Multi-grade geothermal exploitation system

Abstract

The multi-grade geothermal exploitation system comprises at least one single-well recharge well, the bottom end of the single-well recharge well is located on a hydrothermal geothermal layer, and a single-well screen pipe is arranged at the bottom end of the single-well recharge well; the geothermal production well comprises a first well section and a second well section, the bottom ends of the first well section and the second well section are communicated, an opening, located on the ground, of the first well section is a first port, and an opening, located on the ground, of the second well section is a second port; the first well section and the second well section are at least partially located in the rock heat type geothermal layer; a production well screen pipe is arranged at the position, opposite to the single-well screen pipe, of the first well section, and a first one-way valve is arranged at the position, between the first port and the production well screen pipe, of the first well section; the first port forms a monitoring and peak regulation end; and the second port forms a terrestrial heat output end. By adopting the echelon heating mode, effective development of hydrothermal type geothermal resources and rock heat type geothermal resources can be considered, fracturing construction is not needed in the construction process of the multi-grade geothermal exploitation system, and the limitation of a single-grade geothermal exploitation technology is technically filled up.

Description

Technical Field

[0001] This invention relates to the field of geothermal extraction technology, and in particular to a multi-grade geothermal extraction system. Background Technology

[0002] Geothermal energy, as a renewable energy source, is widely distributed across many regions of the Earth, boasting advantages such as cleanliness, environmental friendliness, stability, and reliability. Drilling technology remains the sole means of geothermal resource exploration and development. Geothermal wells are categorized into single-well systems and multi-well systems based on the number of wells, and into open-loop and closed-loop systems based on whether the heat exchange fluid enters the formation. Currently, the more mature and economically viable extraction methods are multi-well open-loop and multi-well closed-loop systems. Multi-well open-loop systems primarily extract hydrothermal geothermal resources, offering high heat extraction efficiency but facing challenges such as difficult reinjection and low extracted heat source temperatures. Multi-well closed-loop systems primarily extract cratonic geothermal resources, with the advantage of "extracting heat without extracting water," but also exhibiting low heat extraction efficiency. Both methods involve energy waste and fail to achieve optimal allocation of geothermal energy resources. In addition, an existing hybrid enhanced geothermal system can extract water from low-temperature hydrothermal reservoirs using multiple sets of single wells and various fracturing technologies. This water is then injected into high-temperature dry-hot reservoirs through injection wells for heating, and finally extracted through production wells. However, none of these methods can meet the requirement of a single geothermal development system simultaneously exploiting both hydrothermal and kerogen geothermal resources within a single cycle.

[0003] Therefore, based on years of experience and practice in related industries, the inventor proposes a multi-grade geothermal extraction system to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-grade geothermal extraction system to solve the problem that a single geothermal development system cannot simultaneously extract hydrothermal and kerogen geothermal resources within one cycle. This invention, by adopting a tiered heating method, can effectively develop both hydrothermal and kerogen geothermal resources. The multi-grade geothermal extraction system does not require fracturing during construction, thus technically filling the limitations of single-grade geothermal extraction technology.

[0005] The objective of this invention is achieved by providing a multi-grade geothermal extraction system, comprising:

[0006] At least one single-well reinjection well is provided for reinjecting low-temperature water; the bottom end of the single-well reinjection well is located in a hydrothermal geothermal layer, and a single-well screen pipe is provided at the bottom end of the single-well reinjection well.

[0007] A geothermal production well includes a first well section and a second well section connected at their bottom ends. The opening of the first well section on the ground is called the first port, and the opening of the second well section on the ground is called the second port. The first well section and the second well section are at least partially located within a crater geothermal layer. A production well screen is installed on the first well section at a position opposite to the single-well screen. A first one-way valve is installed on the first well section between the first port and the production well screen, allowing fluid to flow from top to bottom. The first port constitutes a monitoring and peak-shaving end. The second port constitutes a geothermal output end.

[0008] Low-temperature water injected from the single-well recharge well is reinjected into the hydrothermal geothermal layer through the single-well screen pipe. After being heated by the geothermal primary heating of the hydrothermal geothermal layer, the low-temperature water becomes medium-temperature water. The medium-temperature water enters the first well section through the production well screen pipe and is heated by the geothermal secondary heating of the rock-thermal geothermal layer to form high-temperature water or steam. The high-temperature water or steam is output through the second port.

