A tail-end plug-in downhole heat extraction device

Abstract

This invention belongs to the field of geothermal application technology, specifically relating to a tail-end insertion type downhole heat extraction device. The tail-end insertion type downhole heat extraction device includes: a tube-insertion packer mechanism disposed within the wellbore, with a perforated section provided on the side wall of the wellbore, the tube-insertion packer mechanism being seated below the perforated section; a turbulence pump disposed within the wellbore, the turbulence pump being sealed within the tube-insertion packer mechanism via an insertion connection; a heat exchange unit coaxially disposed within the wellbore, the heat exchange unit being seated above the perforated section; a second annulus is formed between the seated positions of the tube-insertion packer mechanism and the wellbore, and between the seated positions of the heat exchange unit and the wellbore, the second annulus communicating with the perforated section, the upper port of the turbulence pump communicating with the second annulus, and the lower port of the turbulence pump communicating with the lower part of the tube-insertion packer mechanism, the heat exchange unit exchanging heat with the geothermal water in the second annulus via a circulating medium.

Description

Technical Field

[0001] This invention belongs to the field of geothermal application technology, specifically, it relates to a tail-end insertion type downhole heat extraction device. Background Technology

[0002] Geothermal energy, as a representative of green energy, has received widespread attention, with its development scale expanding and its application scenarios becoming increasingly diverse. Currently, conventional geothermal development mainly adopts the "water extraction and heat extraction" development model, but problems such as "incomplete reinjection" are becoming increasingly prominent. In addition, environmental protection policies such as "heat extraction without water extraction" restrict the development of the geothermal energy field. The "heat extraction without water extraction" downhole high-efficiency heat extraction technology is gradually becoming the development trend and inevitable choice for geothermal development.

[0003] The "heat extraction without water extraction" technology involves injecting a heat exchange medium downhole and circulating the heat to the surface through a closed / semi-closed heat exchange structure, without extracting underground hot water to the surface. In single-well coaxial casing heat extraction, the heat exchange medium is injected from the annulus, heated through heat conduction within the wellbore, and then returned to the surface through a central tube at the bottom of the well. Existing downhole heat exchangers extract heat through two pathways: hot water from the aquifer and high-temperature surrounding rock within the wellbore. Heat exchange primarily occurs through natural turbulence, with the heat reservoir around the wellbore continuously transferring heat into the wellbore to replenish the heat carried away by the circulating medium, maintaining the stability of heat exchange. However, natural turbulence provides slow heat replenishment, and the heat reservoir cannot achieve rapid heat recovery; therefore, the heat exchange efficiency of coaxial casing needs improvement.

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

[0005] To address the technical problems described above, this invention aims to provide a tail-end insertion type downhole heat extraction device that can improve underground heat extraction efficiency.

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

[0007] A packer mechanism installed inside a wellbore has a perforated section on the side wall of the wellbore, and the packer mechanism is seated below the perforated section.

[0008] The turbulence pump is installed inside the wellbore and is sealed within the insertion sealing mechanism by means of plugging in;

[0009] A heat exchange unit is coaxially disposed inside the wellbore, and the heat exchange unit is seated above the perforation section;

[0010] A second annulus is formed between the setting position of the insertion packer mechanism and the wellbore, and between the setting position of the heat exchange unit and the wellbore. The second annulus is connected to the perforation section. The upper port of the turbulence pump is connected to the second annulus, and the lower port of the turbulence pump is connected to the lower part of the insertion packer mechanism. The heat exchange unit exchanges heat with the geothermal water in the second annulus through a circulating medium.

[0011] In one specific embodiment, the cannulation sealing mechanism includes:

[0012] outer cylinder;

[0013] A second packer is coaxially mounted on the outer cylinder, and the second packer is located below the perforation section;

[0014] A second ball seat is coaxially disposed inside the outer cylinder. The second ball seat is located below the second packer. Throwing a ball into the second ball seat and pressing it down can cause the second packer to set.

[0015] In one specific embodiment, the cannula sealing mechanism further includes a return tube disposed at the upper end of the outer cylinder, a sealing plug disposed at the lower end of the turbulence pump, the sealing plug being coaxially disposed inside the return tube, a sealing element being disposed between the return tube and the sealing plug, the upper port of the turbulence pump being located above the sealing plug, and the lower port of the turbulence pump communicating with the inner cavity of the sealing plug.

