; S1303 injecting normal temperature high-pressure fluid into the target wellbore, so as to increase the width of the target artificial formation crack or the target original formation crack in the target wellbore, thereby causing the formation rock to undergo elastic deformation and store energy, and the target artificial formation crack The fluid in the crack or the target original formation crack exchanges heat with the energy storage geothermal layer, causing the fluid temperature to rise; S1304 closes the reverse flow pipeline so that the fluid in the formation crack continues to exchange heat with the energy storage geothermal layer, causing the fluid temperature to continue to rise, so as to store heat (preferably, when the width of at least one target artificial formation crack or at least one target original formation crack reaches the target width, it is closed again for heat storage); S1305 uses the high-temperature and high-pressure fluid reversed during the closing process of the target artificial formation crack or the target original formation crack to drive the preset hydroelectric power generation equipment and geothermal power generation equipment to generate electricity, thereby converting the acquired geothermal energy and the elastic deformation energy of the formation rock into electrical energy for energy release. Among them, the specific steps of energy release can refer to the energy release principle of the above embodiments, which will not be repeated here.

[0088] In some embodiments, due to formation heterogeneity, difficulty in obtaining formation cores, or computational errors in the hydraulic fracturing model, the expansion of formation fractures along the length or height direction is uncontrollable. It is possible that during the actual expansion of a formation fracture, the actual expansion height of the fracture does not reach the preset target expansion height, but the actual expansion radius exceeds the preset target expansion radius. Alternatively, the actual expansion radius of the fracture does not reach the preset target expansion radius, but the actual expansion height exceeds the preset target expansion height. Therefore, if not controlled, whether during the process of hydraulic fracturing to form the formation fracture or during the process of modifying the original formation fracture, the target wellbore may be connected to the adjacent wellbore. Therefore, in order to ensure that the target formation fracture does not communicate with adjacent wellbores, in this embodiment, during the process of creating the target artificial fracture by hydraulic fracturing or modifying the original formation fracture (including secondary modification of the original artificial formation fracture or modification of the original natural fracture), it is also necessary to: monitor the actual three-dimensional size (including the actual expansion radius and / or actual expansion height) of the formation fracture (for example, the target artificial formation fracture in the target wellbores during the hydraulic fracturing process, or the original formation fracture in the target wellbores during the modification process) in real time, and when the actual three-dimensional size of the formation fracture obtained by monitoring exceeds a set threshold, stop injecting high-pressure fluid into the target wellbores. The preset threshold can be set to the minimum value between the energy storage three-dimensional size of the formation fracture (such as the target expansion radius and / or the target expansion height, both of which are calculated in advance based on the required energy storage) and the safety three-dimensional size (if the size is exceeded, there is a risk of connection with other adjacent wellbores).

[0089] See also Figure 14 If the cracks in the adjacent wellbore and the artificial formation cracks in the target wellbore currently undergoing hydraulic fracturing are at the same height (or the height difference is less than a preset threshold), the formation cracks in the target wellbore may connect with the existing formation cracks (such as artificial cracks or natural cracks) in the adjacent wellbore during the expansion process. Therefore, it is necessary to set a safe expansion radius R0 to control the fracturing process. Specifically, the safe expansion radius must meet the following conditions: R0<(L0-R 邻 ), where L0 is the distance between the target wellbore and its nearest adjacent wellbore, R 邻 It is the actual expansion radius of the formation fracture of the adjacent wellbore closest to the target wellbore.

[0090] See also Figure 15 If the formation fractures of adjacent wellbores are at different heights from the formation fractures in the target wellbores currently undergoing hydraulic fracturing (or modification), the two wellbores may also be connected if not controlled. Therefore, a safe expansion height H0 needs to be set. Specifically, the safe expansion height must meet the following conditions: H0<(V0-H 邻), where V0 is the vertical distance between the formation fracture initiation point (or perforation) in the target wellbore and the formation fracture initiation point (or perforation) in the nearest adjacent wellbore. 邻 is the actual expansion height of the target formation fracture in the nearest adjacent wellbore; H0' is the actual expansion height of the formation fracture in the monitored target wellbore.

