In-situ power generation method and system for accompanying terrestrial heat of exhausted shale reservoir

Abstract

The invention discloses an exhausted shale reservoir associated terrestrial heat in-situ power generation method and system, and belongs to the technical field of geothermal energy development and utilization. The method comprises the following steps: (1) selecting two production wells in a deep high-temperature shale reservoir in a depletion stage; (2) the fractured casing pipes of the horizontal sections of the production wells are sealed, and the toe ends of the horizontal sections of the two production wells are communicated through sidetracking well sections; and (3) the heat-carrying working medium injected into the production well is heated by the shale reservoir, then heat energy of the heat-carrying working medium is converted into electric energy through a ground ORC power generation system, and the heat-carrying working medium subjected to energy conversion is re-injected into the underground high-temperature shale reservoir again for heat removal. According to the invention, the two exhausted production wells in the high-temperature shale reservoir are transformed to establish a closed circulation heat collection system, so that the well building cost of geothermal development can be effectively reduced, the extraction temperature of a heat-carrying working medium under high circulation flow is ensured, closed circulation heat collection and power generation are integrated, geothermal resources are locally converted into electric energy, and energy conservation and carbon reduction are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal energy development and utilization, and in particular relates to a shale reservoir associated geothermal in-situ power generation method and system based on the transformation of double-depleted production wells. Background Art

[0002] Closed-cycle heat extraction is a commonly used extraction technology for geothermal energy associated with oil and gas reservoirs. During the circulation process, the heat-carrying medium does not come into direct contact with the reservoir rock, which can effectively avoid problems such as scaling of the reservoir and wellbore, and the system is highly controllable. Existing closed-cycle heat extraction systems include vertical well / horizontal well coaxial closed systems and vertical well side-drilling U-shaped well closed systems, and the drilling and construction costs are high. Moreover, the use of the above-mentioned closed-cycle heat extraction system is limited by factors such as the heat storage temperature, the reservoir-wellbore thermal conductivity, and the heat exchange area. The wellhead temperature of the extracted medium is low, and the economic feasibility is poor.

[0003] The shale reservoirs under development in my country are relatively deep, and the formation temperature can reach 80-120°C. Taking the shale gas reservoirs of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Sichuan Basin as an example, the average reservoir temperature exceeds 110°C, and the associated geothermal resources are as high as 1.09×10 13 GJ. As deep shale oil and gas reservoirs gradually become depleted, the established shale gas production wells are often directly abandoned and permanently sealed, resulting in a waste of resources. Of course, the geothermal energy in the depleted shale reservoirs cannot be utilized. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for in-situ power generation associated with depleted shale reservoirs, so as to achieve efficient development and power generation of geothermal resources in deep high-temperature shale reservoirs.

[0005] The technical solution adopted by the present invention is:

[0006] A method for in-situ power generation of geothermal energy associated with a depleted shale reservoir, comprising the following steps:

[0007] (1) Select two abandoned production wells in the depleted shale reservoir;

[0008] (2) The selected production wells are transformed to establish an underground closed-loop heat exchange system. After the transformation, one of the two production wells is an injection well and the other is a production well;

[0009] The horizontal sections of the two production wells have been sealed with fractured casings, and the toes of the horizontal sections of the two production wells are connected through the side drilling section;

[0010] (3) Connecting the surface ORC power generation system in series at the wellheads of the two production wells;

[0011] The heat-carrying fluid injected into the production well is heated by the shale reservoir, and then the thermal energy of the heat-carrying fluid is converted into electrical energy through the ground ORC power generation system. The heat-carrying fluid after energy conversion is re-injected into the underground for heat extraction.

[0012] Preferably, in step (1): the wellbore structures of the two selected abandoned production wells are complete, the production wells both include a vertical well section, an inclined section and a horizontal section, the length of the horizontal section of the production well is between 1000 and 3000 m, and the spacing between the horizontal sections of the two production wells is between 300 and 900 m.

[0013] Preferably, in step (2): the original oil pipe in the production well is pulled out, an expansion casing is lowered into the horizontal section of the production well, and high thermal conductivity cement is injected into the annulus between the expansion casing and the original fracturing casing in the horizontal section of the production well to seal the fracturing casing in the horizontal sections of the two production wells and perform cementing.

