Geothermal power generation method based on long-stop well of oil and gas field

Abstract

According to the geothermal power generation method, an organic working medium is injected into the long-stop well, heat exchange is conducted between geothermal energy in a rock stratum and the organic working medium, so that the organic working medium is converted into a gas state from a liquid state, and the organic working medium is output to the long-stop well and acts with a power generation device for power generation. In the process, a new well does not need to be drilled, investment cost is saved, the requirements for water quantity and water temperature of a heat reservoir are low, circulating flow is always conducted in the environment isolated from the outside to continuously exploit geothermal energy, the condition that conventional geothermal power generation has high requirements for heat storage temperature is overcome, and the method is more suitable for medium and low temperature geothermal resources. And meanwhile, the production process adopts totally-closed circulation, so that the pipeline corrosion and scaling risk can be effectively reduced. Due to the fact that the well way is supported by the artificial well wall, the risk of accidents such as well body collapse during working medium injection is lower, pipeline corrosion can be effectively reduced, and safety is higher.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal power generation, and relates to a geothermal power generation method based on long - term shut - in wells in oil and gas fields. Background Technique

[0002] Typical geothermal power generation technologies include steam Rankine cycle, flash cycle, organic Rankine cycle, Kalina cycle and total flow power generation system. Among these systems, the organic Rankine cycle technology (ORC) is one of the main technologies for utilizing medium - low temperature heat sources. Using organic substances with relatively low boiling points as the circulating working fluid, it can make full use of low - temperature heat energy and convert low - grade heat energy into electrical energy, and is widely used. The working principle of this method is as follows: After the geothermal fluid is pumped from the wellbore to the ground, the low - boiling - point organic working fluid exchanges heat with the geothermal fluid through a heat exchanger to complete preheating and evaporation, then does work through a steam turbine to generate electricity, and finally returns to the heat exchanger through a condenser after condensation by a working fluid pump to complete the cycle.

[0003] Since this technology requires new geothermal wells to be drilled, and the drilling cost accounts for more than half of the upfront investment cost, the drilling cost of this method is high. At the same time, the construction period is relatively long, generally at least more than 2 - 3 years, taking a lot of time and energy to complete the project construction, with a long payback period and poor economy. In addition, the organic Rankine cycle technology uses geothermal water in the heat reservoir to exchange heat with the organic working fluid on the ground. During the process from the wellbore to the ground, the geothermal water has a large heat loss. When the outlet water temperature is not high, the intermediate medium cannot exchange heat well, and the system thermal efficiency is low. That is, this method is based on geothermal water, pumps underground hot water to exchange energy with the ground working fluid, drives the power generation device to generate electricity, has high requirements for the temperature and quantity of geothermal resources, large heat loss, and low overall efficiency of the geothermal power generation system. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a geothermal power generation method based on long - term shut - in wells in oil and gas fields, so as to solve the technical problems that the existing geothermal power generation technology has high requirements for the temperature and quantity of geothermal resources, large heat loss, low overall efficiency of the geothermal power generation system, and poor utilization efficiency of geothermal resources in oil and gas fields.

[0005] The present invention is realized through the following technical solutions:

[0006] A geothermal power generation method based on long - term shut - in wells in oil and gas fields injects an organic working fluid into the long - term shut - in well. Through the heat exchange between the geothermal energy in the rock formation and the organic working fluid, the organic working fluid is changed from a liquid state to a gaseous state, and is output from the long - term shut - in well and acts on a power generation device to generate electricity.

[0007] Preferably, the boiling point of the organic working fluid is 70 - 90 °C.

[0008] Preferably, the organic working fluid is a hydrofluorocarbon.

[0009] Preferably, the injection flow rate of the organic working fluid is 0.5 - 2 m / s.

[0010] Preferably, before injecting the organic working fluid into the long - shut - in well, workover measures are carried out on the long - shut - in well.

[0011] Preferably, the workover measures include pulling out the original production string and washing the well operation.