[0091] Specifically, the actual three-dimensional dynamic changes in the size of the target artificial fracture can be monitored through microseismic, inclinometer, distributed optical fiber, synthetic aperture radar and other methods. The actual three-dimensional dynamic changes in the size of the target artificial fracture can also be obtained by monitoring construction parameters (injection flow, pressure, time, etc.) and combining them with hydraulic fracturing models.

[0092] In some embodiments, the step of setting the preset threshold specifically includes: obtaining the distance L0 between the target wellbore and at least one of its nearest adjacent wellbores, and the actual expansion radius R of the formation fracture in each of the adjacent wellbores. 邻 Based on the spacing L0 and the actual expansion radius R of the formation fracture in the nearest adjacent wellbore 邻 Determine the safe expansion radius R of the target formation fracture in the target wellbore 0， That is: R0<(L0-R 邻 (If there are multiple adjacent wellbores and the actual expansion radius of the formation fractures in each adjacent wellbores is different, the largest actual expansion radius R 邻max , that is, R0<(L0-R 邻max ), where the actual expansion radius R 邻 < spacing L0; determine whether the target expansion radius R0' of the formation fracture in the target wellbore is greater than the safe expansion radius R0; if R0' ≥ R0, use R0 as the set threshold for the target formation fracture in the target wellbore; if R0' < R0, use R0' as the set threshold for the target formation fracture in the target wellbore. Accordingly, once the actual expansion radius of the formation fracture in the target wellbore reaches the set threshold, the injection of high-pressure fluid is stopped.

[0093] For example, if the target wellbore and the nearest adjacent well are 1,000 meters apart, and the actual expansion radius (or length) of the formation fracture created by hydraulic fracturing in the adjacent well is 500 meters, if the actual expansion radius (or length) of the formation fracture created in the target wellbore exceeds 500 meters, there is a risk of the two wellbores connecting through the formation fracture. To prevent the two wellbores from connecting through the formation fracture, the safe expansion radius (or length) of the target formation fracture in the target wellbore is set to 450 meters. Hydraulic fracturing is performed on the target wellbore, and the actual expansion radius (or length) of the artificial formation fracture is monitored in real time. If the target formation fracture's energy storage radius (i.e., target expansion radius) is designed to be 300 meters, which is smaller than the target formation fracture's safe expansion radius (or length) of 450 meters, the energy storage radius (i.e., target expansion radius) is set to the preset threshold of the three-dimensional dimensions of the formation fracture in the current wellbore, i.e., 300 meters. If the target formation fracture's energy storage radius (i.e., target expansion radius) is designed to be 600 meters, which is larger than the target formation fracture's safe expansion radius (or length) of 450 meters, the safe expansion radius is set to the preset threshold of the three-dimensional dimensions of the formation fracture in the wellbore, i.e., 450 meters. Setting the preset threshold for the three-dimensional dimensions of the formation fracture can guide and modify construction parameters and control the maximum expansion radius (or length) or height of the target formation fracture.

[0094] In other embodiments, the step of setting the preset threshold specifically includes: obtaining the height difference V0 between the formation fracture initiation point (or perforation) of the target wellbore and the formation fracture initiation point (such as the perforation position) of at least one of its nearest adjacent wellbores, the actual expansion height H 邻 Determine the safe expansion height H0 of the formation fracture in the target wellbore: H0<(V0-H 邻 ); determining whether a preset target expansion height H0' of the formation fracture in the target wellbore is greater than the safe expansion height H0. If the target expansion height H0' is greater than or equal to the safe expansion height H0, the safe expansion height H0 is used as the set threshold for the formation fracture in the target wellbore. If the target expansion height H0' is less than the safe expansion height H0, the target expansion height H0 is used as the set threshold for the formation fracture in the target wellbore. Accordingly, once the actual expansion height of the formation fracture in the target wellbore is detected to have reached the set threshold, the injection of high-pressure fluid is stopped.

