Thermal energy storage and crude oil secondary exploitation system and method for depleted oil reservoir

Abstract

The invention provides a heat energy storage and crude oil secondary exploitation system and method for an exhausted oil reservoir, and relates to the technical field of new energy utilization and petroleum engineering crossing. The high-temperature heat-conducting oil circulation loop is connected with the solar heat collector and is used for transmitting and utilizing heat energy; the steam power generation loop is connected with the high-temperature side of the high-temperature heat conduction oil circulation loop and used for converting heat energy into electric energy; the exhausted oil reservoir is used as an underground heat energy storage unit and a crude oil secondary exploitation unit; and the at least one hot water well is communicated with the depleted oil reservoir and is used for injecting high-temperature fluid into the depleted oil reservoir or extracting high-temperature oil-water mixed fluid from the depleted oil reservoir. The efficient multi-energy cooperative co-production system has the beneficial effects that the efficient multi-energy cooperative co-production system is constructed by deeply fusing solar photo-thermal conversion, underground heat energy storage, crude oil secondary enhanced exploitation and a cascade power generation technology, and the comprehensive utilization efficiency of energy and the resource development benefit are remarkably improved.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of new energy utilization and petroleum engineering, and in particular to a thermal energy storage and secondary crude oil recovery system and method for depleted oil reservoirs. Background Technology

[0002] As the proportion of renewable energy sources such as wind and solar increases, the intermittency and volatility of their output intensify, leading to a coexistence of energy curtailment during off-peak hours and shortages during peak hours. This necessitates energy storage technologies with large-scale, long-term regulation capabilities. Existing long-term energy storage solutions each have limitations: pumped hydro storage is constrained by terrain and water resources; compressed air storage is highly dependent on geological conditions and has limited efficiency; electrochemical energy storage is costly and unsuitable for seasonal regulation; and molten salt thermal energy storage is difficult to economically expand to large-scale geological scales.

[0003] Meanwhile, although many depleted oil reservoirs have entered the late stages of development, they still contain large amounts of residual crude oil in underground pores that are difficult to extract due to their high viscosity and poor fluidity. Traditional enhanced oil recovery methods (such as steam injection for thermal recovery by burning fossil fuels) can reduce crude oil viscosity, but they suffer from high energy consumption, large carbon emissions, and high costs. Currently, the reuse of depleted oil reservoirs is mostly concentrated on carbon dioxide sequestration and underground gas storage, lacking a systematic process for using waste heat from renewable energy sources for deep thermal energy storage while simultaneously driving green crude oil extraction. Existing single energy storage systems cannot cope with the complex multiphase flow characteristics of oil and water in oil reservoirs and face challenges such as thermodynamic coupling safety, wellbore heat loss, fluid separation and utilization, and multi-source energy coordinated scheduling. There is an urgent need to propose a new, engineering-feasible approach that can achieve long-term peak shaving for the power grid and activate the residual oil and gas value of abandoned oil reservoirs at low cost. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a thermal energy storage and crude oil secondary recovery system and method for depleted oil reservoirs, which are used to solve the technical problems of low utilization rate of residual oil and large volatility of renewable energy in depleted oil reservoirs.