[0014] Preferably, a window is opened at the toe of the horizontal section of one of the production wells, and a directional drilling method is used to side-drill toward the toe of the horizontal section of another production well to form a side-drilled well section; the side-drilled well section includes a side-drilling inclination section and a side-drilling horizontal section, one end of the side-drilling horizontal section is connected to the toe of the horizontal section of one of the production wells through the side-drilling inclination section, and the other end of the side-drilling horizontal section is connected to the toe of the horizontal section of the other production well through a fiberglass casing; a heat exchange casing is lowered into the side-drilling inclination section and the side-drilling horizontal section, and high thermal conductivity cement is injected on the outside of the heat exchange casing for cementing, so as to form an underground closed circulation heat exchange system for heat-carrying fluid in the shale reservoir.

[0015] Preferably, in step (3): the ground ORC power generation system includes a turbine expander, a condenser, a working fluid pump, a generator and a ground insulation pipeline; the wellhead of the production well is connected to the turbine expander, the condenser, the working fluid pump and the wellhead of the injection well in sequence through the ground insulation pipeline, and the turbine expander is also directly driven and connected to the generator.

[0016] Preferably, in the underground heat production process, the liquid working medium is injected from the wellhead of the injection well at an injection rate of 30 to 50 kg / s, and flows through the vertical section, the deflection section, the horizontal section, the side drilling section of the injection well, and the horizontal section, the deflection section, and the vertical section of the production well, and reaches the wellhead of the production well; in the above-mentioned flow process, the liquid organic working medium is heated by the shale reservoir and becomes gaseous;

[0017] After the gaseous working fluid is produced from the wellhead of the production well, it enters the inlet of the turbine expander through the ground insulated pipeline, drives the turbine expander to rotate and do work, and then flows out from the outlet of the turbine expander. In this process, the thermal energy of the heat-carrying working fluid is converted into mechanical energy; at the same time, the turbine expander drives the generator to rotate and generate electricity, converting mechanical energy into electrical energy; the exhaust steam flowing out of the outlet of the turbine expander flows through the condenser and is condensed into liquid at a temperature of 25 to 40°C. The cooling form of the condenser is air cooling. The liquid working fluid is then pressurized by the working fluid pump and then reinjected into the underground through the injection well to extract heat.

[0018] Preferably, the shale reservoir is a deep high-temperature shale reservoir with a burial depth of 3000 to 5000 m, a thickness of 400 to 500 m, and a formation temperature of >120°C.

[0019] Preferably, the organic working fluid is pentafluoropropane.

[0020] A depleted shale reservoir associated geothermal in-situ power generation system transformed by the above method comprises an injection well and a production well, wherein the injection well and the production well both comprise a vertical section, a deflection section and a horizontal section connected in sequence, expansion casings are arranged in the horizontal section of the injection well and the horizontal section of the production well, and high thermal conductivity cement is injected on the outside of the expansion casings; the toe end of the horizontal section of the injection well and the toe end of the horizontal section of the production well are connected through a side-drilling well section, a heat exchange casing is arranged in the side-drilling well section, the side-drilling well section and the toe end of the horizontal section of the production well are butt-jointed by a glass fiber reinforced plastic casing, and high thermal conductivity cement is injected on the outside of the heat exchange casing; the expansion casing and the heat exchange casing are connected; a ground ORC power generation system is connected between the wellhead of the injection well and the wellhead of the production well; and an insulation layer is installed in the vertical section of the production well.

[0021] Preferably, the ground ORC power generation system includes a turbine expander, a condenser, a working fluid pump, a generator and a ground insulation pipeline; the wellhead of the production well is connected to the turbine expander, the condenser, the working fluid pump and the wellhead of the injection well in sequence through the ground insulation pipeline, and the turbine expander is also directly driven and connected to the generator.

