Downhole heat removal tool and method

Abstract

The invention belongs to the technical field of terrestrial heat application, and particularly relates to an underground heat removal tool and method. The downhole heat removal tool comprises a first pipe column arranged in a shaft, and an annular space communicated with a perforation section of the shaft is arranged between the outer wall of the first pipe column and the shaft; the heat exchange unit is arranged in the first tubular column and exchanges heat with the annular space through a circulating medium; and two ports of the turbulent flow unit are respectively communicated with the annular space and a geothermal water reservoir at the bottom of the shaft, so that the geothermal water circularly flows.

Description

Technical Field

[0001] The present invention belongs to the field of geothermal application technology, and in particular, relates to a downhole heat extraction tool and a downhole heat extraction method. 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 downhole heat extraction tool that can improve underground heat extraction efficiency.

[0006] The present invention also proposes an underground heat extraction method, which can improve the underground heat extraction efficiency.

[0007] According to the present invention, a downhole heat extraction tool is provided, comprising:

[0008] a first tubular string disposed in a wellbore, wherein an annular space communicating with a perforation section of the wellbore is disposed between an outer wall of the first tubular string and the wellbore;

[0009] a heat exchange unit disposed in the first pipe column and performing heat exchange with the annular space through a circulating medium; and

[0010] A flow disturbance unit, wherein two ports of the flow disturbance unit are respectively connected to the annular space and the geothermal water reservoir at the bottom of the wellbore, so that the geothermal water circulates.

[0011] In a specific embodiment, the flow disturbance unit includes a flow disturbance pump, which is arranged in the first pipe string, the first port of the flow disturbance pump is connected to the annular space, and the second port of the flow disturbance pump is connected to the geothermal water reservoir at the bottom of the wellbore.

[0012] In a specific embodiment, a first seal and a second seal are provided between the disturbance pump and the first pipe column, the first seal separates the first port and the heat exchange unit, and the second seal separates the first port and the second port. A flow hole connecting the first port with the annular space is provided on the side wall of the first pipe column, and the flow hole is located between the first seal and the second seal.

[0013] In a specific embodiment, a pressure differential sleeve is provided on the first pipe column, and the flow hole is provided on the pressure differential sleeve.

[0014] In a specific embodiment, the first sealing member includes a first sealing cone sleeve and a second sealing cone sleeve that are adapted to each other, the first sealing cone sleeve is arranged in the first pipe column and located above the flow hole, and the second sealing cone sleeve is arranged on the disturbance pump and located above the first port.

[0015] In a specific embodiment, the second sealing member includes a tie-back tube and a sealing plug that fit together. The tie-back tube is arranged on the first pipe column and located below the flow hole. The sealing plug is arranged on the disturbance pump and separates the first port and the second port.

[0016] In a specific embodiment, the heat exchange unit includes an insulation tube intermittently sleeved in the first tube column, and a through hole is provided on the tube wall of the insulation tube.

[0017] In a specific embodiment, the through hole is not higher than the annular space.

[0018] In a specific embodiment, the through hole is configured as a slit shape.

[0019] According to the present invention, a downhole heat extraction method is also provided. Using the downhole heat extraction tool provided by the present invention, during the process in which the heat exchange unit exchanges heat with the annular space by means of a circulating medium, the turbulence unit causes the geothermal water to circulate between the annular space and the geothermal water reservoir.

[0020] Compared with the prior art, the advantages of this application are as follows.

[0021] The present invention sets a first tubular column in the wellbore to form an annular space between the first tubular column and the wellbore. The perforation section of the wellbore is connected to the annular space, so that high-temperature geothermal water can enter the annular space through the perforation section, and the heat of the high-temperature geothermal water can be transferred to the first tubular column. The heat exchange unit is set inside the first tubular column, and the heat exchange unit completes heat extraction by circulating the medium. The two ports of the turbulence unit are respectively connected to the annular space and the geothermal water reservoir at the bottom of the wellbore. During the heat extraction process of the heat exchange unit, the turbulence unit can drive the geothermal water to circulate in the annular space and the geothermal water reservoir, so that the temperature in the annular space is always maintained at a high level, thereby improving the heat extraction efficiency.

[0022] Compared with existing technologies, this invention can increase the heat extraction efficiency of a single well by more than 1.5 times and significantly slow the decline in heat extraction efficiency. Furthermore, the underground thermal water does not return to the surface, achieving the "heat extraction without water extraction" development effect, which can facilitate the development and reuse of conventional mid- to deep-layer geothermal resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be described below with reference to the accompanying drawings.