[0005] Embodiments of the present invention provide a thermal energy storage and crude oil secondary recovery system for depleted oil reservoirs, comprising: Solar collectors; A high-temperature heat transfer oil circulation loop is connected to the solar collector for transmitting and utilizing thermal energy; A steam power generation circuit is connected to the high-temperature side of the high-temperature heat transfer oil circulation circuit and is used to convert thermal energy into electrical energy. Depleted oil reservoirs serve as underground thermal energy storage units and crude oil secondary extraction units; At least one hot water well, connected to the depleted oil reservoir, is used to inject high-temperature fluid into the depleted oil reservoir or to extract high-temperature oil-water mixture from the depleted oil reservoir; At least one cold water well, connected to the depleted oil reservoir, is used to extract cryogenic fluid from the depleted oil reservoir or to reinject cooled fluid into the depleted oil reservoir; A fluid processing unit, connected to the hot water well, includes a first pumping unit, a first impurity filter, and an oil-water separator, used for the extraction, filtration, and separation of underground fluids; The geothermal power generation circuit is connected to the high-temperature water outlet side of the oil-water separator, and is used to generate secondary power using the separated high-temperature hot water. A crude oil storage tank, connected to the crude oil outlet of the oil-water separator, is used to collect the separated crude oil; The high-temperature heat transfer oil circulation loop sequentially transfers the heat captured by the solar collector to the steam power generation loop for power generation. The groundwater extracted from the cold water well is heated by the low-temperature side. The heated groundwater is then injected into the depleted oil reservoir through the hot water well to achieve thermal energy storage and thermal oil recovery. During extraction, the high-temperature oil-water mixture extracted from the hot water well is separated into crude oil and high-temperature hot water by the fluid processing unit. The crude oil enters the crude oil storage tank, and the high-temperature hot water drives the geothermal power generation loop to generate electricity. The tailwater after power generation is reinjected into the depleted oil reservoir through the cold water well to form a closed loop.

[0006] Furthermore, the high-temperature heat transfer oil circulation loop includes heat transfer oil, a heat transfer oil pump, a first heat exchanger, and a second heat exchanger. The first heat exchanger is connected to a steam power generation loop to generate high-temperature and high-pressure steam, and the second heat exchanger is connected to the cold water well to utilize the waste heat of the heat transfer oil to preheat the groundwater.

[0007] Furthermore, the steam power generation circuit includes a steam turbine, a first-stage generator, and a condenser. The steam generated by the first heat exchanger drives the steam turbine to drive the first-stage generator to generate electricity. The steam after doing work is condensed by the condenser and returned to the first heat exchanger for recycling.

[0008] Furthermore, the geothermal power generation circuit includes a secondary heat exchanger, an organic working fluid turbine, and a secondary generator. The secondary heat exchanger receives the high-temperature hot water separated by the oil-water separator and transfers its heat to the organic working fluid. The vaporized organic working fluid drives the organic working fluid turbine to drive the secondary generator to generate electricity. The organic working fluid condenses after doing work and is recycled.

[0009] Furthermore, a second impurity filter and a second extraction pump are installed between the cold water well and the high-temperature heat transfer oil circulation loop to extract low-temperature groundwater for heat exchange with the waste heat of the high-temperature heat transfer oil circulation loop.

[0010] Furthermore, both the hot water well and the cold water well are dual-tube coaxial well structures, with the inner tube used for fluid extraction and the annulus used for fluid injection, thus realizing the same well injection and production function.

[0011] Furthermore, the depleted oil reservoir receives and stores groundwater heated by solar energy. The injected high-temperature water reduces the viscosity of residual crude oil in the reservoir temperature field through heat conduction and forms an oil-water mixture. The thermal energy storage timescale is across seasonal cycles, and the storage capacity is determined by the reservoir pore volume and temperature rise.

[0012] Furthermore, the system forms a closed loop during operation. The low-temperature groundwater extracted from the cold water well is heated and then injected into the oil reservoir through the hot water well. The high-temperature oil-water mixture extracted from the hot water well is separated, and the high-temperature hot water drives the geothermal power generation circuit. The cooled tailwater is reinjected into the depleted oil reservoir through the cold water well to maintain formation pressure balance and working fluid circulation.

