Multi-branch radial well assisted U-shaped well reinforced closed heat removal system and construction method

Abstract

The invention provides a multi-branch radial well assisted U-shaped well reinforced closed heat removal system and a construction method, and relates to the field of geothermal development. The multi-branch radial well assisted U-shaped well reinforced closed heat removal system comprises a main body structure and at least one branch structure; the main body structure comprises a well body, an injection device and an extraction device. The injection device communicates with the first end of the well body and can inject heat taking fluid into the well body. The extraction device communicates with the second end of the well body and can collect heat extraction fluid in the well body; the top ends of the branch structures communicate with the well body, and the bottom ends of the branch structures extend downwards. The branch structures can receive at least part of the heat removal fluid from the well body and enable the heat removal fluid obtained after heat exchange to flow back into the well body. The heat removal effect of the heat removal system can be improved, and the heat energy utilization rate is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of geothermal development, and in particular to a multi-branch radial well assisted U-shaped well reinforced closed heat extraction system and a construction method. BACKGROUND

[0002] Geothermal energy is a renewable clean energy generated by molten magma and radioactive decay in the earth's interior, which has three advantages of stable and continuous output, zero carbon emission and renewable. In the related art, a loop can be formed by a vertical well and a horizontal well in cooperation, so that heat exchange can be realized by geothermal energy to achieve the purpose of geothermal development. However, the heat extraction effect of the above heat extraction system is poor, and the heat energy utilization rate is low. SUMMARY

[0003] The embodiments of the present application provide a multi-branch radial well assisted U-shaped well reinforced closed heat extraction system and a construction method, to solve the problem of poor heat extraction effect and low heat energy utilization rate of the heat extraction system in the related art.

[0004] The multi-branch radial well assisted U-shaped well reinforced closed heat extraction system provided by the embodiments of the present application comprises a main body structure and at least one branch structure.

[0005] The main body structure comprises a well body, an injection device and a production device; the injection device is in communication with a first end of the well body, and the injection device can inject heat extraction fluid into the well body;

[0006] The production device is in communication with a second end of the well body, and the production device can collect the heat extraction fluid in the well body;

[0007] The top end of the branch structure is in communication with the well body, and the bottom end of the branch structure extends downward; the branch structure can receive at least part of the heat extraction fluid from the well body, and make the heat-exchanged heat extraction fluid flow back into the well body.

[0008] By adopting the above technical solution, the closed heat extraction system comprises a main body structure and at least one branch structure, the main body structure comprises a well body, an injection device and a production device, wherein the injection device is in communication with a first end of the well body, the injection device can inject heat extraction fluid into the well body, the production device is in communication with a second end of the well body, and the production device can collect the heat extraction fluid in the well body, so that the heat extraction fluid can flow in the well body from the first end of the well body to the second end of the well body, to realize heat extraction by heat exchange.

[0009] The top end of the branch structure is in communication with the well body, and the bottom end of the branch structure extends downward. The branch structure can receive at least part of the heat extraction fluid from the well body, and make the heat-exchanged heat extraction fluid flow back into the well body, so that the heat extraction fluid in the well body can flow back into the well body after heat exchange through the branch structure, thereby prolonging the heat exchange path of the heat extraction system, improving the heat extraction effect of the heat extraction system, and improving the utilization rate of heat energy.

[0010] In some possible embodiments, the branch structure comprises an outer wall and a flow pipe;

[0011] The outer wall is connected with the well body, and the bottom end of the outer wall extends downward. The first end of the flow pipe is in communication with the well body, and the second end of the flow pipe is in communication with the bottom end of the outer wall.

[0012] In some possible embodiments, the well body is provided with a plurality of separation structures, and the plurality of separation structures are sequentially and spacedly arranged along the extension direction of the well body. The branch structure is accommodated between two adjacent separation structures.

[0013] In some possible embodiments, the separation structure encloses the first end of the outer wall, and the separation structure has a communication port.

[0014] The two adjacent separation structures comprise a first separation structure close to the injection device and a second separation structure close to the production device.

[0015] The first end of the flow pipe is in communication with the communication port of the first separation structure, and the outer wall is in communication with the communication port of the second separation structure.

