Underground turbulence type heat transfer enhancement system for single well closed geothermal exploitation

Abstract

The application discloses a downhole turbulence type heat transfer strengthening system for single well closed geothermal exploitation, which comprises a downhole well tube, a single well closed heat exchange device, a ground heat utilization device and an in-well hydraulic disturbance device, the downhole well tube is at least partially buried underground, the downhole well tube comprises a closed well section and an open well section, the closed well section is in contact with a non-target stratum, and the open well section is in contact with and communicates with a target stratum; the single well closed heat exchange device is at least partially provided with a pipeline in the downhole well tube, and at least part of the pipeline is in contact with and exchanges heat with fluid in the downhole well tube; the ground heat utilization device is used for generating power, heating or / and refrigeration by using heat or / and cold provided by the single well closed heat exchange device; and the in-well hydraulic disturbance device is used for changing the liquid pressure size of the bottom of the closed well section, so that fluid in the target stratum and fluid in the open well section periodically and controllably reciprocate, so as to increase the heat obtained by the single well closed heat exchange device.

Description

Technical Field

[0001] This invention relates to the field of geothermal energy development, and more specifically to a downhole turbulence-type heat transfer enhancement system for single-well closed geothermal extraction. Background Technology

[0002] Compared to other renewable energy sources, geothermal energy offers advantages such as stability, continuity, and reliable power supply, making it ideal for heating and base load applications in power systems. Hydrothermal geothermal resources are the easiest to develop and offer the best economic benefits. However, hydrothermal geothermal resources are not widely distributed, and in practical applications, improper geothermal water reinjection can lead to ecological and environmental problems, such as declining groundwater levels and surface water pollution.

[0003] This year, closed-loop geothermal extraction technology, which extracts heat but not water, has become a new direction in the field of geothermal resource development. This technology typically involves arranging a coaxial casing or U-tube within a well, then using a pump to circulate water within the tube, thereby continuously transporting underground heat / cold energy to the surface. Recently, some researchers have also used heat pipes to replace coaxial casings or U-tubes, thereby reducing the risks during geothermal transmission. Losses and power consumption of the circulating pump. Because the heat extraction medium in the above system only circulates within the pipe and is not connected to the groundwater, there is no need for geothermal water reinjection, which fundamentally avoids the ecological and environmental problems that may be caused during the development of hydrothermal geothermal resources.

[0004] However, the aforementioned single-well closed-loop heating technology can only absorb heat from the underground environment through the well wall. Due to the small heat transfer area and the low thermal conductivity of the rock mass, the heating performance of the single-well closed-loop heating system is poor, resulting in a very long investment recovery period or even difficulty in achieving economic benefits, which greatly limits the promotion of single-well closed-loop heating technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a downhole turbulence-type heat transfer enhancement system for single-well closed-loop geothermal extraction. This system can increase the average heat transfer between the single-well closed-loop heat exchange device and the fluid inside the well, as well as the formation outside the well. It can significantly improve the total heating, power generation, or cooling capacity of the system, thereby greatly enhancing the economic benefits of the single-well closed-loop geothermal system.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions:

[0007] A downhole turbulence-based heat transfer enhancement system, comprising:

[0008] An underground well shaft, at least a portion of which is buried underground, the underground well shaft including a closed section and an open section connected to the closed section, the closed section being in contact with a non-target formation, and the open section being in contact with and connected to the target formation;

[0009] A single-well closed-loop heat exchanger, wherein at least a portion of its pipes are located inside the underground well and at least a portion of the pipes are in contact with the fluid inside the underground well for heat exchange;

[0010] A ground-based thermal utilization device for generating electricity, providing heating, and / or cooling using the heat and / or cooling provided by the single-well closed-loop heat exchanger; and,

[0011] The in-well hydraulic disturbance device is used to change the liquid pressure at the bottom of the closed well section, so that the fluid in the target formation and the fluid in the open well section can flow back and forth periodically in a controlled manner, thereby increasing the heat obtained by the single-well closed heat exchange device.