[0022] The beneficial technical effects of the present invention are as follows:

[0023] The present invention establishes a closed-loop heat exchange system by transforming two exhausted production wells in the high-temperature shale reservoir, which can effectively reduce the well construction cost of geothermal development and has higher economic feasibility. The underground closed-loop heat exchange system formed by the side-drilling connection of two production wells with corresponding conditions has a horizontal heat exchange section of more than 2000m in the high-temperature shale reservoir, which effectively ensures the extraction temperature of the heat-carrying medium under high circulation flow and improves the installed capacity of a single well. Moreover, the heat energy collected by the present invention is used for in-situ power generation through the ground ORC power generation system at the wellhead, that is, the closed-loop heat collection and power generation are integrated, which can convert the high-temperature associated geothermal resources in the deep shale reservoir into electrical energy on-site, which can help oil and gas companies save energy and reduce carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process of the in-situ geothermal power generation method associated with depleted shale reservoirs of the present invention;

[0025] Figure 2 It is a schematic diagram of the structural principle of the depleted shale reservoir associated geothermal in-situ power generation system of the present invention.

[0026] Figure 3 This is a top view of the underground closed-cycle heat exchange system of the depleted shale reservoir associated geothermal in-situ power generation system of the present invention.

[0027] In the figure: 1. Ground insulation pipe; 2. Turbine expander; 3. Generator; 4. Condenser; 5. Working fluid pump; 6. Vertical section of injection well; 7. Inclination section of injection well; 8. Horizontal section of injection well; 9. Inclination section of side drilling; 10. Horizontal section of side drilling; 11. Horizontal section of production well; 12. Inclination section of production well; 13. Vertical section of production well; 14. Deep high-temperature shale reservoir; 15. Overlying strata; 16. Fracturing fractures in horizontal well; 17. High thermal conductivity cement; 18. Original production casing; 19. Expansion casing; 20. Sealing ring. DETAILED DESCRIPTION

[0028] The associated geothermal energy of depleted shale reservoirs is an important geothermal resource. The development and utilization of associated geothermal energy for power generation by utilizing existing abandoned production wells is of great significance for extending the exploitation life of shale reservoirs and improving the energy conservation and carbon reduction benefits of oil and gas companies. Based on the advantages of high temperature in deep shale reservoirs and long horizontal sections in depleted production wells, the present invention performs window side drilling transformation on double depleted production wells, and proposes a shale reservoir associated geothermal in-situ power generation method and system based on the transformation of double depleted production wells. The present invention can effectively improve the closed-cycle heat extraction wellhead temperature and medium- and low-temperature geothermal power generation efficiency, realize the efficient development and utilization of geothermal resources in deep shale reservoirs, improve the economic benefits of energy conservation and carbon reduction for oil and gas companies, and has good market application prospects.

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] like Figure 1 As shown, a method for in-situ power generation associated with depleted shale reservoir geothermal energy comprises the following steps:

[0032] (1) Select two abandoned production wells in the depleted shale reservoir.

[0033] The depleted shale reservoir is a deep high-temperature shale reservoir with a burial depth of 3000-5000m, a thickness of 400-500m, and a formation temperature of >120°C. The wellbore structures of the two abandoned production wells selected are complete, and the production wells include a vertical well section, a deflection section, and a horizontal section. The length of the horizontal section of the production well is between 1000 and 3000m, and the length of the horizontal sections of the two production wells is roughly the same, and the spacing between the horizontal sections of the two production wells is between 300 and 900m.

[0034] (2) The selected production wells are renovated to establish an underground closed-loop heat exchange system. After the renovation, one of the two production wells is an injection well and the other is a production well.

[0035] The hydraulic fractures in the horizontal sections of the two production wells are sealed, and the toes of the horizontal sections of the two production wells are connected through the side drilling section.

[0036] The specific transformation steps are as follows:

[0037] Pull out the original oil pipes in the production well, that is, pull out the original oil pipes in the vertical section, the deflection section and the horizontal section of the production well. Put the expansion casing into the horizontal section of the production well, and inject high thermal conductivity cement into the annulus between the expansion casing and the original fracturing casing of the horizontal section of the production well for cementing, so as to seal the fracturing cracks in the horizontal section and enhance the strength of the wellbore. Open a window at the toe end of the horizontal section of one of the production wells, and use the directional drilling method to side-drill to the toe end of the horizontal section of another production well to form a side-drilling well section. The side-drilling well section includes the side-drilling deflection section and the side-drilling horizontal section. The connection between the toes of the horizontal sections of the two production wells is established through the side-drilling deflection section and the side-drilling horizontal section. Heat exchange casings, or casings with better heat exchange effects, are put into the side-drilling deflection section and the side-drilling horizontal section. One end of the side-drilling horizontal section is butt-jointed with the toe end of the horizontal section of the production well by a glass fiber reinforced plastic casing. The heat exchange casing is connected to the expansion casing, and high thermal conductivity cement is injected into the outside of the heat exchange casing for cementing, forming a circulating heat exchange system for heat-carrying fluid in the shale reservoir.