[0013] A method for thermal energy storage and secondary crude oil recovery in depleted oil reservoirs, employing a thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs, includes the following steps: a. The solar collector collects solar radiation to heat the heat transfer oil, which drives the steam power generation circuit to generate electricity, achieving the first round of power output; b. The waste heat from the heat transfer oil after power generation heats the low-temperature groundwater extracted from the cold water well in the second heat exchanger; c. The heated groundwater is injected into the depleted oil reservoir through hot water wells, storing the thermal energy in the depleted oil reservoir in the form of sensible heat. At the same time, the viscosity of the residual crude oil is reduced through heat conduction to form an oil-water mixture. d. When energy release or crude oil extraction is required, high-temperature oil-water mixtures are extracted from depleted reservoirs using hot water wells; e. After being filtered by the fluid processing unit, the mixed fluid enters the oil-water separation unit, where it is separated into crude oil and high-temperature hot water. The crude oil is then transported to the crude oil storage tank. f. The separated high-temperature hot water drives the geothermal power generation circuit for secondary power generation; g. The cooled tailwater after geothermal power generation is reinjected into the depleted oil reservoir through cold water wells to maintain formation pressure and form a closed-loop circulation of working fluid, enabling continuous operation of cross-seasonal thermal energy storage and secondary crude oil extraction.

[0014] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: The thermal energy storage and crude oil secondary extraction system and method of the present invention for depleted oil reservoirs, by deeply integrating solar photothermal conversion, underground thermal energy storage, crude oil secondary enhanced extraction and cascade power generation technology, constructs a highly efficient multi-energy synergistic co-production system, and achieves a significant improvement in the comprehensive energy utilization efficiency and resource development benefits.

[0015] This system uses heat transfer oil as a medium to distribute solar thermal energy in stages to the steam power generation circuit and the reservoir heat injection circuit. It achieves the first round of power output by driving turbines with high-temperature steam, and injects the waste heat into the depleted reservoir for large-scale underground thermal storage, forming an "underground thermal battery" effect. This effectively solves the problem of unstable power supply caused by the intermittency and fluctuation of solar energy. By using a network of injection and production wells composed of hot water wells and cold water wells, thermal energy storage and thermal oil driving are organically combined. By heating the reservoir with high-temperature water, the viscosity of residual crude oil is reduced, significantly improving its fluidity. This enables the secondary economic exploitation of residual crude oil in dead oil areas of abandoned reservoirs, greatly improving the final recovery rate. The separated high-temperature hot water further drives the organic working geothermal power generation circuit for secondary power generation, fully recovering geothermal energy to obtain additional electricity revenue, forming a "solar thermal-geothermal-crude oil" triple production model. The system can simultaneously achieve energy storage, power generation, and thermal injection for oil recovery when there is sunlight. During periods without sunlight, it relies on underground thermal storage to continuously and stably produce crude oil and baseload electricity, ensuring the continuous production capacity of the oilfield and avoiding production fluctuations caused by heat source interruptions in traditional thermal recovery. Through optimized multi-well network layout and intelligent injection and production control, it can maximize thermal sweep efficiency and crude oil displacement effect. At the same time, it adopts temperature-resistant and corrosion-resistant equipment and filtration and purification devices to ensure long-term reliable operation of the system. Overall, it realizes the recycling of waste resources, the sustainable development of clean energy, and the diversified output of electricity, heat, and oil products, which has significant economic, environmental, and strategic benefits. It provides an innovative technical path for the green transformation and comprehensive energy utilization of depleted oil and gas fields. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system operation process of the thermal energy storage and crude oil secondary recovery system and method for depleted oil reservoirs of the present invention.

[0017] In the diagram: 1. Solar collector; 2. Thermal oil; 3. Thermal oil pump; 4. First heat exchanger; 5. Second heat exchanger; 6. Steam turbine; 7. First-stage generator; 8. Condenser; 9. Second-stage heat exchanger; 10. Organic working fluid turbine; 11. Second-stage generator; 12. Oil-water separator; 13. Crude oil storage tank; 14. First extraction pump; 15. First impurity filter; 16. Hot water well; 17. Depleted oil reservoir; 18. Cold water well; 19. Second impurity filter; 20. Second extraction pump. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0019] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0020] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0022] In the description of this invention, it should be noted that the circuits, electronic components and modules involved in this invention are all prior art, which can be fully implemented by those skilled in the art, and need not be elaborated upon. The content protected by this invention does not involve improvements to the internal structure and method.