[0016] In one specific embodiment, an outer oil pipe is provided at the upper part of the heat exchange unit, and an inner oil pipe is provided inside the outer oil pipe. The two ends of the first annulus between the inner oil pipe and the inner oil pipe are sealed, and a vacuum port communicating with the first annulus is provided on the outer oil pipe.

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

[0018] In one specific embodiment, an isolation valve is provided at the lower part of the heat exchange unit. The isolation valve is configured to allow the first packer to be set by pressurizing the well after ball sealing.

[0019] In one specific embodiment, the isolation valve includes:

[0020] A sleeve coaxially disposed at the lower part of the heat exchange unit, the upper end of the sleeve communicating with the heat exchange unit, and a through hole provided on the sleeve to communicate the inner cavity and the outside; and

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

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

[0023] Thermal sleeve;

[0024] The hanging short section is provided above the heat-conducting sleeve; and

[0025] An insulating tube is intermittently fitted inside the heat-conducting sleeve. The lower end of the insulating tube is lower than the first packer, and the upper end of the insulating tube is connected to the inner oil pipe. The insulating tube is sealed and hung inside the hanging short section.

[0026] In one specific embodiment, the first packer is disposed above the heat-conducting sleeve, and a flow distribution short section is coaxially disposed above the first packer. A circulation hole is provided on the side wall of the flow distribution short section to connect the inner cavity and the outside.

[0027] In one specific embodiment, a guide is coaxially arranged inside the heat-conducting sleeve, the upper end of the guide is a conical surface, and the heat-insulating pipe passes through the guide.

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

[0029] The heat exchange unit of the present invention is connected to the wellhead via an inner oil pipe and an outer oil pipe coaxially sleeved at the top. A vacuum can be drawn between the inner oil pipe and the outer oil pipe, thereby enhancing the heat insulation effect and improving the heat extraction efficiency.

[0030] The present invention includes a flow-turbulence unit below the heat exchange unit, forming a second annulus between the heat exchange unit and the wellbore. The perforated section of the wellbore communicates with the second annulus, allowing high-temperature geothermal water to enter the second annulus through the perforated section. The heat exchange unit can then exchange heat with the geothermal water within the second annulus. The two ends of the flow-turbulence unit are connected to the second annulus and the geothermal reservoir at the bottom of the wellbore, respectively. During the heat extraction process of the heat exchange unit, the flow-turbulence unit drives the geothermal water to circulate within the annular space and the geothermal reservoir, thereby maintaining a consistently high temperature within the second annulus and improving heat extraction efficiency.

[0031] Compared with existing technologies, this invention can increase the heat extraction power of a single well by more than 1.5 times and significantly slow down the decline cycle of heat extraction power. At the same time, the underground thermal water does not return to the surface, achieving the development effect of "extracting heat without extracting water", which can help the development and reuse of conventional medium and deep geothermal resources.

[0032] In the process of entering the well, the present invention first inserts the packer mechanism into the well separately. After the second packer of the packer mechanism is set, the remaining components are then inserted into the well to complete the setting of the first packer. By setting the second packer and the first packer in sequence, the effective setting of the two packers can be ensured. Attached Figure Description

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

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

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

[0036] In the picture:

[0037] 1. Heat exchange unit; 11. Heat-conducting sleeve; 12. Hanging section; 13. Insulation pipe; 131. Hanging component; 132. Second guide shoe; 14. Distribution section; 141. Circulation hole; 15. First telescopic pipe; 151. Small diameter pipe; 152. Large diameter pipe; 16. Guide component; 17. Centralizer; 18. Second telescopic pipe;

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

[0039] 3. Turbulence unit; 30. Insertion tube sealing mechanism; 31. Outer cylinder; 32. Return cylinder; 321. Sealing plug; 33. Second ball seat; 331. Second pressure ball; 34. Turbulence 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 channel; 532. First pressure ball; 54. Inner sleeve; 541. First channel;

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

[0043] 7. First shoe;

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

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

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

[0047] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

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

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

[0050] Figure 1 The structure of a tail-end insertion type downhole heat extraction device 100 according to the present invention is shown. For example... Figure 1 As shown, due to map size limitations, Figure 1 The tail-end insertion type downhole heat extraction device 100 is represented by two parts: the right part is the lower part of the tail-end insertion type downhole heat extraction device 100, and the left part is the upper part of the tail-end insertion type 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 for heat exchange with geothermal water. Specifically, the present invention injects a low-temperature medium from the surface into the well through a circulating medium. After the low-temperature medium flows to the heat exchange unit 1 and exchanges heat with the geothermal water, it becomes a high-temperature medium. Then, the high-temperature medium flows back to the surface, completing the heat extraction. The specific structure of the heat exchange unit 1 is described below.

