Geothermal device and method for reconstruction of abandoned oil and gas wells

Abstract

A geothermal device and method for reconstruction of abandoned oil and gas wells. The geothermal device comprises a heat exchanger arranged at the wellhead of an abandoned oil and gas well and an unpowered heat extractor located inside the abandoned oil-gas well, wherein the unpowered heat extractor comprises a thermal insulation member and an evaporation member; the heat exchanger, the thermal insulation member and the evaporation member are sequentially in communication with each other from top to bottom; a liquid working medium is injected into the unpowered heat extractor, absorbs heat from a crude oil layer and evaporates into a gaseous working medium; the gaseous working medium is sequentially transported through the evaporation member and the thermal insulation member to the heat exchanger, condenses in the heat exchanger to release heat and turns into the liquid working medium; and the liquid working medium flows back to the bottom of the abandoned oil and gas well under the action of gravity. The present invention achieves true "heat extraction without water extraction", and does not require a water pump during operation, thereby reducing operation costs.

Description

A geothermal device and method for the retrofitting of abandoned oil and gas wells.

[0001] This application claims priority to Chinese Patent Application No. 202411054252.2, filed on August 1, 2024, entitled "A Geothermal Device and Method for the Retrofitting of Abandoned Oil and Gas Wells", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of geothermal energy development and utilization technology for abandoned wells, and more specifically, to a geothermal device and method for the transformation of abandoned oil and gas wells. Background Technology

[0003] In most of my country's geothermal areas, oil exploration and drilling have been conducted. As the oil reserves gradually deplete, a large number of abandoned wells with no value for oil extraction have been left behind. Statistics show that the number of abandoned wells in my country was 76,800 in 2005, increasing to 92,000 in 2010, and currently exceeds 100,000. However, abandoned oil fields still contain enormous energy resources, and if these resources are not fully utilized, they could pose significant challenges and harm to urban economies and society.

[0004] Compared to other renewable resources such as solar, wind, and tidal energy, geothermal resources are characterized by their wide distribution, large reserves, cleanliness, environmental friendliness, and stability. However, geothermal energy accounts for only 2% of global renewable energy consumption. The main reason for its low market share is the high investment cost, with drilling costs accounting for up to 50% of the total project investment. Therefore, utilizing existing abandoned wells to develop geothermal energy is expected to become an important way to promote the commercialization of geothermal energy.

[0005] Currently, the conversion of abandoned wells into geothermal wells faces many urgent problems. First, existing conversion methods mainly rely on extracting hot groundwater from abandoned wells, resulting in poor water quality and high difficulty in reinjection, causing ecological pollution. Second, after a period of heat exchange, the temperature in the near-well area is insufficient to replenish the geothermal system, causing a significant drop in heat extraction temperature. Third, existing geothermal temperature monitoring generally uses point detection, and the generated electrical signals are easily subject to electromagnetic interference during transmission, and it is impossible to monitor the temperature data of the entire well simultaneously.

[0006] Therefore, how to overcome the shortcomings of the existing technology mentioned above has become the subject of this application.

[0007] Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a geothermal device and method for the renovation of abandoned oil and gas wells.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A geothermal device for the renovation of abandoned oil and gas wells includes a heat exchanger installed at the wellhead of the abandoned oil and gas well and a non-powered heat extractor located inside the abandoned oil and gas well. The non-powered heat exchanger includes an insulation component and an evaporator, which are connected sequentially from top to bottom. A liquid working fluid is injected into the non-powered heat extractor. The liquid working fluid absorbs heat and evaporates into a gaseous working fluid in the crude oil layer. The gaseous working fluid is transferred to the heat exchanger through the evaporator and the insulation component. The gaseous working fluid condenses and releases heat in the heat exchanger, becoming a liquid working fluid again. The liquid working fluid flows back to the bottom of the abandoned oil and gas well under the action of gravity.

[0011] Furthermore, the insulation component includes a heat insulation layer, a connecting block, and a steam pipe. The heat insulation layer is disposed circumferentially on the well wall of the abandoned oil and gas well, and the steam pipe is disposed in the heat insulation layer along the well depth direction. The steam pipe is connected to the heat insulation layer through the connecting block. A first annular space for the flow of the liquid medium is formed between the steam pipe and the heat insulation layer.