[0009] In a preferred embodiment of the present invention, the multi-grade geothermal extraction system further includes a water collection device for collecting low-temperature water, the outlet of which is connected to the single-well reinjection well and the first port of the first well section via a first water injection pump and a second water injection pump.

[0010] In a preferred embodiment of the present invention, the multi-grade geothermal extraction system further includes a geothermal recovery unit, which includes a heat exchange device connected to the heat demand end. The inlet of the heat exchange device is connected to the second port of the second well section. The heat exchange device is connected to the water collection device to output low-temperature water after heat exchange.

[0011] In a preferred embodiment of the present invention, the second port is connected to the heat exchange device via a cyclone separator and a filter.

[0012] In a preferred embodiment of the present invention, a third valve is provided between the heat exchange device and the water collection device, a first valve is provided between the water collection device and the first water injection pump, and a second valve is provided between the water collection device and the second water injection pump.

[0013] In a preferred embodiment of the present invention, the single-well recharge well adopts a single-layer casing unidirectional circulation structure.

[0014] In a preferred embodiment of the present invention, the geothermal extraction well is a U-shaped well, with the two ends of the U-shaped well on the ground forming the first port and the second port, respectively. The first port and the bottom end of the U-shaped well form the first well section, and the second port and the bottom end of the U-shaped well form the second well section.

[0015] In a preferred embodiment of the present invention, there are multiple single-well reinjection wells, the bottom of each single-well reinjection well is located in multiple hydrothermal geothermal layers, and the bottom of each single-well reinjection well is provided with a single-well screen pipe. The first well section is located in the hydrothermal geothermal layer and the production well screen pipe is provided at the position opposite to each single-well screen pipe.

[0016] In a preferred embodiment of the present invention, the geothermal extraction well is a V-shaped well, with the two ends of the V-shaped well on the ground forming the first port and the second port, respectively. The first port and the bottom of the V-shaped well form the first well section, and the second port and the bottom of the V-shaped well form the second well section.

[0017] In a preferred embodiment of the present invention, the geothermal production well adopts a fishtail-shaped well structure. The first well section is bent away from the second well section and its bottom end is located in the crater geothermal layer. The production well screen is set in the first well section within the hydrothermal geothermal layer and opposite to the single well screen. The second well section is bent away from the first well section and its bottom end is located in the crater geothermal layer. The bottom ends of the first well section and the bottom ends of the second well section are connected by a human-shaped connecting pipe.

[0018] In a preferred embodiment of the present invention, the top end of the human-shaped connecting pipe is connected to an upwardly extending vertical well shaft, a second one-way valve that allows fluid to flow from top to bottom is provided on the vertical well shaft, and the top end of the vertical well shaft is connected to a water collection device.

[0019] As described above, the multi-grade geothermal extraction system of the present invention has the following beneficial effects:

[0020] This invention combines the advantages of multi-well open-loop systems and multi-well closed-loop systems, while also taking into account the development of various types of underground geothermal resources. Multiple layers and types of geothermal resources can be extracted within one cycle, solving the problems of same-layer reinjection, peak regulation difficulties, and waste of geothermal resources. Moreover, the multi-grade geothermal extraction system does not require fracturing construction during construction.

[0021] This invention, by employing a tiered heating method, can effectively develop both medium- and low-temperature hydrothermal geothermal resources and high-temperature kerogen geothermal resources, thereby improving the economic efficiency of the entire geothermal extraction process. Simultaneously, the peak-shaving function of the multi-grade geothermal extraction system increases the system's operational adaptability.

[0022] Compared with existing technologies, this invention realizes multi-level and high-efficiency development of geothermal resources, and technically fills the limitations of single-grade geothermal extraction technology. This invention enables the continuous, stable and environmentally friendly utilization of low, medium and high temperature geothermal resources, which helps to promote the progress of renewable energy technology and has important social and economic effects on promoting the sustainable and healthy development of the geothermal energy industry. Attached Figure Description

[0023] The accompanying drawings are intended only to illustrate and explain the present invention and do not limit the scope of the invention.

[0024] in:

[0025] Figure 1 This is a schematic diagram of Embodiment 1 of the multi-grade geothermal extraction system of the present invention.

