Medium-deep geothermal buried pipe geothermal well enhanced heat exchange system and working and construction method

Abstract

The invention discloses a geothermal well enhanced heat exchange system for a medium-deep geothermal buried pipe, and a working and construction method. The system comprises a heat exchange sleeve, an insulating central pipe is arranged inside the heat exchange sleeve, a return flower pipe connected with the heat exchange sleeve is fixedly connected at the lower end of the insulating central pipe, an auxiliary seal is fixedly connected at the lower end of the return flower pipe, an annulus is formed between the outer walls of the insulating central pipe and the return flower pipe and the inner wall of the heat exchange sleeve, a water inlet for filling cold water into the annulus is provided on the heat exchange sleeve, and a water outlet for hot water to flow out is provided on the top of the insulating central pipe; a sealing device is fixedly connected to the bottom of the heat exchange sleeve, a hole is opened in the center of the sealing device and an extra-long gravity heat pipe is fixedly sleeved thereon, the interior of the extra-long gravity heat pipe is evacuated and filled with pure water, the upper end of the extra-long gravity heat pipe extends into the return flower pipe and the insulating central pipe, the lower end of the extra-long gravity heat pipe is fixed to the bottom of the geothermal well, secondary heat exchange is carried out by means of the temperature difference between the inside and outside of the extra-long gravity heat pipe, heat exchange at the bottom of the heat exchange well is enhanced, and heat exchange efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the field of geothermal heat exchange technology, and specifically relates to a mid-deep geothermal buried pipe geothermal well enhanced heat exchange system and a working and construction method. Background Art

[0002] The geothermal buried pipe technology is a concentric tube geothermal heat exchange technology that "takes heat but not water". It has been widely promoted and applied in Shaanxi, Gansu and Henan. Its main principle is: drill a geothermal well 2500 m to 3500 m deep underground, install a heat exchange casing in the well, and install an insulated central pipe of the same depth in the heat exchange casing. An annulus is formed between the heat exchange casing and the insulated central pipe. Water enters the annulus from the water inlet of the annulus on the ground and flows downward. The underground heat is extracted through the temperature difference between the water in the annulus and the geothermal, and then flows upward from the insulated central pipe at the bottom of the well, thereby transporting the heat to the outlet of the insulated pipe on the ground.

[0003] Continuously increasing the depth of medium-deep geothermal wells is the main way to increase the heat extraction of medium-deep geothermal heat. At present, 30 and 40 oil drilling rigs are mainly used for construction, with a maximum drilling depth of 3500 m. If the drilling depth is further deepened, 50 or 60 oil drilling rigs will be needed, which will not only increase the drilling cost exponentially, but also the construction of 50 or 60 drilling rigs occupies a large area and consumes high electricity power, making it difficult to organize construction in urban construction; in addition, as the drilling depth increases, the construction difficulty increases sharply, the construction period is greatly extended, the construction risk becomes more uncontrollable, and at the same time, the water circulation resistance is increased, and the existing circulation power is unsustainable.

[0004] Given that geothermal wells at a depth of 3500 m have reached a construction bottleneck, there is an urgent need to improve the structure and construction method of the geothermal buried pipe geothermal well heat exchange system, so as to achieve deeper geothermal utilization at a low cost and improve heat exchange efficiency. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a mid-deep geothermal buried pipe geothermal well enhanced heat exchange system and a working and construction method, which enhances the heat exchange at the bottom of the heat exchange well and improves the heat exchange efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The deep-layer geothermal buried pipe geothermal well enhanced heat exchange system comprises a heat exchange sleeve, an insulating central pipe is arranged inside the heat exchange sleeve, a return flower pipe connected to the insulating central pipe is fixedly connected at the lower end, a guide auxiliary seal is fixedly connected at the lower end of the return flower pipe, an annulus is formed between the outer walls of the insulating central pipe and the return flower pipe and the inner wall of the heat exchange sleeve, the heat exchange sleeve is provided with a water inlet for filling cold water into the annulus, and a water outlet for hot water to flow out is arranged at the top of the insulating central pipe;

[0008] The bottom of the heat exchange sleeve is fixedly connected to a seat sealer, the center of the seat sealer has a hole and an extra-long gravity heat pipe is fixedly sleeved thereon, the interior of the extra-long gravity heat pipe is evacuated and filled with pure water, the upper end of the extra-long gravity heat pipe extends into the reflux flower pipe and the insulating central tube, and the lower end of the extra-long gravity heat pipe is fixed to the bottom of the geothermal well.