[0023] It should be further noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Please refer to Figure 1 This invention provides a thermal energy storage and secondary crude oil recovery system and method for depleted oil reservoirs. The thermal energy source of this system is a solar collector 1, which can be a trough, tower, or Fresnel collector, with a preferred heat collection temperature range of 250°C to 400°C. The outlet of the solar collector 1 is connected to a high-temperature heat transfer oil circulation loop via a pipeline.

[0025] Furthermore, the high-temperature heat transfer oil circulation loop uses heat transfer oil 2 as the heat transfer medium, and a heat transfer oil pump 3 is installed in the loop to drive the heat transfer oil 2 to circulate. A first heat exchanger 4 and a second heat exchanger 5 are connected in series in this circulation loop. After absorbing solar radiation energy in the solar collector 1, the heat transfer oil 2 heats up, flows through the first heat exchanger 4 and the second heat exchanger 5 in sequence to release heat, and finally returns to the solar collector 1 to form a closed loop.

[0026] It should be noted that the high-temperature side of the first heat exchanger 4 is connected to the steam power generation circuit. The steam power generation circuit uses water-steam as the working fluid. The first heat exchanger 4 transfers the heat of the high-temperature heat transfer oil 2 to the water to generate high-temperature and high-pressure steam. The steam is transported to the steam turbine 6 through the pipeline, which drives the steam turbine 6 to rotate, thereby driving the first-stage generator 7 to generate electricity and realize the first round of power output. The generated electricity can be connected to the grid or used by the system itself.

[0027] After performing work, the low-pressure steam enters the condenser 8, which can be water-cooled or air-cooled. The steam condenses into liquid water in the condenser, and then returns to the first heat exchanger 4 after being pressurized by the feed water pump (not shown in the figure), forming a closed loop of steam power generation circuit.

[0028] In this embodiment, the present invention uses a depleted oil reservoir 17 as a groundwater thermal energy storage unit and a secondary crude oil recovery unit. The depleted oil reservoir 17 is a sandstone or carbonate reservoir that has been exploited to its economic limit. The injection and production process includes at least one hot water well 16 and at least one cold water well 18, both of which are connected to the reservoir of the depleted oil reservoir 17 through wellbores. The well spacing between the hot water well 16 and the cold water well 18 is preferably 200-500 meters to form an effective heat exchange and displacement front.

[0029] Additionally, the wellhead of cold water well 18 is connected in sequence to a second impurity filter 19 and a second extraction pump 20 via pipelines. The second extraction pump 20 is a temperature- and corrosion-resistant submersible electric pump or screw pump used to extract low-temperature groundwater (approximately the original reservoir temperature) from the depleted reservoir 17. The second impurity filter 19 is used to remove solid particles from the fluid to prevent clogging of subsequent heat exchange equipment.

[0030] The wellhead of hot water well 16 is connected to a fluid processing unit via a pipeline. This pipeline is equipped with a first extraction pump assembly 14 and a first impurity filter 15. The first extraction pump assembly 14 is preferably a high-temperature submersible pump or electric submersible pump with a temperature resistance of not less than 150°C, used to extract high-temperature oil-water mixed fluid from the depleted reservoir 17. The first impurity filter 15 preferably has a filtration accuracy of 30-50 μm, used to remove mechanical impurities such as sand particles from the mixed fluid.

[0031] Furthermore, the core equipment of the fluid processing unit is an oil-water separator 12, whose inlet is connected to the first impurity filter 15 via a pipeline. The oil-water separator 12 can be a three-phase centrifugal separator or a high-efficiency electrostatic desalting and dehydration device, which utilizes the density difference between crude oil and water at high temperatures to achieve efficient separation. The crude oil outlet of the oil-water separator 12 is connected to the crude oil storage tank 13 via a pipeline, and the separated crude oil is collected in the storage tank.

