Tail end insertion type underground heat removal device

Abstract

The invention belongs to the technical field of terrestrial heat application, and particularly relates to a tail end insertion type underground heat removal device. The tail end insertion type underground heat removal device comprises an insertion pipe packing mechanism arranged in a shaft, a perforation section is arranged on the side wall of the shaft, and the insertion pipe packing mechanism is arranged below the perforation section in a setting mode; the turbulent flow pump is arranged in the shaft, and the turbulent flow pump is arranged in the inserting pipe packing mechanism in an inserting and connecting mode in a sealed mode; the heat exchange unit is coaxially arranged in the shaft, and the heat exchange unit is set above the perforation section; a second annulus is formed between the setting position of the insertion pipe packing mechanism and the shaft and the setting position of the heat exchange unit and the shaft, the second annulus is communicated with the perforation section, the upper end opening of the turbulent flow pump is communicated with the second annulus, and the lower end opening of the turbulent flow pump is communicated with the lower portion of the insertion pipe packing mechanism. The heat exchange unit exchanges heat with geothermal water in the second annulus in a medium circulating mode.

Description

Technical Field

[0001] The present invention belongs to the field of geothermal application technology, and in particular relates to a tail-end insertion type 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 a tail-end insertion-type underground heat extraction device, which can improve the underground heat extraction efficiency.

[0006] According to the present invention, a tail-end insertion type downhole heat extraction device is provided, comprising:

[0007] A cannulated isolation mechanism is provided in a wellbore, wherein a perforation section is provided on a side wall of the wellbore, and the cannulated isolation mechanism is set below the perforation section;

[0008] A disturbance flow pump is provided in the wellbore, and the disturbance flow pump is sealed and provided in the cannula isolation mechanism by plugging.

[0009] a heat exchange unit coaxially disposed in the wellbore, wherein the heat exchange unit is set above the perforation section;

[0010] A second annulus is formed between the intubation isolation mechanism and the setting position of the wellbore, and between the heat exchange unit and the setting position of the wellbore. The second annulus is connected to the perforation section. The upper port of the disturbance pump is connected to the second annulus, and the lower port of the disturbance pump is connected to the bottom of the intubation isolation mechanism. The heat exchange unit exchanges heat with the geothermal water in the second annulus by means of a circulating medium.

[0011] In a specific embodiment, the cannula isolation mechanism includes:

[0012] outer cylinder;

[0013] a second packer coaxially arranged on the outer cylinder, wherein the second packer is located below the perforation section;

[0014] A second ball seat is coaxially arranged in the outer cylinder, and the second ball seat is located below the second packer. Throwing a ball into the second ball seat and holding the pressure can set the second packer.

[0015] In a specific embodiment, the intubation sealing mechanism also includes a return tube arranged at the upper end of the outer tube, a sealing plug is provided at the lower end of the disturbance pump, the sealing plug is coaxially arranged in the return tube, and a seal is provided between the return tube and the sealing plug. The upper port of the disturbance pump is located above the sealing plug, and the lower port of the disturbance pump is connected to the inner cavity of the sealing plug.

[0016] In a specific embodiment, an outer oil pipe is provided on the upper part of the heat exchange unit, an inner oil pipe is provided inside the outer oil pipe, both ends of the inner oil pipe and the first annulus between the inner oil pipe are sealed, and a vacuum port connected to the first annulus is provided on the outer oil pipe.

[0017] In a specific embodiment, a first packer is provided on the heat exchange unit, and the first packer is located above the perforation section.

[0018] In a specific embodiment, an isolation valve is provided at the lower portion of the heat exchange unit. The isolation valve is configured to be able to set the first packer by injecting pressure into the well after being sealed by dropping a ball.

[0019] In a specific embodiment, the isolation valve comprises:

[0020] a sleeve coaxially arranged at the lower part of the heat exchange 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 connecting the inner cavity with the outside; and

[0021] A first ball seat is coaxially arranged in the sleeve, and the first ball seat is located above the through hole.

