Underground heat removal device

Abstract

The invention belongs to the technical field of terrestrial heat application, and particularly relates to an underground heat removal device. The underground heat removal device comprises a heat exchange unit used for exchanging heat with geothermal water; the outer oil pipe is arranged at the upper part of the heat exchange unit; the inner oil pipe is arranged in the outer oil pipe, the two ends of a first annular space between the inner oil pipe and the inner oil pipe are sealed, and a vacuumizing opening communicated with the first annular space is formed in the outer oil pipe.

Description

Technical Field

[0001] The present invention belongs to the field of geothermal application technology, and in particular relates to a downhole heat extraction device. Background Art

[0002] As a representative of green energy, geothermal energy has received widespread attention, with its development scale and application scenarios expanding. Currently, conventional geothermal development is primarily based on a "water extraction for heat" model. However, issues such as "incomplete recharge" are becoming increasingly prominent. Coupled with environmental protection policies such as "heat extraction without water extraction," the development of geothermal energy is being constrained. Therefore, "heat extraction without water extraction"—high-efficiency underground heat extraction technology—is gradually becoming a development trend and an inevitable choice for geothermal development.

[0003] The "extract heat without taking water" technology is to inject the heat exchange medium into the well, and circulate the heat to the ground through a closed / semi-closed heat exchange structure, and the underground hot water is not mined to the ground. Among them, the single-well coaxial casing heat extraction is to inject the heat exchange medium from the annulus, heat it through heat conduction from the well wall, and return it to the ground from the central pipe at the bottom of the well. Existing downhole heat exchangers extract heat from two sources: hot water from the aquifer and high-temperature surrounding rock on the well wall. Heat exchange is mainly carried out in the form of natural disturbance flow. The heat storage on the periphery of the well wall continuously transfers heat to the wellbore to supplement the heat carried away by the circulating working medium in the wellbore, thereby maintaining the stability of the heat exchange. However, natural disturbance flow replenishes heat slowly, and the heat storage cannot achieve rapid heat recovery. The heat exchange efficiency of the coaxial casing needs to be improved.

[0004] Therefore, there is an urgent need to develop a technical solution that can improve the heat exchange efficiency of the "heat without water" technology. Summary of the Invention

[0005] In response to the technical problems described above, the present invention aims to provide an underground heat extraction device that can improve underground heat extraction efficiency.

[0006] According to the present invention, a downhole heat extraction device is provided, comprising:

[0007] a heat exchange unit for exchanging heat with geothermal water;

[0008] An external oil pipe provided on the upper portion of the heat exchange unit; and

[0009] The inner oil pipe is arranged inside the outer oil pipe, and both ends of the first annulus between the inner oil pipe and the inner oil pipe are sealed. The outer oil pipe is provided with a vacuum port connected with the first annulus.

[0010] In a specific embodiment, the heat exchange unit exchanges heat with geothermal water through the perforated section of the wellbore, a second annulus connected to the perforated section is provided between the heat exchange unit and the wellbore, both ends of the second annulus are sealed, a flow disturbance unit is provided below the heat exchange unit, the flow disturbance unit and the heat exchange unit are sealed, the flow disturbance unit includes a first port and a second port, the first port is connected to the second annulus, and the second port is connected to the geothermal reservoir below the wellbore.

[0011] In a specific embodiment, a first packer is provided on the heat exchange unit, and the first packer is located above the perforation section. A second packer is provided on the flow disturbance unit, and the second packer is located below the perforation section and the first port.

[0012] In a specific embodiment, an isolation valve is provided below the heat exchange unit. The isolation valve is configured to be sealed by dropping a ball and then pressurizing the well to set the first packer.

[0013] In a specific embodiment, the isolation valve comprises:

[0014] a sleeve coaxially disposed between the heat exchange unit and the turbulent unit, wherein the upper end of the sleeve is in communication with the heat exchange unit, and a through hole is provided on the sleeve for communicating the inner cavity with the outside; and

[0015] A ball seat is coaxially arranged in the sleeve, and the ball seat is located above the through hole.