[0012] Preferably, during the well washing operation, the amount of well - washing fluid used is not less than 2 times the wellbore volume, and the displacement is not less than 600 L / min.

[0013] Preferably, after the well washing operation, it also includes engineering logging, casing integrity evaluation, squeezing and sealing the original perforation section, and casing pressure testing process.

[0014] Preferably, during the casing pressure testing process, pressure testing is carried out at 10 MPa, 15 MPa, 20 MPa, and 25 MPa respectively.

[0015] Preferably, when conducting pressure testing at any one pressure, if the pressure drop is not more than 0.5 MPa within 3 minutes, the pressure testing is qualified. Otherwise, a packer string is lowered for pressure testing to find leaks and plugging is carried out.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] The present invention discloses a geothermal power generation method based on long - shut - in wells in oil and gas fields. The organic working fluid is injected into the long - shut - in well, and heat exchange occurs between the geothermal energy in the rock formation and the organic working fluid, causing the organic working fluid to change from a liquid state to a gaseous state and output from the long - shut - in well, and then acting with a power generation device for power generation. This process does not require drilling new wells, and the existing mature technology can be used to transform the long - shut - in oil and gas wells into geothermal wells. The existing infrastructure of the long - shut - in well can continue to be used, and no additional investment is required for the well - site roads and surrounding equipment and facilities, saving investment costs. At the same time, it has low requirements for the water volume and water temperature of the heat reservoir. Traditional geothermal well power generation uses the high temperature of underground hot water for heat exchange power generation, which has higher requirements for the water output and outlet water temperature. The present invention adopts a closed - loop heat extraction process, always circulating in an environment isolated from the outside to continuously extract geothermal energy, overcoming the condition of high requirements for the heat reservoir temperature in conventional geothermal power generation, being more suitable for medium - low temperature geothermal resources, and making full use of geothermal resources. At the same time, the production process of the present invention adopts a fully enclosed cycle, which can effectively reduce the risks of pipeline corrosion and scaling. Since the artificial wellbore supports the well path, the risk of accidents such as wellbore collapse during the injection of the working fluid is lower. This method can effectively reduce pipeline corrosion and has higher safety.

[0018] Furthermore, the boiling point of the organic working fluid is 70-90 °C, which facilitates its volatilization to carry the geothermal energy in the rock formation out of the wellbore for power generation.

[0019] Furthermore, the organic working fluid is a hydrofluorocarbon, which can make full use of geothermal energy to achieve geothermal power generation.

[0020] Furthermore, the injection flow rate of the organic working fluid is 0.5-2 m / s, which can be fully heated and volatilized to carry the geothermal energy out of the wellbore for power generation.

[0021] Furthermore, before injecting the organic working fluid into the long-abandoned well, workover measures are carried out on the long-abandoned well, and this workover process effectively ensures the smoothness of the wellbore.

[0022] Furthermore, the workover measures include pulling out the original production string and washing the well operation, which can effectively ensure the smoothness of the wellbore of the long-abandoned well.

[0023] Furthermore, during the well washing operation, the amount of well washing fluid used is not less than 2 times the volume of the wellbore, and the displacement is not less than 600 L / min, which effectively ensures the smoothness of the wellbore of the long-abandoned well.

[0024] Furthermore, after the well washing operation, it also includes engineering logging, casing integrity evaluation, squeezing and sealing the original perforation section, and casing pressure test process. Among them, engineering logging and casing integrity evaluation ensure the integrity of the casing wellbore, and the process of squeezing and sealing the original perforation section and casing pressure test ensures that oil and gas will not invade the wellbore.

[0025] Furthermore, during the casing pressure test process, the pressure tests are carried out at 10 MPa, 15 MPa, 20 MPa, and 25 MPa respectively to fully evaluate the integrity of the casing wellbore.