[0009] Furthermore, the heat exchange sleeve comprises a heat exchange sleeve body fixed in the geothermal well and a sleeve head fixedly connected to the upper end of the heat exchange sleeve body, and the water inlet is opened in the sleeve head.

[0010] Furthermore, the outer part of the super-long gravity heat pipe is fixedly sleeved with a self-sealing device, and the bottom surface of the self-sealing device abuts against the top surface of the seat sealing device;

[0011] The lower end of the guide auxiliary seal is tightly attached to the top surface of the self-sealing device.

[0012] Furthermore, the ratio of the flow rate of the water in the annulus to the flow rate of the water in the insulated central tube is 1:1.5, and the circulation flow rate of the hot water and the cold water is 30-60 m 3 / h.

[0013] Furthermore, the length of the heat exchange sleeve is 2500-3000 mm, and the diameter is 219.08 mm.

[0014] Furthermore, the length of the super-long gravity heat pipe is 1500-2000 mm, and the sum of its lengths extending into the reflux flower pipe and the insulation center pipe is 500 m;

[0015] The vacuum pressure inside the ultra-long gravity heat pipe is 30~50 KPa, and the pure water inside is 0.5~1m 3 .

[0016] Furthermore, the outer wall of the super-long gravity heat pipe is provided with fins, and the inner wall thereof is provided with flow diversion strips.

[0017] A working method of a medium-deep geothermal buried pipe geothermal well enhanced heat exchange system comprises the following steps:

[0018] 1) Primary heat exchange

[0019] Cold water is injected into the annulus through the water inlet. As the cold water flows downward along the annulus, it continuously exchanges heat with the geothermal energy through the heat exchange sleeve. When the warm water flows to the bottom of the heat exchange sleeve, it flows into the insulated central tube through the reflux flower pipe.

[0020] 2) Secondary heat exchange

[0021] When the geothermal temperature exceeds 70°C, the pure water at the bottom of the ultra-long gravity heat pipe vaporizes to form saturated steam above 100°C. The saturated steam rises from the bottom of the ultra-long gravity heat pipe to the upper end of the ultra-long gravity heat pipe, exchanges heat with the warm water at the bottom of the insulated central tube, and then turns into condensed water and flows back to the bottom of the ultra-long gravity heat pipe to exchange heat with the geothermal again. This cycle is repeated to achieve enhanced heat exchange.

[0022] The hot water inside the heat-insulating central tube is pumped out from the water outlet by an external water pump.

[0023] A construction method for a medium-deep geothermal buried pipe geothermal well enhanced heat exchange system comprises the following steps:

[0024] S1. First, use a 30 or 40 oil drilling rig to drill a geothermal well with a depth of 2500~3000 m underground, then put a heat exchange casing into the geothermal well, and cement it from the bottom of the geothermal well to 500 m upwards. After the cement solidifies, check whether the pressure bearing capacity and 1 hour pressure drop are qualified; then fix the casing head on the outside of the heat exchange casing, and check whether the pressure bearing capacity and 1 hour pressure drop are qualified;

[0025] S2. Use a lower-level drill bit to drill a small-diameter geothermal well to a depth of 4,000 m. After drilling, install an extra-long gravity heat pipe. The specific installation process is as follows:

[0026] First, use drilling machinery to place the sealing device at the bottom of the heat exchange casing, and fix it to the bottom of the heat exchange casing by expansion glue and expansion tube. Then use construction drilling to assist in continuous lowering of 3 to 4 sections of 500m long ultra-long gravity heat pipes. After each section of ultra-long gravity heat pipe is lowered, the joints of the next section of ultra-long gravity heat pipe and the previous section of ultra-long gravity heat pipe are welded. The bottom of the outer fixed sleeve of the last section of ultra-long gravity heat pipe is connected with a self-sealing device. When the last section of ultra-long gravity heat pipe is lowered to the geothermal well, When the ultra-long gravity heat pipe is installed, desalinated pure water is injected into it from the top, and then the top of the ultra-long gravity heat pipe is sealed and vacuumed. After the vacuuming operation is completed, the bottom of the small drill pipe used for drilling is threadedly connected with the top of the ultra-long gravity heat pipe, and the ultra-long gravity heat pipe is placed in the required position. After the placement, the self-sealer abuts against the seat sealer under the action of gravity to achieve automatic sealing. The drill pipe is reversed and separated from the ultra-long gravity heat pipe, and the ultra-long gravity heat pipe is pulled out of the geothermal well to complete the installation of the ultra-long gravity heat pipe.