[0012] Furthermore, the evaporation unit includes an oil casing and a gas-liquid separator. The oil casing is circumferentially disposed on the well wall of the abandoned oil and gas well. Multiple gas-liquid separators are arranged inside the oil casing, forming a second annular space for the flow of the liquid medium between the gas-liquid separators and the oil casing. Each gas-liquid separator includes a base and a gas collecting pipe. The base is installed on the inner wall of the oil casing, and the gas collecting pipe is mounted on the base. Multiple drainage holes are provided on the base.

[0013] Furthermore, the gas collecting pipe is a variable diameter pipe.

[0014] Furthermore, a third annular space is formed between the insulation component and the evaporation component and the well wall of the abandoned oil and gas well, and the third annular space is filled with high thermal conductivity mud.

[0015] To address the aforementioned technical problems, this application also provides a geothermal method for the retrofitting of abandoned oil and gas wells, applied to the geothermal heat extraction device for the retrofitting of abandoned oil and gas wells as described above, comprising:

[0016] S1. Select abandoned oil and gas wells, inject high thermal conductivity composite materials into them, and enter the fracture network of crude oil layer through perforations on the well wall of abandoned oil and gas wells to enhance the thermal conductivity of the thermal reservoir.

[0017] S2. Lower the non-powered heat exchanger and lower the temperature measuring fiber along with the non-powered heat exchanger to monitor the downhole temperature;

[0018] S3. Fill the third annular space between the abandoned oil and gas well wall and the non-powered heat exchanger with mud, and discharge the gas in the third annular space to increase heat conduction.

[0019] S4. Evacuate the inside of the non-powered heat exchanger and inject a low-boiling-point working fluid.

[0020] Furthermore, the temperature-measuring optical fiber is connected to an optical fiber temperature testing host, which is located at the wellhead of the abandoned oil and gas well. The optical fiber temperature testing host obtains the downhole temperature of the abandoned oil and gas well through the temperature-measuring optical fiber.

[0021] Furthermore, the temperature-measuring optical fiber includes a fiber core, a stainless steel tube, fiber grease, steel wire armor, and a Teflon protective sleeve. There are two fiber cores, each of which is disposed inside the stainless steel tube. The stainless steel tube is filled with the fiber grease. The steel wire armor is sleeved on the outside of the stainless steel tube, and the Teflon protective sleeve is sleeved on the outside of the steel wire armor.

[0022] Furthermore, it also includes an optical fiber protection device, which includes a coupling protector and a steel cable tie. The coupling protector is located at the connection between the insulation component and the evaporator, and is used in conjunction with the temperature-sensing optical fiber. The temperature-sensing optical fiber is fixed to the insulation component and the evaporator by the steel cable tie.

[0023] Furthermore, the injection amount of the low-boiling-point working fluid is adjusted according to the temperature measured by the temperature-sensing optical fiber.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] 1. The internal gas-liquid separation device of the non-powered heat exchanger reduces the gas-liquid entrainment effect and enables long-distance heat transfer. The pipe uses an environmentally friendly low-boiling-point working fluid, which expands the temperature range of usable geothermal water and improves the heat extraction power of a single geothermal well.

[0026] 2. During the circulation process of the non-powered heat exchanger, the internal liquid working fluid flows back to the bottom of the abandoned oil and gas well by gravity. The process does not consume pump power, reduces operating costs, and realizes a true "heat extraction without water extraction" process.

[0027] 3. A distributed fiber optic temperature measurement host is adopted, which is not afraid of electromagnetic interference and can ensure long-term stable temperature measurement in harsh environments. Based on the characteristics of cementing the entire section of abandoned oil and gas wells, a protection device for the temperature measurement fiber optic cable at the coupling is designed. Compared with conventional protection devices on the market, the cost is reduced by 60%, and it is more suitable for the narrow linear space requirements of the well wall and casing of geothermal deep wells.