[0095] For example, the height difference V0 between the perforation of a formation fracture in a target wellbore and the perforation of a formation fracture in the nearest adjacent well is 10 meters. The actual propagation height of the formation fracture created by hydraulic fracturing in the adjacent well is 5 meters. If the actual propagation height of the formation fracture created in the target wellbore exceeds 5 meters, there is a risk of connection between the two wellbores through the formation fracture. To prevent connection between the two wellbores through the formation fracture, a safe propagation height of the target formation fracture in the target wellbore is set at 4 meters. Hydraulic fracturing is performed on the target wellbore, and the actual propagation height of the artificial formation fracture is monitored in real time. If the target formation fracture's energy storage height (i.e., target expansion height) is designed to be 3 meters, which is less than the target formation fracture's safe expansion height of 4 meters, the energy storage radius (i.e., target expansion radius) is set to the preset threshold of the three-dimensional dimensions of the formation fracture in the current wellbore, i.e., 3 meters. If the target formation fracture's energy storage height (i.e., target expansion height) is designed to be 6 meters, which is greater than the target formation fracture's safe expansion height of 4 meters, the safe expansion height is set to the preset threshold of the three-dimensional dimensions of the formation fracture in the wellbore, i.e., 4 meters. Setting the preset threshold of the three-dimensional dimensions of the formation fracture can guide and correct construction parameters and control the maximum expansion radius (or length) or height of the target formation fracture.

[0096] In actual application, it is only necessary to stop injecting the high-pressure fluid when either the actual expansion radius or the actual expansion height reaches the corresponding preset threshold.

[0097] Furthermore, when the safe three-dimensional size is used as a preset threshold, if the actual three-dimensional size of the formation fracture is less than the preset three-dimensional energy storage size, for example, the actual expansion radius may not reach the preset target expansion radius, and / or the actual expansion height may not reach the preset target expansion height. However, in order to ensure that the energy storage capacity of the target wellbore reaches the preset target energy storage capacity, once the safe three-dimensional size is used as the preset threshold, the target expansion height and / or target expansion radius of the target formation fracture need to be recalculated. Then, by adjusting the operation parameters, such as the injection pressure and / or injection flow rate and / or injection fluid density, the final actual expansion radius of the target formation fracture reaches the safe expansion radius, and the final actual expansion height reaches the recalculated target expansion height. For example, if the safe expansion radius R0 is used as the set threshold for the target formation fracture in the target wellbore, the target expansion height of the target formation fracture is recalculated based on the preset target energy storage capacity and the safe expansion radius R0; the operation parameters are adjusted based on the target expansion height and the safe expansion radius R0 so that the final actual expansion radius of the target formation fracture is less than or equal to the safe expansion radius R0, and the final actual expansion height reaches the recalculated target expansion height. For another example, if the safe expansion height H0 is used as the set threshold of the target formation fracture in the wellbore, the target expansion radius of the target formation fracture is recalculated based on the preset target energy storage capacity and the safe expansion height H0; the injection pressure is adjusted according to the latest target expansion radius and the safe expansion height H0, so that the final actual expansion radius of the target formation fracture reaches the latest target expansion radius, and the final actual expansion height is less than or equal to the safe expansion height H0.

[0098] Example 11: The present invention also provides another method for storing and releasing energy and obtaining geothermal energy through formation fractures, which includes the steps of the method in the above-mentioned Example 10, except that when hydraulic fracturing is performed on multiple target wellbores to form multiple target wellbores that are not connected through formation fractures and are capable of storing and releasing energy and obtaining geothermal energy, continuous power supply can be achieved through the synergy between the multiple unconnected target wellbores. For example, when there is a power supply demand, it is determined whether the wellbore temperature of any target wellbore among the multiple target wellbores meets the power generation demand. If not, at least one target wellbore is selected and reversed, thereby converting elastic potential energy into electrical energy; and once the wellbore temperature of any target wellbore meets the power generation demand, the target wellbore is switched to, so that the elastic deformation release energy and geothermal energy are simultaneously converted into electrical energy, thereby achieving continuous power supply.