[0016] In some possible embodiments, the flow pipe separates the outer wall, and a flow cavity is formed between the flow pipe and the outer wall.

[0017] The branch structure is configured to make the heat extraction fluid flow from the communication port of the first separation structure to the inner side of the flow pipe, and flow into the flow cavity through the second end of the flow pipe. The heat extraction pipe in the flow cavity can flow out through the communication port of the second separation structure.

[0018] In some possible embodiments, the separation structure comprises a whipstock and a hydraulic anchor, and the hydraulic anchor is away from the first end of the well body relative to the whipstock.

[0019] In some possible embodiments, the whipstock comprises a whipstock and a connecting rod, and the whipstock is connected with the hydraulic anchor through the connecting rod.

[0020] The whipstock is provided with a whipstock through hole facing the first end of the well body, so that the heat extraction fluid flows through the whipstock through hole towards the hydraulic anchor.

[0021] In some possible implementation manners, the branch structure is obliquely arranged, and in the horizontal direction, the bottom end of the branch structure is closer to the second end of the well body than the top end of the branch structure.

[0022] In some possible implementation manners, the branch structure is obliquely arranged, and in the horizontal direction, the bottom end of the branch structure is closer to the second end of the well body than the top end of the branch structure.

[0023] In some possible implementation manners, the branch structure includes a plurality of heat exchange parts, and the plurality of heat exchange parts are sequentially connected, and each heat exchange part is arranged in one or more high-permeability layers.

[0024] Embodiments of the present application provide a construction method of a multi-branch radial well auxiliary U-shaped well reinforced closed heat extraction system, comprising:

[0025] forming a well body in a stratum;

[0026] forming a branch structure below the well body, the top end of the branch structure being in communication with the well body, and the bottom end of the branch structure extending downwards;

[0027] communicating an injection device with the first end of the well body, so that the injection device can inject a heat extraction fluid into the well body; and communicating a production device with the second end of the well body, so that the production device can collect the heat extraction fluid in the well body. BRIEF DESCRIPTION OF DRAWINGS

[0028] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0029] Figure 1 a structure schematic diagram of a multi-branch radial well auxiliary U-shaped well reinforced closed heat extraction system provided by embodiments of the present application;

[0030] Figure 2 a structure schematic diagram of a separation structure provided by embodiments of the present application;

[0031] Figure 3 a construction process schematic diagram of a multi-branch radial well auxiliary U-shaped well reinforced closed heat extraction system provided by embodiments of the present application;

[0032] Figure 4 a construction process schematic diagram of a multi-branch radial well auxiliary U-shaped well reinforced closed heat extraction system provided by embodiments of the present application;

[0033] Figure 5 A flowchart of a construction method of a multi-limb radial well auxiliary U-shaped well reinforced closed heat extraction system is provided.

[0034] Explanation of reference signs:

[0035] 100, well body;

[0036] 110, vertical section; 120, horizontal section; 130, casing cementing;

[0037] 200, branch structure;

[0038] 210, outer wall; 220, flow conduit;

[0039] 300, separation structure;

[0040] 310, whipstock; 311, whipstock through hole; 312, connecting rod; 320, hydraulic anchor; 330, support;

[0041] 400, circulation assembly;

[0042] 410, heat storage device; 420, heat extraction utilization equipment; 430, water reservoir;

[0043] 500, injection device;

[0044] 600, production device.

[0045] Through the above drawings, the specific embodiments of the present application have been shown, and will be described in more detail hereinafter. These drawings and written descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0046] Geothermal energy is a renewable clean energy generated by molten magma and radioactive decay inside the earth, with three advantages of stable and continuous output, zero carbon emission and renewable. At present, in the field of geothermal resource development, geothermal resources can be divided into high temperature resources and medium and low temperature resources. Among them, high temperature resources (temperature greater than 150 degrees Celsius) are mainly used for power generation, and medium and low temperature resources (temperature greater than 20 degrees Celsius and less than 150 degrees Celsius) support direct utilization fields such as heating, agricultural greenhouse and medical care, so as to realize the utilization of geothermal energy more fully.