[0027] S3. Continuously place several sections of insulating central tubes into the heat exchange sleeve, and seal each other between two adjacent sections of the insulating central tubes. A return flower tube is fixedly connected to the bottom of the bottom section of the insulating central tube, and a guide auxiliary seal is fixedly connected to the bottom of the return flower tube. The guide auxiliary seal presses down the self-sealing device, so that the self-sealing device and the seat seal are completely tightly sealed.

[0028] Furthermore, the acceptance criteria for pressure bearing and 1 h pressure drop in S1 are: pressure bearing is not less than 30 MPa, and 1 h pressure drop is less than 0.2 MPa.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] The present invention changes the structure of the heat exchange system inside the geothermal well in the existing medium-deep geothermal buried pipe technology, and introduces the principle of enhancing heat exchange by converting the pure water inside the ultra-long gravity heat pipe into a gas-liquid phase at the bottom of the well on the basis of the basic principle of the existing closed heat exchange casing and geothermal temperature difference heat exchange. That is, by extending the upper end of the ultra-long gravity heat pipe into an insulated central pipe and plugging the lower end into the bottom of the geothermal well, it has the following two advantages: on the one hand, without upgrading the grade of the oil drilling rig, it is possible to extract and utilize geothermal resources with a depth of 4000m, thereby reducing the comprehensive heating cost of the medium-deep geothermal buried pipe technology; on the other hand, by utilizing the water vapor formed by gasification during the temperature difference heat exchange between the pure water inside the long gravity heat pipe and the geothermal, it exchanges heat with the warm water in the insulated central pipe, thereby enhancing the heat exchange efficiency, and increasing the heat extraction of a single well without increasing the head and power of the geothermal well circulating water pump.

[0031] Without increasing the difficulty of construction, the present invention can extend the depth of geothermal wells from the existing 3500 m to 4000 m by changing the structure of the heat exchange system and providing a professional construction plan, breaking through the bottleneck that the existing 30 and 40 oil drilling rigs can only drill geothermal wells with a depth of 3500 m, achieving deeper geothermal utilization at a low cost and improving heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : Schematic diagram of the structure of the heat exchange system of the present invention.

[0033] In the figure: 1. Casing head; 2. Water inlet; 3. Heat exchange casing; 4. Insulated central tube; 5. Reflux flower tube; 6. Self-sealing device; 7. Sealing device; 8. Extra-long gravity heat pipe; 9. Water outlet; 10. Auxiliary seal. DETAILED DESCRIPTION

[0034] The specific contents of the present invention are further explained in detail below in conjunction with embodiments.

[0035] like Figure 1 As shown, a mid-deep geothermal buried pipe geothermal well enhanced heat exchange system includes a heat exchange sleeve 3, the heat exchange sleeve 3 includes a heat exchange sleeve body fixed in the geothermal well, a sleeve head 1 is fixedly sleeved on the upper end of the heat exchange sleeve body, and the sleeve head 1 is provided with a water inlet 2;

[0036] The heat exchange sleeve 3 is provided with an insulating central tube 4 inside, and a return tube 5 connected thereto is fixedly connected to the lower end of the insulating central tube 4, and an auxiliary seal 10 is fixedly connected to the lower end of the return tube 5. An annulus is formed between the outer walls of the insulating central tube 4 and the return tube 5 and the inner wall of the heat exchange sleeve 3, and a water outlet 9 is provided at the top of the insulating central tube 4. During the heat exchange process, cold water is injected into the annulus from the water inlet 2, and during the downward flow, heat is exchanged with the ground heat, and the temperature continues to rise until it flows into the bottom of the heat exchange sleeve 3, and then flows into the insulating central tube 4 from the return tube 5;

[0037] Preferably, the length of the heat exchange sleeve 3 is 2500-3000 m, and the diameter is increased from the existing 177.8 mm to 219.08 mm;

