Method for storing and releasing energy and obtaining geothermal energy through formation fracture of non-communicated shaft

Abstract

The invention discloses a method for storing and releasing energy and obtaining geothermal energy through formation fractures of a non-communicated shaft. The method comprises the steps that an energy storage geothermal layer containing geothermal resources and not containing 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 This application claims priority to two Chinese invention patent applications filed on June 5, 2024: [Application No.: 2024107219672] [Title: A method and system for storing and releasing energy and obtaining geothermal energy through geological fractures] and [Application No.: 2024112086187] [Title: A method and system for storing and releasing energy and obtaining geothermal energy through existing original geological fractures]. The entire contents of both priority patent applications are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of underground energy storage, and more specifically to a method for storing and releasing energy through geological fissures and obtaining geothermal energy. Background Technology

[0003] Renewable energy sources such as wind and solar power often exhibit significant intermittency, volatility, and randomness. With the large-scale development and high-proportion grid connection of new energy sources, power balance and safe, stable control will face unprecedented challenges. Therefore, the energy storage industry is an inevitable requirement for balancing the volatility of new energy power generation and meeting peak demand. Existing energy storage technologies mainly include mechanical energy storage and electrochemical energy storage. Electrochemical energy storage includes lead-acid batteries, lithium-ion batteries, and hydrogen fuel cell energy storage. Due to high investment and maintenance costs, as well as significant environmental and safety issues, it has not been widely adopted. Mechanical energy storage mainly includes pumped hydro storage and compressed air storage. Pumped hydro storage involves pumping water from a lower to a higher elevation, converting electrical energy into the gravitational potential energy of the water. Therefore, pumped hydro storage often requires specific terrain structures and cannot be applied to relatively flat plains or hilly areas. It also has corresponding requirements regarding the climate and rainfall of the application area. Compressed air storage is a mature energy storage technology, but it requires abandoned mines or underground caverns as the gas storage medium, thus limiting its use to certain specific areas. Geothermal energy is also a major direction for the development of new energy sources. Traditional geothermal energy extraction involves completely contradictory technological approaches: one is to extract geothermal energy through hydraulic fracturing, and the other, to avoid creating fractures in the underlying formation through hydraulic fracturing, targets only faults with well-developed natural fractures in the strata. The hydraulic fracturing method, often referred to as an enhanced geothermal system, requires at least two wellbores connected by formation fractures (one for injection fluid, one for extraction fluid) to work together. During geothermal extraction, the formation fractures are closed, with the fracture gaps supported only by rough surfaces or proppant. The drawbacks of this method include: because the fractures are closed and the gaps are small, the internal friction is high, resulting in significant energy loss of the injected fluid (large parasitic load); because the injection and extraction wells are connected by multiple formation fractures, the injected fluid tends to flow rapidly through the larger fracture gaps, failing to effectively exchange heat with the surrounding rock, causing a "thermal short circuit" and a sharp drop in the temperature at the extraction well outlet.

[0004] 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 geothermal reservoir as the injection well of the multi-well enhanced geothermal system, and simultaneously deploying a shallow microseismic monitoring station around the wellhead; (2) performing large-scale hydraulic fracturing on the vertical well, and performing moment tensor inversion on the stress waves received by the shallow microseismic monitoring station to obtain source mechanism information and determine the important parameters of the main hydraulic fractures; (3) establishing a continuous fracture network model, and displaying the fracture permeability distribution in the geothermal reservoir calculated based on the fracture network model using a geological honeycomb volume image; (4) drilling a multi-target directional well as the production well of the multi-well enhanced geothermal system, and then performing secondary large-scale hydraulic fracturing on the directional well to connect it with the hydraulic fractures of the vertical well, and finally circulating heat extraction. In the above-mentioned prior art, the fracturing well after hydraulic fracturing is only used to obtain geothermal energy, resulting in low power generation efficiency and energy conversion efficiency. Furthermore, because the injection well and production well are connected by multiple formation fractures, and the fluid continuously circulates between them, the injected fluid tends to flow rapidly through formation fractures with large gaps during circulation, failing to effectively exchange heat with the surrounding rock, causing a "thermal short circuit" and resulting in a sharp drop in the production well outlet temperature. In addition, this method suffers from high investment and maintenance costs, susceptibility to flow short circuits, and low geothermal extraction utilization. This method targets faults with well-developed natural fractures in the formation. However, since relying solely on natural fractures is insufficient to meet current geothermal extraction needs, it is only applicable to specific areas with a very large number of natural fractures.

[0005] For example, Chinese invention patent application CN114413494A discloses a device for collecting and utilizing thermal energy from hot dry rock. To avoid the problems of high initiation pressure and uncontrollable crack propagation during hydraulic fracturing in hot dry rock formations, this device directly utilizes the natural fault and fracture zone of hot dry rock as an artificial thermal reservoir between wells. A suitable artificial thermal reservoir has high permeability, well-developed fractures, and a large heat exchange area. A well group is set up 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 fractures or hydraulics. Then, a dual-loop collection system is set up near the wellhead of the production well to collect heat, achieving uninterrupted heat collection. Even if one collection channel fails, the heat from the hot dry rock can still be collected and utilized through the other channel, making the overall device more flexible, convenient, and easy to use. In this existing technology, although natural fractures in the fault are used instead of artificial fractures as channels for the continuous circulation of fluid between the injection well and the production well, it still uses interconnected injection and production wells to collect heat; that is, it still uses an enhanced geothermal system to obtain heat. Furthermore, a flash tower is additionally installed to collect geothermal energy and use the collected geothermal energy to heat the fluid circulating from the production well. This also faces problems such as high investment and maintenance costs, susceptibility to flow short-circuiting, and low geothermal extraction utilization. Moreover, excessive development of faults can lead to geological safety issues. In addition, as mentioned earlier, relying solely on natural fractures, to meet current geothermal extraction needs, it is only suitable for specific areas with a very large number of natural fractures.

[0006] In view of this, there is an urgent need for a new method that can not only meet the requirements of low investment and maintenance costs, adapt to various terrain storage requirements, and effectively exploit geothermal resources. Summary of the Invention

[0007] The purpose of this invention is to provide a method for storing and releasing geothermal energy through formation fractures, which can solve or alleviate the aforementioned problems to a certain extent. This method utilizes the elastic deformation of formation fractures in an independent wellbore, which is not connected to other wellbores, to store and release energy while simultaneously acquiring geothermal resources for power generation and / or heating. In other words, it uses a single wellbore, not connected to other wellbores, as an independent unit for energy storage, release, and thermal energy acquisition. Compared to the traditional method of continuously injecting fluid between connected injection and generation wells to obtain thermal energy, this method is not only lower in cost but also has a higher resource utilization rate.

[0008] To solve the aforementioned technical problems, the present invention specifically adopts the following technical solution: This invention provides a method for storing and releasing geothermal energy through formation fractures, comprising: identifying a geothermal storage layer containing geothermal resources but without oil and gas; injecting high-pressure fluid into a target wellbore in the geothermal storage layer to generate at least one target artificial formation fracture in the geothermal storage layer, or opening at least one existing closed target original formation fracture in the target wellbore in the geothermal storage layer; wherein the target wellbore is not connected to any other wellbore through formation fractures; injecting room-temperature high-pressure fluid into the target wellbore to increase the width of the target artificial formation fracture or the target original formation fracture in the target wellbore, thereby causing elastic deformation of the formation rock. The system stores energy, and the fluid within the target artificial formation fracture or the target original formation fracture exchanges heat with the energy storage geothermal layer, causing the fluid temperature to rise. 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 backflow pipe is closed, allowing the fluid within the formation fracture to continuously exchange heat with the energy storage geothermal layer, causing the fluid temperature to continuously rise, thus storing heat. The high-temperature and high-pressure fluid backflowed during the closure process of the target artificial formation fracture or the target original formation fracture drives 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.

[0009] In some embodiments, the step of using the high-temperature, high-pressure fluid discharged during the closure of the target artificial formation fracture or the target original formation fracture to drive a preset hydroelectric power generation device and a geothermal power generation device to generate electricity, thereby converting the acquired 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, using the fluid discharged during the closure of the target formation fracture to drive the hydroelectric power generation device 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 duration of the target wellbore is greater than or equal to the pre-calculated target closure heat storage duration, using the fluid to drive the geothermal power generation device to generate electricity; and / or, when there is a demand for heating, determining whether the fluid temperature meets the heating demand, and if the fluid temperature meets the heating demand, using the fluid for heating. In some embodiments, the method for storing and releasing 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, while real-time monitoring the actual three-dimensional size of the target artificial formation fracture in the target wellbore; determining whether the actual three-dimensional size reaches a pre-configured preset threshold, and stopping the injection of high-pressure fluid into the target wellbore when the real-time monitoring shows that the actual three-dimensional size reaches the preset threshold, ensuring 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 between a preset energy storage three-dimensional size and a preset safety three-dimensional size. In some embodiments, the actual three-dimensional size includes the actual expansion radius and / or the 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 aforementioned spacing L0, and the actual propagation radius R of the formation fracture in the nearest adjacent wellbore. 邻 Determine the safe propagation radius R0 of the target artificial formation fracture in the target wellbore, wherein the safe propagation radius R0 satisfies the condition: R0 < L0 - R 邻The process involves determining whether the preset target expansion radius R0' of the artificial formation fracture is greater than or equal to the preset safe expansion radius R0. If the target expansion radius R0' is greater than or equal to the safe expansion radius R0, the safe expansion radius R0 is used as a threshold value for the artificial formation fracture in the target wellbore. If the target expansion radius R0' is less than the safe expansion radius R0, the target expansion radius R0' is used as a threshold value for the artificial formation fracture in the target wellbore. In some embodiments, the actual three-dimensional dimensions include the actual expansion radius and / or the actual expansion height. The step of configuring the preset threshold value specifically includes the steps of: obtaining the height difference V0 between the fracture initiation point of the artificial formation fracture in the target wellbore and the fracture initiation point of the nearest formation fracture on the 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 The safe extension height H0 of the target wellbore is determined, wherein the safe extension height H0 satisfies the condition: H0 < V0 - H 邻The process involves determining whether the preset target expansion height H0' of the artificial formation fracture is greater than or equal to the preset 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 target formation fracture in the 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 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 artificial formation fracture in the geothermal energy storage layer specifically includes: recalculating the target expansion height of the formation fracture based on the preset target energy storage 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 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 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 radius of the target formation fracture based on the preset target energy storage capacity and the safe expansion height H0; adjusting the construction parameters 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. In some embodiments, a method for storing and releasing energy through formation fractures and obtaining geothermal energy further includes: when there are multiple target wellbores, if there is a power generation demand, determining whether the outlet temperature of the target wellbore meets the requirements of the geothermal power generation equipment; if no target wellbore has an outlet temperature that meets the requirements of the geothermal power generation equipment, randomly selecting at least one target wellbore for backflow fluid generation; and when the outlet temperature of any target wellbore meets the requirements of the geothermal power generation equipment, using the backflow fluid of any target wellbore for collaborative power generation. The method for determining whether the well outlet temperature meets the requirements of the geothermal power generation equipment includes: simulating the relationship between the well closed heat storage time and the well outlet temperature based on a fluid-structure-thermal coupling numerical model; calculating the required closed heat storage time based on the well outlet temperature required for power generation and / or heating using the fluid-structure-thermal coupling numerical model; and if the closed heat storage time is reached, then the well outlet temperature meets the requirements of the geothermal power generation equipment.In some embodiments, the method for storing and releasing energy through formation fractures and obtaining geothermal energy further includes the steps of: before the fluid is reversed, calculating in advance, based on a preset energy storage cycle efficiency and a hydraulic fracturing model, the minimum volume threshold of 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; correspondingly, controlling the reverse discharge process of 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 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 is greater than or equal to a preset width threshold (which is also calculated in advance based on a preset energy storage cycle efficiency and a hydraulic fracturing model). In some embodiments, the method for storing and releasing geothermal energy through formation fractures further includes the steps of: determining whether the distance between the target wellbore and its nearest adjacent wellbore 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 on its nearest adjacent wellbore is less than or equal to a preset height difference threshold. If so, during energy storage, the method monitors in real time whether the formation fractures between adjacent wellbores are connected. If connection occurs, high-pressure fluid is injected into all connected wellbores simultaneously. During energy release, the high-pressure fluid is simultaneously backflushed through all connected wellbores, and the kinetic energy of the high-pressure fluid and the acquired thermal energy are converted into electrical energy. In other words, all connected wellbores are treated as a single energy storage and release unit capable of independent energy storage and release with 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 existing closed target original formation fracture in the energy storage geothermal layer, the method specifically includes the steps of: identifying at least one existing original formation fracture in the energy storage geothermal layer, screening out at least one closed original formation fracture from the at least one original formation fracture, and screening out at least one target original formation fracture from there; wherein, the step of screening out at least one target original formation fracture specifically includes: the original formation fracture includes original artificial fractures in a closed state, and the step of screening out at least one target formation fracture from there specifically includes the steps of: acquiring first monitoring data of the original artificial fractures in the energy storage formation using a preset monitoring device; combining the first monitoring data with the preset data through a fracture propagation numerical model. The steps of obtaining the first construction parameters of the original artificial fracture, calculating the original length and original height of the original artificial fracture in the energy storage formation; determining whether the original length and original height of the original artificial fracture reach the 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 fracture includes natural fractures in a closed state, and screening out at least one target original formation fracture, specifically including the steps of: obtaining the second monitoring data of the natural fracture in the energy storage geothermal layer through preset monitoring equipment, 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; and utilizing the three-dimensional fracture. A stress-coupled model is used to simulate the opening of the at least one natural fracture during the injection of ambient temperature high pressure fluid into the fracture, and to calculate the energy storage when the width of the at least one natural fracture expands to the target width under the action of the ambient temperature high pressure fluid. It is then determined whether the energy storage reaches the preset target energy storage. If so, the at least one natural fracture is marked as the target original formation fracture.