[0047] In the related art, a circuit can be formed by a matched vertical well and a horizontal well, so that heat exchange can be achieved by geothermal energy to achieve the purpose of geothermal development. For example, the U-shaped well closed heat extraction system is a high-efficiency development technology for medium-deep geothermal energy, which can form a U-shaped circuit through precise connection of a vertical well and a horizontal well to achieve "only heat extraction without water extraction". The low-temperature circulating medium is injected from the horizontal well, flows through the high-temperature and high-permeability rock layer to absorb heat, and is returned from the horizontal well. The whole process is sealed and does not contact with underground water. The U-shaped well closed heat extraction system can reduce the possibility of underground water pollution caused by the entry of circulating water into the stratum, and solve the problems of difficult traditional geothermal recharge and pipe fouling.

[0048] However, the U-shaped closed heat exchange system in the related art usually only extracts heat from a single high-permeability heat layer, and the U-shaped closed heat exchange system is difficult to connect multiple heat sources, so the heat energy utilization rate is low. Moreover, the U-shaped closed heat exchange system in the related art usually only exchanges heat in the horizontal well section, which makes the heat exchange path of the U-shaped closed heat exchange system short and the heat energy recovery rate low.

[0049] To solve the above technical problems, the embodiments of the present application provide a multi-branch radial well assisted U-shaped well reinforced closed heat extraction system and a construction method. The multi-branch radial well assisted U-shaped well reinforced closed heat extraction system comprises a main body structure and at least one branch structure. The main body structure comprises a well body, an injection device and a production device. The injection device is in communication with the first end of the well body, and the injection device can inject heat extraction fluid into the well body. The production device is in communication with the second end of the well body, and the production device can collect the heat extraction fluid in the well body, so that the heat extraction fluid can flow in the well body from the first end of the well body to the second end of the well body to achieve heat exchange and heat extraction.

[0050] The top end of the branch structure is in communication with the well body, and the bottom end of the branch structure extends downward. The branch structure can receive at least part of the heat extraction fluid from the well body, and make the heat-exchanged heat extraction fluid flow back into the well body, so that the heat extraction fluid in the well body can flow back into the well body after heat exchange through the branch structure, thereby extending the heat exchange path of the heat extraction system by setting the branch structure, improving the heat extraction effect of the heat extraction system, and improving the heat energy utilization rate.

[0051] The exemplary embodiments will be described in detail below with reference to the drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0052] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific examples. The following specific examples can be combined with each other, and the same or similar concepts or processes can not be described again in some examples. The embodiments of the present application will be described below with reference to the drawings.

[0053] With reference to Figures 1-4 The embodiments of the present application provide a multi-branch radial well assisted U-shaped well reinforced closed heat extraction system, which comprises a main body structure. The main body structure comprises a well body 100, an injection device 500 and a production device 600.

[0054] The injection device 500 is in communication with the first end of the well body 100, and the injection device 500 can inject heat extraction fluid into the well body 100. The production device 600 is in communication with the second end of the well body 100, and the production device 600 can collect heat extraction fluid in the well body 100, so that the heat extraction fluid can flow in the well body 100 from the first end of the well body 100 to the second end of the well body 100, to realize heat exchange and heat extraction.

[0055] For example, the multi-branch radial well assisted U-shaped well reinforced closed heat extraction system further comprises at least one branch structure 200, the top end of the branch structure 200 is in communication with the well body 100, and the bottom end of the branch structure 200 can extend downward. The branch structure 200 can receive at least part of the heat extraction fluid from the well body 100, and make the heat-exchanged heat extraction fluid flow back into the well body 100.

[0056] By arranging the branch structure 200, the heat extraction fluid in the well body 100 can flow back into the well body 100 after heat exchange through the branch structure 200, so that the heat exchange path of the heat extraction system can be extended by arranging the branch structure 200, the heat extraction effect of the heat extraction system can be improved, and the heat energy utilization rate can be improved.

[0057] In some possible embodiments, the well body 100 can be arranged as a U-shaped well body 100. The U-shaped well body 100 can comprise a vertical section 110 and a horizontal section 120 in communication, wherein the first end of the vertical section 110 is located on the ground, the second end of the vertical section 110 extends downward, and the second end of the vertical section 110 is in communication with the horizontal section 120.