[0038] (3) A ground ORC power generation system is connected in series at the wellheads of the two production wells to form an associated geothermal in-situ power generation system.

[0039] The heat-carrying fluid injected into the production well is heated by the shale reservoir, and then the thermal energy of the heat-carrying fluid is converted into electrical energy through the ground ORC power generation system. The heat-carrying fluid after energy conversion is reinjected into the deep underground high-temperature shale reservoir for heating.

[0040] like Figure 2 As shown, the ground ORC power generation system includes a turbine expander 2, a condenser 4, a working fluid pump 5, a generator 3 and a ground insulation pipe 1. The two production wells after transformation, one of which is an injection well and the other is a production well, the wellhead of the production well is connected with the turbine expander 2, the condenser 4, the working fluid pump 5 and the wellhead of the injection well in sequence through the ground insulation pipe 1, and the turbine expander 2 is also directly driven to the generator 3.

[0041] In the underground heat extraction process, the liquid organic working medium is injected from the wellhead of the injection well, and flows through the vertical section 6 of the injection well, the inclined section 7 of the injection well, the horizontal section 8 of the injection well, the side drilling inclined section 9, the side drilling horizontal section 10, and the horizontal section 11 of the production well, the inclined section 12 of the production well, and the vertical section 13 of the production well, and reaches the wellhead of the production well. In the above-mentioned flow process, the liquid organic working medium is heated by the deep high-temperature shale reservoir 14 and becomes gaseous. After the gaseous working medium is extracted from the wellhead of the production well, it enters the inlet of the turbine expander 2 through the ground insulation pipe 1, drives the turbine expander 2 to rotate and work, and then flows out from the outlet of the turbine expander 2. In this process, the heat energy of the heat-carrying working medium is converted into mechanical energy. At the same time, the turbine expander 2 drives the generator 3 to rotate and generate electricity, converting mechanical energy into electrical energy. The exhaust steam flowing out of the outlet of the turbine expander 2 is condensed into liquid through the condenser 4, and then pressurized by the working fluid pump 5 before being reinjected into the underground deep high-temperature shale reservoir 14 through the injection well for heating.

[0042] The high temperature shale reservoir is used as an evaporator for the power generation medium. The organic medium is pentafluoropropane (R245fa).

[0043] Example 2

[0044] A depleted shale reservoir associated geothermal in-situ power generation system includes an injection well and a production well, wherein the injection well and the production well both include a vertical section, a deflection section and a horizontal section connected in sequence, specifically a vertical section 6 of the injection well, a deflection section 7 of the injection well and a horizontal section 8 of the injection well, as well as a horizontal section 11 of the production well, a deflection section 12 of the production well and a vertical section 13 of the production well. An expansion casing 19 is provided in the horizontal section of the injection well and the horizontal section of the production well, and high thermal conductivity cement 17 is injected outside the expansion casing. The toe end of the horizontal section of the injection well and the toe end of the horizontal section of the production well are connected through a side drilling section. The side-drilling well section includes a side-drilling deflection section 9 and a side-drilling horizontal section 10. One end of the side-drilling horizontal section 10 is connected to the toe end of the horizontal section of the injection well through the side-drilling deflection section 9, and the other end of the side-drilling horizontal section 10 is connected to the toe end of the horizontal section of the production well through a glass fiber reinforced plastic casing. Heat exchange casings are arranged in the side-drilling deflection section 9 and the side-drilling horizontal section 10, and high thermal conductivity cement is injected on the outside of the heat exchange casing. The expansion casing 19 is connected to the heat exchange casing, such as by inserting the heat exchange casing into the expansion casing and connecting them by sealing with a sealing ring 20. A ground ORC power generation system is connected between the wellhead of the injection well and the wellhead of the production well. The ground ORC power generation system includes a turbine expander 2, a condenser 4, a working fluid pump 5, a generator 3 and a ground insulation pipe 1. The wellhead of the production well is connected to the turbine expander 2, condenser 4, working fluid pump 5 and the wellhead of the injection well in sequence through the ground insulation pipeline 1. The turbine expander 2 is also directly driven and connected to the generator 3. In order to further prevent heat loss, insulation materials are also installed in the vertical section 13 of the production well.