[0016] In a specific embodiment, the heat exchange unit includes:

[0017] Thermal sleeve;

[0018] A hanging nipple provided above the thermal sleeve; and

[0019] An insulation pipe is intermittently sleeved in the heat-conducting sleeve, the lower end of the insulation pipe is lower than the first packer, the upper end of the insulation pipe is connected to the inner oil pipe, and the insulation pipe is sealed and hung in the hanging short joint.

[0020] In a specific embodiment, the first packer is arranged above the thermal sleeve, a flow distribution nipple is coaxially arranged above the first packer, and a circulation hole connecting the inner cavity and the outside is provided on the side wall of the flow distribution nipple.

[0021] In a specific embodiment, a telescopic tube is coaxially arranged above the flow distribution short section, and the connecting short section is arranged above the telescopic tube.

[0022] In a specific embodiment, a guide member is coaxially arranged in the heat-conducting sleeve, the upper end of the guide member is arranged to be a cone, and the insulation pipe passes through the guide member.

[0023] In a specific embodiment, the spoiler unit includes:

[0024] an outer cylinder, the second packer, the first port, and the second port being disposed on the outer cylinder;

[0025] a disturbance pump coaxially disposed in the outer cylinder, the disturbance pump comprising an upper port and a lower port; and

[0026] A support sealing ring is sealingly arranged between the outer cylinder and the disturbance pump, the support sealing ring is located below the first port and the upper port, and the second port and the lower port are located below the support sealing ring.

[0027] Compared with the prior art, the advantages of this application are as follows.

[0028] The top of the heat exchange unit of the present invention is connected to the wellhead through a coaxially sleeved inner oil pipe and an outer oil pipe, and a vacuum can be absorbed between the inner oil pipe and the outer oil pipe, thereby enhancing the thermal insulation effect and improving the heat extraction efficiency.

[0029] The present invention provides a heat exchange unit with a flow disturbance unit positioned below it, forming a second annular space between the heat exchange unit and the wellbore. The wellbore's perforated section communicates with the second annular space, allowing high-temperature geothermal water to enter the second annular space through the perforated section. The heat exchange unit can then exchange heat with the geothermal water within the second annular space. The two ports of the flow disturbance unit are connected to the second annular space and the geothermal reservoir at the bottom of the wellbore, respectively. During the heat extraction process, the flow disturbance unit drives the geothermal water to circulate within the annular space and the geothermal water reservoir, thereby maintaining a high temperature within the second annular space and improving heat extraction efficiency.

[0030] Compared with existing technologies, this invention can increase the heat extraction efficiency of a single well by more than 1.5 times and significantly slow the decline in heat extraction efficiency. Furthermore, the underground thermal water does not return to the surface, achieving the "heat extraction without water extraction" development effect, which can facilitate the development and reuse of conventional mid- to deep-layer geothermal resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be described below with reference to the accompanying drawings.

[0032] Figure 1 A schematic diagram showing a downhole heat extraction device according to the present invention is shown;

[0033] Figure 2 A schematic diagram showing the direction of fluid flow during operation of the downhole heat extraction device according to the present invention.

[0034] In the picture:

[0035] 1. Heat exchange unit; 11. Thermal sleeve; 12. Hook-up nipple; 13. Insulation tube; 131. Hook-up piece; 14. Flow distribution nipple; 141. Circulation hole; 15. Telescopic tube; 151. Small-diameter tube; 152. Large-diameter tube; 16. Guide piece; 17. Centralizer;

[0036] 21. External oil pipe; 22. Internal oil pipe; 23. First annulus; 24. Vacuum port; 25. Suspension nipple; 26. Insulation nipple;

[0037] 3. Turbine unit; 31. First port; 32. Second port; 33. Outer cylinder; 34. Turbine pump; 341. Upper port; 342. Lower port; 35. Support seal ring; 36. Damping sub; 361. Damping step; 362. Damping spring;

[0038] 4. Second annulus; 41. First packer; 42. Second packer;

[0039] 5. Isolation valve; 51. Sleeve; 52. Through hole; 53. Ball seat; 531. Second channel; 54. Inner sleeve; 541. First channel;

[0040] 61. Hot water; 62. Cold water; 63. Geothermal water; 64. Geothermal water after heat exchange;

[0041] 7. Shoe guide;

[0042] 10. Wellbore; 101. Geothermal reservoir; 102. Perforation section;

[0043] 100. Underground heat extraction device.