[0010] In some embodiments, it is determined whether the number of the screened target original formation fractures reaches a preset number threshold; if not, the original artificial fractures whose original length and original height do not reach the preset target length threshold and target height threshold are modified a second time, and / or, the natural fractures whose original length and original height do not reach the preset target length threshold and target height threshold are modified; wherein, the step of modifying the original artificial fractures a second time specifically includes: injecting fluid into the original formation fractures through the wellbore according to preset third construction parameters, so that the fracture pressure in the original formation fractures is greater than the fracture propagation pressure, thereby causing the original formation fractures to propagate along their original height and original length; acquiring third monitoring data during the propagation process of the original formation fractures through monitoring equipment; and calculating the original formation fractures along their original height and original length direction based on the third construction parameters and the third monitoring data, combined with the fracture propagation numerical model. The latest length and height after extension; determining whether the latest length and height reach the preset target length threshold and target height threshold, and if so, stopping the injection of high-pressure fluid to obtain the target original formation fracture; wherein, the step of modifying the natural fracture specifically includes: injecting fluid into the natural fracture through the wellbore according to the preset fourth construction parameters, so that the fracture pressure in the natural fracture is greater than the fracture propagation pressure, thereby causing the natural fracture to propagate along the original height and original length direction; acquiring the fourth monitoring data during the propagation process of the natural fracture through the monitoring equipment; calculating the latest length and height of the natural fracture after extension using the fracture propagation numerical model according to the fourth construction parameters and the fourth monitoring data; determining whether the latest length and height of the natural fracture after extension reach the preset target length threshold and target height threshold, and if so, stopping the injection of fluid to obtain the target original formation fracture.

[0011] 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 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 preset threshold, the 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 or natural formation fracture. The preset threshold is the minimum value between a preset energy storage three-dimensional size and a preset safety three-dimensional size.

[0012] Beneficial Effects: Existing technologies CN114016988A and CN118654399A both disclose a method for storing and releasing energy through formation fractures, but neither discloses how to obtain thermal energy. As mentioned earlier, the traditional method of extracting geothermal energy through hydraulic fracturing is usually called an enhanced geothermal system, which requires at least two wellbores connected through formation fractures (one for injecting fluid and one for producing fluid) to work together, and the formation fractures must be in a closed state, with the fracture gaps supported by rough surfaces or proppant. The disadvantages of enhanced geothermal systems include: because the fractures are closed and the gaps between them are small, the internal friction is high, resulting in significant energy loss of the injected fluid (large parasitic load); since the injection well and the production well are connected by multiple formation fractures, the injected fluid can easily flow quickly through the larger fracture gaps, failing to effectively exchange heat with the surrounding rock, causing a "thermal short circuit" and a sharp drop in the temperature at the production well outlet; for the use of medium-low temperature geothermal resources (150℃-250℃), the power generation cost of enhanced geothermal systems is high, and they do not have a cost advantage compared with other renewable energy sources (such as photovoltaic and wind power). The method disclosed in this invention can overcome the above-mentioned drawbacks of the enhanced geothermal system and has the following advantages: (1) The independent energy storage and release unit only needs one well to complete the process of injection-shut-out-explosion (reverse discharge) of heat exchange medium, effectively avoiding the situation of "thermal short circuit" caused by multiple wells being connected through formation fractures; (2) During the energy storage and release process, the fracture is always in an open state, the fracture width is much larger than the gap of the closed fracture, the friction inside the fracture is small, and the energy loss of the injected fluid is greatly reduced (small parasitic load); (3) During the energy storage process, the high-pressure fluid, as the heat exchange medium, is always kept in the formation fracture, and there is enough time to fully exchange heat with the formation, so that the outlet fluid temperature is controllable during the energy release process. Thus, the target width and number of formation fractures required can be calculated in reverse according to the required energy storage. Moreover, for a single well, it is only necessary to inject the corresponding fluid once and then control its heat storage time. Traditional enhanced geothermal systems require fluid to continuously circulate between injection wells and production wells to obtain heat, which means there is no heat storage process. Therefore, it is impossible to quickly and accurately determine whether the collected heat meets the requirements. (4) Energy storage and geothermal energy extraction are carried out simultaneously, which greatly improves the economic value of medium and low temperature geothermal resources.

[0013] Furthermore, 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 between the target expansion radius / target expansion height and the preset safe expansion radius / safe expansion height. This allows multiple energy storage and release units (i.e., a single target wellbore as an energy storage and release unit has the ability to independently store and release energy and obtain thermal energy) that cannot store energy to meet different power supply requirements. Multiple groups are then used for cross-circulation power supply to achieve continuous power supply.

[0014] Ideally, at least some wellbores should reach their predetermined maximum energy storage capacity (e.g., reach the target expansion radius or target expansion height) and their heat storage duration should reach the target heat storage duration. Then, these qualified wellbores can be used to supply power in tandem. This not only ensures continuous power supply but also improves the efficiency and utilization of thermal energy acquisition to a certain extent. However, in practical applications, power demand may be sudden. In such cases, there may be situations where, when power demand arises, no wellbore has reached its target heat storage duration, or even no target wellbore has a formation fracture width that meets the target width. In this situation, it is still necessary to activate one or more unqualified target wellbores to supply power (of course, the specific number of target wellbores activated can be determined based on the actual power demand). When the width of any other target wellbore reaches the target width, or the width reaches the target width and the heat storage duration meets the target heat storage duration, power supply is switched to that target wellbore. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0016] Figure 1 This is a schematic flowchart of an embodiment of a method for storing and releasing energy through geological fractures and obtaining geothermal energy according to the present invention. Figure 2 This is a schematic diagram of a hydraulic fracturing system for vertical and horizontal wells. Figure 3A This is a schematic diagram of an exemplary embodiment of the present invention, in which an electric injection device injects fluid from a water storage tank into formation fractures in a shale formation; Figure 3B This is a schematic diagram of an exemplary embodiment of the present invention, in which high-pressure fluid in a formation fracture is reversed to a water storage tank and used to drive a power generation device to generate electricity; Figure 4A This is a schematic diagram of an electric injection device injecting fluid from a reservoir into formation fractures in a shale formation in another exemplary embodiment of the present invention; Figure 4B This is a schematic diagram of another exemplary embodiment of the present invention, in which high-pressure fluid in a formation fracture is reversed to a water storage tank and used to drive a power generation device to generate electricity; Figure 5 This is a schematic diagram of a system that uses multiple vertical wells and multiple horizontal wells to perform hydraulic fracturing to achieve continuous energy storage and release. Figure 6A This is a schematic flowchart of another embodiment of the method for storing and releasing energy and obtaining geothermal energy through formation fractures according to the present invention. Figure 6B This is a schematic flowchart of another embodiment of the method for storing and releasing energy and obtaining geothermal energy through geological fractures according to the present invention. Figure 7 This is a schematic diagram of the process for screening at least one target artificial fracture from original formation fractures in this invention. Figure 8This is a schematic diagram of the process for secondary modification of artificial cracks in this invention; Figure 9 A functional block diagram of a geothermal energy storage and release system that utilizes existing original geological fractures to obtain geothermal energy, as an exemplary embodiment of the present invention; Figure 10A This is a schematic diagram of an exemplary embodiment of the present invention, in which an electric injection device injects fluid from a water storage tank into formation fractures in a shale formation; Figure 10B This is a schematic diagram illustrating how, in an exemplary embodiment of the present invention, high-temperature and high-pressure fluid from a geological fissure is reversed into a reservoir and used to drive a power generation device to generate electricity. Figure 11A This is a schematic diagram of an electric injection device injecting fluid from a reservoir into formation fractures in a shale formation in another exemplary embodiment of the present invention; Figure 11B This is a schematic diagram illustrating, in another exemplary embodiment of the present invention, the high-temperature and high-pressure fluid within a geological fissure is reversed into a reservoir and used to drive a power generation device to generate electricity. Figure 12 This is a schematic diagram of a system that utilizes multiple vertical and horizontal wells for hydraulic fracturing to achieve continuous energy storage and release and obtain geothermal energy. Figure 13 This is a schematic flowchart of yet another embodiment of a method for storing and releasing energy and obtaining geothermal energy through geological fractures according to the present invention. Figure 14 A schematic diagram illustrating that formation fractures in two adjacent wellbores are located at the same height; Figure 15 This is a schematic diagram illustrating that formation fractures in two adjacent wellbores are located at different heights. Detailed Implementation

[0017] In this document, "and / or" includes any and all combinations of one or more of the listed related items. "Multiple" means two or more, i.e., it includes two, three, four, five, etc. "Fluid" in this document can be, but is not limited to, gases, liquids, emulsions, slurries, and solid particle flows with flow characteristics similar to liquid flows. For example, fluids can include water-based liquids with chemical additives. Furthermore, chemical additives can include, but are not limited to, acids, gels, potassium chloride, surfactants, etc. "Formation" or "reservoir" in this document refers to a porous and permeable rock formation (e.g., shale formations, sandstone formations, carbonate rock formations, etc.) that can serve as a storage space for fluids. Typically, these fluids can be water, hydrocarbons, or gases. In this document, such porous and permeable rock formations capable of storing high-pressure fluids are collectively referred to as "energy storage formations." Shale formations are used as a preferred embodiment in this document because they can store fluids in their internal fractures for extended periods, and therefore, the energy storage and release methods and systems of this application are described in this document. In this article, "hydraulic fracturing," "fracture," or "rupture" refers to the formation of rock fractures that propagate under the influence of external forces (such as high-pressure fluids). "Hydraulic fracturing fracture," "formation fracture," or "fracture" refers to the rock opening created within the formation after hydraulic fracturing operations; these terms are interchangeable. "Bottom-hole pressure" refers to the pressure at or near the initiation depth of the hydraulic fracturing fracture (formation fracture) within the wellbore. When frictional losses are negligible, the bottom-hole pressure is equal to the fracture pressure of the hydraulic fracturing fracture. "Wellbore" refers to the hole formed by drilling or inserting a guide tube into the formation. Generally, wellbores are cylindrical, and therefore their cross-section may be circular. Alternatively, wellbores may have any other cross-section. Wellbores can be open-hole (open-hole wellbore) or casing wellbore (cased wellbore) with a cemented casing bonded to the inner wall of the wellbore. In this paper, the "fracture width" refers to the relative displacement distance between the two walls in the direction perpendicular to the fracture surface. The fracture width is related to the fracture pressure and can be calculated using a mathematical model by real-time monitoring of the fluid pressure at the wellhead or bottom. When the fracture reaches the "target width," it is equivalent to the fracture pressure reaching the "target pressure." Real-time monitoring of the fluid pressure at the wellhead or bottom can determine whether the fracture has reached the "target pressure." In this paper, the "target width" or "target pressure" of the fracture can dynamically change according to the actual situation in different energy storage and release cycles (one cycle refers to completing one energy storage and release process). For example, when the energy storage power supply is insufficient, the "target width" or "target pressure" of the fracture can be smaller than the "target width" or "target pressure" corresponding to a sufficient energy storage power supply.For example, insufficient supply of solar or wind power limits the amount of high-pressure fluid that can be injected into the formation fracture, resulting in a smaller "target width" or "target pressure" of the fracture. Conversely, sufficient supply of solar or wind power allows for a larger amount of high-pressure fluid to be injected, leading to a larger "target width" or "target pressure" of the fracture. In this paper, when the formation fracture is assumed to be circular (or, in engineering practice, can be considered circular or approximately circular), the "expansion radius" of the fracture refers to the radius of the circle. When the formation fracture is assumed to be non-circular (e.g., elliptical), the "expansion radius" of the fracture refers to the fracture half-length. The "expansion height" of the fracture refers to the vertical distance the fracture extends upward or downward from its initiation point (e.g., the perforation location). "Constant" or "unchanged" in this paper does not mean that the absolute change of the specified item is zero, but rather that the change of the specified item is very small, and in engineering practice, the item can be considered constant. For example, the phrase "unchanged bottom hole pressure" in this document can also mean "approximately constant bottom hole pressure," or "unchanged propagation radius" actually means that the "propagation radius" of the formation fracture remains "substantially unchanged" or "approximately constant" under the action of high-pressure fluid; or, "unchanged width of formation fracture" actually means that the "width of formation fracture" remains "substantially unchanged" or "approximately constant" under the action of high-pressure fluid. It should also be recognized that the term "equal to" as used in this disclosure does not mean that the specified items are exactly the same, but is used to specify two items that have negligible differences in engineering practice. For example, the term "equal to" in this disclosure can also mean "approximately equal to." In this document, "geothermal layer" refers to a formation with a high temperature that meets the needs of geothermal power supply and / or heating. For example, to achieve economical continuous heating, the formation temperature of the geothermal layer typically needs to be higher than 60°C, and to achieve economical continuous power supply, the formation temperature of the geothermal layer typically needs to be higher than 120°C. According to the geothermal database for depths below 1000m in China, low geothermal gradients are mainly distributed in mountainous areas such as the Liaodong Hills, southern Greater Khingan Mountains, and Wuyi Mountains, with a typical gradient of 20℃ / km. High geothermal gradients are mainly distributed in the Northeast Plain, North China Plain, and southeastern coastal areas, with gradients mostly in the range of 40-50℃ / km. In central China, geothermal gradients are mostly in the range of 20-26℃ / km, with some areas reaching over 30℃ / km. Therefore, in areas with low geothermal gradients, the temperature of the strata at a depth of 500m in winter does not exceed 20℃. Typically, strata temperatures above 1km are not economically viable for geothermal power generation, and due to the low temperatures, heat pumps (consuming electricity) are needed to further increase the backflow temperature to meet heating requirements. Therefore, preferably, the geothermal layers discussed in this paper are mainly strata below 1km with temperatures above 60℃.In this article, "original formation fractures" refers to rock openings created through hydraulic fracturing (i.e., artificial formation fractures), or naturally occurring fractures within the energy storage formation that contain geothermal resources but not oil or gas (i.e., natural formation fractures), and all of these original formation fractures are in a closed state. "Modification" or "secondary modification" in this article refers to the extension and expansion of existing original formation fractures in the energy storage formation along their original height and / or length under external forces (e.g., ambient temperature high-pressure fluids), while their width, fracture spacing, and number remain unchanged. "Ambient temperature" in this article refers to the temperature under local outdoor natural conditions (affected by latitude and season). "Ambient temperature fluid" refers to fluid stored in outdoor facilities (e.g., reservoirs or tanks) without artificial heating or cooling measures to maintain a certain temperature. "Closed state" in this article refers to a state where the fracture pressure is less than the "fracture closure pressure" or "closure pressure". For example, artificial / natural fractures within depleted oil and gas reservoirs remain in a state of neither closure nor expansion because there is no fluid or oil within them. Similarly, during reverse runoff, formation fractures gradually close as fluid is expelled. In this article, "open" or "open state" refers to a formation fracture that was originally in a "closed state" where, under the influence of external forces (such as high-pressure fluids), the fracture pressure exceeds the "fracture closure pressure" or "closure pressure." For example, the process of a formation fracture that was originally in a closed state gradually increasing its fracture pressure under the influence of external forces (such as high-pressure fluids), and the state where the fracture pressure exceeds the propagation pressure, causing the fracture to propagate along its original length and / or height.