[0012] As described above, the downhole turbulence-type heat transfer enhancement system further includes the following: a storage tank located outside the underground wellbore; the storage tank is connected to a downhole pump via a pumping pipe; the downhole pump is submerged in the fluid within the underground wellbore; and the storage tank is also connected to the underground wellbore via a return pipe equipped with a return valve. One process involves the downhole pump pumping fluid from the underground wellbore into the storage tank via the return pipe, thereby lowering the fluid level in the underground wellbore and allowing fluid from the target formation to flow into the underground wellbore. Another process involves the downhole pump stopping and the return valve on the return pipe being opened, allowing fluid to flow from the storage tank into the underground wellbore, thereby raising the fluid level in the underground wellbore and allowing fluid from the underground wellbore to enter the target formation.

[0013] The downhole turbulence-type heat transfer enhancement system described above is further characterized in that the downhole hydraulic disturbance device includes: an air pump disposed outside the underground wellbore and an exhaust port disposed at the top of the underground wellbore. The air pump is connected to the underground wellbore through a pipeline. One process is: increasing the gas pressure inside the underground wellbore by turning on the air pump, thereby allowing the fluid inside the underground wellbore to enter the target formation; another process is: decreasing the gas pressure inside the underground wellbore by opening the exhaust port, thereby allowing the fluid in the target formation to flow into the underground wellbore.

[0014] As described above, the downhole turbulence-type heat transfer enhancement system further includes the following: a storage tank located outside the underground wellbore, the storage tank being connected to the underground wellbore via a drain pipe equipped with a drain valve, the drain pipe having an air vent; the storage tank also being connected to the underground wellbore via an injection pipe equipped with an injection pump, wherein one process involves: injecting a liquid working fluid with a density less than that of the fluid in the underground wellbore through the air vent, thereby raising the liquid level in the underground wellbore to the surface and connecting it with the liquid level in the storage tank; closing the air vent, and injecting the fluid in the storage tank into the underground wellbore through the injection pump, increasing the pressure in the underground wellbore, thereby allowing the fluid in the wellbore to enter the target formation; another process involves: closing the injection pump, and opening the drain valve to connect the underground wellbore with the storage tank, reducing the pressure in the underground wellbore, thereby allowing the fluid in the target formation to flow into the underground wellbore.

[0015] As described above, in the downhole turbulence-type heat transfer enhancement system, the single-well closed heat exchange device is any one of a coaxial sleeve or U-tube with a single-phase working fluid or a heat pipe downhole heat exchanger with a two-phase working fluid.

[0016] As described above, in the downhole turbulence-type heat transfer enhancement system, the closed section of the underground wellbore adopts any one or a combination of cementing methods such as steel pipe, casing, or cement; the open section of the underground wellbore adopts any one or a combination of open hole, screen pipe, or perforation connection methods.

[0017] As described above, the downhole turbulence-type heat transfer enhancement system further includes a surface heat utilization device that employs any one or a combination of compression, absorption, or adsorption heat pump units; and any one or a combination of ORC, flash, or direct-drive steam generator units.

[0018] In the downhole turbulence-type heat transfer enhancement system described above, the operating time, turbulence frequency, and turbulence intensity of the in-well hydraulic turbulence device are further adjusted according to the geothermal and geological conditions of the underground wellbore.

[0019] The downhole turbulence-based heat transfer enhancement system described above further enhances the connectivity between the target formation and the underground wellbore by performing hydraulic and / or chemical fracturing on the target formation, or by injecting quartz and / or ceramic proppant into the target formation.

[0020] The downhole turbulence-type heat transfer enhancement system described above is further characterized in that the target formation is a water-bearing formation with natural permeability or a permeable formation after the rock mass outside the well has been modified by artificial means; the liquid in the target formation is a naturally occurring original formation fluid such as water, oil or gas, or an artificially injected working fluid such as water, oil or CO2.

[0021] Compared with the prior art, the advantages of this invention are as follows:

[0022] 1. The downhole turbulence-type heat transfer enhancement system for single-well closed geothermal extraction of the present invention is based on the single-well closed heat extraction technology of "extracting heat but not water". Since the heat extraction medium only circulates in the pipe and does not connect with the groundwater, there is no need to reinject geothermal water, which fundamentally avoids the ecological and environmental problems that may be caused in the development of hydrothermal geothermal resources and expands the scope of application of geothermal development technology.