[0044] In this application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn to scale. DETAILED DESCRIPTION

[0045] The present invention will be described below with reference to the accompanying drawings.

[0046] It should be noted that, in this application, the direction of the downhole heat extraction device according to the present invention after entering the well is described as "upper end", "front end" or similar terms, that is, Figure 1 The direction away from the wellhead after the downhole heat extraction device of the present invention is put into the well is described as "lower end", "rear end" or similar terms, that is, Figure 1 Below.

[0047] Figure 1 The structure of the underground heat extraction device 100 according to the present invention is shown. Figure 1 As shown, due to the limitation of the map, Figure 1The downhole heat extraction device 100 is divided into two parts, wherein the right part is the lower part of the downhole heat extraction device 100 , and the left part is the upper part of the downhole heat extraction device 100 .

[0048] like Figure 1 As shown, a downhole heat extraction device 100 includes a heat exchange unit 1, which is used to exchange heat with geothermal water. Specifically, the present invention uses a circulating medium to inject a low-temperature medium from the ground into the well. The low-temperature medium flows into the heat exchange unit 1, exchanges heat with the geothermal water, and becomes a high-temperature medium. The high-temperature medium then flows back to the surface, completing the heat extraction. The specific structure of the heat exchange unit 1 is described below.

[0049] The heat exchange unit 1 is located underground, and therefore a certain distance from the ground. To reduce heat loss from the high-temperature medium as it flows back to the ground, the present invention provides an outer oil pipe 21 above the heat exchange unit 1. An inner oil pipe 22 is coaxially spaced within the outer oil pipe 21. The inner oil pipe 22 is used to transport the medium, forming a first annulus 23 between the outer and inner oil pipes 21, 22. The upper and lower ends of the first annulus 23 are both sealed. Specifically, a seal is provided at the lower portion between the outer and inner oil pipes 21, 22, i.e., a seal is provided at the lower end of the first annulus 23, thereby sealing the lower end of the first annulus 23. An insulation nipple 26 is provided at the upper portion between the outer and inner oil pipes 21, 22, i.e., the insulation nipple 26 is provided at the upper end of the first annulus 23, thereby sealing the lower end of the first annulus 23. A vacuum port 24 is provided on the insulation nipple 26 or the outer oil pipe 21. The vacuum port 24 can be used to set the first annulus 23 to a vacuum state, thereby reducing the heat transfer efficiency between the outer oil pipe 21 and the inner oil pipe 22, thereby preventing the heat of the high-temperature medium from being lost through the outer oil pipe 21 during the process of transporting the high-temperature medium through the inner oil pipe 22.

[0050] According to the present invention, in this embodiment, a heat exchange unit 1 exchanges heat with geothermal water through a perforated section 102 of a wellbore 10. A second annulus 4 communicating with the perforated section 102 is provided between the heat exchange unit 1 and the wellbore 10, with both ends of the second annulus 4 sealed. A flow disturbance unit 3 is provided below the heat exchange unit 1. The flow disturbance unit 3 and the heat exchange unit 1 are sealed, that is, the lower end of the inner cavity of the heat exchange unit 1 is not connected to the upper end of the inner cavity of the flow disturbance unit 3. The flow disturbance unit 3 includes a first port 31 and a second port 32. The first port 31 communicates with the second annulus 4, and the second port 32 communicates with the geothermal reservoir 101 below the wellbore 10.

[0051] Under this configuration, during operation, the heat exchange unit 1 exchanges heat with the geothermal water in the second annulus 4. After the flow disturbance unit 3 is activated, it can promote the circulation of the geothermal water in the second annulus 4 between the perforated section 102 and the geothermal reservoir 101, thereby allowing the geothermal water that has cooled after being extracted to be quickly replaced by the high-temperature geothermal water. This ensures that the geothermal water in the second annulus 4 is always at a higher temperature, thereby improving the heat exchange efficiency of the heat exchange unit 1.