[0058] The horizontal section 120 can be arranged horizontally, and the horizontal section 120 can be arranged in a high-permeability layer. The heights of the two ends of the horizontal section 120 can be the same or approximately the same, so that the flow process of the heat extraction fluid in the horizontal section 120 is more stable.

[0059] For example, the number of vertical segments 110 is multiple, which can include a first vertical segment 110 and a second vertical segment 110. The first vertical segment 110 forms a first end of the well body 100, which can be used to communicate with the injection device. The second vertical segment 110 forms a second end of the well body 100, which can be used to communicate with the production device 600, so that the heat extraction fluid can realize the heat exchange process in the horizontal segment 120.

[0060] The outer side of the well body 100 can be provided with a casing cementing 130 to make the structure of the well body 100 more stable. For example, the outer side of the vertical segment 110 can be provided with a casing cementing, which can be vertically arranged.

[0061] It should be noted that in the well body 100, the height of the horizontal segment 120 is generally lower than that of the vertical segment 110, and the length of the horizontal segment 120 is greater than that of the vertical segment 110. In the heat exchange process of the well body 100, the flow time of the heat extraction fluid in the horizontal segment 120 is greater than that in the vertical segment 110. The horizontal segment 120 of the well body 100 can be used to communicate with the branch structure 200 to improve the possibility of the heat extraction fluid flowing to the branch structure 200 and prolong the flow time of the heat extraction fluid in the branch structure 200.

[0062] In some possible embodiments, the number of branch structures 200 can be one or more. For example, the number of branch structures 200 can be one, which can be arranged in the middle of the horizontal segment 120. The bottom end of the branch structure 200 extends downward to pass through multiple high permeability layers through the branch structure 200, so as to realize the heat exchange process of multiple heat sources.

[0063] The number of branch structures 200 can be multiple, which can be arranged in sequence and in parallel. The multiple branch structures 200 can be arranged in the horizontal segment 120, and the bottom end of the branch structure 200 extends downward to pass through multiple high permeability layers through the multiple branch structures 200.

[0064] For example, the branch structure 200 can include multiple heat exchange parts. The multiple heat exchange parts can be connected in sequence along the height direction, and each heat exchange part is arranged in one or more high permeability layers, so as to pass through multiple high permeability layers through the branch structure 200.

[0065] It is easy to understand that, relative to the horizontal section 120 of the well body 100 located in the same side high permeable layer, the plurality of heat exchange parts of the branch structure 200 can be arranged in the plurality of high permeable layers, the plurality of heat exchange parts can be arranged one by one with the plurality of high permeable layers, the heat exchange part can be arranged in the corresponding high permeable layer, so that the heat exchange part can exchange heat with the corresponding high permeable layer, thereby further improving the heat exchange effect of the branch structure 200.

[0066] For example, the branch structure 200 can be arranged obliquely relative to the vertical direction, and in the horizontal direction, the bottom end of the branch structure 200 can be closer to the second end of the well body 100 relative to the top end of the branch structure 200.

[0067] That is, the included angle between the branch structure 200 and the horizontal section 120 can be less than 90 degrees, and the top end of the branch structure 200 is relative to the first end of the horizontal section 120, so that the heat exchange fluid can flow easily from the horizontal section 120 into the branch structure 200, thereby reducing the possibility of the heat exchange fluid flowing directly from the top end of the branch structure 200, so as to improve the use effect of the branch structure 200 and improve the heat exchange effect of the heat extraction system.

[0068] Referring to Figures 1-4 In some possible embodiments, the well body 100 can be provided with a plurality of separation structures 300, the plurality of separation structures 300 can be arranged in sequence along the extension direction of the well body 100, and the plurality of separation structures 300 can be arranged in sequence in the horizontal section 120.

[0069] The two adjacent separation structures 300 can be used to accommodate the branch structure 200, so that the separation structure 300 can cooperate with the branch structure 200 to realize the stable flow of the heat extraction fluid.