[0024] Figure 1 A schematic diagram showing a downhole heat extraction tool according to the present invention is shown;

[0025] Figure 2 A schematic diagram showing the first tubing string of the downhole heat extraction tool according to the present invention being run into the well;

[0026] Figure 3 A schematic diagram showing the direction of fluid flow during operation of the downhole heat extraction tool according to the present invention;

[0027] Figure 4 for Figure 1 A partial enlarged schematic diagram.

[0028] In the picture:

[0029] 1. First pipe string; 11. Guide sub; 12. Heat-conducting sleeve; 13. Ball seat; 14. Dissolvable ball; 15. Sand control screen; 16. Guide shoe;

[0030] 2. Annular space; 21. First packer; 22. Second packer;

[0031] 3. Heat exchange unit; 31. Insulation tube; 32. Through hole;

[0032] 4. Flow disturbance unit; 41. Flow disturbance pump; 411. First port; 412. Second port; 42. First sealing element; 421. First sealing cone sleeve; 422. Second sealing cone sleeve; 43. Second sealing element; 431. Tieback sleeve; 432. Sealing plug; 5. Pressure differential sleeve; 51. Flow hole;

[0033] 6. Oil pipeline;

[0034] 7. Feeding tool assembly;

[0035] 8. Suspension distribution short section;

[0036] 10. Wellbore; 101. Geothermal water reservoir; 102. Perforation section;

[0037] 100. Underground heat extraction tools.

[0038] 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

[0039] The present invention will be described below with reference to the accompanying drawings.

[0040] It should be noted that, in the present application, the direction of the downhole heat extraction tool according to the present invention close to the wellhead after entering the well is described as "upper end", "front end" or similar terms, and the direction of the downhole heat extraction tool according to the present invention away from the wellhead after entering the well is described as "lower end", "rear end" or similar terms.

[0041] Figure 1 FIG. 1 shows the structure of a downhole heat extraction tool 100 according to the present invention. Figure 1 As shown, the downhole heat extraction tool 100 includes a first tubular string 1, a heat exchange unit 3, and a flow disturbance unit 4. The first tubular string 1 is disposed within a wellbore 10, forming an annular space 2 therebetween. The annular space 2 is connected to a perforated section 102 of the wellbore 10. The flow disturbance unit is configured to drive geothermal water within the geothermal water reservoir 101 to continuously flow into the annular space 2. Simultaneously, the geothermal water within the annular space 2 flows outward from the wellbore 10 through the perforated section 102, thereby maintaining a high temperature within the annular space 2. The geothermal water within the annular space 2 contacts the wall of the first tubular string 1, transferring heat to the interior of the first tubular string 1, raising the temperature of the first tubular string 1 in this area and forming a high-temperature zone. The heat exchange unit 3 is disposed within the first tubular string 1. By circulating a circulating medium through the high-temperature zone of the first tubular string 1, the temperature of the geothermal water within the annular space 2 is continuously transferred to the medium, transporting the heated geothermal water to the surface.

[0042] It is easy to understand that the perforation section 102 of the wellbore 10 is well known to those skilled in the art and can connect the outside of the wellbore 10 with the inner cavity of the wellbore 10 .

[0043] Under this configuration of this embodiment, the medium circulates under the action of heat exchange unit 3, continuously absorbing the heated geothermal water within annular space 2 and transporting it to the surface. Simultaneously, the geothermal water continuously circulates between annular space 2 and geothermal water reservoir 101, thereby maintaining the temperature of the geothermal water within annular space 2 and improving heat extraction efficiency. During this process, the medium and geothermal water circulate in separate paths, preventing the two water elements from intermingling, thereby achieving the effect of extracting heat without extracting water.

[0044] In one embodiment, a first tubular string 1 is coaxially interstitially sleeved within a wellbore 10. An annular space 2 is defined between the outer wall of the first tubular string 1 and the wellbore 10, communicating with the perforated section 102 of the wellbore 10. Specifically, the outer diameter of the first tubular string 1 is smaller than the inner diameter of the wellbore 10, resulting in a gap between the outer wall of the first tubular string 1 and the inner wall of the wellbore 10. A first packer 21 and a second packer 22 are disposed between the first tubular string 1 and the wellbore 10. The first packer 21 is located above the perforated section 102, while the second packer 22 is located below the perforated section 102. Both the first packer 21 and the second packer 22 seal the gap between the wellbore 10 and the first tubular string 1. An annular space 2 communicating with the perforated section 102 is formed between the first packer 21, the second packer 22, the wellbore 10, and the first tubular string 1. In this configuration, geothermal water within the annular space 2 can flow through the perforated section 102 to the outside of the wellbore 10.