[0052] In a specific embodiment, a first packer 41 is provided on the heat exchange unit 1. The first packer 41 is located above the perforated section 102. After being set, the first packer 41 can seal the heat exchange unit 1 from the wellbore 10. A second packer 42 is provided on the flow disturbance unit 3. The second packer 42 is located below the perforated section 102 and the first port 31, and above the second port 32. After being set, the second packer 42 can seal the flow disturbance unit 3 from the wellbore 10. Through this arrangement, on the one hand, the first packer 41 and the second packer 42 jointly form a second annulus 4, providing a basis for the circulation of geothermal water in the geothermal reservoir 101. On the other hand, the first packer 41 can separate the injected cold water 62 from the geothermal water, achieving heat generation without water production. On the other hand, the second packer 42 can separate the first port 31 and the second port 32 of the flow disturbance unit 3, and at the same time separate the perforation section 102 and the geothermal reservoir 101, thereby constructing a circulation path for geothermal water.

[0053] In this embodiment, the first packer 41 is an open-hole packer, which sets in response to pressure from its inner chamber. The second packer 42 is a self-expanding packer, which automatically expands upon encountering downhole fluid. With this arrangement, once the heat exchange unit 1 and the flow disturbance unit 3 are in place in the well, the first packer 41 is set by holding back pressure, and then the second packer 42 is automatically set.

[0054] In a preferred embodiment, an isolation valve 5 is provided below the heat exchange unit 1. Initially, the isolation valve 5 is configured such that its inner cavity communicates with the outside, while its upper portion communicates with the inner cavity of the heat exchange unit 1. With this configuration, during the lowering of the heat exchange unit 1 and the flow disturbance unit 3 into the well, fluid within the wellbore 10 can enter the inner cavity of the heat exchange unit 1 through the isolation valve 5, and then into the inner cavity of the inner oil pipe 22. This enables automatic grouting during tubing lowering, avoids manual grouting at the wellhead, simplifies the construction process, and facilitates lowering. After a ball is dropped into the isolation valve 5, the isolation valve 5 is blocked, and the inner cavity of the isolation valve 5 is disconnected from the inner cavity of the heat exchange unit 1. At this point, pressure can be built up within the heat exchange unit 1 and transferred to the first packer 41, thereby causing the first packer 41 to be set.

[0055] In a specific embodiment, the isolation valve 5 includes a sleeve 51 coaxially disposed between the heat-conducting sleeve 11 of the heat exchange unit 1 and the flow-disturbing unit 3. The sleeve 51 is configured in a generally cylindrical shape with a closed lower end. The upper end of the sleeve 51 communicates with the heat-conducting sleeve 11 of the heat exchange unit 1. A through hole 52 is provided on the side of the sleeve 51, connecting the inner cavity with the exterior. An inner sleeve 54 is coaxially fixedly disposed within the sleeve 51. A first channel 541 is provided on the side wall of the inner sleeve 54. A ball seat 53 is pinned within the inner sleeve 54. A second channel 531 is provided on the side wall of the ball seat 53. The first channel 541, the second channel 531, and the through hole 52 are connected. The ball seat 53 and the inner sleeve 54 are located above the through hole 52. Under this arrangement, during the process of lowering the heat exchange unit 1 and the flow disturbance unit 3 into the well, the fluid inside the wellbore 10 can enter the inner cavity of the heat exchange unit 1 through the through hole 52, the first channel 541, and the second channel 531 of the isolation valve 5, and then enter the inner cavity of the inner oil pipe 22, thereby realizing automatic grouting during the lowering of the pipe string, avoiding manual grouting at the wellhead, simplifying the construction process, and facilitating lowering. After the ball is dropped into the ball seat 53 of the isolation valve 5 to seal, the inner cavity of the isolation valve 5 is blocked, and the inner cavity of the isolation valve 5 and the inner cavity of the heat-conducting sleeve 11 are in a disconnected state. At this time, pressure can be built up in the heat exchange unit 1 to move the ball seat 53 downward relative to the inner sleeve 54, thereby misaligning the first channel 541 and the second channel 531, closing them. After that, pressurization is continued, and the pressure is transmitted to the first packer 41, causing the first packer 41 to be sealed and hung.