[0026] Furthermore, when conducting the pressure test at any one pressure, if the pressure drop is not more than 0.5 MPa within 3 minutes, the pressure test is qualified. Otherwise, the packer string is lowered for pressure test to find leaks and plugging, which effectively ensures the integrity of the casing wellbore. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a schematic structural diagram of the device for carrying out a geothermal power generation method based on long-abandoned wells in the oil and gas field of the present invention.

[0029] Wherein: 1. Casing wellbore; 2. Check valve; 3. Single U-tube heat exchanger; 4. Turbine; 5. Power generation device; 6. Condenser; 7. Liquid storage tank; 8. Working fluid pump. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention generally described and illustrated in the accompanying drawings here may be arranged and designed in a variety of different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but is merely representative of selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0033] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship in which the product of the invention is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0034] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0035] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] The following further describes the present invention in detail with reference to the accompanying drawings:

[0037] Embodiment 1

[0038] The present invention discloses a geothermal power generation method based on long-term shut-in wells in oil and gas fields. An organic working fluid is injected into the long-term shut-in well, and heat exchange occurs between the geothermal energy in the rock formation and the organic working fluid, causing the organic working fluid to change from a liquid state to a gaseous state and output from the long-term shut-in well, and acting with a power generation device to generate electricity.

[0039] In another preferred embodiment of the present invention, the boiling point of the organic working fluid is 70 - 90 °C, which is convenient for its volatilization to carry the geothermal energy in the rock formation out of the well for power generation. At the same time, preferably, the organic working fluid is a hydrofluorocarbon.

[0040] During the power generation process, the injection flow rate of the organic working fluid is 0.5 - 2 m / s, which can be fully heated and volatilized to carry the geothermal energy out of the well for power generation.

[0041] In addition, in order to ensure the smoothness of the wellbore, before injecting the organic working fluid into the long-term shut-in well, workover measures are carried out on the long-term shut-in well. The workover measures include pulling out the original production string and washing the well operation. During the well washing operation, the displacement is not less than 600 L / min, and the amount of washing fluid used is not less than 2 times the volume of the wellbore. After washing the well, it should reach clear water and clean sand, and the mass ratio content of suspended solids < 1 / 20000, which fully ensures the cleaning degree of the wellbore and the smoothness of the wellbore.

[0042] In addition, further, after the well washing operation, it also includes engineering logging, casing integrity evaluation, squeezing and sealing the original perforation section, and casing pressure testing process. Among them, engineering logging and casing integrity evaluation ensure the integrity of the casing wellbore, and the processes of squeezing and sealing the original perforation section and casing pressure testing ensure that oil and gas do not invade the wellbore.

[0043] Further preferably, during the casing pressure test, the tests are carried out at 10 MPa, 15 MPa, 20 MPa and 25 MPa respectively, so as to fully evaluate the integrity of the casing wellbore. At the same time, when the pressure test is carried out at any one of the pressures, if the pressure drop is not more than 0.5 MPa within 3 minutes, the pressure test is qualified. Otherwise, the packer string is used for pressure testing to find leaks. After the leak points are found, chemical plugging of the leak points is carried out with reference to the plugging measures, which fully ensures the integrity of the casing wellbore.

[0044] The present invention discloses a geothermal power generation method based on long-term shut-in wells in oil and gas fields. An organic working fluid is injected into the long-term shut-in wells, and heat exchange occurs between the geothermal energy in the rock formation and the organic working fluid, so that the organic working fluid changes from a liquid state to a gaseous state and is output from the long-term shut-in wells, and acts on a power generation device for power generation. This process does not require drilling new wells, and the existing mature technologies can be used to transform the long-term shut-in wells in oil and gas fields into geothermal wells. The existing infrastructure of the long-term shut-in wells can continue to be used, and no additional investment is required for the well site roads and surrounding equipment facilities, saving investment costs. At the same time, the requirements for the water volume and water temperature of the heat reservoir are low. Traditional geothermal well power generation uses the high temperature of underground hot water for heat exchange power generation, and has relatively high requirements for the water output and outlet water temperature. The present invention adopts a closed-loop heat extraction process, and always circulates in an environment isolated from the outside world to continuously extract geothermal energy, overcoming the condition of high requirements for the heat reservoir temperature in conventional geothermal power generation, and being more suitable for medium and low temperature geothermal resources. At the same time, the production process of the present invention adopts a fully enclosed cycle, which can effectively reduce the risks of pipeline corrosion and scaling. Since the artificial wellbore supports the well path, the risk of accidents such as wellbore collapse during the injection of the working fluid is lower, and this method can effectively reduce pipeline corrosion and has higher safety.