[0023] 2. The downhole turbulence-type heat transfer enhancement system for single-well closed geothermal extraction of the present invention adds an in-well hydraulic disturbance device to the single-well closed geothermal system, which can cause periodic changes in the hydraulic pressure in the well, thereby causing the fluid to flow back and forth between the well and the formation outside the well. This significantly increases the average heat transfer between the single-well closed heat exchange device and the fluid inside the well and the formation outside the well, which can significantly improve the total heating, power generation or cooling capacity of the system and greatly improve the economic benefits of the single-well closed geothermal system. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a first structural schematic diagram of a downhole turbulence-type heat transfer enhancement system for single-well closed geothermal extraction according to an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the second structure of a downhole turbulence-type heat transfer enhancement system for single-well closed geothermal extraction according to an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the third structure of a downhole turbulence-type heat transfer enhancement system for single-well closed geothermal extraction according to an embodiment of the present invention.

[0028] The components include: 1. Single-well closed-loop heat exchanger; 2. Surface heat utilization device; 3. Underground wellbore; 4. In-well hydraulic disturbance device; 5. Closed well section; 6. Open well section; 7. Non-target formation; 8. Target formation; 9. Storage tank; 10. Pumping pipe; 11. Return pipe; 12. Return valve; 13. Downhole pump; 14. Air pump; 15. Exhaust port; 16. Drain pipe; 17. Injection pipe; 18. Drain valve; 19. Air vent; 20. Injection pump; 21. Low-density working fluid. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0030] Example:

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, in the embodiments of this invention are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0033] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" 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.

[0034] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0035] See Figures 1 to 3 This invention provides a downhole turbulence-type heat transfer enhancement system for single-well closed-loop geothermal extraction, which may include: an underground wellbore 3, a single-well closed-loop heat exchanger 1, a surface heat utilization device 2, and an in-well hydraulic disturbance device 4. At least a portion of the underground wellbore 3 is buried underground. The underground wellbore 3 includes a closed well section 5 and an open well section 6 connected below the closed well section 5. The closed well section 5 is in contact with a non-target formation 7, and the open well section 6 is in contact with and connected to the target formation 8. The single-well closed-loop heat exchanger 1 to... A small portion of the pipes are installed within the underground wellbore 3, and at least a portion of the pipes are in contact with the fluid within the underground wellbore 3 for heat exchange. The surface heat utilization device 2 is used to generate electricity, provide heating, and / or cooling using the heat and / or cooling provided by the single-well closed-loop heat exchange device 1. The in-well hydraulic disturbance device 4 is used to change the liquid pressure at the bottom of the closed well section 5, causing the fluid in the target formation 8 and the fluid in the open well section 6 to flow back and forth periodically and in a controlled manner, thereby increasing the heat obtained by the single-well closed-loop heat exchange device 1. Specifically, this embodiment adds an in-well hydraulic disturbance device 4 to the single-well closed-loop geothermal system. The in-well hydraulic disturbance device 4 can periodically change the liquid pressure at the bottom of the closed well section 5, thereby causing the fluid to flow back and forth between the well and the target formation 8, thus increasing the average heat transfer between the single-well closed-loop heat exchange device 1 and the fluid inside the well and the formation outside the well. This can significantly increase the total heating, power generation, or cooling capacity of the system, greatly improving the economic benefits of the single-well closed-loop geothermal system.

[0036] See you again Figure 1 , Figure 1 A downhole turbulence-based heat transfer enhancement system for single-well closed-loop geothermal extraction is demonstrated, comprising four main parts: a single-well closed-loop heat exchanger 1, a surface heat utilization device 2, an underground wellbore 3, and an in-well hydraulic disturbance device 4. The single-well closed-loop heat exchanger 1 enables heat exchange between the surface heat utilization device 2, the fluid inside the well, and the formation outside the well. The surface heat utilization device 2 utilizes the heat / cooling provided by the single-well closed-loop heat exchanger 1 for purposes such as power generation, heating, and cooling. The underground wellbore 3 consists of a closed section 5 and an open section 6. The closed section 5 is in contact with a non-target formation 7, which cannot communicate with the wellbore through the closed section 5. The open section 6 is in contact with a target formation 8, which can communicate with the wellbore through the open section 6. The target formation 8 is permeable, allowing the working fluid to flow from the wellbore into the target formation 8 or vice versa. The in-well hydraulic disturbance device 4 can actively change the liquid pressure at the bottom of the closed well section 5 through manual intervention, so that the fluid in the target formation 8 flows into the well, or the fluid in the well flows into the target formation 8.

