Ultra-long gravity assisted heat pipe geothermal development system comprising underground fluid channeling enhanced heat transfer

Abstract

The invention discloses an ultra-long gravity heat pipe geothermal energy development system containing underground fluid channeling layer enhanced heat transfer, and belongs to the field of geothermal energy underground enhanced heat transfer. High-temperature fluid flows into a shallow aquifer from a deep aquifer through the annular channel between the geothermal well and the heat pipe, vertical flow is formed in the geothermal well, and the fluid comes from a high-temperature rock stratum, so that on one hand, the heated high-temperature fluid can provide a large amount of heat, and on the other hand, heat supplement can be carried out on the rock stratum; in addition, the heat exchange capacity outside the heat pipe can be effectively improved through flowing of fluid in the geothermal well, so that the efficient heat collection performance of the heat pipe system is achieved, in addition, the fluid entering the shallow stratum can form a low-temperature zone in the upper stratum, heat in the deep stratum can be transmitted to the shallow stratum faster, and the heat collection efficiency is improved. Therefore, the average temperature difference between the heat pipe evaporation section and the rock stratum is improved, and the heat collection performance of the system is further improved.

Description

Technical Field

[0001] The present invention belongs to the field of enhanced heat transfer in geothermal wells, and particularly relates to an ultra-long gravity heat pipe geothermal development system including enhanced heat transfer by underground fluid cross-layer flow. Background Art

[0002] Geothermal energy has the advantages of huge reserves and being unaffected by climate and environment. Especially in the current situation where environmental problems are prominent and energy security issues are outstanding, as a renewable green energy, it has received a great deal of attention from countries around the world. Geothermal energy is mainly divided into two categories, shallow geothermal energy and medium-deep geothermal energy. Among them, dry hot rock geothermal energy in deep geothermal energy is considered to be the future of geothermal energy due to its huge reserves and high temperature characteristics. Currently, the main geothermal exploitation systems are enhanced geothermal systems and single-well downhole heat exchange systems. Although it has been developed for more than 50 years, the enhanced geothermal system has not yet achieved commercial operation because of problems such as difficult artificial reservoir formation, pipeline corrosion and scaling, fluid loss, and the risk of triggering earthquakes. In recent years, the "heat and water extraction only" closed single-well technology is becoming a new direction for geothermal energy exploitation. Common single-well technologies include U-shaped downhole heat exchanger geothermal systems, coaxial casing downhole heat exchanger geothermal systems, and ultra-long gravity heat pipe geothermal systems. Among them, the ultra-long gravity heat pipe geothermal system is the most efficient and reliable downhole heat exchanger in single-well heat exchange due to its high heat transfer efficiency, excellent temperature uniformity, and no additional pump power consumption.

[0003] For a single-well downhole heat exchange system, even if an ultra-long gravity heat pipe is used as the downhole heat exchanger, the heat transfer efficiency outside the pipe will significantly limit the heat extraction performance of the system. Especially for dry hot rock geothermal resources, there is no or little fluid in the rock mass, and the thermal conductivity of the rock is generally low. During the long-term operation of the system, the heat extraction performance of the system will gradually decrease. Summary of the Invention

[0004] Aiming at the problem of low heat extraction performance of the existing single-well downhole heat exchange system, the present invention provides an ultra-long gravity heat pipe geothermal development system including enhanced heat transfer by underground fluid cross-layer flow. By using two separate aquifers or artificial flow channels, under the action of the pressure difference formed naturally or artificially between the two aquifers, the fluid forms a vertical flow in the annular space between the heat pipe and the rock formation. Since the fluid comes from the high-temperature rock formation, it can not only provide a large amount of heat to the heat pipe, but also thermally compensate the rock formation above the deep aquifer. In addition, the flow of the fluid in the geothermal well can effectively improve the heat exchange capacity on the heat pipe wall, thereby realizing the high-efficiency heat extraction performance of the heat pipe system. In addition, the fluid entering the shallow formation can form a low-temperature zone in the upper formation, enabling the heat in the deep formation to be transferred to the ground faster, thereby increasing the average temperature difference between the evaporation section of the heat pipe and the rock formation and further improving the heat extraction performance of the system.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer, comprising:

[0007] At least two fluid layers located below the ground surface, with a vertical height difference between the two fluid layers and separated by an impermeable rock formation;

[0008] An ultra-long gravity heat pipe system, which includes an ultra-long gravity heat pipe heat exchanger and ground applications. The ultra-long gravity heat pipe heat exchanger is placed in a geothermal well filled with fluid, and the fluids of the two fluid layers are in communication with the fluid in the geothermal well;

[0009] Wherein, a pressure difference is applied to enable the fluid to flow from the relatively deeper fluid layer into the relatively shallower fluid layer through the geothermal well and form a vertical flow in the geothermal well. The gravity heat pipe system exchanges heat with the fluid in the geothermal well through the ultra-long gravity heat pipe heat exchanger and supplies heat to the ground applications.