[0026] Figure 2 This is a schematic diagram of Embodiment 3 of the multi-grade geothermal extraction system of the present invention.

[0027] In the picture:

[0028] 1. Single-well recharge well;

[0029] 2. Hydrothermal geothermal layer;

[0030] 3. Second water injection pump;

[0031] 4. First check valve;

[0032] 5. Rock-thermal geothermal layer;

[0033] 6. Third valve;

[0034] 7. First well section; 71. First port;

[0035] 8. Second well section; 81. Second port;

[0036] 9. Single-well screen pipe;

[0037] 10. Well screen pipe;

[0038] 11. First water injection pump;

[0039] 12. First valve;

[0040] 13. Water collection device;

[0041] 14. Heat exchange device;

[0042] 15. Filter;

[0043] 16. Hydrocyclone sand separator;

[0044] 17. Second valve;

[0045] 18. Human-shaped connecting pipe;

[0046] 19. Vertical shaft;

[0047] 20. Second check valve. Detailed Implementation

[0048] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0049] The specific embodiments of the present invention described herein are for illustrative purposes only and should not be construed as limiting the invention in any way. Under the teachings of this invention, those skilled in the art can conceive of any possible modifications based on the invention, all of which should be considered within the scope of the invention. It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there may be an intervening element. The terms "mounted," "connected," and "linked" should be interpreted broadly; for example, they can refer to mechanical or electrical connections, or internal communication between two elements, and can be direct or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible embodiments.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0051] like Figure 1 , Figure 2 As shown, the present invention provides a multi-grade geothermal extraction system, comprising:

[0052] At least one single-well reinjection well 1 is used for reinjecting low-temperature water. The bottom end of the single-well reinjection well 1 is located in the hydrothermal geothermal layer 2, and a single-well screen pipe 9 is installed at the bottom end of the single-well reinjection well 1. The single-well reinjection well 1 adopts open-loop extraction technology. The single-well reinjection well 1 reinjects low-temperature water through the single-well screen pipe 9, without the need to combine it with fracturing technology to extract low-grade geothermal water from the hydrothermal geothermal layer 2. After the low-temperature water is injected into the hydrothermal geothermal layer 2 (low-grade heat source water layer), it will be heated once and become medium-temperature water.

[0053] The geothermal extraction well includes a first well section 7 and a second well section 8. The opening of the first well section 7 on the ground is the first port 71, and the opening of the second well section 8 on the ground is the second port 81. The bottom ends of the first well section 7 and the second well section 8 are connected. The first well section 7 and the second well section 8 are at least partially located within the crater geothermal layer 5. Inside the geothermal extraction well, the medium-temperature water from the primary heating process will be reheated in the crater geothermal layer 5 to become high-temperature water or steam. This design utilizes the higher-temperature geothermal resources at a deeper depth to further heat the preheated water.

[0054] On the first well section 7, a production well screen pipe 10 is installed at a position opposite to the single well screen pipe 9. On the first well section 7, a first one-way valve 4 is installed between the first port 71 and the production well screen pipe 10 to allow fluid to flow from top to bottom. The first one-way valve 4 can ensure the safe operation of the system. The geothermal production well belongs to the closed-loop mining technology. Combined with the single well reinjection well 1 of the open-loop mining technology, they can jointly realize the mining of multi-level and multi-grade geothermal energy.

[0055] The first port 71 constitutes the monitoring and peak-shaving terminal. Its design takes into account monitoring and peak-shaving needs during operation, ensuring the stability of the entire operation process through a monitoring system (existing technology) at different stages of heating. The first port 71 can monitor pressure and water volume. When peak-shaving is needed, water can be added through the first port 71 to ensure the operating discharge rate. After closing the second port 81, the first port 71 can be used for reverse circulation to flush out blockages in the hydrothermal geothermal layer 2, ensuring permeability. The peak-shaving function of the first port 71 increases the adaptability of the system operation.

[0056] The second port 81 constitutes the geothermal output end; the heated high-quality heat source (high-temperature water or steam) is output through the second port 81 and enters the heat demand end.