[0070] For example, the number of separation structures 300 can be two, the branch structure 200 can be arranged between the two separation structures 300, and the number of branch structures 200 can be one, so that the heat extraction fluid in the horizontal section 120 can flow into the branch structure 200 when flowing between the two separation structures 300.

[0071] The number of separation structures 300 can be more than three, the branch structure 200 can be arranged between the two adjacent separation structures 300, and the number of branch structures 200 can be multiple, so that the heat extraction fluid in the horizontal section 120 can flow through the separation structure 300 in sequence, thereby flowing into the plurality of branch structures 200.

[0072] In some possible embodiments, the branch structure 200 can include an outer wall 210 and a flow pipe 220. The outer wall 210 can be connected with the well body 100, and the bottom end of the outer wall 210 can extend downward.

[0073] For example, the first end of the flow pipe 220 can be connected to the well body 100, and the second end of the flow pipe 220 can be connected to the bottom end of the outer wall 210, so that the flow pipe 220 and the outer wall 210 can together form a flow loop.

[0074] The following description, in conjunction with the accompanying drawings, describes the cooperation between the partition structure 300 and the branch structure 200. In other words, the flow process of the heat extraction fluid is described using two adjacent partition structures 300 and a branch structure 200 located between the two partition structures 300 as examples.

[0075] Reference Figures 1-4 In some possible implementations, in two adjacent partition structures 300, the partition structure 300 may close the first end of the outer wall 210, and the partition structure 300 may have a communication opening. Specifically, the two adjacent partition structures 300 include a first partition structure 300 near the injection device 500 and a second partition structure 300 near the extraction device 600.

[0076] For example, the first end of the flow channel 220 can be connected to the communication port of the first partition structure 300, and the outer wall 210 can be connected to the communication port of the second partition structure 300. It is easy to understand that the flow channel 220 can separate the outer wall 210, and a flow cavity can be formed between the flow channel 220 and the outer wall 210.

[0077] The branch structure 200 is configured such that the heat-extracting fluid flowing out from the communication port of the first partition structure 300 flows to the inside of the flow pipe 220 and flows into the flow cavity through the second end of the flow pipe 220, and the heat-extracting pipe located in the flow cavity can flow out through the communication port of the second partition structure 300.

[0078] By adopting the above technical solution, when the heat extraction fluid flows in the horizontal section 120 of the well body 100, the heat extraction fluid flows from the first end of the horizontal section 120 toward the second end of the horizontal section 120 (i.e., from left to right in the figure), so that the heat extraction fluid can first flow to the first partition structure 300, and the heat extraction fluid can flow through the communication port of the first partition structure 300 to the first end of the flow pipe 220, and then flow downward through the second end of the flow pipe 220 into the flow cavity, and be located at the bottom of the flow cavity.

[0079] Then, the heat-extracting fluid located at the bottom of the flow chamber can flow upward within the flow chamber. Since the first partition structure 300 closes the horizontal section 120, the heat-extracting fluid in the flow chamber needs to flow out through the connecting port of the second partition structure 300, so that it can flow into the next flow pipe 220.

[0080] In some possible implementations, the partition structure 300 may include a deflector and a hydraulic anchor 320, the hydraulic anchor 320 being located at a first end of the deflector away from the well body 100. The first end of the flow conduit 220 may be located on the side of the hydraulic anchor 320 away from the deflector, and the flow conduit 220 may be fixed by a bracket 330.

[0081] For example, the directional device may include a directional device 310 and a connecting rod 312. The directional device 310 can be connected to the hydraulic anchor 320 via the connecting rod 312. Both the directional device 310 and the connecting rod 312 can be used to introduce heat-extracting fluid, so that the heat-extracting fluid can flow sequentially through the directional device 310 and the connecting rod 312 to the flow pipe 220 located in the support 330.

[0082] The directional drilling device 310 may be provided with a directional drilling through-hole 311. The directional drilling through-hole 311 may face the first end of the well body 100 so that the heat extraction fluid can flow through the directional drilling through-hole 311 toward the hydraulic anchor 320.

[0083] In some possible implementations, the multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system may also include a circulation assembly 400. The circulation assembly 400 may be located on the surface and is capable of circulating the heat extraction fluid from the production unit 600 to the injection unit 500, thereby enabling the circulation process of the heat extraction fluid.