[0010] For the ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer as described above, further, the fluid layer is a naturally occurring aquifer or an artificial flow channel.

[0011] For the ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer as described above, further, the applied pressure difference is caused by formation rock pressure, or formed by artificial fluid extraction, or formed by using a pressure relief pipe.

[0012] For the ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer as described above, further, the fluid is naturally occurring groundwater or artificially injected fluid.

[0013] For the ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer as described above, further, the fluid is a liquid working medium or a gaseous working medium. Among them, the liquid working medium is water, or supercritical carbon dioxide, nitrous oxide or liquid ammonia; the gaseous working medium is air or water vapor.

[0014] For the ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer as described above, further, the ultra-long gravity heat pipe heat exchanger is a gravity heat pipe, or a U-shaped downhole heat exchanger, or a coaxial casing, or a single-well downhole heat exchanger.

[0015] The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer due to underground fluid cross-layer leakage as described above. Further, the ultra-long gravity heat pipe heat exchanger is a gravity heat pipe. The top of the gravity heat pipe is connected to the ground application through a steam pipe, and a steam regulating valve is provided on the steam pipe. The top of the gravity heat pipe is also connected to the ground application through a liquid pipe, and a liquid regulating valve is provided on the liquid pipe.

[0016] The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer due to underground fluid cross-layer leakage as described above. Further, a wellhead sealer is provided at the top of the geothermal well, a separator is provided below the wellhead sealer, and an air insulation layer or backfill material with a lower thermal conductivity is provided between the wellhead sealer and the separator.

[0017] The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer due to underground fluid cross-layer leakage as described above. Further, the fluid layer is horizontally distributed, or inclinedly distributed, or irregularly distributed.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) With the aid of two aquifers or artificial flow channels, under the action of pressure difference, the heat in the high-temperature formation can be quickly transferred to the heat pipe wall surface for heat exchange. At the same time, the convective heat transfer of the fluid can significantly improve the heat exchange efficiency outside the heat pipe, which helps to improve the overall heat extraction rate of the system.

[0020] (2) Since the heat pipe can effectively absorb the fluid temperature, a low-temperature region can be formed after the fluid enters the shallow aquifer or artificial channel, enabling the heat in the deep formation to transfer faster towards the shallow aquifer, thereby increasing the average temperature difference between the evaporation section of the heat pipe and the rock formation and further improving the heat extraction performance of the system.

[0021] (3) By using the separator and the wellhead sealer, the fluid in the well can be kept below the separator, and at the same time, a heat insulation region composed of air can be formed between the separator and the wellhead sealer, which can effectively reduce heat loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic diagram of the ultra-long gravity heat pipe geothermal development system including enhanced heat transfer due to underground fluid cross-layer leakage adopted in the embodiments of the present invention.

[0024] Description of reference numerals: 1. Ground application; 2. Steam pipeline; 3. Steam regulating valve; 4. Liquid regulating valve; 5. Liquid pipeline; 6. Gravity heat pipe; 7. Wellhead seal; 8. Air insulation layer; 9. Separator; 10. Relief pipe or downhole pump pipeline; 11. Shallow aquifer or flow channel; 12. Geothermal well; 13. Deep aquifer or flow channel. Detailed implementation mode

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0026] Embodiment:

[0027] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0028] In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In view of the problem of low heat extraction performance of the single-well downhole heat exchange system in the prior art, this embodiment provides an ultra-long gravity heat pipe geothermal development system including enhanced heat transfer by underground fluid cross-layer flow. It utilizes two separate aquifers or artificial flow channels. Under the action of the pressure difference formed naturally or artificially between the two aquifers, the fluid forms a vertical flow in the annular space between the heat pipe and the rock formation. Since the fluid comes from the high-temperature rock formation, it can not only provide a large amount of heat to the heat pipe, but also thermally compensate the rock formation above the deep aquifer. In addition, the flow of the fluid in the geothermal well can effectively improve the heat transfer capacity on the heat pipe wall, thereby realizing the high-efficiency heat extraction performance of the heat pipe system. Moreover, the fluid entering the shallow formation can form a low-temperature zone in the upper formation, enabling the heat in the deep formation to transfer faster towards the ground, thereby increasing the average temperature difference between the evaporation section of the heat pipe and the rock formation and further improving the heat extraction performance of the system.