[0032] The high-temperature outlet of the oil-water separator 12 is connected to the secondary heat exchanger 9 of the geothermal power generation circuit via a pipeline. The separated high-temperature hot water serves as the heat source for geothermal power generation.

[0033] It is worth noting that the geothermal power generation circuit uses a low-boiling-point organic working fluid. The secondary heat exchanger 9 receives high-temperature hot water from the oil-water separator 12 and transfers its heat to the organic working fluid, causing the organic working fluid to vaporize. The vaporized organic working fluid drives the organic working fluid turbine 10 to rotate, which in turn drives the secondary generator 11 to generate electricity, thus realizing secondary power output.

[0034] After performing work, the organic working fluid vapor enters the condensation system (which can be integrated with condenser 8 or set up independently). After condensing into a liquid state, it is pressurized by the working fluid pump (not shown in the figure) and returned to the secondary heat exchanger 9 for recycling, completing the closed loop of the geothermal power generation circuit.

[0035] Example 1: Synergistic Cogeneration of Solar, Thermal, and Oil Energy under Typical Operating Conditions In this embodiment, the system operates under typical clear weather conditions to maximize energy efficiency and oil recovery.

[0036] During the daytime (energy storage and heat injection phase): Solar collector 1 collects solar energy. Thermal oil 2, driven by thermal oil pump 3, transfers most of the heat to the working fluid in high-temperature heat exchanger 4, generating high-temperature, high-pressure steam. This steam drives steam turbine 6 and first-stage generator 7 to generate electricity. Simultaneously, the cooled thermal oil 2 flows through second heat exchanger 5, transferring residual heat to low-temperature groundwater (treated by low-temperature groundwater pump 20 and low-temperature fluid impurity filter 19) extracted from depleted oil reservoir 17 via cold water well 18. The heated high-temperature groundwater is then injected into depleted oil reservoir 17 through the annulus portion of hot water well 16. The injected high-temperature water not only stores thermal energy but also increases the reservoir temperature, significantly reducing the viscosity of residual crude oil and playing a role in thermal oil displacement.

[0037] In the evening, during peak electricity consumption periods, or during crude oil production periods (recovery and production phases): the system extracts heat energy and crude oil from the depleted reservoir 17. The first extraction pump 14 extracts a high-temperature oil-water mixture through the central part of the hot water well 16. After impurities are removed by the first impurity filter 15, the mixture enters the oil-water separation device 12.

[0038] Crude oil recovery: The crude oil separated in the oil-water separator 12 is transported to the crude oil storage tank 13 for storage, realizing the secondary development of fossil energy; Geothermal power generation: The separated high-temperature hot water (still carrying a large amount of heat energy) is sent to the secondary heat exchanger 9 of the geothermal power generation circuit, which transfers heat to the organic working medium, driving the organic working medium turbine 10 and the secondary generator 11 to generate electricity; Reinjection: The groundwater cooled after power generation is reinjected into the depleted oil reservoir 17 through the annulus of the cold water well 18 to maintain formation pressure.

[0039] This embodiment fully demonstrates the synergistic utilization of solar and geothermal energy, the tiered distribution of heat, and the combined operation of electricity, heat, and oil.

[0040] Example 2: Energy storage release and continuous oil recovery mode during periods of no sunlight In another embodiment, the system operates at night, on cloudy or rainy days, or during periods of low solar irradiance, and relies primarily on the vast thermal energy stored in the depleted reservoir 17 to maintain power supply and crude oil production.

[0041] At this point, solar collector 1 shuts down. The system enters "energy storage and release" mode. The first extraction pump 14 continues to operate, extracting a mixture of crude oil and hot water from the depleted oil reservoir 17, whose viscosity has decreased due to the previous injection of thermal energy.