[0018] The core idea of ​​this invention is to utilize target artificial formation fractures in the geothermal energy storage layer, or target original formation fractures selected from existing original formation fractures in the geothermal layer, for energy storage (specifically, injecting high-pressure fluid into the target artificial or original formation fractures to increase their width), and then sealing them to ensure the heat storage duration of the formation fractures meets power supply needs. Furthermore, during the heat storage process, if there is a power supply demand, the reverse-flowing fluid drives a hydroelectric power generation device to generate electricity; and / or, when the heat storage duration of the target wellbore is greater than or equal to the pre-calculated target closed heat storage duration and there is a power supply demand, the fluid drives a geothermal power generation device to generate electricity. Furthermore, during the process of creating fractures, or during the modification or secondary modification of original formation fractures, it is necessary to monitor the actual three-dimensional size changes of the fractures and / or the distribution of existing original formation fractures in real time. Based on these actual three-dimensional size changes and / or distribution, the injection pressure, flow rate, and other construction parameters of the injected fluid can be controlled. This is to prevent the target wellbore formed in the geothermal reservoir from connecting to other wellbores through formation fractures, which could lead to energy loss and inter-well interference during energy storage, thereby reducing power generation efficiency.

[0019] Example 1: Shale is widely distributed and has extremely low permeability. In the oil and gas field, shale formations are often considered as overlying sealing layers for conventional oil and gas reservoirs, preventing oil and gas from migrating upwards and evaporating to the surface. Simultaneously, shale formations themselves can also serve as fluid storage media. Due to their extremely low permeability, shale formations can store high-pressure fluids from internal formation fractures for extended periods, with only a very small amount of fluid being lost into the pores of the formation rock. For example, Oak Ridge National Laboratory in the United States has injected radioactive fluid waste into artificial formation fractures in shale formations for decades to achieve permanent preservation. Therefore, preferably, this invention stores high-pressure fluids in artificial fractures (i.e., formation fractures created by hydraulic fracturing) in porous and permeable shale formations to achieve long-term energy storage, thus using shale formations as energy storage formations. Of course, this invention can also be applied to other porous and permeable rock formations. Furthermore, the purpose of this invention is not only to convert energy through formation fractures, but more importantly, it is also used to obtain geothermal energy. Therefore, the aforementioned low-permeability rock formations also need to store abundant geothermal energy. Based on the above concept, this invention provides a system for storing and releasing geothermal energy through formation fractures, specifically including: a fracturing device for pumping fracturing fluid into a wellbore that leads to the geothermal energy storage layer, thereby creating formation fractures in the geothermal energy storage layer.

[0020] like Figure 2 As shown, fracturing fluid is pumped into the vertical wellbore 230 and the horizontal wellbore 232 respectively by fracturing devices 210 and 212 arranged on the surface. Once the bottom hole pressure of the vertical wellbore 230 and the horizontal wellbore 232 reaches the fracturing 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 fracturing pressure), formation fractures 240, 242, and 244 in the vertical wellbore 230 will initiate from around the vertical wellbore 230 and extend into the underground rock formation 220 until pumping stops (i.e., hydraulic fracturing operation stops). Correspondingly, formation fractures 246, 248, and 250 in the horizontal wellbore 232 will initiate from around the horizontal wellbore 232 and extend into the underground rock formation 220 until pumping stops. Figure 2 As shown, formation fractures (e.g., Figure 2 Formation fractures 240, 242, 246, and 248 in the shale formation can form planar geometries and propagate along the direction perpendicular to the minimum principal stress of the shale formation. However, under certain geological conditions, formation fractures (e.g., Figure 2 The stratigraphic fractures (244, 250) can interact with pre-existing natural fractures to form complex fracture geometries.

[0021] This system also includes an injection pipe connected to an injection device that pressurizes ambient temperature fluid and injects it into the wellbore, increasing the width of the formation fractures. This causes elastic deformation of the formation rock, storing energy, and allows heat exchange between the fluid within the fractures and the geothermal energy storage layer, raising the fluid temperature. It also includes a backflow pipe connected to a hydroelectric power generation system, a geothermal power generation system, and a heating system. When the fluid in the formation fractures is backflowed through the backflow pipe, it drives the hydroelectric and geothermal power generation systems to generate electricity, and the heating system provides warmth. Finally, it includes a sealing device to close the backflow pipe, allowing continuous heat exchange between the fluid in the formation fractures and the geothermal energy storage layer, resulting in a continuous increase in fluid temperature. The sealing device is preferably a control valve installed on the backflow pipe. Alternatively, to prevent backflow of fluid from the injection pipe, the sealing device may also include a control valve installed on the injection pipe. For fluid recycling, a reservoir for storing the fluid may also be included, with both the injection and backflow pipes connected to the reservoir. Understandably, in order to avoid heat loss and improve the efficiency of geothermal power generation, the well shaft, backflow pipe, hydroelectric power generation equipment, and water storage tank are all insulated.

[0022] See Figure 3A and Figure 3B The injection pipe 330 and backflow pipe 380 connecting the reservoir 320 and the well 340 are equipped with control valves to control the flow and closure of the surface pipes. When power generation is detected (for example, the corresponding control system, or the first power generation equipment, or the relevant personnel 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 hydropower generation equipment 360 and the geothermal power generation equipment 370, will open the control valve corresponding to the backflow pipe 380 between the well and the reservoir (of course, it can also be opened manually by the personnel). This connects the wellbore 340 to the reservoir 320. Under the pressure of rock compression, the high-temperature, high-pressure fluid from the formation fissures 390 within the shale formation 350 is backflowed into the reservoir 320. During this process, the high-temperature, high-pressure fluid first drives the impeller of the hydroelectric power generation device 360 ​​to generate electricity. When it passes the geothermal power generation device 370, it is determined whether the high-temperature, high-pressure fluid meets the requirements for geothermal power generation. If it does, the geothermal power generation device 370 is activated; otherwise, it is not activated, and the fluid is introduced into the heating system for heating (if needed). Of course, if no power supply request is received, the backflow pipe 380 between the wellbore and the reservoir will remain closed, meaning the control valve on the backflow pipe 380 is normally closed. In this case, monitoring for a power supply demand continues. It is understandable 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 fissures can meet the requirements for power generation and / or heating.

[0023] Example 2: To simplify the equipment, unlike Example 1, the injection pipe and the backflow pipe in this example are the same pipe; the hydraulic generator and injection equipment are an integrated power generation and water injection machine. When energy storage is needed, the integrated power generation and water injection machine can pressurize room temperature fluid and input it into the wellbore to increase the width of the formation fractures. When power generation is needed, the integrated power generation and water injection machine can convert the kinetic energy of the backflow fluid into electrical energy. The so-called integrated power generation and water injection machine is a device with both pumping and power generation functions. It can pump water or convert the kinetic energy of water into electrical energy through forward and reverse rotation. Specifically, it can be an electric generator, or a motor that has both generator and motor functions. It can act as a generator driven by a water turbine to generate electricity, or it can be converted into a motor to drive a water pump for pumping water. See details. Figure 4A and Figure 4B After the integrated power generation and water injection unit 410 stops injecting ambient temperature high-pressure fluid into at least one formation fracture, the valve in the pipe 440 between the wellbore 450 and the water storage tank 430 is also closed. When power generation is detected, the control valve corresponding to the pipe 440 between the wellbore 450 and the water storage tank 430 is opened. At this time, under the action of rock compression, the high-temperature and high-pressure fluid heated by the formation in the formation fracture 470 within the shale formation 460 is backflowed into the water storage tank 430 through the pipe 440. In this process, the impeller of the integrated power generation and water injection unit 410 is first driven to rotate to generate electricity, and then passes through the geothermal power generation equipment 420. If the geothermal power generation conditions are met, the geothermal power generation equipment 420 is driven to generate electricity; otherwise, the geothermal power generation equipment 420 remains closed. If there is a heating demand, the fluid is introduced into the heating system if there is a heating demand; otherwise, it flows back to the water storage tank. If no power demand is detected, the pipe 440 between the wellbore 450 and the water storage tank 430 remains closed.

[0024] Example 3: Unlike Example 1, this example uses multiple wells, each connected to the geothermal energy storage layer and formation fractures. It also includes several inlet pipes and backflow pipes that cooperate with each well. The inlet pipes are connected to injection equipment, and the backflow pipes are connected to hydroelectric power generation equipment, geothermal power generation equipment, and a heating system. At the same time, some of the multiple wells are performing water injection, others are performing energy storage, and still others are performing energy release. Alternatively, the injection and backflow pipes can be the same as in Example 2, with the same principle, which will not be elaborated here. This example provides a system for continuous energy storage and release using multiple vertical and horizontal wells for hydraulic fracturing. See [link to example]. Figure 5During hydraulic fracturing, the construction of vertical wellbore 510, vertical well 520, vertical well 530 and horizontal wellbore 540, horizontal wellbore 550, and horizontal wellbore 560 is completed (this case uses three horizontal wellbore or vertical wellbore as an example, but the number of multiple vertical wellbore and horizontal wellbore described in this invention includes all cases with a number greater than 1), so that each vertical wellbore and horizontal wellbore generates at least one formation fracture. During the energy storage and release using the formation, the vertical wellbore 510, vertical wellbore 520, and vertical wellbore 530 and the horizontal wellbore 540, horizontal wellbore 550, and horizontal wellbore 560 cooperate with each other to achieve continuous energy storage and release. For example, while vertical wellbore 510 and horizontal wellbore 540 are performing the injection process, converting electrical energy into formation elastic deformation energy, vertical wellbore 520 and horizontal wellbore 550 have already completed the injection, storing the electrical energy as formation elastic deformation energy and simultaneously acquiring geothermal energy. Vertical wellbore 530 and horizontal wellbore 560, due to power generation needs, are performing a reverse discharge process, converting the stored formation elastic deformation energy and acquired geothermal energy into electrical energy and feeding it into the power grid. Then, vertical wellbore 530 and horizontal wellbore 560 complete the energy release process. 560 executes the injection process. After the injection is completed, the vertical shaft 520 and horizontal shaft 550, which are in the storage process, execute the reverse discharge process to release energy. After the injection is completed, the vertical shaft 510 and horizontal shaft 540 are in the energy storage process and obtain geothermal energy. Taking this as an example, the vertical shaft 510, vertical shaft 520, vertical shaft 530 and horizontal shaft 540, horizontal shaft 550, horizontal shaft 560 are coordinated in a cycle to ensure that they can provide power to the grid at any time to meet the power demand.

[0025] Example 4: This example provides a method for storing and releasing geothermal energy through formation fractures, applied to the aforementioned system for storing and releasing geothermal energy through formation fractures, including: S101 identifying a geothermal energy storage layer containing geothermal resources but without oil and gas. In some embodiments, the energy storage layer without oil and gas includes depleted oil and gas formations. In some embodiments, relevant information of the energy storage layer (preferably shale formation) (e.g., burial depth and thickness) can be identified using intuitive methods, such as obtaining core samples through drilling to identify the burial depth and thickness. In other embodiments, indirect methods can also be used to identify relevant information of the formation, such as interpreting well logging / well logging data and seismic data inversion methods. Furthermore, by analyzing factors such as the thermal conductivity, temperature gradient, and groundwater circulation of underground rocks, a fluid-structure-thermal coupling 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 an extended period (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, while binary cycle power generation requires a wellbore outlet temperature above 50 degrees Celsius), then the geothermal energy storage formation can directly supply electricity or heating. If the wellbore outlet temperature cannot be maintained above the power generation temperature for an extended period, 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.

[0026] S102 performs hydraulic fracturing on the energy storage geothermal layer, causing formation fractures to form. During the hydraulic fracturing operation, the injected fracturing fluid is pumped into the wellbore through surface facilities, such as... Figure 2 Fracturing fluid is pumped into the vertical wellbore 230 and the horizontal wellbore 232 respectively through fracturing devices 210 and 212. Once the bottom hole pressure of the vertical wellbore 230 and the horizontal wellbore 232 reaches the fracturing 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 fracturing pressure), formation fractures 240, 242, and 244 in the vertical wellbore 230 will initiate from around the vertical wellbore 230 and extend into the underground rock formation 220 until pumping stops (i.e., hydraulic fracturing operation stops). Correspondingly, formation fractures 246, 248, and 250 in the horizontal wellbore 232 will initiate from around the horizontal wellbore 232 and extend into the underground rock formation 220 until pumping stops. Figure 2 As shown, formation fractures (e.g., Figure 2 Formation fractures 240, 242, 246, and 248 can form planar geometries and propagate along the direction perpendicular to the minimum principal stress of the shale formation. However, under certain geological conditions, some formation fractures (e.g., Figure 2Formation fractures (244, 250) can interact with pre-existing natural fractures to form complex fracture geometries. In practical applications, the extent of fracture propagation 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, longer fractures need to be designed, allowing for the extraction of more geothermal energy. Conversely, if less energy needs to be stored, shorter fractures are required, resulting in less geothermal energy extraction. Therefore, design parameters for fractures, such as the propagation radius (or propagation length), can be pre-set according to actual needs. When the propagation radius of the fracture reaches the design requirements, pumping fracturing fluid is stopped (i.e., hydraulic fracturing operations are halted), causing the fractures to gradually stop propagating. Furthermore, before hydraulic fracturing operations, the required fluid kinetic energy and thermal energy carried by the hydroelectric and geothermal power generation equipment can be obtained based on their power output. Then, the target propagation radius of the fractures can be calculated using these parameters. During hydraulic fracturing, it is determined whether the expansion radius of the formation fracture is equal to or greater than the target expansion radius. Specifically, the three-dimensional shape of the formation fracture is calculated based on a pre-constructed hydraulic fracturing model, rock mechanical properties, and first construction parameters, and the expansion radius of the formation fracture is obtained based on the three-dimensional shape. In some embodiments, the hydraulic fracturing model can be a two-dimensional PKN model, KGD model, RADIAL model, as well as a pseudo-three-dimensional model and a full three-dimensional model. The first construction parameters are the construction parameters of the surface facility (i.e., the injection equipment in the hydraulic fracturing construction device), including: the injection rate of fracturing fluid, the total injection volume, and the viscosity of fracturing fluid. When it is detected that the expansion radius of a formation fracture is equal to or greater than the target radius, the hydraulic fracturing construction is stopped. Of course, in other embodiments, when to stop the hydraulic fracturing construction can be determined by the operator based on relevant work experience. For example, the operator can determine or calculate the time to stop the hydraulic fracturing construction based on work experience, combined with the injection rate of fracturing fluid, the total injection volume, and the viscosity of 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. This ensures that the formation fractures have a certain storage capacity while preventing the fracture expansion radius from becoming too large and damaging the energy storage formation. In some embodiments, multiple formation fractures will be created during hydraulic fracturing. Specifically, to avoid damage to the energy storage formation due to excessively large fracture expansion radii, hydraulic fracturing is preferably stopped when the expansion radius of one formation fracture is detected to be equal to or greater than the preset target expansion radius. Of course, in other embodiments, hydraulic fracturing can also be stopped when the average expansion radius of all formation fractures is equal to or greater than the preset target expansion radius.It is understood that when hydraulic fracturing is stopped, the formation fractures will not immediately stop propagating. Propagation only stops when the fluid pressure within the fractures approaches equilibrium with the fracturing pressure, i.e., when the fluid pressure is less than the fracturing pressure. Therefore, to avoid excessively large fracture propagation radius, preferably, in some embodiments, hydraulic fracturing is stopped when the fracture propagation radius is approximately equal to (or close to) the target radius (e.g., propagation radius = target radius × 0.90-0.95). Preferably, to reduce the rate of fracturing fluid loss into the surrounding rock within the fractures, enabling the formation fractures in the energy storage formation to store fracturing fluid or high-pressure fluid for extended periods, in some embodiments, an anti-leakage agent is added to the fracturing fluid used in this step of the hydraulic fracturing process.