[0052] Heat exchange unit 1 is located underground, therefore it is a certain distance from the ground. To reduce heat loss during the return of the high-temperature medium to the ground, an outer oil pipe 21 is provided above heat exchange unit 1. An inner oil pipe 22 is coaxially and intermittently sleeved inside the outer oil pipe 21. The inner oil pipe 22 is used to transport the medium. A first annulus 23 is formed between the outer oil pipe 21 and the inner oil pipe 22, and both the upper and lower ends of the first annulus 23 are sealed. Specifically, a sealing element is provided at the lower part between the outer oil pipe 21 and the inner oil pipe 22, that is, a sealing element is provided at the lower end of the first annulus 23, thereby sealing the lower end of the first annulus 23. An insulating short section 26 is provided at the upper part between the outer oil pipe 21 and the inner oil pipe 22, that is, the insulating short section 26 is located 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 short section 26 or the outer oil pipe 21. The first annulus 23 can be set to a vacuum state through the vacuum port 24, thereby reducing the heat transfer efficiency between the outer oil pipe 21 and the inner oil pipe 22. This prevents 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 in the inner oil pipe 22.

[0053] According to the present invention, in this embodiment, the heat exchange unit 1 exchanges heat with geothermal water through the perforated section 102 of the wellbore 10. A second annulus 4 communicating with the perforated section 102 is provided between the heat exchange unit 1 and the wellbore 10, and both ends of the second annulus 4 are sealed. A turbulence-disrupting unit 3 is provided below the heat exchange unit 1, and the turbulence-disrupting unit 3 is sealed to the heat exchange unit 1. 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 turbulence-disrupting unit 3. The turbulence-disrupting unit 3 is configured to allow the geothermal water in the second annulus 4 to circulate with the geothermal water in the geothermal reservoir 101, thereby maintaining the geothermal water in the second annulus 4 at a higher temperature.

[0054] In this configuration, heat exchange unit 1 exchanges heat with the geothermal water in the second annulus 4 during operation. After the turbulence unit 3 is activated, it can promote the geothermal water in the second annulus 4 to circulate between the perforated section 102 and the geothermal reservoir 101, so that the geothermal water that has cooled down after heat extraction can be quickly replaced by high-temperature geothermal water, thereby keeping the geothermal water in the second annulus 4 at a high temperature and improving the heat exchange efficiency of heat exchange unit 1.

[0055] In one specific embodiment, a first packer 41 is provided on the heat exchange unit 1, located above the perforation section 102. After the first packer 41 is set, it can seal the space between the heat exchange unit 1 and the wellbore 10. A second packer 42 is provided on the turbulence unit 3, located below the perforation section 102. After the second packer 42 is set, it can seal the space between the turbulence unit 3 and the wellbore 10.

[0056] In a preferred embodiment, an isolation valve 5 is provided below the heat exchange unit 1. In the initial state, the isolation valve 5 is configured such that its inner cavity is connected to the outside, while its upper part is connected to the inner cavity of the heat exchange unit 1. Under this configuration, during the wellhead insertion process of the heat exchange unit 1 and the turbulence unit 3, the fluid inside the wellbore 10 can enter the inner cavity of the heat exchange unit 1 through the isolation valve 5, and then enter the inner cavity of the inner tubing 22, realizing automatic grouting during the tubing string insertion process, avoiding manual grouting at the wellhead, simplifying the construction process, and facilitating insertion. 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 not connected to the inner cavity of the heat exchange unit 1. At this time, pressure can be applied to the heat exchange unit 1, and the pressure is transmitted to the first packer 41. After the inner cavity of the first packer 41 is subjected to pressure, it can perform the setting and hanging action, thereby setting and hanging the first packer 41.