[0045] In one embodiment, the heat exchange unit 3 is arranged in the first pipe column 1, and the heat of the geothermal water in the annular space 2 can be transferred to the heat exchange unit 3 through the first pipe column 1. The heat exchange unit 3 is configured to be able to exchange heat with the annular space 2 through a circulating medium.

[0046] Specifically, if Figure 1 and Figure 4 As shown, the heat exchange unit 3 includes an insulation tube 31 interstitially sleeved within the first pipe column 1, with a through hole 32 provided on the wall of the insulation tube 31. Preferably, the through hole 32 is no higher than the annular space 2, so that the medium can flow through the annular space 2 during the process of circulating the medium in the heat exchange unit 3.

[0047] In this setting, if Figure 3 As shown, a medium is injected from the wellhead into the annulus between the insulation pipe 31 and the first tubing string 1. When the medium flows downward along the annulus between the insulation pipe 31 and the first tubing string 1 to the first tubing string 1 at the same height as the annular space 2, it can exchange heat with the high-temperature geothermal water in the annular space 2, thereby increasing the temperature of the medium. Afterwards, the medium flows into the insulation pipe 31 through the through hole 32, moves upward along the insulation pipe 31, and finally exits the well. By such a reciprocating circulation of the medium, the heat of the geothermal water can be continuously transported to the ground.

[0048] In a preferred embodiment, the insulation pipe 31 is made of insulation material. Under this setting, the heat loss can be reduced during the upward flow of the heated medium along the insulation pipe 31, thereby improving the heat extraction efficiency.

[0049] It should be noted that during the medium circulation process, the medium can also be injected into the insulation pipe 31 from the wellhead, and the medium absorbs the heat of the geothermal water and is discharged from the annulus between the insulation pipe 31 and the first pipe string 1.

[0050] In a preferred embodiment, Figure 1 and Figure 4 As shown, the through hole 32 is arranged in a slit shape. Further, a slit oil pipe is coaxially arranged in series on the thermal insulation pipe 31, and the slit of the slit oil pipe is the through hole 32.

[0051] According to the present invention, the two ports of the disturbance unit 4 are respectively connected to the annular space 2 and the geothermal water reservoir 101 at the bottom of the wellbore 10. After the disturbance unit 4 is started, the high-temperature geothermal water in the geothermal water reservoir 101 can be pumped into the annular space 2, and the geothermal water in the annular space 2 that has undergone heat exchange with the wellbore 10 is discharged from the perforation section 102, so that the geothermal water circulates and the geothermal water in the annular space 2 is always maintained at a higher temperature level, thereby maintaining a higher heat exchange efficiency during the heat exchange between the medium and the geothermal water in the annular space 2.

[0052] In a specific embodiment, the flow disturbance unit 4 includes a flow disturbance pump 41, which is disposed in the first column 1 and below the heat exchange unit 3. In this embodiment, the flow disturbance pump 41 includes a first port 411 and a second port 412. Figure 1 and Figure 4 As shown, the first port 411 is provided on a radial side of the disturbance pump 41 and communicates with the annular space 2. The second port 412 is provided at the lower end of the disturbance pump 41 and communicates with the geothermal water reservoir 101. When the disturbance pump 41 is turned on, it drives the geothermal water within the geothermal water reservoir 101 to flow upward from the bottom, entering the disturbance pump 41 through the second port 412, and then flowing into the annular space 2 through the first port 411. This replenishes the annular space 2 with higher-temperature geothermal water, raising the temperature of the annular space 2. The geothermal water originally within the annular space 2 is then discharged through the perforated section 102 into the formation outside the wellbore 10.

[0053] According to the present invention, Figure 1 and Figure 4As shown, a first seal 42 and a second seal 43 are provided between the disturbance pump 41 and the first tubing string 1. The first seal 42 is located between the first port 411 and the heat exchange unit 3, sealing the gap between the outer side of the disturbance pump 41 and the inner side of the first tubing string 1, thereby separating the first port 411 from the heat exchange unit 3. The second seal 43 is located between the first port 411 and the second port 412, thereby separating the first port 411 from the second port 412. A flow hole 51 is provided on the sidewall of the first tubing string 1, connecting the first port 411 with the annular space 2. The flow hole is located between the first seal 42 and the second seal 43. After the disturbance pump 41 is turned on, it can drive the geothermal water in the geothermal water reservoir 101 to flow from bottom to top, and enter the disturbance pump 41 from the second port 412, and then flow to the annular space 2 through the first port 411 and the flow hole 51, thereby replenishing the annular space 2 with higher temperature geothermal water and increasing the temperature of the annular space 2. The original geothermal water in the annular space 2 is discharged into the formation outside the wellbore 10 through the perforation section 102.