[0028] 4. Reduce resource waste: Abandoned oil and gas fields have complete geological parameters and vast areas. Converting these abandoned wells into geothermal wells not only reduces exploration and drilling costs but also alleviates the current energy shortage, improves the environment, and promotes economic growth. It simplifies construction procedures, eliminating the need for additional fracturing, thus reducing the cost of geothermal reservoir transformation projects. The fractures created by the perforations of existing oil and gas wells can be utilized by filling them with a highly thermally conductive liquid working fluid to achieve rapid heat transfer from distant locations to the surrounding rocks near the well, promoting the recovery of formation temperature in the near-well area and improving geothermal energy extraction efficiency. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 is a structural schematic diagram of an embodiment of this application;

[0031] Figure 2 is a structural schematic diagram of the thermal insulation component according to an embodiment of this application;

[0032] Figure 3 is a schematic diagram of the evaporator according to an embodiment of this application;

[0033] Figure 4 is a schematic diagram of the structure of the temperature-sensing optical fiber according to an embodiment of this application;

[0034] Figure 5 is a schematic diagram of the structure of the optical fiber protection device according to an embodiment of this application;

[0035] Figure 6 is a structural schematic diagram of the coupling protector according to an embodiment of this application.

[0036] The following are descriptions of the reference numerals and components in the attached drawings: 1. Abandoned oil and gas well; 2. Perforation; 3. Crude oil layer; 4. Fracture network; 5. Non-powered heat exchanger; 51. Heat exchanger; 52. Insulation component; 521. Insulation layer; 522. Connecting block; 523. Steam pipe; 53. Evaporator; 531. Oil casing; 532. Gas-liquid separator; 54. Base; 55. Gas collecting pipe; 6. Temperature measuring optical fiber; 61. Fiber core; 62. Stainless steel pipe; 63. Fiber grease; 64. Steel wire armor; 65. Teflon protective sleeve; 7. Fiber optic temperature testing host; 8. Fiber optic protection device; 81. Coupling protector; 82. Steel cable tie; 9. Mud. Detailed Implementation

[0037] The technical solution of the present invention will now be clearly and completely described through specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] Referring to Figures 1-6, this application discloses a geothermal device for the transformation of abandoned oil and gas wells. Since abandoned oil and gas fields have complete geological parameters and vast sites, this application transforms these abandoned wells into geothermal wells, which not only reduces exploration and drilling costs but also alleviates the current energy shortage, improves the environment, and promotes economic growth. This application includes perforations 2 on the wellbore of an abandoned oil and gas well 1 located in the crude oil layer. A high thermal conductivity composite material is injected through the perforations 2 into the fracture network 4 of the crude oil layer 3, simplifying the construction process, eliminating the need for additional fracturing, and reducing the cost of geothermal reservoir transformation projects. The fracture network 4 generated by the perforations 2 of the abandoned oil and gas well 1, filled with a high thermal conductivity composite material, enables rapid heat transfer from a distant location to the surrounding rock near the well, promoting the recovery of formation temperature in the near-well area and improving geothermal energy extraction efficiency. The high thermal conductivity composite material is injected into the fracture network 4 of the abandoned oil and gas well 1 through the perforation 2 on the well wall. The high thermal conductivity composite material is carried into the fracture network 4 using water as a solvent and a thickening agent-containing carrier liquid. The thickening agent includes plant gums (guar gum, guar gum, konjac, etc.), cellulose derivatives and synthetic polymers. The plastic high thermal conductivity material is made by mixing andalusite, iron powder and graphite powder in a mass ratio of 2:2:6. The thermal conductivity of the plastic high thermal conductivity material is 8.4 W / (m·K).

[0039] The geothermal device includes a heat exchanger 51 located at the wellhead of the abandoned oil and gas well 1, and a non-powered heat extractor 5 located inside the abandoned oil and gas well 1. The non-powered heat extractor 5 includes an insulation component 52 and an evaporator 53. The heat exchanger 51, insulation component 52, and evaporator 53 are connected sequentially from top to bottom, with the evaporator 53 located directly below the insulation component 52. The evaporator 53 and the insulation component 52 are connected by threads. Liquid working fluid is injected into the non-powered heat extractor 5. The liquid working fluid absorbs heat and evaporates into a gaseous working fluid in the crude oil layer 3. The gaseous working fluid is then transferred to the heat exchanger 51 via the evaporator 53 and the insulation component 52. In the heat exchanger 51, the gaseous working fluid condenses, releasing heat and becoming liquid again. The liquid working fluid then flows back into the abandoned oil and gas well 1 under gravity. This achieves a true "heat extraction without water extraction" process, and no water pump is required during operation, thus reducing operating costs.