[0057] In one 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 turbulence unit 3. The sleeve 51 is constructed in a generally closed cylindrical shape at the lower end. The upper end of the sleeve 51 is connected to the heat-conducting sleeve 11 of the heat exchange unit 1. A through hole 52 is provided on the side of the sleeve 51 to connect the inner cavity and the outside. An inner sleeve 54 is coaxially fixedly disposed inside the sleeve 51. A first channel 541 is provided on the side wall of the inner sleeve 54. A first ball seat 53 is disposed inside the inner sleeve 54 by means of a pin. 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. In this configuration, during the insertion of heat exchange unit 1 and turbulence unit 3 into the well, the fluid inside the wellbore 10 can enter the inner cavity of heat exchange unit 1 through the through hole 52, first channel 541 and second channel 531 of isolation valve 5, and then enter the inner cavity of inner tubing 22, realizing automatic grouting during tubing string insertion, avoiding manual grouting at the wellhead, simplifying the construction process, and facilitating insertion. After the ball is inserted into the first ball seat 53 of isolation valve 5 for sealing, the inner cavity of isolation valve 5 is blocked, and the inner cavity of isolation valve 5 is not connected to the inner cavity of heat-conducting sleeve 11. At this time, pressure can be applied to heat exchange unit 1 to make the first ball seat 53 move downward relative to inner sleeve 54, thereby misaligning the first channel 541 and second channel 531, closing both, and keeping isolation valve 5 in a closed state. Then, pressure is continued to be applied, and the pressure is transmitted to the first packer 41, causing the first packer 41 to set and hang.

[0058] To ensure that the inner cavity of the tail-end insertion type downhole heat extraction device 100 is large enough to accommodate the ball during the ball-dropping process to the first ball seat 53, the outer tubing 21 and inner tubing 22 of this invention are of a separate structure. During use, the outer tubing 21 first enters the well along with the other components of the tail-end insertion type downhole heat extraction device 100. The inner diameter of the outer tubing 21 is large enough to accommodate the passage of the first pressure-reducing ball 532. After the outer tubing 21 is in place, its upper end is suspended at the wellhead via a suspension stub 25. Then, the first pressure-reducing ball 532 is dropped into the isolation valve 5 and pressure-reduced to set the first packer 41. Finally, the inner tubing 22 is inserted into the outer tubing 21.

[0059] In one specific embodiment, the heat exchange unit 1 includes a heat-conducting sleeve 11, which is generally cylindrical in shape. A stabilizer 17 is provided on the outer wall of the heat-conducting sleeve 11. A hanging section 12 is coaxially arranged above the heat-conducting sleeve 11. The hanging section 12 is also generally cylindrical in shape, with the inner diameter of the upper part of the inner wall of the hanging section 12 being larger than the inner diameter of the lower part, thereby forming a step within the hanging section 12 for hanging. A heat-insulating pipe 13 is connected to the lower end of the inner oil pipe 22. A hanging member 131 for hanging within the hanging section 12 is provided on the outer wall of the upper end of the heat-insulating pipe 13. The hanging member 131 is configured to fit the inner wall of the hanging section 12, thereby allowing the hanging member 131 to be hung within the hanging section 12. A sealing member for sealing with the hanging member 131 is also provided on the inner wall of the hanging section 12.

[0060] A sealing element for sealing with the outer wall of the inner oil pipe 22 is provided on the inner wall of the lower end of the outer oil pipe 21. The inner diameter of the upper end of the thermal insulation short section 26 is smaller than the inner diameter of the lower end. Specifically, the inner diameter of the upper end of the thermal insulation short section 26 is configured to form a seal with the outer wall of the inner oil pipe 22, and the lower end of the thermal insulation short section 26 is sealed on the outer oil pipe 21.

[0061] With this setup, after the inner oil pipe 22 and the insulation pipe 13 are inserted into the well, the connector 131 of the insulation pipe 13 is sealed and connected to the connector 12. The insulation pipe 13 is coaxially fitted inside the heat-conducting sleeve 11 with a gap, and the lower end of the insulation pipe 13 is located below the first packer 41, thus ensuring successful heat exchange. Simultaneously, the upper end of the inner oil pipe 22 is sealed to the outer oil pipe 21 via the insulation connector 26, and the lower end of the inner oil pipe 22 is sealed to the outer oil pipe 21 via a sealing element. The first annulus 23 can be evacuated through the vacuum port 24. During heat extraction, if... Figure 2 As shown, cold water 62 is injected from the wellhead into the annular space between the outer tubing 21 and the wellbore 10. When the cold water 62 flows downward to the top of the first packer 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. Then, 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. Finally, it flows through the inner tubing 22 to the wellhead to complete the heat extraction.