[0057] Low-temperature water (temperature range 15-30℃, with 20℃ being the optimal reinjection temperature to maintain the stability and recovery of geothermal resources in the hydrothermal geothermal layer 2) injected from the single-well reinjection well 1 is reinjected into the hydrothermal geothermal layer 2 through the single-well screen pipe 9. After being heated by the geothermal primary heat source of the hydrothermal geothermal layer 2, the low-temperature water becomes medium-temperature water (temperature range 40-70℃). The medium-temperature water enters the first well section 7 through the production well screen pipe 10 and flows downward under the shut-off action of the first one-way valve 4. After being heated by the geothermal secondary heat source of the rock-thermal geothermal layer 5, it becomes high-temperature water or steam (temperature range 80-110℃). The high-temperature water or steam is output through the second port 81.

[0058] The hydrothermal geothermal layer 2 supplies medium and low-grade geothermal energy (medium-grade geothermal temperature range 60-90℃, low-grade geothermal temperature range 40-60℃). The temperature of the hydrothermal geothermal layer 2 can reach 90℃. Low-temperature water injected from the single-well reinjection well 1 is reinjected into the hydrothermal geothermal layer 2 through the single-well screen pipe 9. The low-temperature water is heated by the geothermal energy of the hydrothermal geothermal layer 2 to form medium-temperature water of 40-70℃. The crater geothermal layer 5 supplies high-grade geothermal energy (temperature range 120-200℃). The temperature of the crater geothermal layer 5 can reach 200℃. The medium-temperature water enters the first well section 7 through the production well screen pipe 10 and flows downward. When the medium-temperature water flows through the crater geothermal layer 5, it is heated a second time to form high-temperature water or steam of 80-110℃. This invention can extract geothermal energy of multiple grades in one cycle.

[0059] The hydrothermal geothermal layer 2 is a layer with high permeability or a layer with natural faults, in order to improve heat transfer efficiency.

[0060] This invention addresses the shortcomings of low heat extraction efficiency and single heat extraction layer in existing technologies. It improves the heat extraction efficiency of geothermal resources by using the tiered heating function of a multi-grade geothermal extraction system. This ensures efficient geothermal development while meeting the needs of geothermal extraction at different layers. Through primary heating of hydrothermal geothermal resources and secondary heating of kerogen geothermal resources, the comprehensive development of geothermal resources is optimized.

[0061] This invention combines the advantages of multi-well open-loop systems and multi-well closed-loop systems, while also taking into account the development of various types of underground geothermal resources. Multiple layers and types of geothermal resources can be extracted within one cycle, solving the problems of same-layer reinjection, peak regulation difficulties, and waste of geothermal resources. Moreover, the multi-grade geothermal extraction system does not require fracturing construction during construction.

[0062] This invention, by employing a tiered heating method, can effectively develop both medium- and low-temperature hydrothermal geothermal resources and high-temperature kerogen geothermal resources, thereby improving the economic efficiency of the entire geothermal extraction process. Simultaneously, the peak-shaving function of the multi-grade geothermal extraction system increases the system's operational adaptability.

[0063] Compared with existing technologies, this invention realizes multi-level and high-efficiency development of geothermal resources, and technically fills the limitations of single-grade geothermal extraction technology. This invention enables the continuous, stable and environmentally friendly utilization of low, medium and high temperature geothermal resources, which helps to promote the progress of renewable energy technology and has important social and economic effects on promoting the sustainable and healthy development of the geothermal energy industry.

[0064] Furthermore, such as Figure 1 , Figure 2As shown, the multi-grade geothermal extraction system also includes a water collection device 13 for collecting low-temperature water. The outlet of the water collection device 13 is connected to the first port 71 of the single-well reinjection well 1 and the first well section 7 through the first water injection pump 11 and the second water injection pump 3, respectively.

[0065] Furthermore, such as Figure 1 , Figure 2 As shown, the multi-grade geothermal extraction system also includes a geothermal recovery unit, which includes a heat exchange device 14 connected to the heat demand side. The inlet of the heat exchange device 14 is connected to the second port 81 of the second well section 8. The heat exchange device 14 is connected to the water collection device 13 to output the heat-exchanged low-temperature water to it.

[0066] Furthermore, such as Figure 1 , Figure 2 As shown, the second port 81 is connected to the heat exchange device 14 via a hydrocyclone desander 16 and a filter 15. High-temperature water or steam is output from the second port 81 of the second well section 8, filtered by the hydrocyclone desander 16 and the filter 15, and then heat is extracted by the heat exchange device 14, which supplies the heat to the heat demand side. The low-temperature water after heat extraction is then transported to the water collection device 13 for recycling.