[0040] The insulation component 52 includes a heat insulation layer 521, a connecting block 522, and a steam pipe 523. The heat insulation layer 521 is made of a double-layer casing filled with aerogel. The heat insulation layer 521 is arranged circumferentially on the well wall of the abandoned oil and gas well 1. The steam pipe 523 is arranged in the heat insulation layer 521 along the well depth direction. The steam pipe 523 and the heat insulation layer 521 are connected by welding through the connecting block 522, forming a first annular space for liquid medium flow between the steam pipe 523 and the heat insulation layer 521. The evaporation component 53 includes an oil casing 531 and a gas-liquid separation device 532. The oil casing 531 is arranged circumferentially on the well wall of the abandoned oil and gas well 1. The gap between the oil casing 531 and the heat insulation layer 521 and the well wall of the abandoned oil and gas well 1 is greater than 15 mm. The wall thickness of the oil casing 531 can be directly selected according to the formation water pressure. Multiple gas-liquid separators 532 are arranged inside the oil casing 531, forming a second annular space for liquid medium flow between the gas-liquid separators 532 and the oil casing 531. When the liquid working fluid flows back from above, it accumulates in the second annular space between the oil casing 531 and the gas-liquid separators 532, enhancing heat exchange with the external fluid. Each gas-liquid separator 532 includes a base 54 and a gas collecting pipe 55. The base 54 is welded to the inner wall of the oil casing 531. The gas collecting pipe 55 is mounted on the base 51 in a Z-shape. The gas collecting pipe 55 is a reducing pipe with an upper and lower diameter ratio of 1:2, which facilitates the collection of the gaseous working fluid below, thereby preventing the reflux of liquid working fluid from colliding with the gaseous working fluid and causing a gas-liquid entrainment effect. The base 54 has multiple drain holes as channels for the return of the liquid working fluid.

[0041] The gas-liquid separation device 532 can reduce the gas-liquid entrainment effect and realize long-distance heat transfer. The oil casing 531 uses an environmentally friendly low-boiling-point working fluid, which expands the temperature range of usable geothermal water and improves the heat extraction power of a single geothermal well.

[0042] Referring to Figures 1-6, a geothermal method for reactivating abandoned oil and gas wells includes the following steps:

[0043] S1. Select abandoned oil and gas well 1 and inject high thermal conductivity composite material into it. The high thermal conductivity composite material will enter the fracture network 4 of crude oil layer 3 through the perforations on the well wall of abandoned oil and gas well 1, so as to realize the rapid transfer of heat from a distance to the surrounding rocks near the well and enhance the thermal conductivity of the thermal reservoir.

[0044] S2. The insulation component 52 and the evaporator 53 are lowered into the non-powered heat exchanger 5, and the temperature measuring fiber optic cable 6 is lowered into the non-powered heat exchanger 5 together to monitor the downhole temperature;

[0045] S3. Fill the third annular space between the wall of the abandoned oil and gas well 1 and the non-powered heat exchanger 5 with high thermal conductivity mud 9, and discharge the gas in the third annular space to increase heat conduction.

[0046] S4. Evacuate the inside of the non-powered heat exchanger 5 to a vacuum of ≤500Pa and inject liquid working fluid.

[0047] The liquid working fluid is a low-boiling-point working fluid, including isobutane, n-butane, Freon, ammonia, etc. The injection amount of the low-boiling-point working fluid is adjusted according to the temperature measured by the temperature-sensing fiber optic cable 6.