[0062] In a preferred embodiment, the inner diameter of the upper part of the inner wall of the hanging section 12 is larger than the inner diameter of the lower part, and the upper and lower parts of the inner wall of the hanging section 12 are set as a conical surface. Correspondingly, the outer wall of the hanger 131 is set as a structure adapted to the inner wall of the hanging section 12. By setting the conical surface, it can guide the lowering of the insulation pipe 13.

[0063] According to a specific embodiment of the present invention, a first packer 41 is coaxially fixed to the upper end of a heat-conducting sleeve 11. A distribution sub 14 is coaxially disposed above the first packer 41. The distribution sub 14 is generally cylindrical in shape, and a circulation hole 141 communicating the inner cavity and the outside is provided on the side wall of the distribution sub 14. A connecting sub 12 is located above the distribution sub 14. During heat extraction, cold water 62 flows downward from the wellhead along the annular space between the wellbore 10 and the outer tubing 21 to above the first packer 41. It then 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 upper part of the distribution short section 14 is the hanging short section 12, and the inner wall of the hanging short section 12 is sealed with 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 completing heat extraction, the cold water 62 flows upward back to the ground along the inner cavity of the insulation pipe 13.

[0064] According to a preferred embodiment of the present invention, a first telescopic tube 15 is coaxially disposed above the distribution stub 14, and a connecting stub 12 is disposed above the first telescopic tube 15. The first telescopic tube 15 is configured to axially extend and retract to change its length, thereby accommodating the thermal expansion and contraction of the tail-end insertion type 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 movable and sleeved inside the large-diameter tube 152, and protruding 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 showing the relative movement distance of the large-diameter tube 152 and the small-diameter tube 151 and 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 arranged at the upper and lower ends of the first packer 41, respectively. The first cable adapter 81 is connected to the turbulence pump 34 via a cable or other means. The first cable adapter 81 is connected to the second cable adapter 82 via a cable run 83. The upper part of the second cable adapter 82 is connected to the wellhead via a cable. The cable run 83 is located inside the first packer 41, thereby preventing the cable run 83 from affecting the setting and mounting of the first packer 41.

[0066] In a preferred embodiment, a guide 16 is coaxially disposed inside the heat-conducting sleeve 11, with its upper end being a conical surface, through which the insulation pipe 13 passes. On one hand, the guide 16 helps to straighten the insulation pipe 13; on the other hand, it guides the insulation pipe 13 during its insertion into the well. It is easy to understand that the guide 16 does not completely seal the annular space between the heat-conducting sleeve 11 and the insulation pipe 13.

[0067] In a preferred embodiment, a second guide shoe 132 is coaxially disposed at the lower end of the insulation pipe 13, and 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 a specific embodiment of the present invention, the turbulence unit 3 includes a cannulation sealing mechanism 30 and a turbulence pump 34.

[0069] like Figure 1 As shown, in this embodiment, the cannula packing mechanism 30 includes an outer cylinder 31, a return cylinder 32, a second ball seat 33, and a second packer 42.

[0070] The outer cylinder 31 is roughly cylindrical in shape, and the second packer 42 is coaxially mounted on top of the outer cylinder 31. The second ball seat 33 is coaxially mounted inside the outer cylinder 31 and is located below the second packer 42. When the second packer 42 needs to be set, the second pressure-pressurizing ball 331 is dropped into the well, causing it to seal the second ball seat 33. Then, pressure is pressed into the outer cylinder 31 from the wellhead, and the pressure is transmitted to the second packer 42, thereby setting the second packer 42.

[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 they are capable of performing setting and hanging actions in response to internal pressure, so they will not be described in detail here.

[0072] The return sleeve 32 is coaxially disposed at the upper end of the outer sleeve 31 and is used for sealing connection with the sealing plug 321 disposed at the lower end of the turbulence pump 34.

[0073] In this embodiment, the turbulence pump 34 includes an upper port 341 and a lower port 342. In a specific embodiment, the upper port 341 is disposed on the side of the turbulence pump 34, and the lower port 342 is disposed on the lower end face of the turbulence pump 34. A sealing plug 321 is coaxially and sealingly disposed at the lower end of the turbulence pump 34, and the outer diameter of the lower port 342 is smaller than the inner diameter of the upper end of the sealing plug 321, thereby enabling the inner cavity of the sealing plug 321 to communicate with the lower port 342. When the sealing plug 321 is sealed and inserted into the return 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 backstop mechanism is provided between the sealing plug 321 and the return cylinder 32. That is, the sealing plug 321 can only move downward relative to the return cylinder 32, and when the sealing plug 321 is pulled upward, the sealing plug 321 can drive the return cylinder 32 to move upward together. Specifically, the backstop mechanism can be configured as a ratchet, a snap ring, or other similar structure.