[0045] The working process of the present invention is roughly as follows:

[0046] The liquid organic working medium is injected from the wellhead of the injection well, and flows through the vertical section 6 of the injection well, the inclined section 7 of the injection well, the horizontal section 8 of the injection well, the side drilling inclined section 9, the side drilling horizontal section 10, and the horizontal section 11 of the production well, the inclined section 12 of the production well, and the vertical section 13 of the production well, and reaches the wellhead of the production well. In the above-mentioned flow process, the liquid organic working medium is heated by the deep high-temperature shale reservoir 14 and becomes gaseous. After the gaseous working medium is produced from the wellhead of the production well, it enters the inlet of the turbine expander 2 through the ground insulation pipe 1, drives the turbine expander 2 to rotate and do work, and then flows out from the outlet of the turbine expander 2. In this process, the heat energy of the heat-carrying working medium is converted into mechanical energy. At the same time, the turbine expander 2 drives the generator 3 to rotate and generate electricity, converting mechanical energy into electrical energy. The exhaust steam flowing out of the outlet of the turbine expander 2 is condensed into liquid through the condenser 4, and then pressurized by the working fluid pump 5 before being reinjected into the underground deep high-temperature shale reservoir 14 through the injection well for heating.

[0047] The present invention establishes a closed-loop heat extraction system by transforming two exhausted production wells in a high-temperature shale reservoir, which can effectively reduce the well construction costs for geothermal development and power generation, and has higher economic feasibility. The closed-loop heat exchange system formed by the side-drilling connection of two horizontal production wells with corresponding conditions has a horizontal heat exchange section of more than 2000m in the high-temperature shale reservoir, which effectively ensures the extraction temperature of the power generation medium under high circulation flow. Moreover, the heat energy collected by the present invention is used for in-situ power generation through the ground ORC power generation system at the wellhead, that is, the closed-loop heat extraction and power generation are integrated, which can convert the high-temperature associated geothermal resources in the deep shale reservoir into electrical energy on site, which can help oil and gas companies save energy and reduce carbon emissions.

[0048] The parts not mentioned in the above methods can be realized by adopting or drawing on existing technologies.

[0049] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any improvements, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for in-situ power generation of geothermal energy associated with depleted shale reservoirs, characterized in that The following steps are involved: (1) Select two abandoned production wells in the depleted shale reservoir; (2) The selected production wells are transformed to establish an underground closed-loop heat exchange system. After the transformation, one of the two production wells is an injection well and the other is a production well; The horizontal sections of the two production wells have been sealed with fractured casings, and the toes of the horizontal sections of the two production wells are connected through the side drilling section; (3) Connecting the surface ORC power generation system in series at the wellheads of the two production wells; The heat-carrying fluid injected into the production well is heated by the shale reservoir, and then the thermal energy of the heat-carrying fluid is converted into electrical energy through the ground ORC power generation system. The heat-carrying fluid after energy conversion is re-injected into the underground for heat extraction.

2. The method for in-situ power generation of geothermal energy associated with depleted shale reservoirs according to claim 1, characterized in that: In step (1): the wellbore structures of the two abandoned production wells selected are complete, and the production wells include a vertical well section, a deflection section and a horizontal section. The length of the horizontal section of the production well is between 1000 and 3000 meters, and the distance between the horizontal sections of the two production wells is between 300 and 900 meters.

3. The method for in-situ power generation of geothermal energy associated with depleted shale reservoirs according to claim 1, characterized in that: In step (2), the original oil pipe in the production well is pulled out, an expansion casing is lowered into the horizontal section of the production well, and high thermal conductivity cement is injected into the annulus between the expansion casing and the original fracturing casing in the horizontal section of the production well to seal the fracturing casing in the horizontal sections of the two production wells, and cementing is performed.