[0037] For example, the single-well closed-loop heat exchanger 1 includes downhole heat exchangers such as coaxial casing and U-tubes using single-phase working fluid, and heat pipe downhole heat exchangers using two-phase working fluid. The surface heat utilization device 2 includes heat pump units such as compression, absorption, and adsorption types, as well as generator units such as ORC, flash, and direct-drive steam types. The closed section 5 of the underground wellbore 3 includes cementing methods such as steel pipe, casing, and cement, while the open section 6 of the underground wellbore 3 includes connection methods such as open holes, screen pipes, and perforations. The in-well hydraulic disturbance device 4 can be implemented through the downhole pump 13 injection system, gas pressure control system, hydraulic control system, and other systems capable of actively changing the liquid pressure at the bottom of the closed section 5.

[0038] See you again Figure 1In some embodiments, the in-well hydraulic disturbance device 4 is implemented by a downhole pump 13 injection system, which includes a storage tank 9, a pumping pipe 10, a return pipe 11, and a downhole pump 13. The storage tank 9 is located outside the underground wellbore 3, and is connected to the downhole pump 13 via the pumping pipe 10. The downhole pump 13 is submerged in the fluid within the underground wellbore 3. The storage tank 9 is also connected to the underground wellbore 3 via the return pipe 11 equipped with a return valve 12. The downhole pump 13 pumps fluid from the underground wellbore 3 to the storage tank 9 via the return pipe 11, thereby lowering the fluid level in the underground wellbore 3 and allowing fluid from the target formation 8 to flow into the underground wellbore 3. After the downhole pump 13 stops, the return valve 12 on the return pipe 11 is opened, allowing fluid to flow from the storage tank into the underground wellbore 3, thereby raising the fluid level in the underground wellbore 3 and allowing fluid from the underground wellbore 3 to enter the target formation 8. By periodically controlling the opening and closing of the downhole pump 13 and the return valve 12, fluid can flow back and forth between the wellbore and the target formation 8.

[0039] Specifically, the implementation method of this embodiment is as follows:

[0040] S1: After geological exploration, a suitable well location is determined, and the well is drilled to the target depth. Based on the logging data, a closed well section is set in the shallower, low-temperature non-target stratum 7, and an open well section is set in the deeper, high-temperature target stratum 8, thus completing the construction of the underground well 3.

[0041] S2: Based on well logging data, design and install downhole heat exchange devices and surface heat utilization devices 2;

[0042] S3: Install downhole pump 13 100m below the well fluid level and complete the construction of well hydraulic disturbance device 4;

[0043] S4: Debug the downhole heat exchange device and the surface heat utilization device 2 to ensure their stable operation;

[0044] S5: Based on the well hydraulic disturbance device 4, the fluid is periodically circulated between the well and the target formation 8. The specific operation method is as follows: 1) Close the return valve 12 and open the downhole pump 13. The fluid in the well flows into the storage tank 9 on the surface, causing the fluid level in the well to drop, which in turn leads to a decrease in the hydraulic pressure at the bottom of the sealed section, allowing the liquid in the target formation 8 to flow into the well; 2) Open the return valve 12 and close the downhole pump 13. The fluid in the storage tank 9 flows into the well, causing the fluid level in the well to rise, which in turn leads to an increase in the hydraulic pressure at the bottom of the sealed section, allowing the liquid in the well to flow into the target formation 8.

[0045] S6: Real-time recording of the heat extraction performance of the downhole heat exchange device, and accordingly adjusting the operating time, disturbance frequency, and disturbance intensity of the hydraulic system in the well to maximize the heat extraction performance of the downhole heat exchange device.