[0038] Preferably, the thermal conductivity of the insulating central tube 4 is less than 0.02 w / (m·k), and there is almost no heat transfer between it and the annulus, thereby improving the heat exchange efficiency;

[0039] Preferably, the ratio of the flow rate of water in the annulus to the flow rate of water in the insulating central tube 4 is 1:1.5, and the circulation flow rate of water is 30-60 m 3 / h, in the actual construction process, the size of the heat exchange sleeve 3 and the insulation center tube 4 can be designed according to the flow rate ratio and temperature difference;

[0040] The bottom of the heat exchange sleeve 3 is fixedly connected with a sealing device 7, the center of the sealing device 7 has a hole and is fixedly sleeved with an extra-long gravity heat pipe 8, the interior of the extra-long gravity heat pipe 8 is evacuated and filled with desalinated pure water, the upper end of the extra-long gravity heat pipe 8 extends into the reflux flower tube 5 and the insulated central tube 4, and the lower end of the extra-long gravity heat pipe 8 is fixed to the bottom of the geothermal well, the pure water at the bottom of the extra-long gravity heat pipe 8 is heated by geothermal energy to be gasified into water vapor, when the water vapor rises to the upper part of the extra-long gravity heat pipe 8, it exchanges heat with the water flowing into the insulated central tube 4, so that the water inside the insulated central tube 4 is further heated, and the water vapor at the upper part of the extra-long gravity heat pipe 8 releases a large amount of heat energy and condenses into liquid pure water, and continues to flow to the lower part of the extra-long gravity heat pipe 8 and is heated again, and this is repeated to achieve enhanced heat exchange;

[0041] Preferably, the length of the super-long gravity heat pipe 8 is 1500-2000 m, the length of the portion extending into the reflux flower pipe 5 and the insulated central pipe 4 is 500 m, the lower end 1000-1500 m is inserted into the ground through the sealing device 7, and the super-long gravity heat pipe 8 is equipped with 0.5-1 m 3 Desalinated pure water, and the internal vacuum pressure is 30~50 KPa;

[0042] The outer part of the super-long gravity heat pipe 8 is fixedly sleeved with a self-sealing device 6, the bottom surface of the self-sealing device 6 is in contact with the top surface of the sealing device 7, and the surrounding of the self-sealing device 6 is tightly attached to the inner wall of the heat exchange sleeve 3. By guiding the auxiliary seal 10 to press downward, the bottom surface of the self-sealing device 6 is pressed tightly against the upper surface of the sealing device 7, thereby achieving the sealing between the super-long gravity heat pipe 8 and the heat exchange sleeve 3, and effectively preventing water leakage in the annulus;

[0043] Preferably, the self-sealing device 6 is made of a rubber-lined material, that is, the base is made of steel and the outside is wrapped with rubber, thereby improving its mechanical strength and sealing performance;

[0044] Preferably, the outer wall of the super-long gravity heat pipe 8 is equipped with vertical threaded fins with a height of 2 mm, and the radius of the part extending into the reflux flower tube 5 and the insulation center tube 4 after the fins are installed is 100 mm; the radius of the remaining part after the fins are installed is 90 mm, which is convenient for smooth installation;

[0045] Preferably, the inner wall of the super-long gravity heat pipe 8 is sparsely provided with flow strips in the shape of thread grooves and with a trapezoidal cross section, which can promote the condensed water to quickly flow back to the lower part of the super-long gravity heat pipe 8.

[0046] A working method of a medium-deep geothermal buried pipe geothermal well enhanced heat exchange system comprises the following steps:

[0047] 1) Primary heat exchange

[0048] Cold water is injected into the annulus through the water inlet 2. As the cold water flows downward along the annulus, it continuously exchanges heat with the ground heat through the heat exchange sleeve 3. When the warm water flows to the bottom of the heat exchange sleeve 3, it flows into the insulating central pipe 4 through the reflux flower pipe 5.

[0049] 2) Secondary heat exchange

[0050] When the geothermal temperature exceeds 70°C, the water at the bottom of the super-long gravity heat pipe 8 is vaporized to form saturated steam above 100°C. The saturated steam rises from the bottom of the super-long gravity heat pipe 8 to the upper end of the super-long gravity heat pipe 8, exchanges heat with the warm water at the lower part of the insulated central tube 4, turns into condensed water and flows back to the bottom of the super-long gravity heat pipe 8, exchanges heat with the geothermal again and vaporizes, continues to rise to the upper end of the super-long gravity heat pipe 8, exchanges heat with the warm water at the lower part of the insulated central tube 4, and repeats the cycle to achieve enhanced heat exchange;

[0051] The hot water inside the heat-insulating central tube 4 is pumped out from the water outlet 9 by an external water pump, so as to be used for production and life.