[0099] In other embodiments, the target width of the formation fracture is affected not only by the power supply demand but also by the energy storage power supply capacity. For example, under the premise of the same power supply demand, if the energy storage power supply is insufficient, the target width of the formation fracture in the target wellbore is set based on the energy storage power supply. If the energy storage power supply is sufficient, the target width of the formation fracture in the target wellbore is set based on the power supply demand. For example, for a single target wellbore, when the ideal planned energy storage capacity is W1, the width of its formation fracture needs to be increased to the ideal width P0 to meet the energy storage capacity. However, in actual applications, if the current energy storage power supply is insufficient, so that the width of the formation fracture cannot be increased to P0, but can only be increased to P1 (P1 is less than P0), then P1 is the target width of the formation fracture (which is less than the ideal target width P0); if the current energy storage power supply is sufficient, so that the width of the formation fracture can be increased to P0, or even larger (but the formation fracture does not continue to expand), then P0 is the target width of the formation fracture. It can be seen from this that the power supply capabilities of the multiple wellbores that are ultimately not connected are different, and since the input or output power of a single target wellbores is limited, the multiple wellbores are grouped, and the wellbores in the same group store energy or release energy at the same time to increase the power of energy storage or power generation. When one group of wellbores stores energy, the other group of wellbores releases energy at the same time, and so on, alternating in a cycle. This not only increases the power generation power, but also ensures continuous power output. Preferably, the difference in the amount of stored energy between the two groups of wellbores that are alternately powered is less than or equal to the preset energy difference threshold, and the difference in the total heat storage time of the two groups of wellbores (that is, the heat storage time of all the wellbores in each group reaches the time required for their respective preset target closed heat storage time) is less than or equal to the preset time difference threshold, thereby ensuring continuous power supply.

[0100] In other embodiments, the high-pressure fluid discharged from the formation fractures is first used to generate electricity or heat using the thermal energy of the high-pressure fluid, and then the kinetic energy of the high-pressure fluid is used to generate electricity. The advantage of this is that no additional pumping equipment is required when the fluid passes through the heat exchange pipe or thermal power generation equipment. If the kinetic energy of the high-pressure fluid is used to generate electricity first, the fluid will lose most of its pressure and may not be able to pass through the heat exchange pipe or thermal power generation equipment by its own pressure. In addition, using the thermal energy of the high-pressure fluid to generate electricity or heat first can reduce the temperature of the high-pressure fluid, which is beneficial to improving the working efficiency of subsequent hydroelectric power generation equipment and avoiding the situation where the high-pressure and high-temperature fluid changes from liquid to gas due to pressure reduction in the hydroelectric power generation equipment (for example, water is liquid at 110 degrees Celsius and 20MPa, and gas at 0.1MPa).

[0101] Preferably, in order to prevent possible geological risks and loss of injected fluid, the distance between the target wellbore for energy storage and the nearest fault needs to be greater than 2000 meters.