[0042] Through the oil-water separator 12, the system continuously separates and produces crude oil, ensuring the continuous production capacity of the oil field and avoiding the unstable production caused by heat source fluctuations in traditional thermal recovery methods. At the same time, the separated hot water continues to drive the geothermal power generation circuit to provide baseload electricity.

[0043] After power generation, the cooled groundwater is reinjected through Cold Water Well 18. This model highlights the buffering role of depleted oil reservoirs as "underground thermal batteries," enabling stable crude oil extraction and power output through geological energy storage under low solar energy input conditions.

[0044] Example 3: Well Pattern Optimization and Intelligent Control Strategy for Thermal Oil Flooding In another embodiment, in order to optimize the thermal energy storage efficiency and crude oil displacement effect inside the depleted reservoir 17, the well network layout in the depleted reservoir 17 can adopt a combination of multiple injection wells (such as using the annulus of multiple cold water wells 18 or dedicated injection wells) and multiple production wells (such as using the central pipe of multiple hot water wells 16).

[0045] Well patterning can employ classic five-point, seven-point, or nine-point methods to create a uniform thermal displacement front. Numerical simulations optimize well spacing and injection-production pressure differentials to ensure that injected high-temperature water can reach the oil-bearing area to the maximum extent, improving thermal sweep efficiency. This not only allows for more uniform storage of thermal energy within the underground rock framework but also maximizes the utilization of residual oil in dead oil zones, thereby improving thermal energy recovery and ultimately, oil recovery.

[0046] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0047] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs, characterized in that, include: Solar collector (1); A high-temperature heat transfer oil circulation loop is connected to the solar collector (1) for transmitting and utilizing thermal energy; A steam power generation circuit is connected to the high-temperature side of the high-temperature heat transfer oil circulation circuit and is used to convert thermal energy into electrical energy. Depleted oil reservoirs (17) serve as underground thermal energy storage units and crude oil secondary extraction units; At least one hot water well (16) is connected to the depleted reservoir (17) for injecting high-temperature fluid into the depleted reservoir (17) or extracting high-temperature oil-water mixture from the depleted reservoir (17); At least one cold water well (18) is connected to the depleted oil reservoir (17) for extracting cryogenic fluid from the depleted oil reservoir (17) or reinjecting cooled fluid into the depleted oil reservoir (17); The fluid processing unit, connected to the hot water well (16), includes a first pumping unit (14), a first impurity filter (15), and an oil-water separator (12) for the extraction, filtration, and separation of underground fluids; The geothermal power generation circuit is connected to the high-temperature outlet side of the oil-water separator (12) and is used to generate secondary power using the separated high-temperature hot water. The crude oil storage tank (13) is connected to the crude oil outlet of the oil-water separation device (12) and is used to collect the separated crude oil. The high-temperature heat transfer oil circulation loop transfers the heat captured by the solar collector (1) to the steam power generation loop for power generation, and heats the groundwater drawn from the cold water well (18) on the low-temperature side. The heated groundwater is then injected into the depleted oil reservoir (17) through the hot water well (16) to achieve thermal energy storage and thermal oil recovery. During extraction, the high-temperature oil-water mixture drawn from the hot water well (16) is separated into crude oil and high-temperature hot water by the fluid processing unit. The crude oil enters the crude oil storage tank (13), and the high-temperature hot water drives the geothermal power generation loop to generate electricity. The tailwater after power generation is reinjected into the depleted oil reservoir (17) through the cold water well (18) to form a closed loop.

2. The thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs as described in claim 1, characterized in that: The high-temperature heat transfer oil circulation loop includes heat transfer oil (2), heat transfer oil pump (3), first heat exchanger (4) and second heat exchanger (5). The first heat exchanger (4) is connected to the steam power generation loop to generate high-temperature and high-pressure steam, and the second heat exchanger (5) is connected to the cold water well (18) to preheat the groundwater using the waste heat of the heat transfer oil.