[0052] A construction method for a medium-deep geothermal buried pipe geothermal well enhanced heat exchange system comprises the following steps:

[0053] S1. First, use a 30 or 40 oil drilling rig to drill a geothermal well with a depth of 2500~3000 m underground, then put a heat exchange casing 3 into the geothermal well, and cement the well 500 m upward from the bottom of the geothermal well using G-grade cement with a relative density of not less than 1.8. After the cement solidifies for 48 hours, if the pressure is not less than 30 MPa and the pressure drop is less than 0.2 MPa in 1 hour, it is considered qualified; then fix the casing head 1 on the outside of the heat exchange casing 3. If the pressure is not less than 30 MPa and the pressure drop is less than 0.2 MPa in 1 hour, it is considered qualified;

[0054] S2. Use a lower-level drill bit to drill a small-diameter geothermal well, so that the maximum drilling depth of a 30 or 40 oil drilling rig reaches 4000 m. After the drilling is completed, install the extra-long gravity heat pipe 8. The specific installation process is as follows:

[0055] First, use drilling machinery to place the sealing device 7 to the bottom of the heat exchange sleeve 3, and seal it to the bottom of the heat exchange sleeve 3 through expansion glue and expansion tube, and then use construction drilling to assist in lowering 3 to 4 sections of super-long gravity heat pipes 8 with a length of 500m. After each section of super-long gravity heat pipe 8 is lowered, the joint between the next section of super-long gravity heat pipe 8 and the previous section of super-long gravity heat pipe 8 is welded, and the welding grade is level 1. The outer bottom of the last section of super-long gravity heat pipe 8 (that is, the first section of super-long gravity heat pipe from top to bottom after installation is completed) is fixedly sleeved with a self-sealing Sealer 6, when the last section of the super-long gravity heat pipe 8 is lowered to the geothermal well, desalinated pure water is injected from the top of the super-long gravity heat pipe 8, and then the top of the super-long gravity heat pipe 8 is sealed and vacuumed. After the vacuuming operation is completed, the bottom of the small drill pipe used for drilling is threadedly connected with the top of the super-long gravity heat pipe 8, and the super-long gravity heat pipe 8 is placed in the pre-designed position. After being placed in place, the self-sealer 6 abuts against the seat sealer 7 under the action of gravity to achieve automatic sealing. After the sealing is completed, the drill pipe is reversed to separate from the super-long gravity heat pipe 8 and is taken out of the geothermal well;

[0056] S3. Place several sections of 12 m long insulating central tubes 4 into the heat exchange sleeve 3 in succession. Two adjacent sections of the insulating central tubes 4 are threadedly connected, and the joints are sealed with each other by sealant. The bottom of the lowest section of the insulating central tube 4 is fixedly connected with a return tube 5, and the bottom of the return tube 5 is fixedly connected with a guide auxiliary seal 10. The bottom of the return tube 5 is sealed by the guide auxiliary seal 10, and the guide auxiliary seal 10 can press down the self-sealing device 6, thereby strengthening the self-sealing between the self-sealing device 6 and the seat seal 7.

