Butt joint well structure for enhancing heat exchange efficiency of middle-deep geothermal well

Abstract

The application relates to the geothermal development and utilization field and provides a docking well structure for enhancing the heat exchange efficiency of a middle-deep geothermal well, which comprises a water inlet well and a backflow well; the water inlet well is provided with a first vertical section and at least one heat exchange docking section; one end of the heat exchange docking section is communicated with the first vertical section; the backflow well is provided with a second vertical section and a heat exchange path extension section; the upper end of the heat exchange path extension section is communicated with the bottom of the second vertical section; the horizontal distance between any part of the heat exchange path extension section except the upper end and the first vertical section is greater than the horizontal distance between the upper end of the heat exchange path extension section and the first vertical section; and the end, which is away from the first vertical section, of the heat exchange docking section is communicated with the heat exchange path extension section. The application solves the problems of low heat exchange efficiency and large occupied area of the traditional docking well structure.

Description

Technical Field

[0001] This application relates to the field of geothermal development and utilization, and in particular to a docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells. Background Technology

[0002] In the field of geothermal energy development and utilization, medium-deep geothermal resources, as a clean, stable, and abundant energy source, are gradually becoming an important direction for global energy development. With the continuous growth of energy demand and increasing awareness of environmental protection, the development and utilization of medium-deep geothermal resources is of great significance for optimizing the energy structure, reducing carbon emissions, and achieving sustainable development. The effective utilization of medium-deep geothermal energy can provide a stable heat supply for building heating, industrial production, and other applications, reducing dependence on traditional fossil fuels and promoting the green transformation of the energy sector.

[0003] In enhancing the heat exchange efficiency of medium-deep geothermal wells, traditional technologies typically employ horizontal and vertical wells for heat exchange. A horizontal well consists of a vertical section and a horizontal section, with the vertical section connected to the bottom of the vertical well via the horizontal section. Fluid is introduced into the horizontal well to reach deeper underground for heat exchange, and the fluid, having absorbed heat, flows back through the vertical well. The horizontal section's role is to allow the fluid to remain within the target depth area for a longer period to ensure sufficient heat exchange. However, the presence of the horizontal section often results in a significant distance between the horizontal and vertical wells, leading to a large footprint and inconvenient management. Shortening the length of the horizontal section, on the other hand, negatively impacts the heat exchange efficiency. Summary of the Invention

[0004] To address the issues of low heat exchange efficiency and large footprint of traditional docking well structures, this application provides a docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells.

[0005] The technical solution provided in this application for a docking well structure to enhance the heat exchange efficiency of medium-deep geothermal wells is as follows:

[0006] A docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells includes:

[0007] The water inlet well has a first vertical section and at least one heat exchange connection section; one end of the heat exchange connection section is connected to the first vertical section;

[0008] The reflux well has a second vertical section and a heat exchange path extension section; the upper end of the heat exchange path extension section is connected to the bottom of the second vertical section; the horizontal distance between any part of the heat exchange path extension section (except the upper end) and the first vertical section is greater than the horizontal distance between the upper end of the heat exchange path extension section and the first vertical section; the end of the heat exchange docking section opposite to the first vertical section is connected to the heat exchange path extension section.

[0009] By adopting the above technical solution, the horizontal distance between any part of the heat exchange path extension section (except the upper end) and the first vertical section is greater than the horizontal distance between the upper end of the heat exchange path extension section and the first vertical section. This makes the length of the heat exchange docking section in the horizontal direction greater than the horizontal distance between the first vertical section and the second vertical section. As a result, even if the wellheads of the water inlet well and the return well are close to each other, the heat exchange docking section still has sufficient length so that the fluid can fully absorb geothermal heat. In addition, compared with the vertical structure, the design of the heat exchange path extension section can extend the heat exchange time of the fluid and further improve the heat exchange effect.

[0010] Optionally, the heat exchange path extension includes a first extension and a second extension; the horizontal distance between the first extension and the first vertical section gradually increases from top to bottom.

[0011] The top of the second extension section is connected to the bottom of the first extension section; at least one of the heat exchange docking sections is connected to the bottom of the second extension section.

[0012] By adopting the above technical solution, the horizontal distance between the first extension section and the first vertical section gradually increases, making the allowable length of the heat exchange docking section larger and increasing the fluid heat exchange time. The second extension section is set up, and at least one heat exchange docking section is connected to the bottom of the second extension section, which can further increase the length and depth of the geothermal exchange path, thereby enhancing the heat exchange efficiency of medium and deep geothermal wells.