[0045] Example 2

[0046] The geothermal power generation device used in the present invention is shown in Figure 1 , specifically including a single U-tube heat exchanger 3; a check valve 2 is installed at the injection port of the single U-tube heat exchanger 3. The injection port of the single U-tube heat exchanger 3 is connected to a working fluid pump 8 through a pipeline, the production outlet of the single U-tube heat exchanger 3 is connected to a turbine 4 through a pipeline, the turbine 4 is connected to a power generation device 5 through a pipeline, the turbine 4 is connected to a condenser 6 through a pipeline, the condenser 6 is connected to a liquid storage tank 7 through a pipeline, and the liquid storage tank 7 is connected to the working fluid pump 8 through a pipeline.

[0047] The operation process of the device is as follows: First, lower the single U-tube heat exchanger 3 into the wellbore 1 of the long-abandoned well. The heat exchanger is lowered to the formation with high geothermal content inside the long-abandoned well, generally to the bottom of the long-abandoned well. Install a check valve 2 at the injection port of the single U-tube heat exchanger 3. The injection port of the single U-tube heat exchanger 3 is connected to the working fluid pump 8 through a pipeline. The production outlet of the single U-tube heat exchanger 3 is connected to the turbine 4 through a pipeline. The turbine 4 is connected to the power generation device 5 through a pipeline. The turbine 4 is connected to the condenser 6 through a pipeline. The condenser 6 is connected to the liquid storage tank 7 through a pipeline. The liquid storage tank 7 is connected to the working fluid pump 8 through a pipeline.

[0048] The single U-tube heat exchanger is a heat exchange container with a U-shaped shape of appropriate length installed in the long-abandoned well, which can realize the heat exchange between the organic working fluid and the pipe wall. The check valve is a one-way opening and closing valve installed at the injection port end of the single U-tube heat exchanger to prevent the reverse flow of the fluid medium.

[0049] For the long-abandoned well, install a single U-tube heat exchanger in the casing wellbore, inject an organic liquid working fluid into the heat exchanger, utilize the low boiling point characteristic of the organic working fluid, absorb heat through the pipe wall and then undergo a phase change, convert into a high-temperature gaseous working fluid, and utilize the generated heat energy to realize medium and low-temperature geothermal power generation of the long-abandoned well through the ground power generation system.

[0050] The long-abandoned well in the present invention is a vertical well or a directional well. This long-abandoned well is an oil and gas well where the production, water injection or workover operations have ended, the standard drift can pass smoothly, there is no downhole debris, the cementing quality is qualified, and the casing pressure test is qualified, but it has not completed the scrapping approval procedures or been approved for cancellation according to the procedures, including shut-down oil and gas wells and temporarily closed low-yield and inefficient oil and gas wells.

[0051] Before lowering the single U-tube heat exchanger, it is necessary to carry out well flushing operations, remove the original production string and accessories, use a drift tool to reach the artificial bottom hole, and carry out large-displacement reverse circulation well flushing to ensure the smoothness of the wellbore. Before lowering the single U-tube heat exchanger, it is necessary to carry out wellbore engineering logging to detect the damage and corrosion of the casing to ensure the integrity of the casing wellbore. Before lowering the single U-tube heat exchanger, it is necessary to carry out squeeze sealing operations on the original production layer section to ensure that oil and gas will not invade the wellbore.