[0075] In a preferred embodiment, a first guide shoe 7 is provided at the lower end of the outer cylinder 31, which can play a guiding role during the process of the outer cylinder 31 entering the well.

[0076] In a preferred embodiment, a second telescopic tube 18 is provided between the upper end of the turbulence 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 will inevitably change during the extension and retraction process, and the fluid inside can be exchanged with the outside through the connecting hole, thereby making the extension and retraction process of the second telescopic tube 18 smoother.

[0077] The tail-end insertion downhole heat extraction device 100 is suitable for medium-deep hydrothermal geothermal development, and is applied to two-section vertical wells or highly deviated wells. After drilling, a suitable well section is selected for perforation. After perforation is completed, the tail-end insertion downhole heat extraction device 100 is run in. The process of running the tail-end insertion downhole heat extraction device 100 is as follows.

[0078] First, from bottom to top, connect the first guide shoe 7, outer cylinder 31, second ball seat 33, second packer 42, and return sleeve 32 in sequence. Use tubing and a drop tool to lower the tubing into the wellbore 10. After it is in place, insert the second pressure-reducing ball 331. After the second pressure-reducing ball 331 is pumped into place, pressure is built up inside the tubing. Once the specified pressure is reached, the second packer 42 completes its setting and sealing. Then, the drop tool performs the drop procedure, removing the drop tool and all other downhole tools above it from the wellbore 10. The first guide shoe 7, outer cylinder 31, second ball seat 33, second packer 42, and return sleeve 32 remain downhole, completing the first tubing string setup.

[0079] The second packer 331 is made of a soluble material, which is well known to those skilled in the art and can dissolve after a period of time when exposed to downhole fluid. After the second packer 42 completes its setting and sealing, the second packer 331 dissolves, thereby allowing the second ball seat 33 to flow smoothly.

[0080] Since the second packer 42 needs to be inserted into the second ball seat 33 to achieve setting and mounting, the present invention separates the second packer 42 and the turbulence pump 34 and inserts them into the well in sequence.

[0081] After the first tubing string is lowered, the sealing plug 321, the turbulence pump 34, the second telescopic pipe 18, the isolation valve 5, the heat exchange unit 1, and the remaining upper components (except for the inner oil pipe 22 and the insulation pipe 13) are connected from bottom to top and lowered into the well. After being lowered into place, the sealing plug 321 and the return sleeve 32 are inserted and sealed, separating the upper port 341 and the lower port 342 of the turbulence 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-retaining ball 532 is dropped into the wellhead and pumped into the first ball seat 53. Pressure is retained in the pipe. After the specified pressure is reached, the isolation valve 5 is closed, and further pressure is retained. After the specified pressure is reached, the first packer 41 is set and sealed.

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

[0083] like Figure 2 As shown, after the tail-end insertion type downhole heat extraction device 100 is inserted into the well, it forms an injection-production circulation channel and a forced turbulence channel.

[0084] The forced turbulence channel is defined as follows: geothermal reservoir 101 - hole of the first guide shoe 7 - inner cavity of the second ball seat 33 - inner cavity of the second packer 42 - inner cavity of the sealing plug 321 - lower port 342 - turbulence pump 34 - upper port 341 - second annulus 4, perforation section 102 - formation - geothermal reservoir 101. During heat extraction, the turbulence pump 34 is activated, disturbing the geothermal water and causing it to circulate continuously within the forced turbulence channel. This achieves rapid heat replenishment of the second annulus 4 (heat-conducting sleeve 11), improving the heat extraction efficiency of heat exchange unit 1. After the turbulence pump unit is running stably, heat is extracted through the injection-production circulation channel.

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

[0086] When the tail-end insertion type downhole heat extraction device 100 requires subsequent maintenance, firstly, the wellhead insulation short section 26 is removed, and the inner oil pipe 22 and insulation pipe 13 are pulled out of the wellhead together. Then, the outer oil pipe 21 is pulled up to release the first packer 41, and the tail-end insertion type downhole heat extraction device 100 is pulled out of the wellbore 10. Necessary replacement and maintenance are carried out on the vulnerable parts. After the maintenance is completed, it is re-entered into the well according to the aforementioned entry method.