[0056] To ensure that the inner cavity of the downhole heat extraction device 100 is sufficiently large to accommodate the ball during the ball drop process into the ball seat 53, the outer and inner tubing 21 and 22 of the present invention are constructed as separate components. During operation, the outer tubing 21 is lowered into the wellbore along with the other components of the downhole heat extraction device 100. Once in place, the upper end of the outer tubing 21 is suspended from the wellhead via a suspension nipple 25. A ball is then dropped into the isolation valve 5, and pressure is built up to set the first packer 41. Finally, the inner tubing 22 is inserted into the outer tubing 21.

[0057] In a specific embodiment, the heat exchange unit 1 includes a heat-conducting sleeve 11, which is configured to be generally cylindrical. A centralizer 17 is provided on the outer wall of the heat-conducting sleeve 11. A hooking nipple 12 is coaxially provided above the heat-conducting sleeve 11. The hooking nipple 12 is configured to be generally cylindrical. The inner diameter of the upper portion of the inner wall of the hooking nipple 12 is larger than the inner diameter of the lower portion, thereby forming a step within the hooking nipple 12 for hooking. The lower end of the inner oil pipe 22 is connected to the heat-conducting pipe 13. The outer wall of the upper end of the heat-conducting pipe 13 is provided with a hooking member 131 for hooking within the hooking nipple 12. The hooking member 131 is configured to be compatible with the inner wall of the hooking nipple 12, so that the hooking member 131 can be hooked within the hooking nipple 12. A sealing member is also provided on the inner wall of the hooking nipple 12 for sealing with the hooking member 131.

[0058] A seal is provided on the inner wall of the lower end of the outer oil pipe 21 for sealing against the outer wall of the inner oil pipe 22. The inner diameter of the upper end of the thermal insulation sub 26 is smaller than that of the lower end. Specifically, the inner diameter of the upper end of the thermal insulation sub 26 is configured to form a seal with the outer wall of the inner oil pipe 22. The lower end of the thermal insulation sub 26 is sealingly provided on the outer oil pipe 21.

[0059] With this arrangement, after the inner oil pipe 22 and the insulation pipe 13 are put into the well, when the attachment piece 131 of the insulation pipe 13 is sealed and attached to the attachment nipple 12, the insulation pipe 13 is coaxially sleeved in the heat-conducting sleeve 11, and the lower end of the insulation pipe 13 is located below the first packer 41, thereby ensuring successful heat exchange. At the same time, the upper end of the inner oil pipe 22 is sealed with the outer oil pipe 21 by the insulation nipple 26, and the lower end of the inner oil pipe 22 is sealed with the outer oil pipe 21 by the sealing member. When performing heat extraction work, as shown in FIG. Figure 2 As shown, cold water 62 is injected from the wellhead into the annular space between the outer oil pipe 21 and the wellbore 10. When the cold water 62 flows downward to the top of the first seal 41, it enters the annular space between the heat-conducting sleeve 11 and the insulation pipe 13 and continues to flow downward. At this time, the cold water 62 can exchange heat with the geothermal water in the second annulus 4 through the heat-conducting sleeve 11 and become hot water 61. Thereafter, the hot water 61 enters the insulation pipe 13 from the bottom port of the insulation pipe 13, flows upward along the insulation pipe 13, and finally flows to the wellhead through the inner oil pipe 22 to complete heat extraction.

[0060] In a preferred embodiment, the inner diameter of the upper portion of the inner wall of the hanging sub 12 is larger than the inner diameter of the lower portion, and a tapered surface is provided between the upper and lower portions of the inner wall of the hanging sub 12. Accordingly, the outer wall of the hanging member 131 is provided with a structure adapted to the inner wall of the hanging sub 12. The provision of the tapered surface can serve as a guide for lowering the insulation pipe 13.