[0046] In some embodiments, the downhole pump 13 can also be used to directly extract geothermal water from the well for purposes such as bathing and heating.

[0047] See Figure 2 As an optional implementation, in some embodiments, the hydraulic disturbance device 4 in the well is implemented by a pneumatic control system, which includes an air pump 14 and an exhaust port 15. The air pump 14 is located outside the underground wellbore 3; the exhaust port 15 is located at the top of the underground wellbore 3. The air pump 14 is connected to the underground wellbore 3 via a pipeline, sealing the wellhead of the underground wellbore 3. The air pump 14 can increase the gas pressure inside the well, and the exhaust port 15 can decrease the gas pressure inside the well. By opening the air pump 14 to increase the gas pressure inside the underground wellbore 3, the pressure inside the well can be increased, allowing fluid inside the underground wellbore 3 to enter the target formation 8. By opening the exhaust port 15 to release the gas and liquid pressure inside the well, the gas pressure inside the underground wellbore 3 can be decreased, allowing fluid from the target formation 8 to flow into the underground wellbore 3. By periodically controlling the opening and closing of the air pump 14 and the exhaust port 15, the fluid can flow back and forth between the well and the target formation 8.

[0048] Specifically, the implementation method of this embodiment is as follows:

[0049] S1: After geological exploration, a suitable well location is determined, and the well is drilled to the target depth. Based on the logging data, a closed well section is set in the shallower, low-temperature non-target stratum 7, and an open well section is set in the deeper, high-temperature target stratum 8, thus completing the construction of the underground well 3.

[0050] S2: Based on well logging data, design and install downhole heat exchange devices and surface heat utilization devices 2;

[0051] S3: Seal the annular space at the wellhead and connect it to the air pump 14. At the same time, install the exhaust port 15 at the wellhead and establish the hydraulic disturbance device 4 inside the well.

[0052] S4: Debug the downhole heat exchange device and the surface heat utilization device 2 to ensure their stable operation;

[0053] S5: Based on the well hydraulic disturbance device 4, the fluid is periodically circulated between the well and the target formation 8. The specific operation method is as follows: 1) Turn off the air pump 14, open the exhaust port 15, depressurize the gas and liquid in the well, reduce the hydraulic pressure at the bottom of the sealed section, and then let the liquid in the well flow into the target formation 8; 2) Turn on the air pump 14, close the exhaust port 15, pressurize the gas in the well, increase the hydraulic pressure at the bottom of the sealed section, and then let the fluid in the target formation 8 flow into the well.

[0054] S6: Records the heat extraction performance of the downhole heat exchanger in real time, and adjusts the running time, disturbance frequency and disturbance intensity of the hydraulic disturbance device 4 in the well to maximize the heat extraction performance of the downhole heat exchanger.

[0055] See Figure 3 As an optional implementation, in some embodiments, the in-well hydraulic disturbance device 4 is implemented by a hydraulic control system, which includes a storage tank 9, a drain pipe 16, an injection pipe 17, and an injection pump 20; the drain pipe 16 is equipped with a drain valve 18 and a vent 19. The storage tank 9 is located outside the underground wellbore 3, and is connected to the underground wellbore 3 via the drain pipe 16 with the drain valve 18. The drain pipe 16 is equipped with a vent 19. The storage tank 9 is also connected to the underground wellbore 3 via the injection pipe 17 with the injection pump 20. By injecting a liquid working fluid with a density lower than the fluid inside the underground wellbore 3 into the underground wellbore 3 through the vent 19, the liquid level inside the underground wellbore 3 can be raised to the surface and connected to the liquid level in the storage tank 9. The wellhead is sealed, and the liquid working medium in the storage tank 9 can be pressurized and injected into the well through the injection pump 20, thereby increasing the pressure inside the well and allowing the liquid inside the well to enter the target formation 8. After the injection pump 20 is shut off, the wellhead pressure can be connected to the pressure in the storage tank 9 by opening the drain valve 18 located on the drain pipe 16, thereby reducing the pressure inside the well and allowing the fluid in the target formation 8 to flow into the well. By periodically controlling the opening and closing of the injection pump 20 and the drain valve 18, the fluid can flow back and forth between the well and the target formation 8.