[0087] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0088] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0089] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[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 on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tail-end insertion type downhole heat extraction device, characterized in that, include: A packer mechanism (30) is installed inside the wellbore (10). A perforation section (102) is provided on the side wall of the wellbore (10). The packer mechanism (30) is seated below the perforation section (102). The packer mechanism (30) includes: an outer cylinder (31); a second packer (42) coaxially disposed on the outer cylinder (31) and located below the perforation section (102); and a second ball seat (33) coaxially disposed inside the outer cylinder (31) and located below the second packer (42). Pressuring the ball into the second ball seat (33) can cause the second packer (42) to be seated. A turbulence pump (34) is installed inside the wellbore (10), and the turbulence pump (34) is sealed inside the insertion sealing mechanism (30) by means of plugging; A heat exchange unit (1) is coaxially arranged inside the wellbore (10), the heat exchange unit (1) is seated above the perforation section (102), and a first packer (41) is provided on the heat exchange unit (1), the first packer (41) being located above the perforation section (102); A second annulus (4) is formed between the setting position of the insertion packer mechanism (30) and the wellbore (10) and the setting 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 turbulence pump (34) is connected to the second annulus (4). The lower port (342) of the turbulence pump (34) is connected to the lower part of the insertion packer mechanism (30). The heat exchange unit (1) exchanges heat with the geothermal water in the second annulus (4) through a circulating medium. An outer oil pipe (21) is provided at the upper part of the heat exchange unit (1), and an inner oil pipe (22) is provided inside the outer oil pipe (21). The outer oil pipe and the inner oil pipe are separate structures. The two ends of the first annulus (23) between the inner oil pipe (22) and the outer oil pipe (21) are sealed. A vacuum port (24) communicating with the first annulus (23) is provided on the outer oil pipe (21). The heat exchange unit (1) includes: a heat-conducting sleeve (11); a hanging short section (12) disposed above the heat-conducting sleeve (11); and an insulation pipe (13) intermittently sleeved inside the heat-conducting sleeve (11), the lower end of the insulation pipe (13) being lower than the first packer (41), the upper end of the insulation pipe (13) being connected to the inner oil pipe (22), the insulation pipe (13) being sealed and hung inside the hanging short section (12), and the upper end of the insulation pipe (13) being connected to the lower end of the inner oil pipe (22); The first packer (41) is disposed above the heat-conducting sleeve (11), and a flow distribution short section (14) is coaxially disposed above the first packer (41). A circulation hole (141) connecting the inner cavity and the outside is disposed on the side wall of the flow distribution short section (14). An isolation valve (5) is provided at the lower part of the heat exchange unit (1). The isolation valve (5) is configured to allow the first packer (41) to be set by pressurizing the well after ball sealing. The isolation valve (5) includes: a sleeve (51) coaxially disposed at the lower part of the heat exchange unit (1), the upper end of the sleeve (51) communicating with the heat exchange unit (1), and a through hole (52) communicating the inner cavity and the outside on the sleeve (51); an inner sleeve (54) coaxially fixedly disposed inside the sleeve (51), and a first channel (541) disposed on the side wall of the inner sleeve; and a first ball seat (53) coaxially disposed inside the inner sleeve (54) by a pin, and a second channel (531) disposed on the side wall of the first ball seat (53). In the initial state, the first channel, the second channel, and the through hole are connected, and the first ball seat and the inner sleeve are located above the through hole. After the ball is inserted into the first ball seat for sealing, the first ball seat can be moved downward relative to the inner sleeve by pressure, so that the first channel and the second channel are misaligned and closed.

2. The tail-end insertion type downhole heat extraction device according to claim 1, characterized in that, The insertion sealing mechanism (30) further includes a return tube (32) disposed at the upper end of the outer cylinder (31), a sealing plug (321) disposed at the lower end of the turbulence pump (34), the sealing plug (321) being coaxially disposed inside the return tube (32), a sealing element being disposed between the return tube (32) and the sealing plug (321), the upper port (341) of the turbulence pump (34) being located above the sealing plug (321), and the lower port (342) of the turbulence pump (34) communicating with the inner cavity of the sealing plug (321).

3. The tail-end insertion type downhole heat extraction device according to claim 1 or 2, characterized in that, A guide (16) is coaxially arranged inside the heat-conducting sleeve (11), and the upper end of the guide (16) is set as a conical surface. The heat-insulating pipe (13) passes through the guide (16).

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