[0054] According to the present invention, in a preferred embodiment, a differential pressure sleeve 5 is provided on the first tubing string 1, and a flow hole 51 is provided on the differential pressure sleeve 5. Initially, the flow hole 51 is closed. When the differential pressure sleeve 5 is subjected to pressure, the flow hole 51 can be opened. It will be readily understood that the specific structure of the differential pressure sleeve 5 is well known to those skilled in the art and will not be further described here.

[0055] According to the present invention, in a preferred embodiment, the first sealing element 42 includes a first sealing cone sleeve 421 and a second sealing cone sleeve 422 that fit together. Specifically, the first sealing cone sleeve 421 is fixedly mounted on the inner wall of the first tubular column 1 and is located above the flow hole 51. The inner wall of the first sealing cone sleeve 421 is configured as a tapered surface that gradually increases from bottom to top. The second sealing cone sleeve 422 is fixedly mounted on the outer wall of the flow pump 41 and is located above the first port 411. The outer wall of the second sealing cone sleeve 422 is configured as a tapered surface that gradually increases from bottom to top. In this arrangement, when the flow pump 41 is assembled into the first tubular column 1, the flow pump 41 enters the first tubular column 1 axially from top to bottom. When the first sealing cone sleeve 421 and the second sealing cone sleeve 422 axially abut, the inner wall of the first sealing cone sleeve 421 and the inner wall of the second sealing cone sleeve 422 form a seal, thereby positioning the flow pump 41 with the first tubular column 1.

[0056] In one embodiment, the structure of the second sealing member 43 is similar to that of the first sealing member 42 .

[0057] In a preferred embodiment, the second sealing member 43 comprises a matching tieback tube 431 and a sealing plug 432. Specifically, the tieback tube 431 is cylindrical and disposed on the first tubing string 1 below the flow hole 51. The sealing plug 432 is cylindrical and disposed on the flow pump 41 between the first port 411 and the second port 412, separating the first port 411 and the second port 412. Specifically, the first port 411 is disposed on the side of the flow pump 411, and the second port 412 is axially disposed within the lower end of the flow pump 411. The sealing plug 432 is coaxially disposed at the lower end of the flow pump 411, thereby enclosing the second port 412 and separating it from the first port 411. The outer wall of the sealing plug 432 forms a seal with the inner wall of the tieback tube 431. With this arrangement, the sealing plug 432 and the tieback tube 431 can form an effective seal within a certain range of relative axial displacement. When the disturbance pump 41 is assembled into the first pipe column 1, the first seal 42 and the second seal 43 need to be sealed at the same time. The second seal 43 is set to a structure that can achieve sealing without precise positioning, which can reduce the processing accuracy required for the first seal 42 and the second seal 43 and reduce costs.

[0058] According to the present invention, in a specific embodiment, the first packer 21 is a bidirectionally anchored and releasable packer. A ball seat 13 is coaxially fixedly disposed within the interior of the first tubular string 1, and the ball seat 13 is located below the first packer 21. After a soluble ball 14 is placed into the ball seat 13 to seal it, pressure is applied to the interior of the first tubular string 1, which can transmit the pressure to the first packer 21 and the differential pressure sleeve 5. Furthermore, the ball seat 13 is located below the flow disturbance unit 4. The structure of the bidirectionally anchored and releasable packer is well known to those skilled in the art, and it can be anchored and set when subjected to pressure.

[0059] According to the present invention, in a specific embodiment, the second packer 22 is a water-swelling packer. The structure of a water-swelling packer is well known to those skilled in the art, and the packer can be automatically set when exposed to water.

[0060] In a preferred embodiment, Figure 2 As shown, the first tubular string 1 includes a guide nipple 11, a heat-conducting sleeve 12, a differential pressure sleeve 5, a tie-back sleeve 431, a sand control screen 15 and a guide shoe 16, which are coaxially arranged from top to bottom.