[0013] Optionally, the first extended segment is straight, and the angle α between it and the horizontal plane satisfies: 70°≤α≤80°.

[0014] By adopting the above technical solution, the first extension section is straight, and the angle between it and the horizontal plane is controlled at 70°-80°, which can both extend the heat exchange path and meet the strength and construction requirements of the first extension section.

[0015] Optionally, both the inlet well and the return well are equipped with reinforced casings.

[0016] By adopting the above technical solution, reinforcing casings are installed in the inlet and return wells, which can enhance the stability of the docking well structure and prevent well collapse; in addition, the reinforcing casings can also prevent fluid leakage.

[0017] Optionally, the docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells also includes support components and multiple partition components;

[0018] The support member and the plurality of the partition members are all located inside the reinforced casing within the return well;

[0019] The support extends along the axial direction of the corresponding reinforcing sleeve and is located in the middle of the reinforcing sleeve; a plurality of partitions are located in the gap between the support and the inner wall of the reinforcing sleeve, the plurality of partitions are spaced apart circumferentially, and the partitions are respectively connected to the support and the corresponding reinforcing sleeve; the support and the plurality of partitions together divide the interior of the reinforcing sleeve into a plurality of independent fluid channels.

[0020] By adopting the above technical solution, the setting of support components and separators can further improve the support effect on the wellbore; the presence of support components can force the fluid in the middle of the reinforced casing to flow to the edge, avoiding the fluid in the middle from not being able to absorb enough heat.

[0021] Optionally, the separator is elongated and extends in a spiral direction.

[0022] By adopting the above technical solution, the separator is long and extends in a spiral direction, so that the fluid channel inside the reinforced casing is spiral. The spirally extended fluid channel can increase the flow path and time of the fluid in the channel, further enhancing the heat exchange efficiency of the geothermal well; and the spiral flow can also disturb the fluid, thereby enhancing heat exchange.

[0023] Optionally, the separator is a thermally conductive metal component, and the surface of the separator has protrusions.

[0024] By adopting the above technical solution, the separator is made of thermally conductive metal and has raised parts on its surface, which can greatly enhance the heat transfer area and heat transfer effect; the setting of the raised parts can also disturb the fluid and avoid the formation of a boundary layer on the inner wall of the reinforced sleeve, thereby affecting the heat transfer efficiency.

[0025] Optionally, there are multiple heat exchange docking sections, and at least one of the multiple heat exchange docking sections has two ends connected to the middle area of ​​the first vertical section and the middle area of ​​the heat exchange path extension section, respectively.

[0026] By adopting the above technical solution, the heat exchange area of ​​the geothermal well can be increased by connecting multiple heat exchange sections in the water inlet well.

[0027] Optionally, the plurality of fluid channels include at least one first flow channel and at least one second flow channel; the top of the first flow channel is connected to the first heat exchange section, and the upper and lower ends of the first flow channel are closed;

[0028] The support is an inner tube with a closed lower end opening and a through hole communicating with the first flow channel on the lower side wall of the support.

[0029] By adopting the above technical solution, multiple fluid channels include a first flow channel and a second flow channel. The top of the first flow channel is connected to the first heat exchange section and the upper and lower ends are closed. The support is an inner tube with a closed lower opening and a through hole on the lower side wall that is connected to the first flow channel. This allows the fluid entering the first flow channel from the first heat exchange section to flow downwards and then flow upwards out of the return well after entering the inner tube through the through hole, thereby effectively extending the heat exchange path.

[0030] In summary, this application includes at least one of the following beneficial technical effects:

[0031] 1. The design of the extended heat exchange path of the return well ensures that even if the wellheads of the inlet well and the return well are close together, the heat exchange connection section still has sufficient length so that the fluid can fully absorb geothermal heat; the design of the extended heat exchange path can also extend the heat exchange time of the fluid, thereby further improving the heat exchange effect.

[0032] 2. By setting up support components and partitions, the support effect on the wellbore can be improved, and the heat exchange area can be increased. The presence of support components can force the fluid in the middle of the reinforced casing to flow to the edge, so as to prevent the fluid in the middle from not absorbing enough heat.