[0048] This application also includes a temperature-sensing optical fiber 6, which extends into the abandoned oil and gas well 1 to monitor the downhole temperature. The temperature-sensing optical fiber 6 is connected to an optical fiber temperature testing host 7 via a multimode jumper. The optical fiber temperature testing host 7 is located at the wellhead of the abandoned oil and gas well 1. The optical fiber temperature testing host 7 acquires the downhole temperature of the abandoned oil and gas well 1 through the temperature-sensing optical fiber 6. The distributed optical fiber temperature testing host 7 utilizes the spontaneous Raman scattering principle and optical time-domain reflectometry (OTDR) technology generated when laser light propagates in the temperature-sensing optical fiber 6 to acquire, analyze, and display spatial temperature distribution information. When a laser pulse of a certain energy and width is injected into the temperature-sensing optical fiber 6, it continuously generates backscattered Raman light while propagating forward in the fiber. The intensity of this backscattered Raman light changes depending on the temperature of the scattering point in the fiber. After optical filtering, photoelectric conversion, amplification, and analog-to-digital conversion, the backscattered Raman light is sent to a signal processor, which can calculate the temperature information in real time. Simultaneously, the temperature information is located based on the light propagation speed in the fiber and the time of the backscattered light echo.

[0049] The temperature-sensing optical fiber 6 comprises a fiber core 61, a stainless steel tube 62, fiber grease 63, steel wire armor 64, and a Teflon protective sleeve 65. The fiber core 61 consists of two high-temperature resistant cores, each with an external coating. Each core 61 is housed within the stainless steel tube 62, which is made of 304 stainless steel and filled with fiber grease 63. The steel wire armor 64 is fitted over the stainless steel tube 62, and the Teflon protective sleeve 65 is fitted over the steel wire armor 64. This design ensures the temperature-sensing optical fiber 6 can operate long-term in high-temperature environments, guarantees even heating within a small area, and protects the fiber 6 from physical structural damage caused by friction and scratches.

[0050] Preferably, as shown in Figures 5-6, this embodiment also includes an optical fiber protection device 8. The optical fiber protection device 8 includes a coupling protector 81 and a steel cable tie 82. The coupling protector 81 is welded to the connection between the insulation component 52 and the evaporator 53 to prevent the temperature-sensing optical fiber 6 from directly colliding with the well wall when it is lowered into the well. The coupling protector 81 works in conjunction with the temperature-sensing optical fiber 6, which is fixed to the insulation component 52 and the evaporator 53 by the steel cable tie 82. The optical fiber 6 under test in this application is not afraid of electromagnetic interference and can ensure long-term stable temperature measurement in harsh environments. Compared with conventional protection devices on the market, the cost is reduced by 60%, and it is more suitable for the narrow linear space requirements of the well wall and casing in deep geothermal wells.

[0051] Preferably, as shown in Figure 1, in this embodiment, a third annular space is formed between the oil casing 531 and the insulation layer 521 and the well wall of the abandoned oil and gas well 1. The third annular space is filled with mud 9 to improve the heat absorption capacity of the non-powered heat exchanger 5 at a lower cost. The mud 9 comprises the following raw materials by weight percentage: 30% soil powder, 15% non-fluorescent anti-collapse lubricant, 15% compound ammonium salt, 5% thickening agent and water loss reducer, 10% sulfonated asphalt, 10% HA resin, 5% graphite powder, 2.5% NAT, 2.5% NFA, 2.5% coating agent (FA367), and 2.5% polyacrylamide (PAM).

[0052] The operating principle of this application is that the heat-conducting liquid working fluid absorbs heat and evaporates into a gaseous working fluid at the bottom of the abandoned oil and gas well 1. The gaseous working fluid passes through the evaporation element and insulation in sequence to the ground heat exchanger 51, where it condenses and releases heat to become a liquid working fluid. The liquid working fluid flows back into the abandoned oil and gas well 1 under the action of gravity, realizing a true "heat extraction without water extraction" process. Moreover, no water pump is required during operation, reducing operating costs.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A geothermal device for the retrofitting of abandoned oil and gas wells, characterized in that, The system includes a heat exchanger installed at the wellhead of an abandoned oil and gas well and a non-powered heat exchanger located inside the abandoned oil and gas well. The non-powered heat exchanger includes an insulation component and an evaporator, which are connected sequentially from top to bottom. A liquid working fluid is injected into the non-powered heat exchanger. The liquid working fluid absorbs heat and evaporates into a gaseous working fluid in the crude oil layer. The gaseous working fluid is transferred to the heat exchanger through the evaporator and the insulation component. The gaseous working fluid condenses and releases heat in the heat exchanger, becoming a liquid working fluid. The liquid working fluid flows back to the bottom of the abandoned oil and gas well under the action of gravity.