[0061] The guide sub 11 is provided at the upper end of the first tubular string 1. The guide sub 11 can guide downhole tools such as the flow disturbance unit 4 and the heat exchange unit 3 when they enter the first tubular string 1.

[0062] The thermal sleeve 12 is located within the annular space 2; that is, it forms the inner wall of the annular space 2. Made of a material with high thermal conductivity, the thermal sleeve 12 improves the heat exchange efficiency between the geothermal water within the annular space 2 and the medium within the first tubular string 1. Furthermore, a first seal 42 is located between the differential pressure sleeve 5 and the thermal sleeve 12.

[0063] The sand control screen 15 is arranged below the second packer 22 to play a role in sand control and filtering.

[0064] The guide shoe 16 is provided at the lower end of the first pipe string 1 .

[0065] According to the present invention, a downhole heat extraction method is also provided. Using the downhole heat extraction tool 100 provided by the present invention, during the process of heat exchange unit 3 exchanging heat with the annular space 2 by means of a circulating medium, the turbulence unit 4 causes the geothermal water to circulate between the annular space 2 and the geothermal water reservoir 101.

[0066] In a specific embodiment, the steps of implementing a downhole heat extraction method using the downhole heat extraction tool 100 are as follows.

[0067] The downhole heat extraction tool 100 is suitable for medium-deep hydrothermal geothermal development. The applicable well type is a two-opening vertical well or a highly deviated well. After drilling the well, a suitable well section is selected for perforation to form a perforation section 102 on the wellbore 10.

[0068] After perforation is completed, the delivery tool assembly 7 and the first tubing string 1 are lowered into the wellbore 10 through the tubing 6. Figure 2 As shown, when the perforation section 102 is located between the first packer 21 and the second packer 22 of the first tubular string 1 , the first tubular string 1 is run into position.

[0069] Then, a soluble ball 14 is dropped into the wellhead and pumped into the ball seat 13. The pressure in the first tubing string 1 is built up. Once the predetermined pressure is reached, the first packer 21 (a bidirectionally anchored releasable packer) is set. Further pressure is built up to increase the pressure in the first tubing string 1. Once the predetermined pressure is reached, the differential pressure sleeve 5 opens, and the flow hole 51 is opened. Simultaneously, the second packer 22 (a water-swellable packer) expands in the liquid environment of the wellbore 10 and sets the packer.

[0070] The running tool assembly 7 and the first tubing string 1 are released from each other, and the running tool assembly 7 is lifted out through the oil pipe 6. The soluble ball 14 dissolves by itself, and the first tubing string 1 is put into the well.

[0071] After the first tubing string 1 is lowered into the well, the flow disturbance unit 4 is installed on the surface below the heat exchange unit 3. Several insulated pipes 31 are connected above the heat exchange unit 3. The armored cables of the flow disturbance unit 4 are secured to the insulated pipes 31 with cable clips. These cables provide power to the flow disturbance pump 41 and transmit control and monitoring signals. The heat exchange unit 3 and flow disturbance unit 4 are lowered into the first tubing string 1 through the insulated pipes 31. In a preferred embodiment, the insulated pipes 31 are double-layer insulated oil pipes.

[0072] After the heat exchange unit 3 and the flow disturbance unit 4 are lowered into place, the insulation pipe 31 and the flow disturbance pump cable are hung at the wellhead using the hanging flow distribution nipple 8. At this point, the entire downhole heat extraction tool 100 completes the well operation.

[0073] like Figure 3 As shown, after the downhole heat extraction tool 100 is put into place in the well, a dual isolation channel of injection-production circulation and forced turbulence is formed, and the turbulence pump 41 is turned on to continuously replenish the geothermal water in the geothermal water reservoir 101 below the wellbore 10 into the annular space 2, thereby achieving rapid heat replenishment of the annular space 2 and improving the heat extraction efficiency of the heat exchange unit 3. After the turbulence pump 41 is running stably, the surface injection-production circulation unit (not shown in the figure) is turned on to inject cold water (medium) into the annular space between the insulation pipe 31 and the first tubing string 1. When flowing through the heat-conducting sleeve 12, the water exchanges heat with the geothermal water in the annular space 2, then flows upward along the insulation pipe 31, exchanges heat in the surface heat exchanger (not shown in the figure), and is then injected back into the annular space between the insulation pipe 31 and the first tubing string 1, completing the injection-production cycle.

[0074] When the downhole heat extraction tool 100 requires later maintenance, the heat exchange unit 3, the flow disturbance unit 4 and other accessories can be lifted out of the wellhead for replacement and maintenance by lifting the insulation pipe 31, and the first pipe string 1 does not need to be removed.