[0061] According to the present invention, in a specific embodiment, a first packer 41 is coaxially fixed to the upper end of the thermal sleeve 11. A flow distribution sub 14 is coaxially disposed above the first packer 41. The flow distribution sub 14 is constructed in a generally cylindrical shape and has a circulation hole 141 disposed on its sidewall, connecting the inner cavity with the outside. The attachment sub 12 is located above the flow distribution sub 14. When heat extraction is performed, the cold water 62 flows downward from the wellhead along the annular space between the wellbore 10 and the outer oil pipe 21 to the top of the first seal 41, and enters the annular space between the distribution short section 14 and the insulation pipe 13 through the circulation hole 141 of the distribution short section 14. Since the distribution short section 14 is above the hanging short section 12, and the inner wall of the hanging short section 12 is sealed from the outer wall of the insulation pipe 13, the cold water 62 can only flow downward to the annular space between the insulation pipe 13 and the heat-conducting sleeve 11. After the cold water 62 completes heat extraction, it flows upward along the inner cavity of the insulation pipe 13 back to the ground.

[0062] According to the present invention, in a preferred embodiment, a telescopic tube 15 is coaxially arranged above the flow distribution nipple 14, and the hook nipple 12 is arranged above the telescopic tube 15. The telescopic tube 15 is configured to be able to axially expand and contract to change its length, thereby adapting to the thermal expansion and contraction of the downhole heat extraction device 100. Specifically, the telescopic tube 15 includes a large-diameter tube 152 and a small-diameter tube 151. The small-diameter tube 151 is axially movable and sleeved inside the large-diameter tube 152. Convex rings that can abut against each other are provided on the inner wall of the large-diameter tube 152 and the outer wall of the small-diameter tube 151, thereby indicating the relative movement distance of the large-diameter tube 152 and the small-diameter tube 151, thereby preventing the large-diameter tube 152 and the small-diameter tube 151 from separating.

[0063] In a preferred embodiment, a guide member 16 is coaxially disposed within the thermal sleeve 11. The upper end of the guide member 16 is tapered, and the insulation tube 13 passes through the guide member 16. This member not only straightens the insulation tube 13 but also guides the insulation tube 13 during its entry into the well. As will be readily understood, the guide member 16 does not enclose the annular space between the thermal sleeve 11 and the insulation tube 13.

[0064] According to the present invention, in a specific embodiment, the flow disturbance unit 3 includes an outer cylinder 33 and a flow disturbance pump 34 .

[0065] The outer cylinder 33 is constructed to be roughly cylindrical and is coaxially fixed to the lower end of the sleeve 51 of the isolation valve 5. A first port 31 and a second port 32 are provided on the outer cylinder 33. The first port 31 and the second port 32 both connect the inner cavity of the outer cylinder 33 with the outside.

[0066] The first port 31 is provided on the upper outer wall of the outer cylinder 33 , the second port 32 is provided on the lower outer wall of the outer cylinder 33 , and the second packer 42 is provided on the outer cylinder 33 and located between the first port 31 and the second port 32 .

[0067] The disturbance pump 34 is coaxially arranged inside the outer tube 33. The disturbance pump 34 includes an upper port 341 and a lower port 342. A support sealing ring 35 is provided between the outer wall of the disturbance pump 34 and the inner wall of the outer tube 33. The support sealing ring 35 is located between the upper port 341 and the lower port 342, so that the fluid above and below the disturbance pump 34 can only be exchanged through the inside of the disturbance pump 34.

[0068] Furthermore, the support seal ring 35 is located between the first port 31 and the upper port 341. The first port 31 is in communication with the upper port 341, and the second port 32 is in communication with the lower port 342. After the second packer 42 seals the annular space between the outer wall of the outer tube 33 and the inner wall of the wellbore 10, the disturbance pump 34 is activated. The geothermal water in the second annulus 4 can only circulate along the path from the first port 31 to the upper port 341, inside the disturbance pump 34, to the lower port 342, to the second port 32, to the geothermal reservoir 101, to the formation outside the wellbore 10, to the perforated section 102, to the second annulus 4, and finally to the first port 31.