2. A geothermal device for the retrofitting of abandoned oil and gas wells according to claim 1, characterized in that, The insulation component includes a heat insulation layer, a connecting block, and a steam pipe. The heat insulation layer is arranged circumferentially on the well wall of the abandoned oil and gas well, and the steam pipe is arranged in the heat insulation layer along the well depth direction. The steam pipe is connected to the heat insulation layer through the connecting block. A first annular space for the flow of the liquid medium is formed between the steam pipe and the heat insulation layer.

3. A geothermal device for the retrofitting of abandoned oil and gas wells according to claim 1, characterized in that, The evaporation unit includes an oil casing and a gas-liquid separator. The oil casing is arranged circumferentially on the well wall of the abandoned oil and gas well. The gas-liquid separator is arranged in multiple groups inside the oil casing. A second annular space for the flow of the liquid medium is formed between the gas-liquid separator and the oil casing. Each of the gas-liquid separation devices includes a base and a gas collecting pipe. The base is installed on the inner wall of the oil casing, and the gas collecting pipe is mounted on the base. The base has multiple drain holes.

4. A geothermal device for the renovation of abandoned oil and gas wells according to claim 3, characterized in that, The gas collecting pipe is a variable diameter pipe.

5. A geothermal device for the retrofitting of abandoned oil and gas wells according to claim 1, characterized in that, The insulation component and the evaporator component form a third annular space with the well wall of the abandoned oil and gas well, and the third annular space is filled with high thermal conductivity mud.

6. A geothermal method for the retrofitting of abandoned oil and gas wells, characterized in that, The method, applied to the geothermal apparatus for retrofitting abandoned oil and gas wells as described in any one of claims 1 to 5, comprises: S1. Select abandoned oil and gas wells, inject high thermal conductivity composite materials into them, and enter the fracture network of crude oil layer through perforations on the well wall of abandoned oil and gas wells to enhance the thermal conductivity of the thermal reservoir. S2. Lower the non-powered heat exchanger and lower the temperature measuring fiber along with the non-powered heat exchanger to monitor the downhole temperature; S3. Fill the third annular space between the abandoned oil and gas well wall and the non-powered heat exchanger with mud, and discharge the gas in the third annular space to increase heat conduction. S4. Evacuate the inside of the non-powered heat exchanger and inject a low-boiling-point working fluid.

7. A geothermal method for redeveloping abandoned oil and gas wells according to claim 6, characterized in that, The temperature-measuring optical fiber is connected to an optical fiber temperature testing host, which is located at the wellhead of the abandoned oil and gas well. The optical fiber temperature testing host obtains the downhole temperature of the abandoned oil and gas well through the temperature-measuring optical fiber.

8. A geothermal method for redeveloping abandoned oil and gas wells according to claim 6, characterized in that, The temperature-measuring optical fiber includes a fiber core, a stainless steel tube, fiber grease, steel wire armor, and a Teflon protective sleeve. There are two fiber cores, each of which is located inside the stainless steel tube. The stainless steel tube is filled with the fiber grease. The steel wire armor is fitted over the outside of the stainless steel tube, and the Teflon protective sleeve is fitted over the outside of the steel wire armor.

9. A geothermal method for redeveloping abandoned oil and gas wells according to claim 6, characterized in that, It also includes an optical fiber protection device, which includes a coupling protector and a steel cable tie. The coupling protector is located at the connection between the insulation component and the evaporator, and is used in conjunction with the temperature-sensing optical fiber. The temperature-sensing optical fiber is fixed to the insulation component and the evaporator by the steel cable tie.

10. A geothermal method for redeveloping abandoned oil and gas wells according to claim 6, characterized in that, The injection volume of the liquid working fluid is adjusted according to the temperature measured by the temperature-sensing optical fiber.

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