[0033] 3. The fluid in the first heat exchange section can enter the first flow channel and flow downward. After entering the inner tube through the through hole, the fluid flows upward and out of the return well, thereby effectively extending the heat exchange path and making full use of geothermal energy. Attached Figure Description

[0034] Figure 1 This is a cross-sectional view of a first embodiment of the docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells provided in this application;

[0035] Figure 2 This is a cross-sectional view of a second embodiment of the docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells provided in this application;

[0036] Figure 3 This is a schematic diagram of the support and partition components in the second embodiment of the docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells provided in this application;

[0037] Figure 4 This is a cross-sectional view of a third embodiment of the docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells provided in this application;

[0038] Figure 5 This is a schematic diagram of the support and separator components in the third embodiment of the docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells provided in this application.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1. Water inlet well; 11. First vertical section; 12. Heat exchange docking section; 121. First heat exchange section;

[0041] 2. Return well; 21. Second vertical section; 22. First extension section; 23. Second extension section;

[0042] 3. Reinforced sleeve; 31. Fluid channel; 311. First flow channel; 312. Second flow channel;

[0043] 4. Support component; 41. Through hole;

[0044] 5. Divider. Detailed Implementation

[0045] The following is in conjunction with the appendix Figures 1 to 5 This application will be described in further detail. Figure 1 , Figure 2 and Figure 4 The arrows in the diagram indicate the direction of fluid flow.

[0046] Example 1

[0047] like Figure 1 As shown in the figure, this application discloses a docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells, including a water inlet well 1, a return well 2, and a reinforced casing 3.

[0048] The water inlet well 1 has a first vertical section 11 and a heat exchange connection section 12. One end of the heat exchange connection section 12 is connected to the bottom of the first vertical section 11. In this embodiment, the two ends of the heat exchange connection section 12 have different heights, with the higher end connected to the bottom of the first vertical section 11. The overall depth of the water inlet well 1 is 2000m-3500m. For example, the depth of the first vertical section 11 is 2500m, while the depth of the heat exchange connection section 12 ranges from 2500m to 3500m.

[0049] The reflux well 2 has a second vertical section 21 and a heat exchange path extension section. The horizontal distance L between the second vertical section 21 and the first vertical section 11 satisfies: 30m ≤ L ≤ 50m. The heat exchange path extension section includes a first extension section 22 and a second extension section 23. The top of the first extension section 22 is connected to the bottom of the second vertical section 21, and the horizontal distance between the first extension section 22 and the first vertical section 11 gradually increases from top to bottom. The first extension section 22 is straight, and the angle α between it and the horizontal plane satisfies: 70° ≤ α ≤ 80°.

[0050] The top of the second extension segment 23 is connected to the bottom of the first extension segment 22. The heat exchange docking section 12 is connected to the bottom of the second extension segment 23. The shape of the second extension segment 23 is not strictly required; for example, it can be a straight line. The horizontal distance between the second extension segment 23 and the first vertical segment 11 gradually increases from top to bottom. The angle β between the second extension segment 23 and the horizontal plane satisfies: 80°≤β≤90°.

[0051] The overall depth of the return well 2 is the same as the overall depth of the inlet well 1. For example, the depth of the second vertical section 21 is 350m, the bottom depth of the first extension section 22 is 2500m, and the bottom depth of the second extension section 23 is 3500m.

[0052] Existing docking well structures mainly include horizontal and vertical wells. A horizontal well has a vertical and a horizontal section, with the bottom of the vertical section connected to the bottom of the vertical well via the horizontal section. During heat exchange, the medium penetrates deep underground from the vertical section of the horizontal well, and after heat exchange, flows back to the surface through the vertical well. However, this structure suffers from poor heat exchange efficiency and insignificant temperature rise of the medium. To enhance heat dissipation, current methods typically involve increasing the well depth or increasing the horizontal distance between the horizontal and vertical wells. However, increasing the well depth significantly increases drilling costs; while increasing the horizontal distance between the horizontal and vertical wells, although increasing the length of the heat exchange path, results in a larger surface space occupied by the docking well structure, and the greater distance between the horizontal and vertical wells also hinders management.

[0053] In this embodiment, since the horizontal distance between any part of the heat exchange path extension section of the return well 2 (excluding the upper end) and the first vertical section 11 is greater than the horizontal distance between the upper end of the heat exchange path extension section and the first vertical section 11, the allowable length of the heat exchange docking section 12 is much greater than the horizontal distance between the first vertical section 11 and the second vertical section 21. Even if the first vertical section 11 and the second vertical section 21 are relatively close, the heat exchange docking section 12 can still have sufficient length to allow the fluid to fully exchange heat. In addition, within the same depth range, the heat exchange path extension section itself is longer than the traditional vertical structure, which helps to extend the heat exchange path.

[0054] Both the inlet well 1 and the return well 2 are equipped with reinforcing casings 3. The reinforcing casings 3 are coaxially aligned with the corresponding wellbore, providing support for both wells and preventing collapse. The interior of the reinforcing casings 3 allows for fluid flow while preventing leakage. The reinforcing casings 3 are primarily made of oilfield casing, but at the connection point between the heat exchange section 12 and the return well 2, the reinforcing casing 3 can be made of fiberglass to ensure a secure connection.