[0027] S103 injects a room-temperature, high-pressure fluid into the formation fracture, increasing the fracture width and causing elastic deformation of the formation rock for energy storage. Furthermore, the fluid within the fracture exchanges heat with the energy storage geothermal layer, raising its temperature. In some embodiments, the fluid pressure injected into the fracture is greater than the minimum principal stress of the energy storage formation but less than the fracture propagation pressure, causing the fracture width to gradually increase while the propagation radius remains constant (because the fluid pressure is less than the fracture propagation pressure, the fracture does not propagate, i.e., the fracture radius remains constant). Of course, in other embodiments, the constant or unchanged propagation radius of the fracture can be understood as remaining constant or unchanged over a period of time. For example, when the width of a formation fracture changes due to the action of high-pressure fluid, its propagation radius will also gradually change (i.e., continue to propagate). However, within a certain time period (e.g., one hour), the change in the propagation radius is negligible in engineering practice. Alternatively, when a formation fracture propagates due to the action of high-pressure fluid, after a certain period, particles added to the high-pressure fluid may fill or partially fill the propagating fracture. 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 of the pressure drop curve after hydraulic fracturing operation.

[0028] 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 propagation pressure of the formation fracture; if so, maintaining the second construction parameters for injecting ambient temperature high-pressure fluid into the formation fracture; otherwise, adjusting the second construction parameters for injecting ambient temperature high-pressure fluid into the formation fracture (i.e., the construction parameters of the injection equipment) so that the current fluid pressure is always maintained between the propagation pressure and the minimum principal stress of the energy storage formation. In some embodiments, the second construction parameters include: the fluid injection rate and the total injection volume. Specifically, the fluid pressure can be adjusted by regulating the injection rate or the amount of fluid injected by the injection equipment, and the fluid pressure can be monitored by a pre-installed pressure monitoring device.

[0029] In some implementations, the width of the formation fracture is inferred from the required fluid kinetic energy and the thermal energy carried by the fluid. When injecting room-temperature 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 one formation fracture is equal to or greater than the target width, and / or when the average width of all formation fractures is equal to or greater than the target width, the injection of room-temperature 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 room-temperature high-pressure fluid into at least one formation fracture, thereby maintaining the bottom hole pressure and keeping the width of the formation fracture unchanged (at this time, since the pipelines between the wellbore, the reservoir, and the injection equipment are all in a closed state, the bottom hole pressure remains unchanged after the injection of room-temperature high-pressure fluid is stopped); otherwise, the injection of room-temperature high-pressure fluid into the formation fracture continues. The width of the formation fracture is calculated based on its height, radius of propagation, and bottom hole pressure. It is understood that the width of the fracture at different locations is 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 can also refer to the width of any single formation fracture. For example, in some embodiments, during the injection of ambient temperature high-pressure fluid into the formation fracture, the width data of all formation fractures are acquired, and the average width of all formation fractures is obtained. When this average width is equal to or greater than a preset target width, power to the injection equipment is stopped, thereby stopping the injection of high-pressure fluid into the formation fracture.

[0030] In some embodiments, the target width of the formation fracture is preset 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 avoiding damage to the energy storage formation due to excessively large fracture width. It is understood that, given the presence of multiple formation fractures, to prevent damage to the energy storage formation due to excessively large fracture width, preferably, when it is detected (or determined) that the width of one formation fracture is equal to or greater than the preset target width, step S108 is executed, stopping the supply of power to the injection equipment. This causes the injection equipment to stop injecting room-temperature high-pressure fluid into at least one formation fracture, thereby maintaining a constant bottom-hole pressure and thus a constant fracture width. Of course, in other embodiments, when insufficient power is detected in the injection equipment (e.g., weather changes causing insufficient solar or wind power supply; specifically, when all or most of the solar and wind power generation is consumed by end-users, leaving no surplus power for the injection equipment), the supply of power to the injection equipment is stopped, causing the injection equipment to stop injecting room-temperature high-pressure fluid into at least one formation fracture, thereby maintaining a constant bottom-hole pressure and thus a constant fracture width. Preferably, in some embodiments, one or more additives can be added beforehand to the fluid in the reservoir (i.e., one or more additives can be added to the fluid injected into the formation fractures), such as bactericides, scale removers, mineral salts (e.g., KCl, NaCl, CaCl2, NaSiO4, etc.), and filtration inhibitors, wherein the mineral salts are used to balance the electrolyte of the energy storage formation. As a specific example... Figure 3A As shown, the grid-powered injection device 310 injects fluid from the reservoir 320 through the injection pipe 330 to the wellbore 340, and then into the hydraulic fracturing fracture 390 within the shale formation 350. This causes the fracture width to expand, and the surrounding rock undergoes elastic deformation to store energy. Simultaneously, the surrounding rock heats the fluid in the fracture, thus extracting geothermal energy. It is assumed that the radius of the circular fracture is 500m (the radius of expansion is as follows). Figure 3A (As shown by the double-headed arrow R), at a distance of 500 meters from the ground, the average Young's modulus of the rock is 20 GPa. The fluid pressure within the fracture is 3 MPa higher than the minimum principal stress of the shale formation, and the formation temperature is 50°C. According to fracture mechanics, the energy stored by elastic deformation of the shale formation around the fracture can be calculated to be 2.8 × 10⁻⁶. 11 J, i.e., 78530kw h, according to heat transfer theory, the available geothermal energy can be calculated to be 7.2 × 10⁻⁶. 12 J, i.e., 2019343kw h.

[0031] S104 utilizes the fluid discharged during the closure of formation fractures to drive a hydroelectric power generation system when there is a demand for power generation. The reservoir and the wellbore corresponding to the formation fracture are connected via pipes and a discharge pipe. When the injection of high-pressure fluid into the formation fracture stops, both the discharge pipe and the injection pipe are closed; specifically, the control valves within both the discharge pipe and the injection pipe are closed. Therefore, when a demand for power generation is detected, the control valve corresponding to the discharge pipe is opened to allow the discharge pipe to flow. This allows the high-pressure fluid within the formation fracture to be discharged back into the reservoir under the pressure of the rock. During this discharge process, the hydroelectric power generation system is driven, converting the kinetic energy of the fluid into electrical energy. For example, see [link to relevant documentation]. Figure 3A and Figure 3B Both the injection pipe 330 and the backflow pipe 380 connecting the reservoir and the well are equipped with control valves to control the flow and closure of the surface pipes. When power generation is detected (e.g., by the corresponding control system, the hydroelectric power generation equipment, or by the relevant personnel receiving a power supply request from an external source, such as the power grid or other control systems), the control valve corresponding to the backflow pipe 380 between the well and the reservoir is opened (or can be opened manually by the personnel). This connects the well and the reservoir, and under the pressure of the rock, the high-temperature and high-pressure fluid in the formation fissures is backflowed into the reservoir. During this process, the high-temperature and high-pressure fluid drives the impeller of the hydroelectric power generation equipment located in front to rotate and generate electricity. S105 utilizes the fluid to drive the geothermal power generation equipment to generate electricity when the fluid temperature meets the requirements. When the fluid passes through the geothermal power generation equipment 370, the determining device assesses whether the high-temperature, high-pressure fluid meets the requirements for geothermal power generation. If it does, the geothermal power generation equipment 370 is activated to generate electricity, thus converting geothermal energy into electrical energy, achieving the acquisition and application of geothermal energy. If it does not meet the requirements, the geothermal power generation equipment 370 is not activated. Of course, if no power supply request is received, the backflow pipe 380 between the wellbore and the reservoir will remain closed, meaning the control valve within the backflow pipe 380 is normally closed. In this case, monitoring for a power supply demand continues.

[0032] S106, when there is a heating demand, determines whether the fluid temperature meets the demand. If the fluid temperature meets the demand, the fluid is used for heating. After the fluid passes through the geothermal power generation equipment 370, regardless of whether power generation has been utilized, it first determines whether there is still a heating demand. If there is a heating demand, it also determines whether the fluid temperature meets the demand. Only when the fluid temperature meets the demand is the fluid discharged into the heating system for heating, thus realizing another aspect of geothermal acquisition and application. Of course, it is understandable that the fluid after heating can also be eventually discharged into a storage tank to achieve fluid recycling and reuse.

[0033] Example 5: Referring to Example 3, when there are multiple target wells, if there is a power generation demand, it can be determined whether the well outlet temperature meets the requirements of the geothermal power generation equipment; and the well with the outlet temperature meeting the requirements of the geothermal power generation equipment can be selected for backflow fluid generation. The purpose of this step is to determine whether the fluid has accumulated enough geothermal energy to be used for geothermal power generation. If it cannot meet the power generation demand, the geothermal energy will be wasted in the absence of heating demand. Of course, in the case of only one well, since power generation has the highest priority, this step can be ignored. Specifically, the method for determining whether the well outlet temperature meets the requirements of the geothermal power generation equipment includes: simulating the relationship between the well closed heat storage time and the well outlet temperature based on a fluid-structure-thermal coupling numerical model; calculating the required closed heat storage time based on the well outlet temperature required for power generation and / or heating demand using the fluid-structure-thermal coupling numerical model; if the closed heat storage time is reached, the well outlet temperature meets the requirements of the geothermal power generation equipment. In this example, since the formation energy storage is above 1000 meters, a heat pump is not required for heating; instead, the different power supply demands are met by controlling the heat storage time. In addition, this step can also be applied to the collaborative work of multiple wells. When the power generation demand is higher than the power that a single well can provide, this step can be used to select multiple wells to work together to meet the power generation demand.

[0034] Example 6: As mentioned earlier, traditional geothermal energy extraction often targets faults with well-developed natural fractures in the formation, or employs multi-well methods using multi-stage hydraulic fracturing. However, relying solely on natural fractures is insufficient to meet current geothermal extraction needs, and excessive exploitation of faults can lead to geological safety issues. Furthermore, multi-stage hydraulic fracturing for geothermal energy extraction faces problems such as high investment and maintenance costs, susceptibility to flow short-circuiting, and low geothermal utilization rates. Preferably, this invention stores high-pressure fluid in artificial fractures (i.e., formation fractures created by hydraulic fracturing) within porous and permeable shale formations, thereby achieving long-term energy storage; that is, using shale formations as energy storage formations. Of course, this invention can also be applied to other porous and permeable rock formations.

[0035] See Figure 6A The flowchart below is an exemplary embodiment of the present invention of a method for storing and releasing geothermal energy through formation fractures and obtaining geothermal energy. Specifically, the method includes the following steps: In step S100, at least one energy storage geothermal layer (i.e., reservoir) with abundant geothermal resources but no oil or gas and with at least one original formation fracture is identified. In some embodiments, the oil and gas-free energy storage formation includes depleted oil and gas formations that have undergone hydraulic fracturing. That is, the energy storage formation contains at least one artificial fracture (e.g., a formation fracture created by hydraulic fracturing), and this artificial fracture is currently closed due to depletion. In other embodiments, the oil and gas-free energy storage formation may also include an energy storage formation with at least one natural fracture. Of course, the oil and gas-free energy storage formation may contain both at least one artificial fracture (i.e., an original artificial fracture) and at least one natural fracture (i.e., an original natural fracture).

[0036] In some embodiments, the method for identifying energy storage formations (preferably shale formations) is the same as in the above embodiments, and will not be repeated here. Preferably, if the wellbore outlet temperature can be maintained above the power generation temperature for a long period of time through simulation (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, while binary cycle power generation requires a wellbore outlet temperature above 50 degrees Celsius), then the geothermal energy storage formation can be directly used for power generation or heating and is marked. 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 and is marked. That is, geothermal energy storage formations are classified and marked by simulation using the above-mentioned fluid-solid-thermal coupling numerical model.

[0037] In some embodiments, logging techniques and seismic information can be used to identify and predict natural and man-made fractures within a formation. For example, electromagnetic direction finders, CT scanners, micro-Lambda logging, annular sonic logging, imaging logging (FMI), full-bore formation microresistivity imaging (FMI), DSI dipole shear wave imagers, microseismic monitoring, and downhole television (BHTV) can measure the dip angle, orientation, width, apparent porosity, and degree of filling and opening of reservoir fractures, and can even identify micro-fractures and submicroscopic fractures. Of course, nonlinear theoretical methods can also detect and identify natural and man-made fractures in formations, such as fractal theory and neural network techniques. These methods can describe the distribution patterns and fractal dimensions of fractures, as well as the connectivity of fracture networks. Analysis of tectonic stress can also predict natural and man-made fractures within strata. For example, the principal curvature of tectonic surfaces can be used to study fracture problems in oil and gas reservoirs, a mechanical model of longitudinal bending folds can be simulated using buckled thin plates, an analytical calculation method for paleostress fields of faults can be established, and numerical simulation methods can be used to study the influence of tectonic stress fields on fracture development.