[0067] Furthermore, such as Figure 1 , Figure 2 As shown, a third valve 6 is installed between the heat exchange device 14 and the water collection device 13, a first valve 12 is installed between the water collection device 13 and the first water injection pump 11, and a second valve 17 is installed between the water collection device 13 and the second water injection pump 3. The aforementioned devices or processes are isolated from each other by installing these valves.

[0068] Furthermore, such as Figure 1 , Figure 2 As shown, the single-well reinjection well 1 adopts a single-layer casing unidirectional circulation structure. The single-well reinjection well 1 does not require formation fracturing or reverse circulation extraction of the extracted water. The single-well screen pipe 9 and the production well screen pipe 10 are set in the high-permeability water layer, which facilitates the geothermal heating of the low-temperature water by the hydrothermal geothermal layer 2 to form medium-temperature water, and allows the medium-temperature water to flow smoothly to the production well screen pipe 10, realizing the extraction of geothermal energy by the geothermal production well.

[0069] Geothermal extraction wells can adopt various structural forms. Examples are as follows:

[0070] Example 1:

[0071] like Figure 1 As shown, the geothermal extraction well adopts a U-shaped well. The two ends of the U-shaped well on the ground form the first port 71 and the second port 81, respectively. The first port 71 and the bottom end of the U-shaped well form the first well section 7, and the second port 81 and the bottom end of the U-shaped well form the second well section 8.

[0072] The low-temperature water in the water collection device 13 is injected into the single-well reinjection well 1 through the first injection pump 11, and then reinjected into the hydrothermal geothermal layer 2 through the single-well screen pipe 9. The function of the hydrothermal geothermal layer 2 is to realize the primary heating process of the injected low-temperature water. In this embodiment, it is recommended to select a high-permeability layer or a layer with natural faults for the hydrothermal geothermal layer 2 to improve heat transfer efficiency.

[0073] Through a single heating process, the resulting medium-temperature water enters the first section of the U-shaped well through the production screen pipe 10. Due to the action of the first one-way valve 4, the medium-temperature water flows to the location within the crater geothermal layer 5 (the horizontal pipe section of the U-shaped well). Through secondary geothermal heating in the crater geothermal layer 5, high-temperature water or steam is output at the second port 81 of the U-shaped well. Heating within the U-shaped well utilizes the higher thermal energy of the deeper strata to further increase the water temperature.

[0074] High-temperature water or steam is output from the second port 81 of the U-shaped well, processed by the cyclone desander 16 and filter 15, and then heat is extracted by the heat exchanger 14 to supply the heat demand side. The low-temperature water after heat extraction is then transported to the water collection device 13 for recycling.

[0075] Furthermore, there are multiple single-well reinjection wells 1, and the bottom of each single-well reinjection well 1 is located in multiple hydrothermal geothermal layers 2. A single-well screen pipe 9 is installed at the bottom of each single-well reinjection well 1. The first well section 7 is located in the hydrothermal geothermal layer 2 and a production well screen pipe 10 is installed at a position opposite to each single-well screen pipe 9.

[0076] That is, if there are multiple hydrothermal geothermal layers 2 available for exploitation in the strata, and the strata have good permeability, a single-well reinjection well 1 can be drilled for each hydrothermal geothermal layer 2, and a production well screen pipe 10 can be set in the same layer of the first well section 7 of the U-shaped well, so as to achieve comprehensive utilization of multi-layer geothermal resources.

[0077] Numerical simulations show that, under the same inlet temperature, the outlet temperature of the second port 81 of this system will increase by more than 20%. After 20 years of operation, the outlet temperature will decrease by only 3°C, while the temperature of a conventional U-shaped geothermal well system will decrease by more than 10°C.

[0078] Example 2:

[0079] The geothermal extraction well adopts a V-shaped well. The two ends of the V-shaped well on the ground form the first port 71 and the second port 81, respectively. The first port 71 and the bottom of the V-shaped well form the first well section 7, and the second port 81 and the bottom of the V-shaped well form the second well section 8.

[0080] The geothermal extraction process in this embodiment is the same as the U-shaped well in Embodiment 1.