[0084] For example, the circulation component 400 may include a heat storage device 410, a heat extraction and utilization device 420 and a water storage tank 430 that cooperate with each other, wherein the heat storage device 410 is capable of storing heat extraction fluid from the extraction device 600, and the heat extraction and utilization device 420 is capable of realizing the energy conversion process through the heat extraction fluid.

[0085] The water storage tank 430 can be used to receive the heat-extracting fluid from the heat-extracting and utilization equipment 420, thereby storing the heat-extracting fluid after heat exchange in the water storage tank 430 to realize the circulation process of the heat-extracting fluid.

[0086] In summary, the multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system includes a main structure and at least one branch structure 200. The main structure includes a well body 100, an injection device 500, and a production device 600. The injection device 500 is connected to the first end of the well body 100 and can inject heat extraction fluid into the well body 100. The production device 600 is connected to the second end of the well body 100 and can collect the heat extraction fluid inside the well body 100, so that the heat extraction fluid can flow from the first end of the well body 100 to the second end of the well body 100 to achieve heat exchange and heat extraction.

[0087] The top end of the branch structure 200 is connected to the well body 100, and the bottom end of the branch structure 200 extends downward. The branch structure 200 can receive at least part of the heat-extracting fluid from the well body 100 and allow the heat-extracting fluid to flow back into the well body 100 after heat exchange. This allows the heat-extracting fluid in the well body 100 to flow back into the well body 100 after heat exchange through the branch structure 200. Thus, by setting the branch structure 200, the heat exchange path of the heat extraction system can be extended, improving the heat extraction effect of the heat extraction system and increasing the thermal energy utilization rate.

[0088] Reference Figures 1-5 This application provides a construction method for a multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system, including: S101, forming a well body in the formation.

[0089] For example, a connected well body 100 can be formed in the formation by a drilling rig or other equipment. The well body 100 may include a connected vertical section 110 and a horizontal section 120, wherein the first end of the vertical section 110 is located on the ground, the second end of the vertical section 110 extends downward, and the second end of the vertical section 110 is connected to the horizontal section 120.

[0090] Then, the well body 100 can be formed by well washing and well scraping, so that the heat extraction fluid can flow inside the well body 100, thereby enabling the heat exchange process to be realized through the well body 100.

[0091] In some possible implementations, after the formation of the well body 100 in the formation, the method further includes: S102, forming a branch structure below the well body, the top end of the branch structure being connected to the well body, and the bottom end of the branch structure extending downwards.

[0092] The branch structure 200 may include an outer wall 210 and a flow pipe 220. The outer wall 210 may be connected to the well body 100, and the bottom end of the outer wall 210 may extend downward.

[0093] For example, the first end of the flow pipe 220 can be connected to the well body 100, and the second end of the flow pipe 220 can be connected to the bottom end of the outer wall 210, so that the flow pipe 220 and the outer wall 210 can together form a flow loop.

[0094] A branch structure 200 is formed below the well body 100, including: an outer wall 210 is formed below the well body 100, the structure of the outer wall 210 can be integrally formed with the structure of the well body 100, so that the forming process of the outer wall 210 is more convenient.

[0095] During the forming process of the outer wall 210, the horizontal section 120 can be anchored by the hydraulic anchor 320, thereby enabling the hydraulic anchor 320 to play a certain positioning role and making the formation position of the branch structure 200 more accurate.

[0096] Then, the directional drilling tool can provide guidance, allowing the drill bit to move downwards at an angle within the horizontal section 120, thereby achieving the directional drilling and drilling process of the branch structure 200. Subsequently, cement can be used to cement the outer wall 210 to make its structure more stable and reduce the possibility of collapse.

[0097] After the outer wall 210 is formed below the well body 100, a branch structure 200 is formed below the well body 100, including forming a flow channel 220 on the inner wall of the outer wall 210. For example, the flow channel 220 can be placed inside the outer wall 210 by means of a continuous pipe and a safety release, and then the flow channel 220 can be set so that the flow channel 220 and the outer wall 210 can together form the branch structure 200.