4. The method for in-situ power generation of geothermal energy associated with depleted shale reservoirs according to claim 3, characterized in that: A window is opened at the toe of the horizontal section of one of the production wells, and a directional drilling method is used to side-drill toward the toe of the horizontal section of another production well to form a side-drilled well section; the side-drilled well section includes a side-drilling inclination section and a side-drilling horizontal section, one end of the side-drilling horizontal section is connected to the toe of the horizontal section of one of the production wells through the side-drilling inclination section, and the other end of the side-drilling horizontal section is connected to the toe of the horizontal section of the other production well through a glass fiber reinforced plastic casing; a heat exchange casing is lowered into the side-drilling inclination section and the side-drilling horizontal section, and high thermal conductivity cement is injected on the outside of the heat exchange casing for cementing, so as to form an underground closed circulation heat exchange system for heat-carrying fluid in the shale reservoir.

5. The method for in-situ power generation of geothermal energy associated with depleted shale reservoirs according to claim 1, characterized in that: In step (3): the ground ORC power generation system includes a turbine expander, a condenser, a working fluid pump, a generator and a ground insulation pipeline; the wellhead of the production well is connected to the turbine expander, the condenser, the working fluid pump and the wellhead of the injection well in sequence through the ground insulation pipeline, and the turbine expander is also directly driven to the generator.

6. The method for in-situ power generation of geothermal energy associated with depleted shale reservoirs according to claim 5, characterized in that: In the underground heat production process, the liquid medium is injected from the wellhead of the injection well at an injection rate of 30-50 kg / s, and flows through the vertical section, deflection section, horizontal section, side drilling section of the injection well, and the horizontal section, deflection section, and vertical section of the production well to reach the wellhead of the production well; in the above-mentioned flow process, the liquid organic medium is heated by the shale reservoir and becomes gaseous; After the gaseous working fluid is produced from the wellhead of the production well, it enters the inlet of the turbine expander through the ground insulated pipeline, drives the turbine expander to rotate and do work, and then flows out from the outlet of the turbine expander. In this process, the thermal energy of the heat-carrying working fluid is converted into mechanical energy; at the same time, the turbine expander drives the generator to rotate and generate electricity, converting mechanical energy into electrical energy; the exhaust steam flowing out of the outlet of the turbine expander flows through the condenser and is condensed into liquid at a temperature of 25 to 40°C. The cooling form of the condenser is air cooling. The liquid working fluid is then pressurized by the working fluid pump and then reinjected into the underground through the injection well to extract heat.

7. The method for in-situ power generation of geothermal energy associated with depleted shale reservoirs according to claim 1, characterized in that: The shale reservoir is a deep high-temperature shale reservoir with a burial depth of 3000-5000m, a thickness of 400-500m, and a formation temperature of >120°C.

8. The method for in-situ power generation of geothermal energy associated with depleted shale reservoirs according to claim 1, characterized in that: The organic working fluid is pentafluoropropane.

9. A depleted shale reservoir associated geothermal in-situ power generation system transformed by any of the methods of claims 1 to 9, characterized in that: The invention comprises an injection well and a production well, each of which comprises a vertical section, a deflection section and a horizontal section connected in sequence, an expansion casing is arranged in the horizontal section of the injection well and the horizontal section of the production well, and high thermal conductivity cement is injected on the outside of the expansion casing; the toe end of the horizontal section of the injection well and the toe end of the horizontal section of the production well are connected through a side-drilling section, a heat exchange casing is arranged in the side-drilling section, the side-drilling section and the toe end of the horizontal section of the production well are butt-jointed by a glass fiber reinforced plastic casing, and high thermal conductivity cement is injected on the outside of the heat exchange casing; the expansion casing and the heat exchange casing are connected; a ground ORC power generation system is connected between the wellhead of the injection well and the wellhead of the production well; and an insulation layer is installed in the vertical section of the production well.

10. The depleted shale reservoir associated geothermal in-situ power generation system according to claim 9, characterized in that: The ground ORC power generation system includes a turbine expander, a condenser, a working fluid pump, a generator and a ground insulation pipeline; the wellhead of the production well is connected with the turbine expander, the condenser, the working fluid pump and the wellhead of the injection well in sequence through the ground insulation pipeline, and the turbine expander is also directly driven and connected to the generator.

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