[0081] Example 3:

[0082] like Figure 2 As shown, the geothermal production well adopts a fishtail-shaped well structure. The first well section 7 is bent away from the second well section 8 and its bottom end is located in the crater geothermal layer 5. The production well screen pipe 10 is set in the first well section 7 within the hydrothermal geothermal layer 2 and is located opposite the single well screen pipe 9. The second well section 8 is bent away from the first well section 7 and its bottom end is located in the crater geothermal layer 5. The bottom end of the first well section 7 and the bottom end of the second well section 8 are connected by a human-shaped connecting pipe 18.

[0083] The top end of the man-shaped connecting pipe 18 is connected to an upwardly extending vertical shaft 19. A second one-way valve 20 is installed on the vertical shaft 19 to allow fluid to flow from top to bottom. The top end of the vertical shaft 19 is connected to a water collection device 13. The vertical shaft 19 serves as the process shaft for the man-shaped connecting pipe 18, and can be used for construction, cleaning, and other operations of the man-shaped connecting pipe 18.

[0084] The low-temperature water in the water collection device 13 is injected into the single-well reinjection well 1 through the first water injection pump 11, and then reinjected into the hydrothermal geothermal layer 2 through the single-well screen pipe 9. The hydrothermal geothermal layer 2 realizes the primary heating of the injected low-temperature water.

[0085] Through a heating process, the medium-temperature water obtained enters the first well section 7 through the well screen pipe 10. Due to the action of the first one-way valve 4, the medium-temperature water flows downward to the position of the first well section 7 located in the crater geothermal layer 5. The medium-temperature water is heated a second time in the crater geothermal layer 5 in the human-shaped connecting pipe 18, and high-temperature water or steam is output from the second port 81 of the second well section 8.

[0086] High-temperature water or steam is output from the second port 81, processed by the cyclone separator 16 and filter 15, and then heat is extracted by the heat exchanger 14 to supply the heat demand side. The low-temperature water after heat extraction is sent to the water collection device 13 for recycling.

[0087] During the construction of the multi-grade geothermal extraction system of this invention:

[0088] The first section 7 and the second section 8 of the single-well reinjection well 7 and geothermal production well are all buried underground pipes. Screen pipes (single-well screen pipe 9 and production well screen pipe 10) are installed in key parts to connect with the formation. Cementing is carried out using staged cementing technology, and cementing is only performed on the upper part to reduce costs while ensuring downhole safety. The upper part of the second section 8 is cemented with heat-insulating cement to improve heat extraction efficiency while ensuring downhole safety.

[0089] As described above, the multi-grade geothermal extraction system of the present invention has the following beneficial effects:

[0090] This invention combines the advantages of multi-well open-loop systems and multi-well closed-loop systems, while also taking into account the development of various types of underground geothermal resources. Multiple layers and types of geothermal resources can be extracted within one cycle, solving the problems of same-layer reinjection, peak regulation difficulties, and waste of geothermal resources. Moreover, the multi-grade geothermal extraction system does not require fracturing construction during construction.

[0091] This invention, by employing a tiered heating method, can effectively develop both medium- and low-temperature hydrothermal geothermal resources and high-temperature kerogen geothermal resources, thereby improving the economic efficiency of the entire geothermal extraction process. Simultaneously, the peak-shaving function of the multi-grade geothermal extraction system increases the system's operational adaptability.

[0092] Compared with existing technologies, this invention realizes multi-level and high-efficiency development of geothermal resources, and technically fills the limitations of single-grade geothermal extraction technology. This invention enables the continuous, stable and environmentally friendly utilization of low, medium and high temperature geothermal resources, which helps to promote the progress of renewable energy technology and has important social and economic effects on promoting the sustainable and healthy development of the geothermal energy industry.