[0098] In some possible implementations, after the branch structure 200 is formed below the well body 100, the construction method further includes: S103, connecting the injection device to the first end of the well body so that the injection device can inject heat-extracting fluid into the well body; and connecting the extraction device to the second end of the well body so that the extraction device can collect heat-extracting fluid in the well body.

[0099] The injection device 500 is connected to the first end of the well body 100, and the injection device 500 can inject heat-extracting fluid into the well body 100. The extraction device 600 is connected to the second end of the well body 100, and the extraction device 600 can collect the heat-extracting fluid in the well body 100, so that the heat-extracting fluid can flow from the first end of the well body 100 to the second end of the well body 100 to achieve heat exchange and heat extraction.

[0100] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0101] In the description of this invention, it should be understood that the terms “comprising” and “having” as used herein, and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0102] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can be a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, the terms "first," "second," etc., 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.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system, characterized in that, Includes the main structure and at least one branch structure; The main structure includes a well body, an injection device, and a production device; the injection device is connected to the first end of the well body and can inject heat-extracting fluid into the well body. The extraction device is connected to the second end of the well body, and the extraction device can collect the heat extraction fluid in the well body; The top end of the branch structure is connected to the well body, and the bottom end of the branch structure extends downward; the branch structure can receive at least part of the heat-extracting fluid from the well body and allow the heat-extracting fluid to flow back into the well body after heat exchange.

2. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to claim 1, characterized in that, The branch structure includes an outer wall and flow channels; The outer wall is connected to the well body, and the bottom end of the outer wall extends downward; the first end of the flow pipe is connected to the well body, and the second end of the flow pipe is connected to the bottom end of the outer wall.

3. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to claim 2, characterized in that, The well body is provided with multiple partition structures, which are arranged sequentially at intervals along the extension direction of the well body, and the branch structure is accommodated between two adjacent partition structures.

4. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to claim 3, characterized in that, The partition structure closes the first end of the outer wall, and the partition structure has a communication opening; The two adjacent partition structures include a first partition structure closer to the injection device and a second partition structure closer to the extraction device; The first end of the flow pipe is connected to the communication port of the first partition structure, and the outer wall is connected to the communication port of the second partition structure.

5. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to claim 4, characterized in that, The flow channel separates the outer wall, and a flow cavity is formed between the flow channel and the outer wall; The branch structure is configured such that the heat extraction fluid flows from the connection port of the first partition structure to the inside of the flow pipe, and flows through the second end of the flow pipe to the flow cavity, and the heat extraction pipe located in the flow cavity can flow out through the connection port of the second partition structure.

6. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to claim 4, characterized in that, The separation structure includes a deflector and a hydraulic anchor, the hydraulic anchor being located at a first end of the deflector away from the well body.

7. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to claim 6, characterized in that, The directional device includes a directional generator and a connecting rod, and the directional generator is connected to the hydraulic anchor via the connecting rod. The directional drilling device is provided with a directional drilling through-hole, which faces the first end of the well body, so that the heat extraction fluid flows through the directional drilling through-hole toward the hydraulic anchor.

8. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to any one of claims 1-7, characterized in that, The branch structure is inclined, and in the horizontal direction, the bottom end of the branch structure is closer to the second end of the well body than the top end of the branch structure.

9. The multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system according to any one of claims 1-7, characterized in that, The number of branch structures is multiple, and the multiple branch structures are arranged sequentially at intervals, with the extension directions of the multiple branch structures arranged in parallel. And / or, the branch structure includes a plurality of heat exchange sections, which are connected in sequence, and each heat exchange section is respectively used to be disposed within one or more high permeability layers.

10. A construction method for a multi-branch radial well-assisted U-shaped well enhanced closed-loop heat extraction system, characterized in that, include: A well body is formed in the formation; A branch structure is formed below the well body, the top end of the branch structure is connected to the well body, and the bottom end of the branch structure extends downward; The injection device is connected to the first end of the well body so that the injection device can inject heat-extracting fluid into the well body. The extraction device is connected to the second end of the well body so that the extraction device can collect the heat-extracting fluid in the well body.

Images