[0069] In a preferred embodiment, a damping subsection 36 is provided at the upper end of the disruptor pump 34. A damping spring 362 is disposed between the upper end surface of the damping subsection 36 and the lower end surface of the sleeve 51 of the isolation valve 5. A damping step 361 is provided on the inner wall of the outer cylinder 33 for abutting the lower end surface of the damping subsection 36. When the disruptor pump 34 vibrates during operation due to instability, the damping subsection 36 and the damping spring 362 can absorb some of the vibration impact of the disruptor pump 34, thereby protecting the disruptor pump 34.

[0070] In a preferred embodiment, at least one flow hole is axially provided on the damping sub 36, and at least one flow hole is also provided on the lower end of the sleeve 51. With this arrangement, when the damping sub 36 moves axially due to the disturbance pump 34, fluid can enter or flow out of the cavity between the damping sub 36 and the sleeve 51 through the flow hole, thereby making the movement of the damping sub 36 smoother and reducing impact.

[0071] In a preferred embodiment, a guide shoe 7 is provided at the lower end of the outer cylinder 33 , and the guide shoe 7 can play a guiding role when the flow disturbance unit 3 is placed into the well.

[0072] like Figure 1As shown, the downhole heat extraction device 100 is suitable for hydrothermal geothermal development in medium- to deep-layer formations, and is suitable for use in vertical wells with two openings or highly deviated wells. After drilling, a suitable section is perforated, forming a perforated section 102 in the wellbore 10. The flow disturbance unit 3, isolation valve 5, heat exchange unit 1, and external oil pipe 21 are connected in sequence from bottom to top, and then lowered into the wellbore. Once fully lowered into position, the first packer 41 is positioned above the perforated section 102, and the second packer 42 is positioned below it.

[0073] like Figure 2 As shown, after the tool string is lowered into place, the pressure-holding ball of the isolation valve 5 is put into the wellhead and pumped to the ball seat 53. The pressure in the pipe is held, and when the specified pressure is reached, the ball seat 53 moves downward relative to the inner sleeve 54, the isolation valve 5 is closed, and the pressure is further held. When the specified pressure is reached, the first packer 41 is used to complete the setting and sealing. The second packer 42 is set after self-expansion in the wellbore water environment for a period of time.

[0074] After the first and second packers 41 and 42 are set, the insulation pipe 13 and inner tubing 22 are connected on the surface and lowered into position, so that the attachment member 131 of the inner tubing 22 is attached to the sub 12, completing the sealing connection. A vacuum pump is then connected to the vacuum port 24 of the wellhead insulation sub 26 to evacuate the air from the first annulus 23 between the inner tubing 22 and outer tubing 21, achieving the vacuum insulation effect.

[0075] After the downhole heat extraction device 100 is lowered, an injection-production cycle and a forced disturbance flow channel are formed, and the two channels are isolated from each other. Figure 2 As shown, the disturbance pump 34 is turned on to disturb the geothermal water 63 in the geothermal reservoir 101 near the wellbore, so as to quickly replenish the heat of the heat-conducting sleeve 11 of the heat exchange unit 1 and improve the heat extraction efficiency of the heat exchange unit 1. After the disturbance pump 34 is running stably, Figure 2 In the direction shown, cold water 62 is injected into the annular space between the wellbore 10 and the outer oil pipe 21, and hot water 61 is recovered to complete the injection-production cycle.

[0076] When the tool string needs later maintenance, first remove the wellhead insulation short section 26, lift the inner oil pipe 22 and the insulation pipe 13 out of the wellhead, then lift the outer oil pipe 21, unseal the packer in the tool string, and complete the recovery operation of the entire tool string. After that, the packer can be replaced, the necessary replacement and maintenance of the consumable parts of the spoiler unit 3 can be carried out, and the necessary maintenance of other key accessories in the tool string can be carried out. After the maintenance is completed, the tool string can be re-lowered according to the tool string running plan.

[0077] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0078] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0079] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations 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 any one or more embodiments or examples.