[0102] In other embodiments, to reduce the frictional resistance of fluid flow in the fractures, at the end of the energy release process, the volume of high-pressure fluid retained in the formation fractures is greater than or equal to a preset volume threshold, thereby ensuring that the fracture width of the formation fractures during the energy storage and release cycles is greater than or equal to a preset width threshold (the smaller the fracture width, the greater the frictional resistance). Both the preset volume threshold and the preset width threshold can be calculated using a physical model (such as a hydraulic fracturing model). For example, to ensure that the impact of frictional resistance loss of fluid flow in the fracture on the energy storage cycle efficiency is less than 10%, the hydraulic fracturing model, using known information (such as fracture height, fracture length, rock Young's modulus, rock Poisson's ratio, rock fracture behavior, fluid displacement, etc.), calculates that the minimum fracture width cannot be less than 0.3 cm (i.e., the preset width threshold). The corresponding minimum volume of high-pressure fluid in the formation fracture cannot be less than 1000 cubic meters, and the volume of high-pressure fluid used for backflow is 5000 cubic meters. Therefore, 1000 cubic meters is used as the preset volume threshold, and at the end of the energy release process, the volume of high-pressure fluid retained in the formation fractures is no less than 1000 cubic meters. For example, to minimize the impact of frictional resistance losses caused by fluid flow in fractures on energy storage cycle efficiency by less than 5%, a hydraulic fracturing model, utilizing known information (such as fracture height, fracture length, rock Young's modulus, rock Poisson's ratio, rock fracture dynamics, and fluid displacement), calculates that the minimum fracture width cannot be less than 0.5 cm (i.e., the preset width threshold). The corresponding minimum volume of high-pressure fluid within the fracture cannot be less than 1,500 cubic meters, and the volume of high-pressure fluid used for backflow is 4,500 cubic meters. 1,500 cubic meters then serves as the preset volume threshold. At the end of the energy release process, the volume of high-pressure fluid retained in the formation fractures must be no less than 1,500 cubic meters. Generally, these two thresholds can be set based on the desired energy storage cycle efficiency. In special circumstances (such as when emergency power generation or emergency energy storage is required), the thresholds can be adjusted upward or downward based on actual conditions.

[0103] In other embodiments, although a preset threshold is set to prevent multiple target wellbores ultimately formed by fracturing from being connected, or multiple target wellbores after being transformed from being connected, in actual applications, if the formation fractures of two target wellbores are very close, and when fluid is injected into both target wellbores simultaneously for energy storage, the deformation of adjacent formation fractures may cause squeezing and interference, or even rupture, causing the two target wellbores to be connected, forming two connected energy storage and release units, which may easily cause flow loss.

[0104] Therefore, during the energy storage process, adjacent formation fractures between adjacent target wellbores are monitored in real time (for example, formation fractures in two adjacent target wellbores that are located at the same height and the spacing between the two formation fractures is less than a preset spacing, or two formation fractures in two adjacent target wellbores that are located at different heights and the height difference is less than a preset height difference threshold). If connectivity occurs, high-pressure fluid is injected into all connected wellbores at the same time; when releasing energy, the high-pressure fluid is discharged back through all connected wellbores at the same time, and the kinetic energy of the high-pressure fluid and the acquired thermal energy are converted into electrical energy.

[0105] In other embodiments, the target wellbore is an abandoned oil or gas well. Before injecting high-pressure fluid into the target wellbore to create the target artificial formation fractures, it is necessary to isolate the existing perforations or hydraulic fractures. This isolation can be achieved through cement plugging, the use of packers, and other methods.

[0106] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A method for storing and releasing energy through stratum fractures and obtaining geothermal energy, characterized in that include: Identify geothermal reservoirs that contain geothermal resources but no oil or gas; injecting a high-pressure fluid into a target wellbore in the energy storage geothermal layer to generate at least one target artificial formation fracture in the energy storage geothermal layer, or to open at least one target original formation fracture in a closed state in the target wellbore in the energy storage geothermal layer; wherein the target wellbore is not connected to any other wellbore through the formation fracture; injecting a normal temperature and high pressure fluid into the target wellbore, so that the width of the target artificial formation fracture or the target original formation fracture in the target wellbore increases, thereby causing the formation rock to elastically deform and store energy, and the fluid in the target artificial formation fracture or the target original formation fracture to exchange heat with the energy storage geothermal layer, thereby increasing the temperature of the fluid; When the width of at least one target artificial formation fracture or at least one target original formation fracture in the target wellbore reaches a target width, closing the backflow pipe so that the fluid in the formation fracture continuously exchanges heat with the energy storage geothermal layer, causing the fluid temperature to continuously increase for heat storage; Utilizing the high-temperature and high-pressure fluid discharged during the closing process of the target artificial formation fracture or the target original formation fracture to drive the preset hydroelectric power generation equipment and geothermal power generation equipment to generate electricity, thereby converting the acquired geothermal energy and the elastic deformation energy of the formation rock into electrical energy for energy release; The step of utilizing the high-temperature and high-pressure fluid discharged during the closing process of the target artificial formation fracture or the target original formation fracture to drive the preset hydroelectric power generation equipment and geothermal power generation equipment to generate electricity, thereby converting the obtained geothermal energy and the elastic deformation energy of the formation rock into electrical energy for energy release, specifically includes: When there is a demand for power generation, the fluid discharged during the closing process of the target formation fracture is used to drive the hydroelectric power generation equipment to generate electricity; the target formation fracture includes the target artificial formation fracture or the target original formation fracture; and / or, when the heat storage time of the target wellbore is greater than or equal to the pre-calculated target closed heat storage time, using the fluid to drive the geothermal power generation equipment to generate electricity; And / or, when there is a heating demand, it is determined whether the fluid temperature reaches the heating demand, and when the fluid temperature reaches the heating demand, the fluid is used for heating.

2. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 1, characterized in that: Also includes the steps: In the process of injecting high-pressure fluid into the target wellbore to generate at least one target artificial formation fracture in the energy storage geothermal layer, real-time monitoring of the actual three-dimensional size of the target artificial formation fracture in the target wellbore; Determine whether the actual three-dimensional size reaches a pre-configured preset threshold, and when real-time monitoring shows that the actual three-dimensional size reaches the set threshold, stop injecting high-pressure fluid into the target wellbore to ensure that the target wellbore does not connect to other adjacent wellbores through the target artificial formation fracture; wherein the preset threshold is the minimum value of the preset energy storage three-dimensional size and the preset safety three-dimensional size.

3. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 2, characterized in that: The actual three-dimensional size includes an actual expansion radius and / or an actual expansion height. The step of configuring the preset threshold specifically includes the steps of: Obtain the distance L0 between the target wellbore and its nearest adjacent wellbore, and the actual expansion radius R of the formation fracture in the nearest adjacent wellbore. 邻 Or actual extended height H 邻 ; Based on the distance L0 and the actual propagation radius R of the formation fracture in the nearest adjacent wellbore 邻 Determine the safe expansion radius R0 of the target artificial formation fracture in the target wellbore, and the safe expansion radius R0 satisfies the condition: R0<L0-R 邻 ; determining whether a preset target expansion radius R0' of the target artificial formation fracture is greater than or equal to a preset safety expansion radius R0; if the target expansion radius R0' is greater than or equal to the safety expansion radius R0, using the safety expansion radius R0 as a set threshold for the target artificial formation fracture in the target wellbore; and if the target expansion radius R0' is less than the safety expansion radius R0, using the target expansion radius R0' as a set threshold for the target artificial formation fracture in the target wellbore; or, Obtain the height difference V0 between the initiation point of the target artificial formation fracture and the initiation point of the nearest formation fracture on its nearest adjacent wellbore, and the actual expansion height H of the nearest formation fracture on the nearest adjacent wellbore. 邻 ; Based on the height difference V0 and the actual propagation height H of the nearest formation fracture on the nearest adjacent wellbore 邻 Determine a safe expansion height H0 of a target artificial formation fracture in the target wellbore, wherein the safe expansion height H0 satisfies the condition: H0<V0-Hne; Determine whether a preset target expansion height H0' of the target artificial formation fracture is greater than or equal to a preset safety expansion height H0; if the target expansion height H0' ≥ the safety expansion height H0, use the safety expansion height H0 as a set threshold for the target formation fracture in the target wellbore; if the target expansion height H0' < the safety expansion height H0, use the target expansion height H0 as a set threshold for the target formation fracture in the target wellbore.

4. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 3, characterized in that: If the safety expansion radius R0 is used as a set threshold value for a target formation fracture in the target wellbore, the steps of injecting high-pressure fluid into the target wellbore to generate at least one target artificial formation fracture in the energy storage geothermal layer specifically include: Recalculating the target expansion height of the target formation fracture based on the preset target energy storage and the safe expansion radius R0; Adjusting construction parameters according to the recalculated target expansion height and the safe expansion radius R0 so that the final actual expansion radius of the target formation fracture is less than or equal to the safe expansion radius, and the final actual expansion height is greater than or equal to the recalculated target expansion height; or, If the safety expansion height H0 is used as a set threshold value for a target formation fracture in the target wellbore, the steps of injecting high-pressure fluid into the target wellbore to generate at least one target artificial formation fracture in the energy storage geothermal layer specifically include: Recalculate the target expansion radius of the target formation fracture based on the preset target energy storage and the safe expansion height H0; The construction parameters are adjusted according to the recalculated target expansion radius and the safe expansion height H0, so that the final actual expansion radius of the target formation fracture is greater than or equal to the recalculated target expansion radius, and the final actual expansion height is less than or equal to the safe expansion height.

5. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 1, characterized in that: Also includes: In the case where there are multiple target wellbores, if there is a demand for power generation, determining whether the outlet temperature of the target wellbores meets the requirements of the geothermal power generation equipment; If the outlet temperature of no target wellbore meets the requirements of the geothermal power generation equipment, randomly select the target wellbore to discharge fluid for power generation; and when the outlet temperature of any target wellbore meets the requirements of the geothermal power generation equipment, use the discharge fluid of any target wellbore to perform synergistic power generation; The method for determining whether the wellbore outlet temperature meets the requirements of the geothermal power generation equipment includes: The relationship between the wellbore closed heat storage time and the wellbore outlet temperature is simulated based on the fluid-solid-thermal coupling numerical model. Based on the wellbore outlet temperature required for power generation and / or heating, the required closed thermal storage time is calculated using a fluid-solid thermal coupling numerical model; If the closed heat storage time is reached, the wellbore outlet temperature will meet the requirements of the geothermal power generation equipment.

6. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 1, characterized in that: Also includes the steps: Before the backflow of fluid, the minimum volume threshold of the high-temperature and high-pressure fluid that needs to be retained in the target artificial formation fracture or the target original formation fracture when the energy release of the target artificial formation fracture or the target original formation fracture is completed is calculated in advance based on the preset energy storage cycle efficiency and the hydraulic fracturing model; accordingly, Based on the minimum volume threshold, the backflow process of the high-temperature and high-pressure fluid in the target artificial formation fracture or the target original formation fracture is controlled so that when the energy release ends, the volume of the high-temperature and high-pressure fluid remaining in the target artificial formation fracture or the target original formation fracture is greater than or equal to the minimum volume threshold, thereby ensuring that the fracture width of the formation fracture is greater than or equal to the preset width threshold during the energy storage and release cycle.

7. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 3, characterized in that: Also includes the steps: Determine whether the distance between the target wellbore and at least one of its nearest adjacent wellbores is less than or equal to a preset distance threshold; or whether the height difference between the initiation point of the target artificial formation fracture or the target original formation fracture in the target wellbore and the initiation point of the nearest formation fracture in the nearest adjacent wellbore is less than or equal to a preset height difference threshold, If so, during the energy storage process, real-time monitoring is performed to determine whether the formation fractures between adjacent wellbores are connected. If so, high-pressure fluid is injected into all connected wellbores simultaneously when the connected target wellbores and their adjacent wellbores are used to store energy. When releasing energy, the high-pressure fluid is discharged back through all connected wellbores simultaneously, and the kinetic energy of the high-pressure fluid and the acquired thermal energy are converted into electrical energy.

8. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 1, characterized in that: Before the step of injecting high-pressure fluid into the target wellbore in the energy storage geothermal layer to open at least one target original formation fracture in the energy storage geothermal layer that is in a closed state, the method specifically includes the steps of: identifying at least one original formation fracture in the energy storage geothermal layer, screening at least one original formation fracture in a closed state from the at least one original formation fracture, and screening at least one target original formation fracture from the at least one original formation fracture; The step of selecting at least one target original formation fracture comprises: The original formation fractures include original artificial fractures in a closed state, and the step of screening out at least one target formation fracture from the original formation fractures specifically includes the following steps: Acquiring first monitoring data of original artificial fractures in the energy storage formation using a preset monitoring device; Calculating the original length and original height of the original artificial fracture in the energy storage formation by combining the first monitoring data and the pre-acquired first construction parameters of the original artificial fracture through a numerical model of fracture propagation; Determining whether the original length and original height of the original artificial fracture reach a preset target length threshold and target height threshold, and if so, marking the original artificial fracture as the target original formation fracture; and / or, The original formation fractures include natural fractures in a closed state, and the step of screening out at least one target original formation fracture from the natural fractures specifically includes the following steps: Acquiring second monitoring data of the natural fractures in the energy storage geothermal layer through a preset monitoring device, and performing inversion based on the second monitoring data to obtain the distribution of the at least one natural fracture; the second monitoring data includes: well logging data and seismic data; Obtaining the three-dimensional stress distribution of the energy storage geothermal layer through tectonic stress analysis; Using a three-dimensional fracture-stress coupling model, simulating the opening of the at least one natural fracture during the process of injecting a normal temperature, high-pressure fluid into the at least one natural fracture, and calculating the amount of stored energy when the width of the at least one natural fracture expands to a target width under the action of the normal temperature, high-pressure fluid; It is determined whether the energy storage capacity reaches a preset target energy storage capacity, and if so, the at least one natural fracture is marked as a target original formation fracture.

9. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 8, characterized in that: Determine whether the number of the target original formation fractures screened out reaches a preset number threshold; if not, perform secondary transformation on the original artificial fractures whose original lengths and original heights do not reach the preset target length thresholds and target height thresholds, and / or transform the natural fractures whose original lengths and original heights do not reach the preset target length thresholds and target height thresholds; The step of performing secondary transformation on the original artificial cracks specifically includes: Injecting fluid into the original formation fracture through the wellbore according to a preset third construction parameter, so that the fracture pressure in the original formation fracture is greater than the fracture expansion pressure, thereby causing the original formation fracture to expand along its original height and original length; Acquiring third monitoring data during the expansion of the original formation fracture through monitoring equipment; Calculate the latest length and latest height of the original formation fracture after extending along the original height and original length according to the third construction parameter and the third monitoring data in combination with the fracture propagation numerical model; determining whether the latest length and the latest height reach a preset target length threshold and a target height threshold, and if so, stopping the injection of the high-pressure fluid to obtain the target original formation fracture; The step of transforming the natural fractures specifically includes: injecting fluid into the natural fracture through the wellbore according to a preset fourth construction parameter, so that the fracture pressure in the natural fracture is greater than the fracture expansion pressure, thereby causing the natural fracture to expand along the original height and original length; Acquiring fourth monitoring data during the natural fracture expansion process by the monitoring device; Calculating the latest length and latest height of the natural fracture after extension using a numerical model of fracture extension according to the fourth construction parameter and the fourth monitoring data; It is determined whether the latest length and the latest height of the natural fracture reach a preset target length threshold and a target height threshold. If so, the fluid injection is stopped to obtain the target original formation fracture.

10. The method for storing and releasing energy and obtaining geothermal energy through formation fractures according to claim 9, characterized in that: During the secondary transformation of the original artificial fracture or the transformation of the natural fracture, the actual three-dimensional size of the transformed original artificial fracture or the transformed natural fracture is monitored in real time to determine whether the actual three-dimensional size reaches a pre-configured preset threshold. When the real-time monitoring shows that the actual three-dimensional size reaches the set threshold, the injection of high-pressure fluid into the wellbore is stopped to ensure that the target wellbore is not connected to other adjacent wellbores through the transformed artificial formation fracture or natural formation fracture.

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