[0030] See Figure 1 , an ultra-long gravity heat pipe geothermal development system including enhanced heat transfer by underground fluid cross-layer flow provided in this embodiment includes: at least two fluid layers located below the ground and a gravity heat pipe system. Among them, the two fluid layers have a vertical height difference and are separated by an impermeable rock formation; the gravity heat pipe system includes an ultra-long gravity heat pipe heat exchanger and a ground application 1. The ultra-long gravity heat pipe heat exchanger is placed in a geothermal well 12 filled with fluid, and the fluids of the two fluid layers are in fluid communication with the fluid in the geothermal well 12; a pressure difference is applied to enable the fluid to flow from the relatively deeper fluid layer through the geothermal well 12 into the relatively shallower fluid layer and form a vertical flow in the geothermal well 12. The gravity heat pipe system exchanges heat with the fluid in the geothermal well 12 through the ultra-long gravity heat pipe heat exchanger and supplies the heat to the ground application 1.

[0031] As an alternative embodiment, the fluid layer is a naturally occurring aquifer or an artificial flow channel. The applied pressure difference is caused by formation rock pressure, or formed by artificially extracting fluid, or formed by using a pressure relief pipe. The fluid is naturally occurring groundwater or artificially injected fluid. The fluid is a liquid working medium or a gaseous working medium, wherein the liquid working medium is water, or supercritical carbon dioxide, nitrous oxide or liquid ammonia; the gaseous working medium is air or water vapor. The ultra-long gravity heat pipe heat exchanger is a gravity heat pipe 6, or a U-shaped downhole heat exchanger, or a coaxial casing, or a single-well downhole heat exchanger. The top of the gravity heat pipe 6 is connected to the ground application 1 through a steam pipe 2, and a steam regulating valve 3 is provided on the steam pipe 2. The top of the gravity heat pipe 6 is also connected to the ground application 1 through a liquid pipe 5, and a liquid regulating valve 4 is provided on the liquid pipe 5. The top of the geothermal well 12 is provided with a wellhead seal 7, and a separator 9 is provided below the wellhead seal 7. An air insulation layer 8 or a backfill material with a lower thermal conductivity is provided between the wellhead seal 7 and the separator 9. The fluid layer is horizontally distributed, or inclinedly distributed, or irregularly distributed.

[0032] In some embodiments, there is a deep aquifer (or artificial flow channel) and a shallow aquifer (or artificial flow channel). There is a certain distance between the two aquifers and they are separated by an impermeable rock formation. At the same time, the geothermal well has a certain space for fluid flow. Under the action of the pressure difference, the fluid flows from the deep aquifer into the shallow aquifer through the geothermal well and forms a vertical flow in the geothermal well. This pressure difference can be caused by formation rock pressure, or can be formed by artificially extracting fluid or using a pressure relief pipe.

[0033] In some embodiments, the gravity heat pipe is placed in a geothermal well filled with fluid. The fluid can be naturally occurring groundwater or artificially injected fluid. The geothermal well connects different aquifers or flow channels. Under the action of the pressure difference, the fluid flows in from the deep aquifer and flows into the shallow aquifer through the geothermal well, realizing the rapid transfer of heat far from the heat pipe to the heat pipe for heat exchange. At the same time, the fluid flowing along the heat pipe can effectively enhance the heat exchange capacity outside the pipe due to the flow effect. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer by underground fluid cross-layer, wherein the ultra-long gravity heat pipe can be replaced by a U-shaped downhole heat exchanger, a coaxial casing and any single-well downhole heat exchanger.

[0034] In some embodiments, the number of aquifers or artificial flow channels can be two or multiple. At the same time, the distribution mode of the aquifers or artificial flow channels can be horizontal distribution, or inclined distribution or irregular distribution.

[0035] In some embodiments, the artificial fluid extraction or pressure relief pipe can extract fluid through a shallow aquifer using a downhole pump, or can insert a pipe body into the shallow aquifer or shallow channel through a borehole to drain the fluid and form a pressure difference. The pipe body can be a steel pipe or other pipe materials with a certain structural strength.

[0036] In some embodiments, the gravity heat pipe system is connected to a ground application. The circulating working fluid absorbs heat and vaporizes in the evaporation section of the heat pipe. The circulating working fluid in the gas state enters the steam pipe through the adiabatic section of the heat pipe and enters the ground utilization through a steam control valve. After releasing heat, it liquefies and enters the gravity heat pipe through a liquid pipe and a liquid control valve to form a closed cycle.

[0037] In some embodiments, a thermal insulation system is also provided. The thermal insulation system includes a separator, an air thermal insulation layer, and a wellhead sealer. The air thermal insulation layer can also replace the air in the annular space with a backfill material with a lower thermal conductivity.

[0038] In some embodiments, the fluid working medium flowing in the downhole, aquifer or artificial flow channel can be a liquid working medium. The liquid working medium can be water, or supercritical carbon dioxide, nitrous oxide, liquid ammonia, etc., or can be a gaseous working medium, such as air, water vapor, etc.