[0022] In a specific embodiment, the heat exchange unit includes:

[0023] Thermal sleeve;

[0024] A hanging nipple provided above the thermal sleeve; and

[0025] The 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.

[0026] 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.

[0027] 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.

[0028] Compared with the prior art, the advantages of this application are as follows.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] During the process of entering the well, the present invention first puts the intubation isolation mechanism into the well alone. After the second packer of the intubation isolation mechanism is set, the remaining components are put into the well to complete the setting of the first packer. By setting the second packer and the first packer in sequence, it can be ensured that the two packers are effectively set. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be described below with reference to the accompanying drawings.

[0034] Figure 1 A schematic diagram showing a tail-end insertion type downhole heat extraction device according to the present invention is shown;

[0035] Figure 2 A schematic diagram showing the direction of fluid flow during operation of the tail-end insertion-type downhole heat extraction device according to the present invention.

[0036] In the picture:

[0037] 1. Heat exchange unit; 11. Thermal sleeve; 12. Hooking nipple; 13. Insulation tube; 131. Hooking piece; 132. Second guide shoe; 14. Distribution nipple; 141. Circulation hole; 15. First telescopic tube; 151. Small-diameter tube; 152. Large-diameter tube; 16. Guide piece; 17. Centralizer; 18. Second telescopic tube;

[0038] 21. External oil pipe; 22. Internal oil pipe; 23. First annulus; 24. Vacuum port; 25. Suspension nipple; 26. Insulation nipple;

[0039] 3. Flow disturbance unit; 30. Intubation sealing mechanism; 31. Outer tube; 32. Tieback tube; 321. Sealing plug; 33. Second ball seat; 331. Second pressure-holding ball; 34. Flow disturbance pump; 341. Upper port; 342. Lower port;

[0040] 4. Second annulus; 41. First packer; 42. Second packer;

[0041] 5. Isolation valve; 51. Sleeve; 52. Through hole; 53. First ball seat; 531. Second passage; 532. First pressure-holding ball; 54. Inner sleeve; 541. First passage;

[0042] 61. Hot water; 62. Cold water; 63. Geothermal water; 64. Geothermal water after heat exchange;

[0043] 7. First guide shoe;

[0044] 81. First cable conversion connector; 82. Second cable conversion connector; 83. Cable routing;

[0045] 10. Wellbore; 101. Geothermal reservoir; 102. Perforation section;

[0046] 100. Tail-end insertion type underground heat extraction device.

[0047] 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

[0048] The present invention will be described below with reference to the accompanying drawings.

[0049] It should be noted that, in this application, the direction close to the wellhead after the tail-end insertion type downhole heat extraction device according to the present invention is inserted into the well is described as "upper end", "front end" or similar terms, that is, Figure 1 and the direction away from the wellhead after the tail-end insertion type downhole heat extraction device of the present invention is entered into the well is described as "lower end", "rear end" or similar terms, that is, Figure 1 Below.

[0050] Figure 1 The structure of the tail-end insertion type downhole heat extraction device 100 according to the present invention is shown. Figure 1 As shown, due to the limitation of the map, Figure 1 The tail-end inserted downhole heat extraction device 100 is divided into two parts, wherein the right part is the lower part of the tail-end inserted downhole heat extraction device 100 , and the left part is the upper part of the tail-end inserted downhole heat extraction device 100 .

[0051] like Figure 1 As shown, a tail-end insertion-type 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.

[0052] 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.

[0053] 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 is configured to circulate the geothermal water in the second annulus 4 with the geothermal water in the geothermal reservoir 101, thereby maintaining the geothermal water in the second annulus 4 at a relatively high temperature.

[0054] 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.

[0055] In a specific embodiment, a first packer 41 is provided on the heat exchange unit 1. The first packer 41 is located above the perforation 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 perforation section 102. After being set, the second packer 42 can seal the flow disturbance unit 3 from the wellbore 10.