3. The thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs as described in claim 2, characterized in that: The steam power generation circuit includes a steam turbine (6), a first-stage generator (7) and a condenser (8). The steam generated by the first heat exchanger (4) drives the steam turbine (6) to drive the first-stage generator (7) to generate electricity. The steam after doing work is condensed by the condenser (8) and returned to the first heat exchanger (4) for recycling.

4. The thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs as described in claim 1, characterized in that: The geothermal power generation circuit includes a secondary heat exchanger (9), an organic working fluid turbine (10), and a secondary generator (11). The secondary heat exchanger (9) receives the high-temperature hot water separated by the oil-water separator (12) and transfers its heat to the organic working fluid. The vaporized organic working fluid drives the organic working fluid turbine (10) to drive the secondary generator (11) to generate electricity. The organic working fluid condenses after doing work and is recycled.

5. The thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs as described in claim 1, characterized in that: A second impurity filter (19) and a second extraction pump (20) are provided between the cold water well (18) and the high-temperature heat transfer oil circulation loop, for extracting low-temperature groundwater and exchanging heat with the waste heat of the high-temperature heat transfer oil circulation loop.

6. The thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs as described in claim 1, characterized in that: Both the hot water well (16) and the cold water well (18) are dual-tube coaxial well structures, with the inner tube used for fluid extraction and the annulus used for fluid injection, thus realizing the same well injection and production function.

7. The thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs as described in claim 1, characterized in that: The depleted oil reservoir (17) receives and stores groundwater heated by solar energy. The injected high-temperature water reduces the viscosity of the residual crude oil in the reservoir temperature field through heat conduction and forms an oil-water mixture. The thermal energy storage timescale is across seasonal cycles, and the storage capacity is determined by the reservoir pore volume and temperature rise.

8. The thermal energy storage and secondary crude oil recovery system for depleted oil reservoirs as described in claim 1, characterized in that: When the system is running, a closed loop is formed. The low-temperature groundwater extracted by the cold water well (18) is heated and then injected into the oil reservoir through the hot water well (16). The high-temperature oil-water mixture extracted by the hot water well (16) is separated, and the high-temperature hot water drives the geothermal power generation circuit. The cooled tailwater is reinjected into the depleted oil reservoir (17) through the cold water well (18) to maintain the formation pressure balance and working fluid circulation.

9. A method for thermal energy storage and secondary crude oil recovery in a depleted oil reservoir, employing the thermal energy storage and secondary crude oil recovery system for a depleted oil reservoir as described in any one of claims 1-8, characterized in that, Includes the following steps: a. The solar collector (1) collects solar radiation to heat the heat transfer oil (2), and the heat transfer oil (2) drives the steam power generation circuit to generate electricity, thus realizing the first round of power output; b. The residual heat of the heat transfer oil (2) after power generation heats the low-temperature groundwater drawn from the cold water well (18) in the second heat exchanger (5); c. The heated groundwater is injected into the depleted oil reservoir (17) through a hot water well (16), storing the heat energy in the depleted oil reservoir (17) in the form of sensible heat, and at the same time reducing the viscosity of the residual crude oil through heat conduction to form an oil-water mixture; d. When energy release or crude oil extraction is required, high-temperature oil-water mixtures are extracted from depleted reservoirs (17) via hot water wells (16); e. After being filtered by the fluid processing unit, the mixed fluid enters the oil-water separation device (12) and is separated into crude oil and high-temperature hot water. The crude oil is then transported to the crude oil storage tank (13). f. The separated high-temperature hot water drives the geothermal power generation circuit for secondary power generation; g. The cooled tailwater after geothermal power generation is reinjected into the depleted oil reservoir (17) through a cold water well (18) to maintain formation pressure and form a closed-loop circulation of working fluid, thereby realizing the continuous operation of cross-seasonal thermal energy storage and secondary crude oil extraction.

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