[0038] In step S102P, at least one target artificial fracture (i.e., a target original formation fracture) is screened from at least one original formation fracture in step S100. In some embodiments, parameters of the formation fractures for energy storage are planned in advance according to energy storage requirements, such as energy storage capacity (including fluid kinetic energy and thermal energy) and economic costs. These parameters include, for example, target width, target length threshold, target height threshold, and target number of fractures. The target length threshold and target height threshold can also be derived from the required fluid kinetic energy and the thermal energy carried by the fluid, and the target width of existing formation fractures. Therefore, when the parameters of the identified artificial fracture reach the above target values, it indicates that it meets the energy storage requirements. Thus, high-pressure fluid can be directly injected into it to change its width (even causing deformation) for energy storage; otherwise, it does not meet the energy storage requirements. Specifically, see [link to relevant documentation]. Figure 7 Step S102P includes the following steps: acquiring first monitoring data of the artificial fractures identified in step S100 from the monitoring equipment; 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 with the first construction parameters (e.g., injection rate, wellhead and bottom hole pressure) obtained in advance through a fracture propagation numerical model; and determining whether the original length and original height of each artificial fracture meet the preset target length threshold and target height threshold. If so, it is marked as a target artificial fracture; otherwise, the screening continues until all target artificial fractures are screened out.

[0039] In some embodiments, as described above, the first monitoring data is obtained using various monitoring devices, such as electromagnetic direction finders, CT scanners, micro-Lambda logging, annular sonic logging, imaging logging (FMI), full-bore formation microresistivity imaging (FMI), DSI dipole shear wave imagers, microseismic monitoring, and downhole television (BHTV). Specifically, it includes the dip angle, orientation, width, apparent porosity, and degree of filling and opening of artificial fractures in the formation.

[0040] In some embodiments, the first construction parameters mentioned above include the injection rate and the wellhead and bottomhole pressures. Typically, the first construction parameters for each existing artificial fracture in the formation can be obtained in advance.

[0041] In other embodiments, if the number of target artificial cracks ultimately screened is less than a preset target artificial crack number threshold (typically, the target artificial crack number threshold is calculated in advance based on current energy storage needs, such as energy storage capacity and economic costs), artificial cracks that do not meet the preset target values ​​(e.g., artificial cracks whose original length and / or original height do not meet the corresponding target length threshold and / or target height threshold), i.e., the remaining artificial cracks not marked as target artificial cracks, can be further modified. Specifically, the number of artificial cracks to be modified can be the difference between the current target artificial crack number and the target artificial crack number threshold, or it can be set according to the current target energy storage. See [link to documentation]. Figure 8 The specific steps for secondary modification of artificial cracks include: injecting high-pressure fluid into the artificial crack through the wellbore according to preset third construction parameters, so that the crack pressure inside the artificial crack is greater than the crack propagation pressure, thereby causing the artificial crack to propagate along its original height and original length; calculating the latest length and latest height of the artificial crack after its extension along its original height and original length according to the preset third construction parameters and the third monitoring data obtained in real time, combined with the crack propagation numerical model; then determining whether the latest length and latest height reach the preset target length threshold and target height threshold. If so, the injection of high-pressure fluid is stopped, and the target artificial crack is obtained; otherwise, the injection of high-pressure fluid continues to extend it along its original height and original length, so that the artificial crack is modified into the target artificial crack through secondary modification, until the height and length of the target artificial crack reach the preset target threshold.

[0042] In step S104P, room temperature high-pressure fluid is injected into at least one target artificial crack using an electric power-driven injection device, thereby increasing the crack width of the at least one target artificial crack to the target width, thus converting electrical energy into the elastic deformation energy of the stratum rock for storage, and simultaneously obtaining geothermal energy.

[0043] In some embodiments, the injection device is an integrated power generation and water injection unit. When energy storage is required, the integrated power generation and water injection unit 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 unit can convert the kinetic energy of the backflow fluid into electrical energy.

[0044] In some embodiments, step S104P specifically includes: injecting high-pressure fluid into the target artificial fracture according to preset second construction parameters, 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 (i.e., the minimum principal stress or closure pressure of the formation); if so, adjusting the second construction parameters so that the fluid pressure injected into the target artificial fracture is greater than the closure pressure and less than the expansion pressure of the formation fracture; otherwise, continuing to monitor.

[0045] In some embodiments, since the target artificial fracture (i.e., the target original formation fracture) is originally in a closed state, the initial fluid pressure injected into the closed target artificial fracture is less than the closure stress. However, as the fluid is continuously injected, the fracture pressure inside the target artificial fracture gradually increases and eventually exceeds the closure pressure, causing the closed target artificial fracture to become open, that is, to open the artificial fracture.

[0046] In some embodiments, the second construction parameters include the fluid injection rate and the total injection volume. Specifically, the fluid pressure can be adjusted by regulating the injection rate or the amount of high-pressure fluid injected through 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 parameters (e.g., fluid injection rate, volume, etc.), the injected fluid pressure is made greater than the formation closure pressure and less than the expansion pressure of the target artificial fracture, so that the width of the target artificial fracture gradually increases while the expansion radius remains unchanged or constant (because the fluid pressure is less than the formation fracture expansion pressure, the target artificial fracture will not expand, i.e., the fracture radius remains unchanged or constant, and its length and height will not change), thereby converting electrical energy into the elastic deformation energy of the formation rock for storage.

[0047] Of course, in other embodiments, the idea that the expansion radius of the formation fracture / target artificial fracture remains constant or unchanged can be understood as remaining constant or unchanged 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 time (e.g., one hour), the change in the expansion radius can be ignored in engineering practice; or, when the formation fracture expands due to the action of high-pressure fluid, after a certain time, particles or other substances added to the high-pressure fluid will fill or partially fill the continuing expansion fracture.

[0048] 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 of the pressure drop curve after hydraulic fracturing operation.

[0049] Specifically, in some embodiments, before injecting ambient temperature high-pressure fluid into at least one target artificial crack (i.e., before performing step S104P), the step further includes: setting up at least one reservoir for storing the fluid underground or on the ground. The reservoir is connected to the wellbore via a pipe (e.g., a surface pipe).

[0050] Preferably, in some embodiments, one or more additives may be added to the fluid in the reservoir beforehand (i.e., one or more additives may be added to the fluid injected into the formation fractures), such as bactericides, scale removers, mineral salts (e.g., KCl, NaCl, CaCl2, NaSiO4, etc.) and filtration prevention agents, wherein the mineral salts are used to balance the electrolyte of the energy storage formation.

[0051] When the water storage tank is located on the ground, preferably, in order to reduce fluid loss, in some embodiments, the water storage tank is provided with a shielding structure to prevent fluid evaporation, for example, a plastic or metal film is covered over the water storage tank.

[0052] S106P: Determine whether the width of at least one target artificial fracture is equal to or greater than a preset target width. If yes, proceed to step S108; otherwise, proceed to step S110. S108: Stop injecting room-temperature high-pressure fluid into at least one target formation fracture, i.e., at least one target artificial fracture, thereby maintaining the bottom hole pressure constant or with negligible change, so that the width of the target formation fracture remains constant or with negligible change. S110: Continue injecting room-temperature high-pressure fluid into at least one target artificial fracture and proceed to 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 bottom hole pressure. It is understood that the width at different locations within the target artificial fracture is not equal. 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 can also refer to the width of any single target artificial fracture. For example, in some embodiments, for the same wellbore, during the injection of ambient temperature high-pressure fluid into each target artificial fracture, the width data of all target artificial fractures are acquired, and the average width of all target artificial fractures is obtained by averaging the widths. When the average width is equal to or greater than a preset target width, power supply to the injection equipment is stopped, so that the injection equipment stops injecting ambient temperature high-pressure fluid into each target artificial fracture. In some embodiments, the target width of the target artificial fracture is preset by professionals according to the mechanical characteristics of the energy storage formation and different energy storage requirements, ensuring that the target artificial fracture has a certain storage capacity while avoiding damage to the energy storage formation caused by excessively large target artificial fracture widths. It is understood that, since there are multiple target artificial fractures, in order to avoid damage to the energy storage formation caused by excessively large target artificial fracture widths, preferably, when it is detected (or determined) that the width of one target artificial fracture is equal to or greater than the preset target width, the injection of ambient temperature high-pressure fluid into at least one target artificial fracture is stopped, thereby keeping the bottom hole pressure constant or with negligible changes, so that the fracture width remains constant or with negligible changes. As a specific example Figure 10A As shown, the power grid-powered injection device 500 injects fluid from the reservoir 510 through the injection pipe 5200 to the wellbore 530 and then into the hydraulic fracturing fracture 590 (i.e., the target artificial fracture) in the shale formation 540. This causes the width of the formation fracture to expand, and the surrounding rocks undergo elastic deformation to store energy. At the same time, the surrounding rocks heat the fluid in the fracture to obtain geothermal energy.

[0053] S114: The high-temperature, high-pressure fluid discharged during the closure of at least one target artificial fracture drives 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 method further includes step S112: monitoring whether there is a power generation demand, and if a power generation demand is detected, executing step S114; otherwise, continuing to monitor whether there is a power generation demand. Of course, in other embodiments, when insufficient power is detected to be supplied to the injection device 500 (for example, weather changes causing insufficient solar or wind power supply, specifically, when all or most of the solar and wind power generation is consumed by the end users supplying electricity, and there is no surplus power to supply the injection device), step S108 is executed to stop supplying power to the injection device 500, so that the injection device 500 stops injecting room-temperature, high-pressure fluid into at least one target artificial fracture, thereby maintaining a constant bottom-hole pressure and keeping the fracture width constant. Furthermore, by connecting the power generation device to the power grid, a stable power supply to the electrical equipment can be achieved.

[0054] S118: The high-temperature, high-pressure fluid discharged due to the closure of at least one target artificial fracture drives a preset geothermal power generation device to generate electricity. In some embodiments, before executing step S118, the method further includes step S116: determining whether the high-temperature, high-pressure fluid meets the requirements for geothermal power generation. If the requirements are met, step S118 is executed; otherwise, monitoring continues to determine if there is a demand for power generation. When the high-temperature, high-pressure fluid discharged during the closure of the target formation fracture drives a hydroelectric power generation device and still meets the requirements for geothermal power generation (e.g., the well outlet temperature is greater than or equal to the power generation temperature required by the geothermal power generation device), the control valve connecting the discharge pipeline to the geothermal power generation device is opened, so that the high-temperature, high-pressure fluid discharged during the closure of the target formation fracture drives the geothermal power generation device to generate electricity. In other embodiments, when it is determined in step S116 that the high-temperature, high-pressure fluid does not meet the requirements for geothermal power generation, the method further includes step S120: determining whether the high-temperature, high-pressure fluid meets the requirements for heating. If yes, step S122 is executed; otherwise, the high-temperature, high-pressure fluid is discharged into a water storage tank. S122: The high-temperature, high-pressure fluid is connected to an external heating system for heating. The reservoir and the wellbore corresponding to the formation fracture are connected via pipelines and a reverse discharge pipeline. When the injection of normal-temperature, high-pressure fluid into the formation fracture stops, both the reverse discharge and injection pipelines are closed. Specifically, the control valves within both pipelines are closed. Therefore, when a power generation demand is detected, the control valve corresponding to the reverse discharge pipeline is opened to allow flow. This allows the high-temperature, high-pressure fluid within the formation fracture to be reversed through the pipeline into the reservoir under rock compression. During this reverse discharge process, the hydroelectric power generation equipment is driven, converting the fluid's kinetic energy into electrical energy. See details... Figure 10A and Figure 10BThe injection pipe 520S and backflow pipe 570S connecting the reservoir 510S and the well 530S are both equipped with control valves to control the flow and closure of the surface pipes. When power generation is detected (for example, the corresponding control system, the first power generation equipment, or the relevant personnel 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 well and the reservoir (of course, it can also be opened manually by the personnel), thereby allowing the well 530S and the reservoir to flow smoothly. The pools 510S are connected, and under the action of rock compression, the high-temperature and high-pressure fluid in the stratum fissures 590S in the shale stratum 540S is backflowed into the reservoir 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 it passes through the geothermal power generation equipment 560S, it is determined whether the high-temperature and high-pressure fluid meets the requirements for geothermal power generation. If it does, the geothermal power generation equipment 560S is turned on to generate electricity. If it does not meet the requirements, 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 a heating demand is detected and the fluid temperature reaches the heating demand).

[0055] The cyclical storage and release of electrical energy, along with the acquisition of geothermal energy for power generation, can be achieved through the repeated cycles of steps S104P-S118. For example, during the day, excess solar power is stored as the elastic deformation energy of the rock surrounding at least one target artificial fissure, while geothermal energy is acquired. At night, when solar power generation is not possible, the elastic deformation energy of the energy storage stratum 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 come from wind power generation or other forms of power generation. In other embodiments, if the high-temperature, high-pressure fluid discharged during the closure of the target stratum fissure drives a hydroelectric power generation device to generate electricity but does not meet the requirements for geothermal power generation, but meets the requirements for heating, if the heating demand is detected, it is determined whether the fluid temperature meets the heating requirements. Only if the fluid temperature meets the heating requirements will the fluid be supplied to the heating system through the discharge pipe. It is understood that the heated fluid can also eventually be discharged into a reservoir to achieve fluid recycling and reuse.

[0056] Example 7: See Figure 6BThis is a flowchart illustrating a method for storing and releasing energy and obtaining thermal energy through formation fractures, as well as another exemplary embodiment of the present invention. Specifically, the method includes the steps described in Embodiment Six above. The difference is that in this embodiment, step S102P involves screening at least one target natural fracture from the energy storage formation. Correspondingly, in S104P, room-temperature high-pressure fluid is injected into the target natural fracture to increase the width of the at least one target natural fracture, thereby converting electrical energy into the elastic deformation energy of the formation rock for storage and simultaneously obtaining geothermal energy. In S106P, it is determined whether the width of the target natural fracture reaches a preset target width. If so, in S108, the injection of room-temperature high-pressure fluid into the natural fracture is stopped, thereby maintaining the bottom hole pressure unchanged or with negligible changes, so that the width of the target formation fracture remains unchanged or with negligible changes. In S114 and S118, the high-temperature high-pressure fluid discharged during the closure of the natural fracture drives 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.