[0039] In a complete embodiment, as Figure 1 shown, an ultra-long gravity heat pipe geothermal development system including enhanced heat transfer of underground fluid crossflow is used for geothermal resource exploitation. The geothermal development system consists of a geothermal well multi-aquifer or multi-flow channel system, an ultra-long gravity heat pipe, a separator, a ground utilization system, and an air thermal insulation layer. Among them, the geothermal well multi-aquifer or multi-flow channel system includes a shallow aquifer or flow channel 11, a deep aquifer or flow channel 13, a geothermal well 12, a separator 9, and a pressure relief pipe 10. The ultra-long gravity heat pipe system includes a gravity heat pipe 6, a steam pipe 2, a ground application 1, a steam control valve 3, a liquid control valve 4, and a liquid pipe 5. The air thermal insulation system includes an air thermal insulation layer 8, a wellhead sealer 7, and a separator 9. The evaporation section of the gravity heat pipe 6 is sequentially placed into the fluid-filled geothermal well 12 with a shallow aquifer or flow channel 11 and a deep aquifer or flow channel 13. Depending on the pressure relief pipeline or natural pressure difference, the fluid flows from the deep aquifer through the annular channel in the geothermal well into the shallow aquifer. During the process of the fluid flowing into the geothermal well, heat rapidly transfers from a position far from the heat pipe to the heat pipe for heat exchange. At the same time, the flowing action of the fluid can effectively improve the heat transfer between the heat pipe wall and the fluid, thereby further improving the heat extraction performance of the system. After placing the gravity heat pipe 6, connect the gravity heat pipe 6 to the steam pipe 2, the steam control valve 3, the ground application 1, the liquid control valve 4, and the liquid pipe 5 in sequence, and then connect the gravity heat pipe 6 again to form a closed loop.

[0040] During operation, the working fluid vaporizes and rises after obtaining heat in the evaporation section of the gravity heat pipe 6, passes through the adiabatic section of the gravity heat pipe 6, enters the ground application 1 through the steam regulating valve 3 and the steam pipeline 2, liquefies after releasing heat, and then the liquid enters the interior of the gravity heat pipe 6 through the liquid pipeline 5 and the liquid regulating valve 4, gradually obtains heat and vaporizes again while flowing back to the heat pipe evaporation section.

[0041] It should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0042] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0043] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0044] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable ordinary technical personnel in the art to understand the content of the present invention and implement it accordingly, and should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the essence of the content of the present invention should be covered within the protection scope of the present invention.

Claims

1. An ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer Characterized in that, Comprising: At least two fluid layers located below the ground surface, with a vertical height difference between the two fluid layers and separated by an impermeable rock formation; An ultra-long gravity heat pipe system, which includes an ultra-long gravity heat pipe heat exchanger and ground applications, the ultra-long gravity heat pipe heat exchanger is placed in a geothermal well filled with fluid, and the fluids of the two fluid layers are in communication with the fluid of the geothermal well; Wherein, a pressure difference is applied to enable the fluid to flow from the relatively deeper fluid layer into the relatively shallower fluid layer through the geothermal well and form a vertical flow in the geothermal well, and the gravity heat pipe system exchanges heat with the fluid of the geothermal well through the ultra-long gravity heat pipe heat exchanger and supplies the heat to the ground applications.

2. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The fluid layer is a naturally occurring aquifer or an artificial flow channel.

3. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The applied pressure difference is caused by formation rock pressure, or formed by artificial fluid extraction, or formed by using a pressure relief pipe.

4. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The fluid is naturally occurring groundwater or artificially injected fluid.

5. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The fluid is a liquid working medium or a gaseous working medium, wherein the liquid working medium is water, or supercritical carbon dioxide, nitrous oxide or liquid ammonia; the gaseous working medium is air or water vapor.

6. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The ultra-long gravity heat pipe heat exchanger is a gravity heat pipe, or a U-shaped downhole heat exchanger, or a coaxial casing, or a single-well downhole heat exchanger.

7. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The ultra-long gravity heat pipe heat exchanger is a gravity heat pipe, the top of the gravity heat pipe is connected to the ground application through a steam pipe, a steam regulating valve is provided on the steam pipe, the top of the gravity heat pipe is also connected to the ground application through a liquid pipe, and a liquid regulating valve is provided on the liquid pipe.

8. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The top of the geothermal well is provided with a wellhead seal, a separator is provided below the wellhead seal, and an air insulation layer or a backfill material with a lower thermal conductivity is provided between the wellhead seal and the separator.

9. The ultra-long gravity heat pipe geothermal development system including enhanced heat transfer through underground fluid cross-layer according to claim 1, Characterized in that, The fluid layer is horizontally distributed, or inclinedly distributed, or irregularly distributed.

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