[0093] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A multi-grade geothermal extraction system, characterized in that, include: At least one single-well recharge well (1) is used for recharge of low-temperature water; the bottom end of the single-well recharge well (1) is located in the hydrothermal geothermal layer (2), and a single-well screen pipe (9) is provided at the bottom end of the single-well recharge well (1); A geothermal extraction well includes a first well section (7) and a second well section (8) connected at the bottom. The opening of the first well section (7) on the ground is a first port (71), and the opening of the second well section (8) on the ground is a second port (81). The first well section (7) and the second well section (8) are at least partially located within a crater geothermal layer (5). An extraction well screen pipe (10) is installed on the first well section (7) at a position opposite to the single well screen pipe (9). A first one-way valve (4) is installed on the first well section (7) between the first port (71) and the extraction well screen pipe (10) to allow fluid to flow from top to bottom. The first port (71) constitutes a monitoring and peak-shaving end. The second port (81) constitutes a geothermal output end. Low-temperature water injected from the single-well recharge well (1) is recharged to the hydrothermal geothermal layer (2) through the single-well screen pipe (9). The low-temperature water is heated by the geothermal primary heating of the hydrothermal geothermal layer (2) to form medium-temperature water. The medium-temperature water enters the first well section (7) through the production well screen pipe (10) and is heated by the geothermal secondary heating of the rock-thermal geothermal layer (5) to form high-temperature water or steam. The high-temperature water or steam is output through the second port (81).

2. The multi-grade geothermal extraction system as described in claim 1, characterized in that, The multi-grade geothermal extraction system also includes a water collection device (13) for collecting low-temperature water. The outlet of the water collection device (13) is connected to the single-well reinjection well (1) and the first port (71) of the first well section (7) through a first water injection pump (11) and a second water injection pump (3).

3. The multi-grade geothermal extraction system as described in claim 2, characterized in that, The multi-grade geothermal extraction system also includes a geothermal recovery unit, which includes a heat exchange device (14) connected to the heat demand side. The inlet of the heat exchange device (14) is connected to the second port (81) of the second well section (8). The heat exchange device (14) is connected to the water collection device (13) to output the heat-exchanged low-temperature water to it.

4. The multi-grade geothermal extraction system as described in claim 3, characterized in that, The second port (81) is connected to the heat exchange device (14) through a cyclone separator (16) and a filter (15).

5. The multi-grade geothermal extraction system as described in claim 3, characterized in that, A third valve (6) is provided between the heat exchange device (14) and the water collection device (13), a first valve (12) is provided between the water collection device (13) and the first water injection pump (11), and a second valve (17) is provided between the water collection device (13) and the second water injection pump (3).

6. The multi-grade geothermal extraction system as described in any one of claims 1 to 5, characterized in that, The single-well recharge well (1) adopts a single-layer casing unidirectional circulation structure.

7. The multi-grade geothermal extraction system as described in claim 6, characterized in that, The geothermal extraction well is a U-shaped well. The two ends of the U-shaped well on the ground form the first port (71) and the second port (81), respectively. The first port (71) and the bottom end of the U-shaped well form the first well section (7), and the second port (81) and the bottom end of the U-shaped well form the second well section (8).

8. The multi-grade geothermal extraction system as described in claim 7, characterized in that, The number of single-well reinjection wells (1) is multiple, and the bottom end of each single-well reinjection well (1) is located in multiple hydrothermal geothermal layers (2). The bottom end of each single-well reinjection well (1) is provided with a single-well screen pipe (9). The first well section (7) is located in the hydrothermal geothermal layer (2) and the production well screen pipe (10) is provided at the position opposite to each single-well screen pipe (9).

9. The multi-grade geothermal extraction system as described in claim 6, characterized in that, The geothermal extraction well is a V-shaped well. The two ends of the V-shaped well on the ground form the first port (71) and the second port (81), respectively. The first port (71) and the bottom of the V-shaped well form the first well section (7), and the second port (81) and the bottom of the V-shaped well form the second well section (8).

10. The multi-grade geothermal extraction system as described in claim 6, characterized in that, The geothermal extraction well adopts a fishtail-shaped well structure. The first well section (7) is bent away from the second well section (8) and its bottom end is located in the rock-thermal geothermal layer (5). The first well section (7) is located in the hydrothermal geothermal layer (2) and the extraction well screen pipe (10) is set at a position opposite to the single well screen pipe (9). The second well section (8) is bent away from the first well section (7) and its bottom end is located in the rock-thermal geothermal layer (5). The bottom end of the first well section (7) and the bottom end of the second well section (8) are connected by a human-shaped connecting pipe (18).

11. The multi-grade geothermal extraction system as described in claim 10, characterized in that, The top end of the human-shaped connecting pipe (18) is connected to an upwardly extending straight well shaft (19), and a second one-way valve (20) is provided on the straight well shaft (19) to allow fluid to flow from top to bottom. The top end of the straight well shaft (19) is connected to a water collection device (13).

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