[0057] In other embodiments, when it is determined that the high-temperature and high-pressure fluid discharged in reverse does not meet the requirements for geothermal power generation after driving the preset hydropower equipment, it is determined whether it meets the requirements for heating. If it does, 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 storage tank.

[0058] In some embodiments, the step of screening 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 structural stress analysis; simulating the opening of the at least one natural fracture during the injection of fluid into the at least one natural fracture using a three-dimensional fracture-stress coupling model, and calculating the energy storage capacity of the at least one natural fracture; determining whether the energy storage capacity reaches the target energy storage capacity, and if so, marking the corresponding natural fracture as the target natural fracture.

[0059] Furthermore, when it is determined that the energy storage capacity of at least one natural fracture has not reached the target energy storage capacity, the natural fracture can be modified. Specifically, the steps for modifying the natural fracture include: injecting room temperature high-pressure fluid into the natural fracture through the wellbore according to the preset fourth construction parameters, so that the fracture pressure in the natural fracture is greater than the fracture propagation pressure, thereby causing the natural fracture to propagate along the original height and original length directions; calculating the latest length and latest height of the extended natural fracture using a fracture propagation numerical model based on the fourth construction parameters and real-time monitoring data; and determining whether the latest length and latest height of the extended natural fracture reach the preset target length threshold and target height threshold. If so, stop injecting room temperature high-pressure fluid; otherwise, continue injecting room temperature high-pressure fluid.

[0060] In practical applications, the extent of the natural fracture's 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; if less energy needs to be stored, a shorter formation fracture needs to be designed. Therefore, the parameters of the target formation fracture can be set in advance according to actual needs, such as the target width, target length threshold, target height threshold, and target fracture number threshold. When it is determined that the identified natural fracture has reached the desired target threshold (target length threshold and target height threshold), room temperature 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 has not reached the desired target threshold, room temperature high-pressure fluid can be injected into it to modify it, causing it to expand along the height or length direction until it meets the corresponding target threshold (including the target length threshold, target height threshold, and target fracture number threshold).

[0061] In some embodiments, the step of injecting room-temperature high-pressure fluid into at least one target natural fissure using an electrically driven injection device specifically includes: injecting room-temperature high-pressure fluid into the target natural fissure according to preset second construction parameters, so that the fissure pressure in the target natural fissure gradually increases; monitoring the fissure pressure in the target natural fissure in real time and determining whether the fissure pressure is greater than the closing pressure, so that the closed target natural fissure becomes open; if the fissure pressure is greater than the closing pressure, adjusting the second construction parameters so that the fluid pressure injected into the target natural fissure is greater than the closing pressure and less than the expansion pressure of the target natural fissure, thereby gradually increasing the width of the target natural fissure to the target width.

[0062] Of course, if the target natural crack is obtained through modification, since the natural crack is currently in an open state, when injecting room temperature high pressure fluid into the target natural crack through the injection device, it is only necessary to ensure that the pressure of the injected room temperature high pressure fluid is greater than the closing pressure and less than the expansion pressure of the target natural crack, so that the crack width of the target natural crack gradually increases to the target width.

[0063] Typically, during the injection of ambient temperature high-pressure fluid, energy storage, and even reverse discharge, fluid loss can lead to a loss of only 70%-80% of the target stored energy in the final reverse discharge. Therefore, to minimize the low energy output due to fluid loss, the target length and / or width and / or number of target natural / artificial cracks can be increased. For example, the fluid loss from a natural crack can be calculated simultaneously with the energy storage of that crack, allowing for the calculation of the number, target length threshold, and target height threshold of the target natural cracks based on the fluid loss, stored energy, and target stored energy.

[0064] Of course, in other embodiments, at least one target artificial fracture and at least one target natural fracture can be selected simultaneously from the existing original formation fractures for energy storage (and the order of identifying the target artificial fractures and target natural fractures can be adjusted according to actual needs). The number of target artificial fractures and target natural fractures, as well as the corresponding target thresholds (e.g., target widths), are set according to the current energy storage requirements. Of course, if the data of the corresponding target artificial fractures and / or target natural fractures do not reach their respective preset target number thresholds, the existing artificial fractures can be modified a second time, and / or the natural fractures can be modified. The specific modification methods are the same as the corresponding modification methods in embodiments six and seven above, and will not be repeated here.

[0065] Example 8: Unlike Examples 6 or 7, this example uses multiple wells, each connected to the energy storage geothermal layer and the target formation fractures. It also includes several injection pipes and backflow pipes that cooperate with each well. Injection equipment is connected to the injection pipes, and hydroelectric power generation equipment, geothermal power generation equipment, and a heating system are connected to the backflow pipes. However, the multiple wells are not connected to each other through formation fractures. At the same time, some of the wells are performing secondary modification processes by injecting fluid, while others are performing energy storage and still others are performing energy release. Alternatively, the injection pipe and backflow pipe in the process of injecting ambient temperature high-pressure fluid can be the same pipe; the principle is the same and will not be elaborated here.

[0066] When there are multiple wells, if there is a demand for power generation, it can be determined whether the outlet temperature of the wells meets the requirements of the geothermal power generation equipment. At least one well with an outlet temperature meeting the requirements of the geothermal power generation equipment can then be selected for backflushing fluid to generate electricity. The purpose of this step is to determine whether the fluid has accumulated enough geothermal energy for geothermal power generation. Of course, if there is only one well, this step can be disregarded because power generation has the highest priority. Specifically, the method for determining whether the well outlet temperature meets the requirements of the geothermal power generation equipment includes: simulating the relationship between the well's closed heat storage time and the well outlet temperature based on a fluid-structure-thermal coupling numerical model; calculating the required target closed heat storage time using the fluid-structure-thermal coupling numerical model based on the well outlet temperature required for power generation (including hydropower and geothermal power generation) and / or heating demand; if the actual closed heat storage time of any well reaches the corresponding target closed heat storage time, then it is determined that the outlet temperature of the corresponding well meets the requirements of the geothermal power generation equipment. Furthermore, this step can also be applied to the collaborative operation of multiple wells. When the power generation demand is higher than the power that a single well can provide, this step can be used to select multiple wells that can work collaboratively to meet the power generation demand. Specifically, the required number of wells is calculated based on the desired power generation needs.

[0067] See Figure 12This embodiment provides a system for continuously storing and releasing 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 (this example uses three horizontal or vertical wells, but the number of multiple vertical and horizontal wells described in this invention includes all cases greater than 1). Each vertical and horizontal well has at least one formation fracture in a closed state. During the energy storage and release using the formation, vertical wells 710, 720, and 730 and horizontal wells 740, 750, and 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, converting electrical energy into formation elastic deformation energy, vertical well 720 and horizontal well 750 have already completed the injection. Therefore, the electrical energy can be converted into formation elastic deformation energy for storage, while simultaneously acquiring 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 acquired geothermal energy into electrical energy and putting it into the grid. After releasing energy, vertical well 730 and horizontal well 760 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. Vertical well 710 and horizontal well 740, after completing the injection, are in the energy storage process and acquire geothermal energy. Taking this example, the vertical wells 710, 720, and 730, and the horizontal wells 740, 750, and 760, work together in a cycle to ensure that electrical energy can be provided to the grid at any time to meet the electricity demand.

[0068] Example 9: The present invention also provides a system for storing and releasing geothermal energy through formation fractures, see [link to example]. Figure 9The system specifically includes: a stratum identification device 02, used to identify at least one energy storage geothermal layer with abundant geothermal resources but no oil or gas and at least one original stratum fracture; wherein the original stratum fracture includes natural fractures and / or, artificial fractures in a closed state; a stratum fracture screening device 04, used to screen at least one target stratum fracture from the at least one original stratum fracture identified by the stratum identification device 02; wherein the at least one target stratum fracture includes at least one target artificial fracture and / or, at least one target natural fracture; an injection device 06, used to inject room temperature high-pressure fluid into at least one target stratum fracture, thereby increasing the fracture width of at least one target stratum fracture to a target width, thereby converting electrical energy into the elastic deformation energy of the stratum rock for storage and obtaining geothermal energy; and a power generation device 12, including a hydroelectric power generation device and a geothermal power generation device, used to compress the rock during the closure of the target stratum fracture by the high temperature and high pressure fluid in the target stratum fracture. During reverse discharge, driven by the high-temperature, high-pressure fluid, the elastic deformation energy of the formation rock and the acquired geothermal energy are converted into electrical energy. The reverse discharge pipe is connected to the aforementioned hydroelectric power generation equipment and geothermal power generation equipment. The fluid in the formation fissures is discharged 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 first to generate electricity. If the demand for geothermal power generation is still met after the hydroelectric power generation equipment is driven (for example, by detecting the temperature of the high-temperature, high-pressure fluid through a temperature detection device, or whether the well outlet temperature meets the heating temperature required by the geothermal generating equipment), the geothermal power generation equipment is driven to generate electricity. If the demand for geothermal power generation is not met, it is determined whether the demand for heating is met. If it is met, the high-temperature, high-pressure fluid is connected to the heating system for heating. If the demand for heating is not met, it is directly discharged into the water storage tank. A sealing device is used to close the reverse discharge pipe so that the fluid in the formation fissures and the energy storage geothermal layer continue to exchange heat, causing the fluid temperature to continue to rise. Preferably, the sealing device is a control valve installed on the reverse discharge pipe. Of course, to prevent fluid from flowing back into the injection pipe, the sealing device may also include a control valve installed on the injection pipe. In some embodiments, the system further includes a reservoir 14, connected to the injection device 06, for storing fluid. Further, in some embodiments, the reservoir is connected to the wellbore corresponding to the original formation fracture via a backflow pipe, and the wellbore or backflow pipe is provided with a control valve for controlling the opening (i.e., flow) or closing (i.e., non-flow) of the wellbore or backflow 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 command indicating that the control valve of the backflow pipe should be opened is generated and sent to the control valve to control the control valve to open, thereby connecting the reservoir and the wellbore; otherwise, the monitoring for a power generation demand continues.

[0069] Specifically, in some embodiments, the backflow pipe between the reservoir and the well is normally closed / non-flowing (specifically, the valve in the backflow pipe is normally closed). When the power generation device 12 receives a first control command from the monitoring device indicating the opening of the control valve corresponding to the backflow pipe (e.g., a control command from the power grid or other control system connected to the power generation device 12, or a control command issued by the operator), the power generation device 12 will open the backflow pipe between the well and the reservoir (specifically, open the control valve corresponding to the backflow pipe), so that under the action of rock compression, the high-temperature and high-pressure fluid in the formation fissures is backflowed into the reservoir through the backflow pipe and drives the hydraulic generator in the power generation device 12. The impeller of the electric device rotates to generate electricity. A judgment device then determines whether the high-temperature, high-pressure fluid discharged during the power generation process drives the hydroelectric power generation equipment to meet geothermal power generation requirements. If the geothermal power generation requirements are met, a second control command indicating the activation of the geothermal power generation equipment is generated and sent to the equipment, causing it to generate electricity. If the power generation equipment 12 does not receive a first control command indicating the opening of the control valve of the discharge pipe, it keeps the discharge pipe closed. Meanwhile, the monitoring device continues to monitor for power supply demand. Alternatively, in some embodiments, personnel can determine the power supply demand and manually control the opening and closing of the valves in the injection / discharge pipe. In other embodiments, if the geothermal power generation conditions are not met, the geothermal power generation equipment is shut down, and the system further determines whether heating requirements are met. If heating requirements are met, the discharged high-temperature, high-pressure fluid flows into the heating system for heating.

[0070] Specifically, see Figure 10A and Figure 10BThe injection pipe 520 and backflow pipe 570 connecting the reservoir 510 and the well 530 are both equipped with control valves to control the flow and closure of the surface pipes. When power generation is detected (e.g., the corresponding control system, the first power generation equipment, or the relevant personnel receive a power supply request from an external source, 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, opens the control valve corresponding to the backflow pipe 570 between the well and the reservoir (of course, it can also be opened manually by the personnel), thereby allowing the well 530 and the reservoir to flow smoothly. The pools 510 are interconnected, and under the action of rock compression, the high-temperature and high-pressure fluid in the stratum fissures 590 within the shale stratum 540 is backflowed into the reservoir 510. During 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 it passes through the geothermal power generation equipment 560, it is determined whether the high-temperature and high-pressure fluid meets the requirements for geothermal power generation. If it does, the geothermal power generation equipment 560 is turned on to generate electricity. If it does not meet the requirements, 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 a heating demand is detected and the fluid temperature reaches the heating demand).

[0071] Of course, if no power supply request is received, the backflow pipe 570 between the wellbore and the reservoir will remain closed, meaning the control valve on the backflow pipe 570 will be normally closed. In this case, it is sufficient to continue monitoring for any power supply demand. It is understandable that even if there is a power supply and / or heating demand, it is necessary to determine whether the fluid in the formation fissures can meet the requirements for power generation and / or heating.

[0072] 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 existing 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 first construction parameters of the existing 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 a fracture propagation numerical model combined with the first monitoring data and the first construction parameters; and 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. If so, the corresponding artificial fracture is marked as a target artificial fracture, and the injection device is triggered 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, the injection device is triggered to inject high-pressure fluid into the target artificial fracture to perform secondary modification on the artificial fracture. Of course, when the target artificial crack is obtained through modification, the first control module is also used to trigger the injection device to inject high-pressure fluid into the target artificial crack for energy storage. In some embodiments, the formation fracture screening device further includes: a second calculation module, used to invert the distribution of the at least one natural fracture by means of the well logging data and the seismic data; a third calculation module, used to obtain the three-dimensional stress distribution of the energy storage formation by means of tectonic stress analysis; a fourth calculation module, used to simulate the opening of the natural fracture during the injection of fluid into the natural fracture using a three-dimensional fracture-stress coupling model, and to calculate the energy storage capacity of the natural fracture; a second control module, used to determine whether the energy storage capacity reaches the preset target energy storage capacity, and if so, to mark the corresponding natural fracture as the target natural fracture and to trigger the injection device 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, to trigger the injection device to modify the natural fracture. Of course, when the target natural fracture is obtained through modification, the second control module is also used to trigger the injection device to inject room temperature high-pressure fluid into the target natural fracture for energy storage and geothermal energy acquisition; In some embodiments, the formation fracture screening device further 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, generating a third control command indicating to stop injecting room temperature high pressure fluid, and sending it to the injection device 06, so that the injection device 06 stops injecting room temperature high pressure fluid into at least one target formation fracture, so that the width of the target formation fracture remains unchanged.