[0080] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A downhole heat extraction device, characterized in that: include: A heat exchange unit (1) for exchanging heat with geothermal water; an external oil pipe (21) provided on the upper portion of the heat exchange unit (1); as well as An inner oil pipe (22) is arranged inside the outer oil pipe (21), and both ends of a first annulus (23) between the inner oil pipe (22) and the inner oil pipe (21) are sealed. A vacuum port (24) communicating with the first annulus (23) is provided on the outer oil pipe (21).

2. The downhole heat extraction device according to claim 1, characterized in that: The heat exchange unit (1) exchanges heat with geothermal water through a perforated section (102) of a wellbore (10); a second annulus (4) communicating with the perforated section (102) is provided between the heat exchange unit (1) and the wellbore (10); both ends of the second annulus (4) are sealed. A flow disturbance unit (3) is provided below the heat exchange unit (1), and the flow disturbance unit (3) and the heat exchange unit (1) are sealed. The flow disturbance unit (3) comprises a first port (31) and a second port (32), wherein the first port (31) is in communication with the second annulus (4), and the second port (32) is in communication with a geothermal reservoir (101) below the wellbore (10).

3. The downhole heat extraction device according to claim 2, characterized in that: A first packer (41) is provided on the heat exchange unit (1), and the first packer (41) is located above the perforation section (102); a second packer (42) is provided on the flow disturbance unit (3), and the second packer (42) is located below the perforation section (102) and the first port (31).

4. The downhole heat extraction device according to claim 3, characterized in that: An isolation valve (5) is provided below the heat exchange unit (1). The isolation valve (5) is configured to be able to set the first packer (41) by pumping pressure into the well after ball sealing.

5. The downhole heat extraction device according to claim 4, characterized in that: The isolation valve (5) comprises: a sleeve (51) coaxially arranged between the heat exchange unit (1) and the turbulent unit (3), the upper end of the sleeve (51) being in communication with the heat exchange unit (1), and a through hole (52) for connecting the inner cavity with the outside being provided on the sleeve (51); and A ball seat (53) is coaxially arranged in the sleeve (51), and the ball seat (53) is located above the through hole (52).

6. The downhole heat extraction device according to any one of claims 3 to 5, characterized in that: The heat exchange unit (1) comprises: Thermal sleeve (11); A hanging short section (12) arranged above the heat-conducting sleeve (11); and An insulation pipe (13) is intermittently sleeved in the heat-conducting sleeve (11), the lower end of the insulation pipe (13) is lower than the first packer (41), the upper end of the insulation pipe (13) is connected to the inner oil pipe (22), and the insulation pipe (13) is sealed and hung in the hanging short section (12).

7. The downhole heat extraction device according to claim 6, characterized in that: The first packer (41) is arranged above the heat-conducting sleeve (11), a distribution nipple (14) is coaxially arranged above the first packer (41), and a circulation hole (141) is provided on the side wall of the distribution nipple (14) for connecting the inner cavity and the outside.

8. The downhole heat extraction device according to claim 7, characterized in that: A telescopic tube (15) is coaxially arranged above the flow distribution short section (14), and the connecting short section (12) is arranged above the telescopic tube (15).

9. The downhole heat extraction device according to claim 6, characterized in that: A guide member (16) is coaxially arranged in the heat-conducting sleeve (11), the upper end of the guide member (16) is arranged as a cone, and the heat-insulating pipe (13) passes through the guide member (16).

10. The downhole heat extraction device according to any one of claims 3 to 5, characterized in that: The spoiler unit (3) comprises: an outer cylinder (33), wherein the second packer (42), the first port (31) and the second port (32) are provided on the outer cylinder (33); a disturbance flow pump (34) coaxially arranged in the outer cylinder (33), the disturbance flow pump (34) comprising an upper port (341) and a lower port (342); and A support sealing ring (35) is sealed between the outer cylinder (33) and the disturbance pump (34), wherein the support sealing ring (35) is located below the first port (31) and the upper port (341), and the second port (32) and the lower port (342) are located below the support sealing ring (35).

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