[0056] 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. Under this configuration, during the lowering of the heat exchange unit 1 and the flow disturbance unit 3 into the well, the 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, thereby enabling automatic grouting during tubing lowering, avoiding manual grouting at the wellhead, simplifying the construction process, and facilitating 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 transmitted to the first packer 41. After the inner cavity of the first packer 41 is pressurized, it can be set, thereby setting the first packer 41.

[0057] 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 first ball seat 53 is pinned within the inner sleeve 54. A second channel 531 is provided on the side wall of the first ball seat 53. The first channel 541, the second channel 531, and the through hole 52 are connected. The first ball seat 53 and the inner sleeve 54 are located above the through hole 52. Under this configuration, 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 first 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 disconnected. At this time, pressure can be built up in the heat exchange unit 1 to move the first ball seat 53 downward relative to the inner sleeve 54, thereby misaligning the first channel 541 and the second channel 531, closing them, and closing the isolation valve 5. Then, pressurization is continued, and the pressure is transmitted to the first packer 41, causing the first packer 41 to be sealed and hung.

[0058] To ensure that the inner cavity of the tail-end insertion-type downhole heat extraction device 100 is sufficiently large to accommodate the ball during the process of dropping it into the first ball seat 53, the outer oil pipe 21 and inner oil pipe 22 of the present invention are of a split structure. During use, the outer oil pipe 21 is first lowered into the well, following the other components of the tail-end insertion-type downhole heat extraction device 100. The outer oil pipe 21 has a larger inner diameter, which is sufficient to accommodate the passage of the first pressure-holding ball 532. After the outer oil pipe 21 is properly positioned in the well, the upper end of the outer oil pipe 21 is suspended from the wellhead via the suspension nipple 25. The first pressure-holding ball 532 is then dropped into the isolation valve 5, and after the pressure is held to set the first packer 41, the inner oil pipe 22 is then inserted into the outer oil pipe 21.

[0059] 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.

[0060] 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.

[0061] With this arrangement, after the inner oil pipe 22 and the insulation pipe 13 are put into the well, the attachment piece 131 of the insulation pipe 13 is sealed and attached to the attachment nipple 12, and the insulation pipe 13 is coaxially sleeved in the heat-conducting sleeve 11. 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 and the outer oil pipe 21 are sealed by the insulation nipple 26, and the lower end of the inner oil pipe 22 and the outer oil pipe 21 are sealed by the sealing member. The first annulus 23 can be made into a vacuum state through the vacuum port 24. When performing heat extraction work, if 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 inlet at the lower end of the insulation pipe 13, and flows upward along the insulation pipe 13, and finally flows to the wellhead through the inner oil pipe 22 to complete heat extraction.

[0062] 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.

[0063] 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.

[0064] According to the present invention, in a preferred embodiment, a first telescopic tube 15 is coaxially arranged above the flow distribution nipple 14, and the hook nipple 12 is arranged above the first telescopic tube 15. The first 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 tail-end inserted downhole heat extraction device 100. Specifically, the first telescopic tube 15 includes a large-diameter tube 152 and a small-diameter tube 151. The small-diameter tube 151 is axially movably sleeved inside the large-diameter tube 152, and 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.

[0065] In a preferred embodiment, a first cable adapter 81 and a second cable adapter 82 are coaxially disposed at the upper and lower ends of the first packer 41. The first cable adapter 81 is connected to the disturbance pump 34 via a cable or other means. The first cable adapter 81 is connected to the second cable adapter 82 via a cable line 83. The upper portion of the second cable adapter 82 is connected to the wellhead via a cable. The cable line 83 is located inside the first packer 41 to prevent it from interfering with the setting of the first packer 41.

[0066] 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.

[0067] In a preferred embodiment, a second guide shoe 132 is coaxially provided at the lower end of the insulation pipe 13. The second guide shoe 132 is provided with holes for circulating cold water 62 and hot water 61. The second guide shoe 132 can play a guiding role during the process of the insulation pipe 13 entering the well.