[0073] 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, it generates a third control command indicating that the injection of ambient temperature high pressure fluid is stopped and sends it to the injection device 06 so that the injection device 06 stops injecting ambient temperature high pressure fluid into at least one target formation fracture, so that the width of the target formation fracture remains unchanged.

[0074] Specifically, in some embodiments, the injection device 06 is installed in the injection pipeline (i.e., the pipeline connecting the reservoir and the wellbore and supplying fluid injection). When the injection device 06 stops injecting room temperature high pressure fluid into at least one formation fracture, the injection device 06 puts the injection pipeline in a closed / non-flowing state. Specifically, the injection device 06 closes the valve in the injection pipeline.

[0075] In some embodiments, the injection device 06 includes: a fluid injection module 062 for injecting ambient temperature high-pressure fluid into at least one formation fracture; a pressure monitoring module 064 for real-time monitoring of the injected fluid pressure; and a pressure judgment module 066 connected to the fluid injection module 062 and the pressure monitoring module 064 for judging whether the injected fluid pressure is greater than the energy storage formation closure pressure and less than the formation fracture propagation pressure. If so, the pressure judgment module 066 does not operate; otherwise, the pressure judgment module 066 generates a fourth control command indicating the adjustment of the second construction parameter (i.e., the operating 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 propagation pressure and the energy storage formation closure pressure.

[0076] In some embodiments, the pressure judgment module 066 is further configured to determine whether the crack pressure within the natural / artificial crack is greater than the crack propagation pressure during the modification of the natural / artificial crack. If so, the pressure judgment module 066 performs no operation; otherwise, the pressure judgment module 066 generates a fifth control command indicating the adjustment of the third / fourth construction parameters (i.e., the operating parameters 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 / fourth construction parameters so that the crack pressure within the natural / artificial crack is greater than the crack propagation pressure, thereby enabling the natural / artificial crack to propagate along its original height and length.

[0077] In some embodiments, the second control device 10 is further configured to monitor whether the injection device calculates the latest length and height of the natural crack after extension using a crack propagation numerical model based on the fourth construction parameters and the fourth monitoring data monitored in real time by the monitoring equipment, or calculates the latest length and height of the artificial crack after extension using a crack propagation numerical model based on the third construction parameters and the third monitoring data monitored in real time by the monitoring equipment; and to determine whether the latest length and height of the natural / artificial crack after extension reach the preset target length threshold and target height threshold, and when it is determined that the latest length and height reach the preset target length threshold and target height threshold, control the injection module to stop injecting fluid.

[0078] In other embodiments, to simplify the equipment, the difference is that the injection pipe and the backflow pipe are the same pipe; the hydraulic generator and the injection equipment are an integrated power generation and water injection machine. When energy storage is needed, 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 needed, the integrated power generation and water injection machine can convert the kinetic energy of the backflow fluid into electrical energy.

[0079] A water-generating and power-generating integrated machine is a device that combines the functions of a water pump and a power generator. It can pump water or convert the kinetic energy of water into electrical energy through forward and reverse rotation. Specifically, it can be an electric generator, or a motor that functions as both a generator and an electric motor. It can act as a generator driven by a water turbine to generate electricity, or it can be converted into an electric motor to drive a water pump for pumping water.

[0080] See details Figure 11A and Figure 11B After 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 storage tank 630 is also closed. When power generation is detected, the control valve corresponding to the pipeline 640 between the wellbore 650 and the water storage tank 630 is opened. At this time, under the action of rock compression, the high temperature and high pressure fluid heated by the formation in the formation fracture 670 in the shale formation 660 is back-discharged into the water storage tank 630 through the pipeline 640. 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 passes through the geothermal power generation equipment 620. At this time, if it is determined that the high temperature and high pressure fluid meets the conditions for geothermal power generation, the geothermal power generation equipment 620 is driven to generate electricity. Otherwise, the geothermal power generation equipment 620 remains closed and it is determined whether there is a heating demand. If there is a heating demand, the fluid is introduced into the heating system 680. Otherwise, it flows back to the water storage tank. If no power demand is detected, the pipe 640 between the well shaft 650 and the water storage tank 630 remains closed.

[0081] Example 10: Based on the same inventive concept, this invention also provides another method for storing and releasing geothermal energy through geological fractures, see [link to example]. Figure 13 The method in this embodiment specifically includes the following steps: S1301 Identifying an energy storage geothermal layer containing geothermal resources but without oil and gas; S1302 Injecting high-pressure fluid into a target wellbore in the energy storage geothermal layer, causing at least one target artificial formation fracture to be generated in the energy storage geothermal layer, or opening at least one existing target original formation fracture in the target wellbore that is in a closed state; wherein, the target wellbore is not connected to other wellbores in the energy storage geothermal layer through formation fractures; S1303 Injecting room temperature high-pressure fluid into the target wellbore, causing the width of the target artificial formation fracture or the target original formation fracture in the target wellbore to increase, thereby causing the formation rock to undergo elastic deformation for energy storage, and the target artificial formation fracture... The fluid within the fissure or the target original stratum fracture exchanges heat with the geothermal storage layer, causing the fluid temperature to rise. In step S1304, the backflow pipe is closed, allowing the fluid within the stratum fracture to continue exchanging heat with the geothermal storage layer, causing the fluid temperature to rise continuously for heat storage (preferably, the pipe is closed for heat storage when the width of at least one target artificial stratum fracture or at least one target original stratum fracture reaches the target width). In step S1305, the high-temperature, high-pressure fluid backflowed during the closure of the target artificial stratum fracture or the target original stratum fracture drives a pre-set hydroelectric power generation device and a geothermal power generation device to generate electricity, thereby converting the acquired geothermal energy and the elastic deformation energy of the stratum rock into electrical energy for energy release. The specific steps of energy release can be referred to the energy release principles of the above embodiments, and will not be repeated here.

[0082] In some embodiments, the propagation of formation fractures along their length or height is uncontrollable due to formation heterogeneity, difficulty in obtaining formation cores, or calculation errors in the hydraulic fracturing model. During actual fracture propagation, the actual fracture height may not reach the preset target height, but the actual propagation radius may exceed the preset target radius. Alternatively, the actual fracture propagation radius may not reach the preset target radius, but the actual propagation height may exceed the preset target height. Therefore, without control, whether during the formation of formation fractures through hydraulic fracturing or during the modification of the original formation fractures, communication between the target wellbore and adjacent wellbores may occur. Therefore, to ensure that the target formation fracture does not connect with adjacent wellbores, this embodiment requires the following during the process of creating the target artificial fracture through hydraulic fracturing or modifying the original formation fracture (including secondary modification of the original artificial formation fracture or modification of the original natural fracture): real-time monitoring of the actual three-dimensional dimensions (including the actual expansion radius and / or actual expansion height) of the formation fracture (e.g., the target artificial formation fracture in the target wellbore during hydraulic fracturing, or the original formation fracture in the target wellbore during modification). When the monitored actual three-dimensional dimensions of the formation fracture exceed a set threshold, the injection of high-pressure fluid into the target wellbore is stopped. The preset threshold can be set as the minimum of the energy storage three-dimensional dimensions of the formation fracture (e.g., the target expansion radius and / or target expansion height, both calculated in advance based on the required energy storage) and the safety three-dimensional dimensions (exceeding which would pose a risk of connection with other adjacent wellbores).

[0083] See Figure 14 If the fractures in adjacent wellbores and the artificial formation fractures in the target wellbore undergoing hydraulic fracturing are at the same height (or the height difference is less than a preset threshold), the formation fractures in the target wellbore may connect with existing formation fractures (such as artificial or natural fractures) in adjacent wellbores during the propagation process. Therefore, a safe propagation radius R0 needs to be set to control the fracturing process. Specifically, the safe propagation radius must meet the condition: R0 < (L0 - R0) / ( ... 邻 ), where L0 is the distance between the target wellbore and its nearest adjacent wellbore, and R 邻 The actual radius of formation fracture expansion in the adjacent wellbore closest to the target wellbore.

[0084] See Figure 15 If the formation fractures in adjacent wellbores are at different heights from those in the target wellbore undergoing hydraulic fracturing (or modification), the two wellbores may connect if left uncontrolled. Therefore, a safe expansion height H0 needs to be set. Specifically, the safe expansion height must meet the condition: H0 < (V0 - H0). 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 its nearest adjacent wellbore. H 邻 H0' represents the actual extension height of the target formation fracture in the nearest adjacent wellbore; H0' represents the actual extension height of the formation fracture in the monitored target wellbore.

[0085] Specifically, the actual three-dimensional dynamic changes of the target artificial crack can be monitored by methods such as microseismic monitoring, tiltmeters, distributed optical fibers, and synthetic aperture radar. Alternatively, the actual three-dimensional dynamic changes of the target artificial crack can be calculated by monitoring construction parameters (injection flow rate, pressure, time, etc.) and combining them with a hydraulic fracturing model.

[0086] In some embodiments, the step of setting the aforementioned 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 fractures in each of the adjacent wellbores. 邻 Based on the spacing L0 and the actual propagation radius R of the formation fracture in the nearest adjacent wellbore. 邻 Determine the safe propagation radius R of the target formation fracture in the target wellbore. 0， That is: R0 < (L0 - R 邻 (If there are multiple adjacent wellbores closest to the wellbore, and the actual propagation radius of the formation fractures in each adjacent wellbore is different, then the largest actual propagation radius R shall be used.) 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 is detected to reach the set threshold, the injection of high-pressure fluid is stopped.

[0087] For example, if the target wellbore and the nearest adjacent well are 1000 meters apart, and the actual expansion radius (or length) of the formation fracture generated after hydraulic fracturing in the adjacent well is 500 meters, there is a risk that the two wellbores will connect through the formation fracture if the actual expansion radius (or length) of the formation fracture generated in the target wellbore exceeds 500 meters. To avoid this connection, the safe expansion radius (or length) of the target formation fracture in the target wellbore is set at 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 designed energy storage radius (i.e., target propagation radius) of the target formation fracture is 300 meters, which is less than the safe propagation radius (or length) of 450 meters, then the energy storage radius (i.e., target propagation 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 designed energy storage radius (i.e., target propagation radius) of the target formation fracture is 600 meters, which is greater than the safe propagation radius (or length) of 450 meters, then the safe propagation 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 of the three-dimensional dimensions of the formation fracture can guide and correct construction parameters, and control the maximum value of the propagation radius (or length) or height of the target formation fracture.

[0088] In other embodiments, the step of setting the aforementioned preset threshold specifically includes: obtaining the height difference V0 between the formation fracture initiation point (or perforation) of the target wellbore and the nearest formation fracture initiation point (e.g., perforation location) in at least one adjacent wellbore, and the actual propagation height H. 邻 Determine the safe propagation height H0 of the formation fracture in the target wellbore: H0 < (V0 - H 邻 The system determines whether the 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 reach the set threshold, the injection of high-pressure fluid is stopped.

[0089] For example, if the perforation height difference (V0) between the formation fracture in the target well and the formation fracture in the nearest adjacent well is 10 meters, and the actual expansion height of the formation fracture generated after hydraulic fracturing in the adjacent well is 5 meters, there is a risk that the two wells will connect through the formation fracture if the actual expansion height of the formation fracture generated in the target well exceeds 5 meters. To avoid this connection, the safe expansion height of the target formation fracture in the target well is set at 4 meters. Hydraulic fracturing is performed on the target well, and the actual expansion height of the artificial formation fracture is monitored in real time. If the designed energy storage height (i.e., target propagation height) of the target formation fracture is 3 meters, which is less than the safe propagation height of 4 meters, then the energy storage radius (i.e., target propagation radius) is set to the preset threshold of the three-dimensional dimensions of the formation fracture in the current wellbore, which is 3 meters. If the designed energy storage height (i.e., target propagation height) of the target formation fracture is 6 meters, which is greater than the safe propagation height of 4 meters, then the safe propagation height is set to the preset threshold of the three-dimensional dimensions of the formation fracture in the wellbore, which is 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 value of the propagation radius (or length) or height of the target formation fracture.

[0090] In practical applications, high-pressure fluid injection can be stopped as soon as either the actual expansion radius or the actual expansion height reaches the corresponding preset threshold.

[0091] Furthermore, when the safe three-dimensional size is used as a preset threshold, if the actual three-dimensional size of the formation fracture is smaller than the preset energy storage three-dimensional size—for example, the actual expansion radius may not reach the preset target expansion radius, or / and the actual expansion height may not reach the preset target expansion height—it is necessary to recalculate the target expansion height and / or target expansion radius of the formation fracture once the safe three-dimensional size is used as the preset threshold. Then, by adjusting construction parameters, such as injection pressure and / or injection flow rate and / or injection fluid density, the final actual expansion radius of the 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 formation fracture is recalculated based on the preset target energy storage and the safe expansion radius R0. Construction parameters are then adjusted according to the target expansion height and the safe expansion radius R0, so that the final actual expansion radius of the 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 example, if the safe expansion height H0 is used as the set threshold for 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 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.

[0092] Example 11: This invention also provides another method for storing and releasing geothermal energy through formation fractures, which includes the steps in the method of Example 10 above. The difference is that when hydraulic fracturing is performed on multiple target wells to form multiple target wells that are not connected by formation fractures but can store and release energy and obtain geothermal energy, continuous power supply can be achieved through the synergistic effect between the multiple non-connected target wells. For example, when there is a power supply demand, it is determined whether the well temperature of any of the multiple target wells meets the power generation demand. If not, at least one target well is selected for reverse discharge, thereby converting elastic potential energy into electrical energy. And once the well temperature of any target well meets the power generation demand, the system switches to that target well, so that elastic deformation release energy and geothermal energy are simultaneously converted into electrical energy, thereby achieving continuous power supply.