[0052] The organic working fluid is the environmentally friendly organic working fluid R245fa with a low ODP (ozone depletion potential) and a low GWP (global warming potential).

[0053] The technical solution of the operation process is specifically as follows:

[0054] ① Carry out workover measures on the long-abandoned well, such as removing the original production string, well flushing operations, engineering logging, casing integrity evaluation, squeezing and sealing the original perforated section, casing pressure test, etc.

[0055] ②Install a single U-tube heat exchanger in the casing wellbore of the long-term shut-in well. The injection port of the single U-tube heat exchanger is connected to the working fluid pump through a pipeline, and the production outlet of the single U-tube heat exchanger is connected to the turbine through a pipeline.

[0056] ③Install a check valve at the inlet end of the single U-tube heat exchanger. The check valve ensures that the liquid working fluid runs along the injection port pipeline of the U-tube and does not produce a reverse flow phenomenon.

[0057] ④The liquid working fluid is injected into the single U-tube heat exchanger through the working fluid pump. The low-temperature working fluid takes heat by contacting the pipe wall. When it flows to the bottom of the U-tube, the temperature rises to the highest. After the liquid working fluid absorbs heat, it becomes a high-temperature gaseous working fluid and then returns from the production outlet of the U-tube heat exchanger to the wellhead.

[0058] ⑤The high-temperature gaseous working fluid enters the turbine to drive the power generation device to generate electricity.

[0059] ⑥After the high-temperature gaseous working fluid enters the turbine, exhaust gas is generated. It enters the condenser and is cooled into a liquid working fluid. The liquid working fluid enters the liquid storage tank for storage, and then is pressurized by the working fluid pump and enters the injection port of the single U-tube heat exchanger to complete the cycle.

[0060] A medium and low temperature geothermal power generation method based on long-term shut-in wells in oil and gas fields provided by the present invention transforms the long-term shut-in wells into geothermal wells, utilizes the low boiling point characteristics of organic working fluids, and through the heat exchange between the geothermal energy of the heat reservoir and the pipe wall, the low-temperature working fluid takes heat by contacting the pipe wall, and can realize the efficient power generation utilization of geothermal energy.

[0061] The present invention does not require drilling new wells. The existing mature technology can be used to transform the long-term shut-in wells in oil and gas fields into geothermal wells, saving investment costs. The existing infrastructure of the long-term shut-in wells can continue to be used, and no additional investment is required for the well site roads and surrounding equipment facilities. The construction period is short and the investment recovery period is short. Transforming the long-term shut-in wells into geothermal wells can save a large amount of drilling time and drilling costs because no new wells need to be drilled. At the same time, the operation period of the long-term shut-in wells is short, greatly shortening the investment recovery period. The requirements for the water volume and water temperature of the heat reservoir are low. Traditional geothermal well power generation uses the high temperature of underground hot water for heat exchange power generation, and has higher requirements for the water output and outlet water temperature. The present invention makes full use of the heat of the rock formation itself for heat exchange and adopts a closed-loop heat extraction process, overcoming the characteristic of high requirements for the quality of geothermal water. It can effectively reduce pipeline corrosion and has higher safety. The production process of the present invention adopts a fully closed cycle, which can effectively reduce the risks of pipeline corrosion and scaling. Since the artificial wellbore is cemented and completed to support the well path, the risk of accidents such as wellbore collapse during the injection of the working fluid is lower.

[0062] Example 3

[0063] In order to further explain the technical solution of the present invention, the following examples are used for illustration:

[0064] The working process of the method of the present invention is as follows:

[0065] I. Construction Preparation

[0066] 1. After verifying that the construction well number is consistent with the ring stamp well number, lift out the original well string and accessories.

[0067] 2. Conduct flushing and scraping operations on the casing wellbore to ensure the smoothness of the wellbore.