[0068] According to the present invention, in a specific embodiment, the flow disturbance unit 3 includes a cannula isolation mechanism 30 and a flow disturbance pump 34 .

[0069] like Figure 1 As shown, in this embodiment, the intubation isolation mechanism 30 includes an outer tube 31 , a tie-back tube 32 , a second ball seat 33 and a second packer 42 .

[0070] The outer barrel 31 is constructed in a generally cylindrical shape, with the second packer 42 coaxially mounted on top of the outer barrel 31. A second ball seat 33 is coaxially mounted within the outer barrel 31 and positioned below the second packer 42. To set the second packer 42, a second pressure-holding ball 331 is dropped into the wellbore, sealing the second ball seat 33. Pressure is then held in place from the wellhead into the outer barrel 31, transferring this pressure to the second packer 42, thereby setting it.

[0071] It is easy to understand that the specific structures of the first packer 41 and the second packer 42 are well known to those skilled in the art, and can perform setting and hanging actions in response to internal pressure, and will not be described in detail here.

[0072] The connection tube 32 is coaxially arranged at the upper end of the outer tube 31 and is used for sealing connection with the sealing plug 321 provided at the lower end of the disturbance pump 34 .

[0073] In this embodiment, the turbulence pump 34 includes an upper port 341 and a lower port 342. In one specific embodiment, the upper port 341 is disposed on a side of the turbulence pump 34, and the lower port 342 is disposed on the lower end surface of the turbulence pump 34. A sealing plug 321 is coaxially and sealingly disposed at the lower end of the turbulence pump 34. The outer diameter of the lower port 342 is smaller than the inner diameter of the upper end of the sealing plug 321, thereby connecting the inner cavity of the sealing plug 321 with the lower port 342. When the sealing plug 321 is sealingly inserted into the tieback sleeve 32, the upper port 341 communicates with the second annulus 4, and the lower port 342 communicates with the geothermal reservoir 101 below the wellbore 10 through the sealing plug 321.

[0074] Preferably, a retaining mechanism is provided between the sealing plug 321 and the tie-back tube 32. This means that the sealing plug 321 can only move downward relative to the tie-back tube 32. When the sealing plug 321 is lifted upward, the sealing plug 321 can move the tie-back tube 32 upward. Specifically, the retaining mechanism can be a ratchet, a retaining spring, or other structure.

[0075] In a preferred embodiment, a first guide shoe 7 is provided at the lower end of the outer cylinder 31 , and the first guide shoe 7 can play a guiding role when the outer cylinder 31 is placed into the well.

[0076] In a preferred embodiment, a second telescopic tube 18 is disposed between the upper end of the disturbance pump 34 and the sleeve 51 of the isolation valve 5. The structure of the second telescopic tube 18 is similar to that of the first telescopic tube 15. A connecting hole communicating with the inner cavity of the second telescopic tube 18 is also provided at the lower end of the sleeve 51. With this arrangement, the internal volume of the second telescopic tube 18 inevitably changes during its extension and contraction, allowing the fluid inside to exchange with the outside through the connecting hole, thereby making the extension and contraction process of the second telescopic tube 18 smoother.

[0077] The tail-end insertion downhole heat extraction device 100 is suitable for hydrothermal development in medium- to deep-level geothermal formations, and is applicable to vertical wells with two openings or highly deviated wells. After drilling, a suitable well section is selected for perforation. After perforation is complete, the tail-end insertion downhole heat extraction device 100 is lowered. The process for lowering the tail-end insertion downhole heat extraction device 100 is as follows.

[0078] First, connect the first guide shoe 7, outer tube 31, second ball seat 33, second packer 42, and tie-back tube 32 in sequence from bottom to top. Use tubing to lower the first guide shoe 7, outer tube 31, second ball seat 33, second packer 42, and tie-back tube 32 into the wellbore 10 through the release tool. Once in place, drop the second pressure-holding ball 331 into the wellbore. After the second pressure-holding ball 331 is pumped into place, the pressure in the tubing builds up. Once the specified pressure is reached, the second packer 42 is set. The release tool then executes the release process, lifting the release tool and the downhole tools above it out of the wellbore 10. The first guide shoe 7, outer tube 31, second ball seat 33, second packer 42, and tie-back tube 32 remain in the wellbore, completing the first run of the tubing string.