[0056] Specifically, the implementation method of this embodiment is as follows:

[0057] S1: After geological exploration, a suitable well location is determined, and the well is drilled to the target depth. Based on the logging data, a closed well section is set in the shallower, low-temperature non-target stratum 7, and an open well section is set in the deeper, high-temperature target stratum 8, thus completing the construction of the underground well 3.

[0058] S2: Based on well logging data, design and install downhole heat exchange devices and surface heat utilization devices 2;

[0059] S3: Seal the annular space at the wellhead and connect it to the storage tank through the drain pipe 16 and the injection pipe 17 to establish a hydraulic disturbance device 4 in the well.

[0060] S4: Open the drain port 19: Inject low-density working fluid 21 into the well from the storage tank, so that the static liquid level in the well continues to rise until the annular space in the well is filled with low-density working fluid 21, and then close the drain port 19.

[0061] S5: Debug the downhole heat exchange device and the surface heat utilization device 2 to ensure their stable operation;

[0062] S6: Based on the well hydraulic disturbance device 4, the fluid is periodically circulated between the well and the target formation 8. The specific operation method is as follows: close the drain valve 18, open the injection pump 20 to increase the hydraulic pressure in the well, and then allow the fluid in the well to flow into the target formation 8; open the drain valve 18 and close the injection pump 20 to decrease the hydraulic pressure in the well, and then allow the fluid in the target formation 8 to flow into the well.

[0063] S7: Records the heat extraction performance of the downhole heat exchanger in real time, and adjusts the running time, disturbance frequency and disturbance intensity of the hydraulic disturbance device 4 in the well to maximize the heat extraction performance of the downhole heat exchanger.

[0064] See you again Figures 1-3 For example, the operating time, disturbance frequency, and disturbance intensity of the hydraulic system in the wellbore 4 can be flexibly adjusted according to the actual geothermal and geological conditions to achieve the best heat transfer performance enhancement effect. Additionally, hydraulic, chemical, or other artificial fracturing methods can be used on the target formation 8, and proppants such as quartz or ceramics can be injected into the target formation 8 to improve the connectivity between the target formation 8 and the underground wellbore 3. The target formation 8 can be a naturally permeable water-bearing formation or a permeable formation after artificial modification of the surrounding rock mass. The liquid in the target formation 8 can be naturally occurring formation fluids such as water, oil, and gas, or artificially injected working fluids such as water, oil, and CO2.

[0065] In summary, compared with existing geothermal energy utilization technologies, the heat transfer enhancement system of this invention is based on a single-well closed-loop heat extraction technology that "extracts heat but not water." Since the heat extraction medium circulates only within the pipe and is not connected to groundwater, there is no need for geothermal water reinjection, fundamentally avoiding the ecological and environmental problems that may arise during the development of hydrothermal geothermal resources and expanding the scope of geothermal development technology. Furthermore, this invention adds a hydraulic disturbance device 4 to the single-well closed-loop geothermal system, enabling periodic changes in the hydraulic pressure within the well. This causes the fluid to flow back and forth between the well and the surrounding formation, significantly increasing the average heat transfer between the single-well closed-loop heat exchanger 1, the fluid within the well, and the surrounding formation. This significantly improves the system's total heating, power generation, or cooling capacity, greatly enhancing the economic benefits of the single-well closed-loop geothermal system.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A downhole turbulence-based heat transfer enhancement system, characterized in that, include: An underground well shaft, at least a portion of which is buried underground, the underground well shaft including a closed section and an open section connected to the closed section, the closed section being in contact with a non-target formation, and the open section being in contact with and connected to the target formation; A single-well closed-loop heat exchanger, wherein at least a portion of its pipes are located inside the underground well and at least a portion of the pipes are in contact with the fluid inside the underground well for heat exchange; A ground-based thermal utilization device for generating electricity, providing heating and / or cooling using the heat and / or cooling provided by the single-well closed-loop heat exchanger; and... The in-well hydraulic disturbance device is used to change the liquid pressure at the bottom of the closed well section, so that the fluid in the target formation and the fluid in the open well section can flow back and forth periodically in a controlled manner, thereby increasing the heat obtained by the single-well closed heat exchange device.