[0093] In other embodiments, the target width of the formation fracture is influenced not only by the power supply demand but also by the energy storage power supply capacity. For example, under 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, if its ideal 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 requirement. However, in practical applications, if the current energy storage power supply is insufficient, making it impossible for the formation fracture width to increase to P0, but only 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, making it possible for the formation fracture width to increase to P0, or even larger (but the formation fracture does not continue to expand), then P0 is the target width of the formation fracture. Therefore, the power supply capacity of the multiple disconnected wells will differ. Furthermore, since the input or output power of a single target well is limited, the wells are grouped, with wells in the same group simultaneously storing or releasing energy to increase the power of energy storage or generation. While one group stores energy, another group releases energy simultaneously, and this cycle repeats, not only increasing power generation but also ensuring continuous power output. Preferably, the difference in energy storage between the two groups of wells supplying power in the cycle is less than or equal to a preset energy difference threshold, and the difference in the total heat storage time of the two groups (i.e., the time required for all wells in each group to reach their respective preset target closed heat storage time) is less than or equal to a preset time difference threshold, thereby ensuring continuous power supply.

[0094] In other embodiments, the high-pressure fluid flushed from formation fractures is first used for power generation or heating using its thermal energy, and then for power generation using its kinetic energy. The advantage of this is that no additional pumping equipment is needed when the fluid passes through heat exchange pipes or thermal power generation equipment. If the kinetic energy of the high-pressure fluid is used for power generation first, the fluid will lose most of its pressure and may not be able to pass through the heat exchange pipes or thermal power generation equipment under its own pressure. Furthermore, using the thermal energy of the high-pressure fluid for power generation or heating first can lower the temperature of the high-pressure fluid, which is beneficial for improving the operating efficiency of subsequent hydroelectric power generation equipment and avoiding the situation where the high-pressure, high-temperature fluid changes from a liquid to a gaseous state due to pressure reduction in the hydroelectric power generation equipment (for example, water is a liquid at 110 degrees Celsius and 20 MPa, but a gaseous state at 0.1 MPa).

[0095] Preferably, to prevent potential geological risks and leakage of injected fluid, the target wellbore of the energy storage needs to be more than 2,000 meters away from the nearest fault.

[0096] In other embodiments, to reduce the frictional resistance of fluid flow in the fracture, at the end of the energy release process, the volume of high-pressure fluid retained in the formation fracture is greater than or equal to a preset volume threshold. This ensures that the fracture width in the formation fracture is greater than or equal to a preset width threshold during energy storage and release cycles (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%, a hydraulic fracturing model can be used to calculate, using known information (such as fracture height, fracture length, rock Young's modulus, rock Poisson's ratio, rock fracture toughness, fluid displacement, etc.), 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 backflushing is 5000 cubic meters. Therefore, 1000 cubic meters is used as the preset volume threshold, ensuring that at the end of the energy release process, the volume of high-pressure fluid retained in the formation fracture is not less than 1000 cubic meters. For example, to ensure that the frictional resistance loss of fluid flowing in the fracture has less than 5% impact on the energy storage cycle efficiency, a hydraulic fracturing model can be used to calculate, using known information (such as fracture height, fracture length, rock Young's modulus, rock Poisson's ratio, rock fracture toughness, fluid displacement, etc.), that the minimum fracture width cannot be less than 0.5 cm (i.e., a preset width threshold). The corresponding minimum volume of high-pressure fluid within the fracture cannot be less than 1500 cubic meters, while the volume of high-pressure fluid used for backflushing is 4500 cubic meters. Therefore, 1500 cubic meters is used as the preset volume threshold, ensuring that the volume of high-pressure fluid retained in the formation fracture at the end of the energy release process is no less than 1500 cubic meters. Normally, these two thresholds can be set according to the desired energy storage cycle efficiency. In special cases (such as emergency power generation or emergency energy storage), the thresholds can be adjusted based on the actual situation.

[0097] In other embodiments, although a preset threshold is set to ensure that the multiple target wells formed by fracturing are not interconnected, or that the multiple target wells after modification are not interconnected, in actual applications, if the formation fractures of two target wells are very close together, and when fluid is injected into both target wells simultaneously for energy storage, the deformation of adjacent formation fractures will cause compression and interference, or even rupture, causing the two target wells to connect and form two connected energy storage and release units. This can easily lead to flow loss.

[0098] Therefore, during energy storage, real-time monitoring is conducted on adjacent formation fractures between adjacent target wellbores (e.g., formation fractures at the same height in two adjacent target wellbores with a spacing less than a preset distance, or formation fractures at different heights in two adjacent target wellbores with a height difference less than a preset height difference threshold). If a connection occurs, high-pressure fluid is simultaneously injected into all connected wellbores. During energy release, the high-pressure fluid is simultaneously backflushed through all connected wellbores, and the kinetic energy of the high-pressure fluid and the acquired thermal energy are converted into electrical energy.

[0099] In other embodiments, the target wellbore is an abandoned oil and gas well. Before injecting high-pressure fluid into the target wellbore to create the target artificial formation fracture, it is necessary to isolate any existing perforations or hydraulic fracturing fractures. Isolation can be achieved through methods such as cement sealing or using packers.

[0100] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, characterized in that... include: A geothermal storage layer containing geothermal resources but without oil and gas was identified; High-pressure fluid is injected into the 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 existing target original formation fracture in the target wellbore in the energy storage geothermal layer that is in a closed state; wherein the target wellbore is not connected to any other wellbore through formation fractures; Injecting room temperature high-pressure fluid into the target wellbore increases the width of the target artificial formation fracture or the target original formation fracture in the target wellbore while keeping the expansion radius unchanged or constant. This causes the formation rock to undergo elastic deformation and store energy. Furthermore, the fluid in the target artificial formation fracture or the target original formation fracture exchanges heat with the energy storage geothermal layer, causing the fluid temperature to rise. 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 discharge pipe is closed to allow the fluid in the formation fracture to continuously exchange heat with the energy storage geothermal layer, causing the fluid temperature to continuously rise for heat storage. The high-temperature and high-pressure fluid discharged during the closure of the target artificial stratum fracture or the target original stratum fracture drives the preset hydropower generation equipment and geothermal power generation equipment to generate electricity, thereby converting the acquired geothermal energy and the elastic deformation energy of the stratum rock into electrical energy for energy release. The steps of using the high-temperature, high-pressure fluid discharged during the closure of the target artificial stratum fracture or the target original stratum fracture to drive a pre-set hydroelectric power generation device and a geothermal power generation device to generate electricity, thereby converting the acquired geothermal energy and the elastic deformation energy of the stratum rock into electrical energy for energy release, specifically include: When there is a demand for power generation, the fluid discharged during the closure of the target formation fracture is used to drive a hydroelectric power generation device 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 duration of the target wellbore is greater than or equal to the pre-calculated target closed heat storage duration, the geothermal power generation equipment is used to generate electricity by fluid drive; And / or, when there is a heating demand, determine whether the fluid temperature meets the heating demand, and if the fluid temperature meets the heating demand, use the fluid for heating.

2. The method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 1, is characterized in that... It also includes the following steps: During 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, the actual three-dimensional size of the target artificial formation fracture in the target wellbore is monitored in real time. Determine whether the actual three-dimensional size reaches a pre-configured preset threshold. When the actual three-dimensional size reaches the preset threshold in real-time monitoring, 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. The preset threshold is the minimum value between the preset energy storage three-dimensional size and the preset safety three-dimensional size.

3. The method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 2, is characterized in that... The actual three-dimensional dimensions include the actual expansion radius and / or the actual expansion height. The step of configuring the preset threshold specifically includes the following steps: Obtain the distance L0 between the target wellbore and its nearest neighbor wellbore, and the actual propagation radius R of the formation fracture in the nearest neighbor wellbore. 邻 Or actual extended height H 邻 ; Based on the aforementioned spacing L0, and the actual propagation radius R of the formation fracture in the nearest adjacent wellbore. 邻 Determine the safe propagation radius R0 of the target artificial formation fracture in the target wellbore, wherein the safe propagation 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 safe expansion radius R0; if the target expansion radius R0' ≥ the safe expansion radius R0, use the safe expansion radius R0 as the set threshold of the target artificial formation fracture in the target wellbore; if the target expansion radius R0' < the safe expansion radius R0, use the target expansion radius R0' as the set threshold of 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 extension height H of the nearest formation fracture on its 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 propagation height H0 of the target artificial formation fracture in the target wellbore, wherein the safe propagation 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' is greater than or equal to the safe expansion height H0, use the safe expansion height H0 as the set threshold for the target formation fracture in the target wellbore; if the target expansion height H0' is less than the safe expansion height H0, use the target expansion height H0 as the set threshold for the target formation fracture in the target wellbore.

4. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 3, is characterized in that... If the safe expansion radius R0 is used as the set threshold for the target formation fracture in the target wellbore, the specific 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 include: The target propagation height of the target formation fracture is recalculated based on the preset target energy storage and the safe propagation radius R0. The construction parameters are adjusted based on 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 safe expansion height H0 is used as the set threshold for the target formation fracture in the target wellbore, the specific 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 include: The target expansion radius of the target formation fracture is recalculated based on the preset target energy storage and the safe expansion height H0. The construction parameters are adjusted 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.

5. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 1, characterized in that... Also includes: If there are multiple target wells, and there is a demand for power generation, determine whether the outlet temperature of the target wells meets the requirements of the geothermal power generation equipment. If no target well has an outlet temperature that meets the requirements of the geothermal power generation equipment, the reverse-flow fluid of a target well is randomly selected for power generation; and when the outlet temperature of any target well meets the requirements of the geothermal power generation equipment, the reverse-flow fluid of that target well is used for collaborative power generation. The methods for determining whether the wellbore outlet temperature meets the requirements of geothermal power generation equipment include: The relationship between the wellbore closure heat storage time and the wellbore outlet temperature was simulated using a fluid-structure-thermal coupling numerical model. Based on the wellbore outlet temperature required for power generation and / or heating, the required closed heat storage time is calculated using a fluid-structure-thermal coupling numerical model. If the closed heat storage period is reached, the well outlet temperature will meet the requirements of the geothermal power generation equipment.

6. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 1, characterized in that... It also includes the following steps: Before the reverse flow of fluid, the minimum volume threshold of high-temperature, high-pressure fluid to be retained in the target artificial formation fracture or the target original formation fracture at the end of energy release is calculated based on a preset energy storage cycle efficiency and hydraulic fracturing model; accordingly, Based on the minimum volume threshold, the reverse discharge process of 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 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 is greater than or equal to the preset width threshold during the energy storage and energy release cycle.

7. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 3, characterized in that... It also includes the following steps: Determine whether the distance between the target wellbore and its nearest adjacent wellbore 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 on its nearest adjacent wellbore is less than or equal to a preset height difference threshold. If so, during the energy storage process, the formation fractures between adjacent wells are monitored in real time to see if they become connected. If they do, when storing energy using the connected target well and its adjacent wells, high-pressure fluid is injected into all connected wells at the same time. When releasing energy, the high-pressure fluid is simultaneously discharged through all connected wells, and the kinetic energy of the high-pressure fluid and the acquired thermal energy are converted into electrical energy.

8. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in 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 existing target original formation fracture in the energy storage geothermal layer that is in a closed state, the specific steps include: identifying at least one existing original formation fracture in the energy storage geothermal layer, 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 from it. The step of selecting at least one target original formation fracture specifically includes: The original formation fractures include original artificial fractures in a closed state. The step of screening out at least one target formation fracture specifically includes the following steps: The first monitoring data of the original artificial cracks in the energy storage geothermal layer are obtained using the preset monitoring equipment; By combining the first monitoring data and the first construction parameters of the original artificial crack obtained in advance using the crack propagation numerical model, the original length and original height of the original artificial crack in the energy storage geothermal layer are calculated. Determine whether the original length and original height of the original artificial fracture reach the preset target length threshold and target height threshold, respectively. If so, mark the original artificial fracture as the target original formation fracture; and / or, The original formation fractures include natural fractures in a closed state. The step of screening out at least one target original formation fracture specifically includes the following steps: The second monitoring data of the natural fractures in the energy storage geothermal layer is obtained by acquiring the second monitoring data through a preset monitoring device, and the distribution of the at least one natural fracture is obtained by inversion based on the second monitoring data; the second monitoring data includes: well logging data and seismic data; The three-dimensional stress distribution of the energy storage geothermal layer was obtained through structural stress analysis. Utilizing three-dimensional cracks A stress coupling model is used to simulate the opening of the at least one natural fracture during the injection of room temperature high pressure fluid into the at least one natural fracture, and to calculate the stored energy when the width of the at least one natural fracture expands to the target width under the action of the room temperature high pressure fluid. Determine whether the energy storage has reached the preset target energy storage. If so, mark the at least one natural fracture as the target original formation fracture.

9. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 8, characterized in that... Determine whether the number of the target original stratum fractures screened out reaches a preset number threshold; if not, perform secondary modification on the original artificial fractures whose original length and original height do not reach the preset target length threshold and target height threshold, and / or modify the natural fractures whose original length and original height do not reach the preset target length threshold and target height threshold; The step of secondary modification of the original artificial crack specifically includes: According to the preset third construction parameters, fluid is injected into the original formation fracture through the wellbore, so that the fracture pressure in the original formation fracture is greater than the fracture propagation pressure, thereby causing the original formation fracture to propagate along its original height and original length. Third monitoring data on the propagation process of the original formation fractures were obtained through monitoring equipment; Based on the third construction parameters and the third monitoring data, and combined with the crack propagation numerical model, the latest length and latest height of the original stratum crack after extending along the original height and original length are calculated; Determine whether the latest length and the latest height have reached the preset target length threshold and target height threshold. If so, stop injecting the high-pressure fluid and obtain the target original formation fracture. The step of modifying the natural cracks specifically includes: According to the preset fourth construction parameters, fluid is injected into the natural fracture through the wellbore, so that the fracture pressure in the natural fracture is greater than the fracture propagation pressure, thereby causing the natural fracture to propagate along the original height and original length. The monitoring equipment is used to obtain fourth monitoring data during the propagation process of the natural crack; Based on the fourth construction parameters and the fourth monitoring data, the latest length and height of the natural crack after extension are calculated using a crack propagation numerical model. Determine whether the latest length and height of the natural fracture have reached the preset target length threshold and target height threshold. If so, stop injecting fluid and obtain the target original formation fracture.

10. A method for storing and releasing geothermal energy and obtaining geothermal energy through formation fractures in a non-connected wellbore, as described in claim 9, characterized in that: 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 natural fracture is monitored in real time to determine whether the actual three-dimensional size reaches a preset threshold. When the actual three-dimensional size reaches the preset 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 modified artificial formation fracture or the natural formation fracture.

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