[0079] The second pressure-holding ball 331 is made of a soluble material, which is well known to those skilled in the art and dissolves after a period of exposure to downhole fluid. After the second packer 42 is set, the second pressure-holding ball 331 dissolves, thereby unblocking the second ball seat 33.

[0080] Since the second packer 42 needs to drop the second pressure-holding ball 331 into the second ball seat 33 to be set, the second packer 42 and the disturbance pump 34 are separately placed into the well in sequence in the present invention.

[0081] After the first string is lowered, the sealing plug 321, the flow pump 34, the second telescopic pipe 18, the isolation valve 5, the heat exchange unit 1, and the remaining upper components (except the inner oil pipe 22 and the insulation pipe 13) are connected in sequence from bottom to top and lowered into the well. After being lowered into place, the sealing plug 321 and the tie-back sleeve 32 are inserted and sealed, separating the upper port 341 and the lower port 342 of the flow pump 34, so that the upper port 341 is connected to the second annulus 4 and the lower port 342 is connected to the geothermal reservoir 101. The first pressure-holding ball 532 is dropped at the wellhead and pumped into the first ball seat 53. The pressure in the pipe is held up. After reaching the specified pressure, the isolation valve 5 is closed, and the pressure is further held up. After reaching the specified pressure, the first packer 41 is set.

[0082] After the first packer 41 is set, the insulation pipe 13 and the inner oil pipe 22 are connected sequentially from bottom to top, and then inserted into the outer oil pipe 21. When it is lowered into place, the hanging member 131 of the insulation pipe 13 is hooked onto the hanging nipple 12. Finally, a vacuum pump is connected to the vacuum port 24 of the wellhead insulation nipple 26 to evacuate the air in the first annulus 23 between the inner oil pipe 22 and the outer oil pipe 21, achieving the vacuum insulation effect. At this point, the tail-end insertion-type downhole heat extraction device 100 is successfully installed in the well.

[0083] like Figure 2 As shown, after the tail-end inserted downhole heat extraction device 100 is put into the well, an injection and production circulation channel and a forced turbulent flow channel are formed.

[0084] The forced turbulence channel is geothermal reservoir 101 - hole of first guide shoe 7 - inner cavity of second ball seat 33 - inner cavity of second packer 42 - inner cavity of sealing plug 321 - lower port 342 - turbulence pump 34 - upper port 341 - second annulus 4, perforation section 102 - formation - geothermal reservoir 101. While heat extraction is in progress, turbulence pump 34 is turned on, disturbing the geothermal water, causing it to continuously circulate within the forced turbulence channel, rapidly replenishing heat to the second annulus 4 (heat-conducting sleeve 11) and improving the heat extraction efficiency of heat exchange unit 1. After the turbulence electric pump unit stabilizes, heat is extracted through the injection-production circulation channel.

[0085] The injection and production circulation channel is a ground heat exchanger (not shown) connected to the wellhead - the annular space between the outer oil pipe 21 and the wellbore 10 - the circulation hole 141 of the distribution short joint 14 - the annular space between the insulation pipe 13 and the thermal sleeve 11 - the second guide shoe 132 or the hole on the side wall of the insulation pipe 13 - the inner cavity of the insulation pipe 13 - the inner cavity of the inner oil pipe 22 - the ground heat exchanger connected to the wellhead. In the process of heat extraction, cold water 62 is injected from the wellhead into the annular space between the outer oil pipe 21 and the wellbore 10. When it flows along the injection and production circulation channel to the annular space between the insulation pipe 13 and the thermal sleeve 11, it exchanges heat with the geothermal water in the second annulus 4 through the thermal sleeve 11, thereby converting the cold water 62 into hot water 61. After that, the hot water continues to flow along the injection and production circulation channel, flows back to the wellhead, and circulates along the injection and production circulation channel again after heat exchange in the ground heat exchanger.