[0068] 3. Carry out engineering logging and wellbore integrity evaluation. Use downhole multi-arm caliper logging tool and magnetic wall thickness logging tool to conduct casing damage detection, detect the damage and corrosion of the casing, and ensure the integrity of the casing wellbore.

[0069] 4. Perform squeeze sealing operation on the original pay zone to ensure that oil and gas do not invade the wellbore.

[0070] 5. Wait for coagulation for 48 hours, conduct casing pressure test. The pressure is increased from 10 MPa to 15 MPa, 20 MPa, 25 MPa respectively, and the pressure drop is less than 0.5 MPa in each 3-minute stage. After the pressure test is qualified, carry out the subsequent procedures.

[0071] II. Construction Operations

[0072] Step 1: Install the check valve 2 at the injection port end of the single U-tube heat exchanger 3.

[0073] Step 2: Lower the single U-tube heat exchanger 3 into the casing wellbore 1 of the shut-in well. The heat exchanger is lowered to the formation with high geothermal content inside the shut-in well, generally to the bottom of the shut-in well.

[0074] Step 3: Store the liquid organic working medium in the liquid storage tank 7, start the working medium pump 8, and inject the liquid working medium into the injection port end of the single U-tube heat exchanger 3 through the working medium pump 8.

[0075] Step 4: The liquid working medium contacts the pipe wall to absorb heat and is transformed into a high-temperature and high-pressure gaseous working medium under the action of geothermal heat. The gaseous working medium returns to the wellhead through the production outlet end of the U-tube heat exchanger 3.

[0076] Step 5: The gaseous working medium enters the turbine 4 to drive the power generation device 5 to generate electricity.

[0077] Step 6: After the high-temperature gaseous working medium enters the turbine 4, exhaust gas is generated and enters the condenser 6 to be cooled into a liquid working medium.

[0078] Step 7: The liquid working medium enters the liquid storage tank 7 for storage.

[0079] Step 8: The liquid working medium is pressurized by the working medium pump 8 again and enters the injection port of the single U-tube heat exchanger 3 to complete the cycle.

[0080] The circulation path of the organic working fluid is as follows: working fluid pump 8 → injection port of single U-tube heat exchanger 3 → heat exchange → outlet of single U-tube heat exchanger 3 → turbine 4 → condenser 6 → liquid storage tank 7 → working fluid pump 8.

[0081] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A geothermal power generation method based on long-term shut-in wells in oil and gas fields, characterized in that, an organic working fluid is injected into the long-term shut-in well, and heat exchange occurs between the geothermal energy in the rock formation and the organic working fluid, causing the organic working fluid to change from a liquid state to a gaseous state and outputting from the long-term shut-in well to act with a power generation device for power generation.

2. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 1, characterized in that, the boiling point of the organic working fluid is 70-90 °C.

3. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 1, characterized in that, the organic working fluid is a hydrofluorocarbon.

4. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 1, characterized in that, the injection flow rate of the organic working fluid is 0.5-2 m / s.

5. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 1, characterized in that, before injecting the organic working fluid into the long-term shut-in well, well workover measures are carried out on the long-term shut-in well.

6. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 5, characterized in that, the well workover measures include pulling out the original production string and well flushing operation.

7. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 6, characterized in that, during the well flushing operation, the amount of flushing fluid used is not less than 2 times the wellbore volume, and the displacement is not less than 600 L / min.

8. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 6, characterized in that, after the well flushing operation, it also includes engineering logging, casing integrity evaluation, squeezing and sealing the original perforation section, and casing pressure testing process.

9. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 8, characterized in that, during the casing pressure testing process, pressure testing is carried out at 10 MPa, 15 MPa, 20 MPa, and 25 MPa respectively.

10. The geothermal power generation method based on long-term shut-in wells in oil and gas fields according to claim 6, characterized in that, when pressure testing is carried out at any one pressure, if the pressure drop within 3 minutes is not greater than 0.5 MPa, the pressure testing is qualified; otherwise, the packer string is lowered for pressure testing to find leaks and plugging is carried out.

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