Claims

1. A construction method for a medium-deep geothermal buried pipe geothermal well enhanced heat exchange system, characterized in that: The system comprises a heat exchange sleeve (3) fixed inside a geothermal well, an insulating central tube (4) being provided inside the heat exchange sleeve (3), a return tube (5) being fixedly connected to the lower end of the heat exchange sleeve (4) and communicating therewith, a guide auxiliary seal (10) being fixedly connected to the lower end of the return tube (5), an annulus being formed between the outer walls of the heat exchange sleeve (4) and the return tube (5) and the inner wall of the heat exchange sleeve (3), a water inlet (2) for filling the annulus with cold water, and a water outlet (9) for hot water to flow out being provided at the top of the heat exchange sleeve (4); The heat exchange sleeve (3) comprises a heat exchange sleeve body fixed in the geothermal well and a sleeve head (1) fixedly connected to the upper end of the heat exchange sleeve body, and a water inlet (2) is provided in the sleeve head (1); The bottom of the heat exchange sleeve (3) is fixedly connected to a sealing device (7), the center of the sealing device (7) is opened and a super-long gravity heat pipe (8) is fixedly sleeved thereon, the interior of the super-long gravity heat pipe (8) is evacuated and filled with pure water, the upper end of the super-long gravity heat pipe (8) extends into the interior of the reflux flower pipe (5) and the insulating central pipe (4), and the lower end of the super-long gravity heat pipe (8) is fixed to the bottom of the geothermal well; The super-long gravity heat pipe (8) is externally fixedly sleeved with a self-sealing device (6), and the bottom surface of the self-sealing device (6) abuts against the top surface of the seat sealing device (7); The lower end of the auxiliary seal (10) is in close contact with the top surface of the self-sealing device (6); The construction method includes the following steps: S1. First, a 30 or 40 oil drilling rig is used to drill a geothermal well with a depth of 2500-3000 m underground, and then a heat exchange casing (3) is placed in the geothermal well. Cement is used to cement the well from the bottom of the geothermal well to 500 m upwards. After the cement solidifies, the pressure bearing capacity and 1-hour pressure drop are inspected and tested to be qualified; then the casing head (1) is fixedly sleeved on the outside of the heat exchange casing (3), and the pressure bearing capacity and 1-hour pressure drop are inspected and tested to be qualified; S2. Use a lower-level drill bit to drill a small-diameter geothermal well to a depth of 4000 m. After the drilling is completed, install the extra-long gravity heat pipe (8). The specific installation process is as follows: First, use the drilling machine to place the sealing device (7) to the bottom of the heat exchange casing (3), fix it to the bottom of the heat exchange casing (3) by using the expansion glue and the expansion tube, and then lower 3 to 4 sections of 500 mm long. m ultra-long gravity heat pipe (8), after each section of the ultra-long gravity heat pipe (8) is lowered, the joint between the next section of the ultra-long gravity heat pipe (8) and the previous section of the ultra-long gravity heat pipe (8) is welded, and the outer bottom of the last section of the ultra-long gravity heat pipe (8) is fixedly sleeved with a self-sealing device (6). When the last section of the ultra-long gravity heat pipe (8) is lowered into the geothermal well, desalinated pure water is injected from the top of the ultra-long gravity heat pipe (8), and then the top of the ultra-long gravity heat pipe (8) is sealed and vacuumed. After the vacuuming operation is completed, the bottom of the small drill pipe used for drilling is threadedly connected to the top of the ultra-long gravity heat pipe (8), and the ultra-long gravity heat pipe (8) is dropped into the required position. After being dropped into place, the self-sealing device (6) abuts against the sealing device (7) under the action of gravity to achieve automatic sealing, and the drill pipe is reversed and separated from the ultra-long gravity heat pipe (8), and the installation of the ultra-long gravity heat pipe (8) is completed; S3. Several sections of the heat-exchange central tube (4) are continuously placed inside the heat-exchange sleeve (3). Two adjacent sections of the heat-exchange central tube (4) are sealed and connected to each other. A return tube (5) is fixedly connected to the bottom of the bottom section of the heat-exchange central tube (4). A guide auxiliary seal (10) is fixedly connected to the bottom of the return tube (5). The guide auxiliary seal (10) presses down the self-sealing device (6) so that the self-sealing device (6) and the seat seal (7) are completely tightly sealed.

2. The construction method of the mid-deep geothermal buried pipe geothermal well enhanced heat exchange system according to claim 1 is characterized in that: The ratio of the flow rate of the water in the annulus to the flow rate of the water in the insulating central tube (4) is 1:1.5, and the circulation flow rate of the hot water and the cold water is 30~60 m 3 / h.

3. The construction method of the mid-deep geothermal buried pipe geothermal well enhanced heat exchange system according to any one of claims 1 to 2, characterized in that: The outer wall of the super-long gravity heat pipe (8) is provided with fins, and the inner wall thereof is provided with flow diversion strips.

4. The construction method of the mid-deep geothermal buried pipe geothermal well enhanced heat exchange system according to claim 1, characterized in that: The acceptance criteria for pressure bearing and 1 h pressure drop in S1 are: pressure bearing is not less than 30 MPa, and 1 h pressure drop is less than 0.2 MPa.

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