[0086] When the tail-end inserted downhole heat extraction device 100 requires later maintenance, first dismantle 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 to release the first packer 41, lift the tail-end inserted downhole heat extraction device 100 out of the wellbore 10, perform necessary replacement and maintenance on the wearing parts, and after the maintenance is completed, re-enter the well according to the above-mentioned well entry method.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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 tail-end insertion type downhole heat extraction device, characterized in that: include: A cannulated isolation mechanism (30) is provided in a wellbore (10), a perforation section (102) is provided on the side wall of the wellbore (10), and the cannulated isolation mechanism (30) is set below the perforation section (102); a disturbance flow pump (34) disposed in the wellbore (10), the disturbance flow pump (34) being sealed and disposed in the cannula isolation mechanism (30) by plugging; a heat exchange unit (1) coaxially arranged in the wellbore (10), wherein the heat exchange unit (1) is sealed above the perforation section (102); A second annulus (4) is formed between the intubation isolation mechanism (30) and the sealing position of the wellbore (10) and the sealing position of the heat exchange unit (1) and the wellbore (10). The second annulus (4) is connected to the perforation section (102). The upper port (341) of the disturbance pump (34) is connected to the second annulus (4). The lower port (342) of the disturbance pump (34) is connected to the bottom of the intubation isolation mechanism (30). The heat exchange unit (1) exchanges heat with the geothermal water in the second annulus (4) by means of a circulating medium.

2. The tail-end insertion type downhole heat extraction device according to claim 1, characterized in that: The cannula sealing mechanism (30) comprises: outer cylinder(31); a second packer (42) coaxially arranged on the outer cylinder (31), wherein the second packer (42) is located below the perforation section (102); A second ball seat (33) is coaxially arranged in the outer cylinder (31), and the second ball seat (33) is located below the second packer (42). Throwing a ball into the second ball seat (33) to hold pressure can seal the second packer (42).

3. The tail-end insertion type downhole heat extraction device according to claim 2, characterized in that: The cannula sealing mechanism (30) further comprises a tie-back tube (32) arranged at the upper end of the outer tube (31); a sealing plug (321) is arranged at the lower end of the disturbance pump (34); the sealing plug (321) is coaxially arranged in the tie-back tube (32); a sealing member is arranged between the tie-back tube (32) and the sealing plug (321); an upper port (341) of the disturbance pump (34) is located above the sealing plug (321); and a lower port (342) of the disturbance pump (34) is communicated with the inner cavity of the sealing plug (321).

4. The tail-end insertion type downhole heat extraction device according to any one of claims 1 to 3, characterized in that: An outer oil pipe (21) is provided at the upper portion of the heat exchange unit (1), an inner oil pipe (22) is provided inside the outer oil pipe (21), both ends of a first annulus (23) between the inner oil pipe (22) and the outer oil pipe (21) are sealed, and a vacuum port (24) communicating with the first annulus (23) is provided on the outer oil pipe (21).

5. The tail-end insertion type downhole heat extraction device according to claim 4, 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).

6. The tail-end insertion type downhole heat extraction device according to claim 5, characterized in that: An isolation valve (5) is provided at the lower part of the heat exchange unit (1). The isolation valve (5) is configured to be sealed by dropping a ball and then being able to set the first packer (41) by pressurizing the well.

7. The tail-end insertion type downhole heat extraction device according to claim 6, characterized in that: The isolation valve (5) comprises: a sleeve (51) coaxially arranged at the lower part of the heat exchange unit (1), 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 first ball seat (53) is coaxially arranged in the sleeve (51), and the first ball seat (53) is located above the through hole (52).

8. The tail-end insertion type downhole heat extraction device according to claim 6, 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).

9. The tail-end insertion type downhole heat extraction device according to claim 8, 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.

10. The tail-end insertion type 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).

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