[0075] If necessary, the first packer 21 can be unsealed by running a recovery tool, and the first tubing string 1 can be lifted out of the well to complete the replacement and maintenance of the packer and other functional units in the first tubing string 1. After the maintenance is completed, the tool can be re-run according to the above steps to ensure the safe operation of the forced flow disturbance downhole heat extraction tool.

[0076] The present invention uses a single well forced turbulence to make the geothermal water circulate for energy replenishment, thereby achieving efficient heat exchange underground. Compared with conventional coaxial casing heat exchange technology, the heat exchange efficiency is higher and can significantly slow down the decline period of heat extraction power.

[0077] The cold water (medium) injected into the injection-production circulation channel flows in the opposite direction to the hot water in the formation in the forced disturbance flow channel, realizing convection heat replenishment and higher heat exchange efficiency.

[0078] The disturbance pump 41 is provided with a second sealing cone sleeve 422, which simplifies the pipe string structure. At the same time, the first packer 21 does not need to be designed with a cable structure. The overall lowering of the downhole heat extraction tool 100 is completed by successively lowering the pipe string in two trips. The construction process is simple and reliable.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A downhole heat extraction tool, characterized in that: include: A first tubular string (1) is disposed in a wellbore (10), wherein an annular space (2) communicating with a perforation section of the wellbore (10) is provided between an outer wall of the first tubular string (1) and the wellbore (10); a heat exchange unit (3) disposed in the first pipe column (1) for performing heat exchange with the annular space (2) via a circulating medium; and A flow disturbance unit (4), wherein two ports of the flow disturbance unit (4) are respectively connected to the annular space (2) and the geothermal water reservoir (101) at the bottom of the wellbore (10), thereby allowing the geothermal water to circulate.

2. The downhole heat extraction tool according to claim 1, characterized in that: The disturbance unit (4) comprises a disturbance pump (41), the disturbance pump (41) being arranged in the first pipe string (1), the first port (411) of the disturbance pump (41) being in communication with the annular space (2), and the second port (412) of the disturbance pump (41) being in communication with the geothermal water reservoir (101) at the bottom of the wellbore (10).

3. The downhole heat extraction tool according to claim 2, characterized in that: A first seal (42) and a second seal (43) are provided between the disturbance pump (41) and the first pipe column (1); the first seal (42) separates the first port (411) from the heat exchange unit (3); the second seal (43) separates the first port (411) from the second port (412); a flow hole (51) is provided on the side wall of the first pipe column (1) for connecting the first port (411) with the annular space (2); the flow hole is located between the first seal (42) and the second seal (43).

4. The downhole heat extraction tool according to claim 3, characterized in that: A pressure differential sleeve (5) is provided on the first pipe column (1), and the flow hole (51) is provided on the pressure differential sleeve (5).

5. The downhole heat extraction tool according to claim 3, characterized in that: The first sealing member (42) comprises a first sealing cone sleeve (421) and a second sealing cone sleeve (422) adapted to each other, wherein the first sealing cone sleeve (421) is arranged in the first pipe column (1) and is located above the flow hole (51), and the second sealing cone sleeve (422) is arranged on the disturbance pump (41) and is located above the first port (411).

6. The downhole heat extraction tool according to claim 3, characterized in that: The second sealing member (43) comprises a tie-back tube (431) and a sealing plug (432) adapted to each other. The tie-back tube (431) is arranged on the first pipe column (1) and is located below the flow hole (51). The sealing plug (432) is arranged on the disturbance pump (41) and separates the first port (411) and the second port (412).

7. The downhole heat extraction tool according to any one of claims 1 to 6, characterized in that: The heat exchange unit (3) comprises a heat-insulating tube (31) intermittently sleeved within the first tube column (1), and a through hole (32) is provided on the tube wall of the heat-insulating tube (31).

8. The downhole heat extraction tool according to claim 7, characterized in that: The through hole (32) is not higher than the annular space (2).

9. The downhole heat extraction tool according to claim 7, characterized in that: The through hole (32) is configured in a slit shape.

10. A method for extracting heat from a well, characterized in that: When using the downhole heat extraction tool according to any one of claims 1 to 9, the heat exchange unit (3) exchanges heat with the annular space (2) by means of a circulating medium, and the flow disturbance unit (4) causes the geothermal water to circulate between the annular space (2) and the geothermal water reservoir (101).

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