2. The downhole turbulence-type heat transfer enhancement system according to claim 1, characterized in that, The in-well hydraulic disturbance device includes: a storage tank located outside the underground wellbore; the storage tank is connected to a downhole pump via a pumping pipe; the downhole pump is submerged in the fluid within the underground wellbore; and the storage tank is also connected to the underground wellbore via a return pipe equipped with a return valve. One process involves the downhole pump pumping fluid from the underground wellbore into the storage tank via the return pipe, thereby lowering the fluid level in the underground wellbore and allowing fluid from the target formation to flow into the underground wellbore. Another process involves the downhole pump stopping and the return valve on the return pipe being opened, allowing fluid to flow from the storage tank into the underground wellbore, thereby raising the fluid level in the underground wellbore and allowing fluid from the underground wellbore to enter the target formation.

3. The downhole turbulence-type heat transfer enhancement system according to claim 1, characterized in that, The hydraulic disturbance device inside the well includes: an air pump installed outside the underground well and an exhaust port installed at the top of the underground well. The air pump is connected to the underground well via a pipeline. One process is to increase the gas pressure inside the underground well by turning on the air pump, thereby allowing the fluid inside the underground well to enter the target formation. Another process is to decrease the gas pressure inside the underground well by opening the exhaust port, thereby allowing the fluid in the target formation to flow into the underground well.

4. The downhole turbulence-type heat transfer enhancement system according to claim 1, characterized in that, The in-well hydraulic disturbance device includes: a storage tank located outside the underground wellbore, the storage tank being connected to the underground wellbore via a drain pipe equipped with a drain valve, and the drain pipe having an air vent; the storage tank is also connected to the underground wellbore via an injection pipe equipped with an injection pump, wherein one process is as follows: injecting a liquid working fluid with a density less than that of the fluid in the underground wellbore into the underground wellbore through the air vent, thereby raising the liquid level in the underground wellbore to the surface and connecting it with the liquid level in the storage tank; closing the air vent, and injecting the fluid in the storage tank into the underground wellbore through the injection pump, increasing the pressure in the underground wellbore, thereby allowing the fluid in the wellbore to enter the target formation; another process is as follows: closing the injection pump, and opening the drain valve to connect the underground wellbore with the storage tank, reducing the pressure in the underground wellbore, thereby allowing the fluid in the target formation to flow into the underground wellbore.

5. The downhole turbulence-type heat transfer enhancement system according to any one of claims 1 to 4, characterized in that, The single-well closed-loop heat exchanger is any one of a coaxial sleeve or U-tube with a single-phase working fluid or a heat pipe downhole heat exchanger with a two-phase working fluid.

6. The downhole turbulence-type heat transfer enhancement system according to any one of claims 1 to 4, characterized in that, The closed section of the underground wellbore adopts any one or a combination of cementing methods such as steel pipe, casing, or cement; the open section of the underground wellbore adopts any one or a combination of open hole, screen pipe, or perforation connection methods.

7. The downhole turbulence-type heat transfer enhancement system according to any one of claims 1 to 4, characterized in that, The ground heat utilization device adopts any one or a combination of compression, absorption, or adsorption heat pump units; and any one or a combination of ORC, flash, or direct steam drive generator units.

8. The downhole turbulence-type heat transfer enhancement system according to any one of claims 1 to 4, characterized in that, The operating time, disturbance frequency, and disturbance intensity of the hydraulic disturbance device inside the well are adjusted according to the geothermal and geological conditions of the underground well.

9. The downhole turbulence-type heat transfer enhancement system according to any one of claims 1 to 4, characterized in that, The connectivity between the target formation and the underground wellbore is improved by hydraulic and / or chemical fracturing of the target formation or by injecting quartz and / or ceramic proppant into the target formation.

10. The downhole turbulence-type heat transfer enhancement system according to any one of claims 1 to 4, characterized in that, The target formation is a naturally permeable water-bearing formation or a permeable formation after the rock mass outside the well has been modified by artificial means; the liquid in the target formation is a naturally occurring primary formation fluid such as water, oil or gas, or an artificially injected working fluid such as water, oil or CO2.

Images