[0055] The implementation principle of this embodiment is as follows: fluid is introduced into the water well 1. When the fluid flows through the first vertical section 11 and the heat exchange docking section 12, it continuously absorbs geothermal heat. After absorbing heat, the fluid enters the return well 2 (the second extension section 23) and then flows back upward until it returns to the ground.

[0056] Among them, the heat exchange path extension section of the return well 2 is inclined to extend the heat exchange time of the fluid, thereby improving the heat exchange effect.

[0057] Example 2

[0058] The difference between this embodiment and Embodiment 1 is that:

[0059] like Figures 2 to 3 As shown, the docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells also includes a support member 4 and multiple partitions 5. The support member 4 and the partitions 5 are both located inside the reinforced casing 3 within the return well 2. The support member 4 is strip-shaped and extends along the axial direction of the corresponding reinforced casing 3, and is located in the middle of the reinforced casing 3. The partitions 5 are located in the gap between the support member 4 and the inner wall of the reinforced casing 3, and are evenly spaced circumferentially. Each partition 5 is connected to both the support member 4 and the corresponding reinforced casing 3. Together, the support member 4 and the partitions 5 divide the interior of the reinforced casing 3 into multiple independent fluid channels 31. The presence of the support member 4 forces the fluid originally located in the middle of the reinforced casing 3 to flow towards the edges, thus preventing the fluid in the middle of the reinforced casing 3 from absorbing heat slowly due to its large diameter. The support member 4 and the partitions 5 together support the reinforced casing 3, thereby preventing deformation of the reinforced casing 3.

[0060] The separator 5 is elongated and extends in a spiral direction. This makes the fluid channel 31 also spiral, allowing the fluid to flow spirally within the channel, which helps to enhance the heat exchange rate. The separator 5 is made of a thermally conductive metal, enabling it to transfer geothermal heat to the fluid. The separator 5 also increases the heat exchange area. Specifically, the separator 5 can be made of stainless steel.

[0061] Furthermore, the surface of the separator 5 has protrusions that can disturb the fluid, thereby preventing the formation of a boundary layer on the inner wall of the reinforced sleeve 3 and thus affecting the heat exchange efficiency.

[0062] Example 3

[0063] The difference between this embodiment and Embodiment 2 is as follows:

[0064] like Figures 4 to 5As shown, there are multiple heat exchange docking sections 12, and the heights of these sections are not entirely the same. At least one of the multiple heat exchange docking sections 12 has its two ends connected to both the middle region of the first vertical section 11 and the middle region of the extended heat exchange path, respectively. Specifically, setting multiple heat exchange docking sections 12 helps to divert the fluid flow, thereby improving heat exchange efficiency. Connecting both ends of the first heat exchange section 121 to both the middle region of the first vertical section 11 and the middle region of the extended heat exchange path prevents the first heat exchange section 121 from being too deep, thus helping to reduce drilling costs. The first heat exchange section 121 can be connected to either the first extension section 22 or the second extension section 23 of the extended heat exchange path, depending on actual needs; no mandatory limitation is made here.

[0065] Furthermore, the multiple fluid channels 31 include at least one first flow channel 311 and at least one second flow channel 312. The top of the first flow channel 311 is connected to the first heat exchange section 121, and the upper and lower ends of the first flow channel 311 are closed. The support member 4 is an inner tube with a closed lower end opening. A through hole 41 communicating with the first flow channel 311 is provided on the lower side wall of the support member 4. The fluid in the first heat exchange section 121 can flow downward along the first flow channel 311 after entering the interior of the first flow channel 311. Then, the fluid enters the interior of the support member 4 through the through hole 41 on the lower side wall of the support member 4, and then flows upward along the support member 4 and flows out of the support member 4 until it returns to the ground. The fluid in the heat exchange docking section 12, which is connected to the bottom of the second extension section 23, can flow upward through the second flow channel 312 after entering the return well 2, and thus return to the ground.

[0066] In this process, the fluid in the shallow first heat exchange section 121 can flow downwards after entering the first flow channel 311, thereby continuing to absorb heat and extending the heat exchange path. This can compensate for the limited heat absorbed by the fluid when flowing through the shallow first heat exchange section 121.

[0067] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells, characterized in that, include: The water inlet well (1) has a first vertical section (11) and at least one heat exchange docking section (12); one end of the heat exchange docking section (12) is connected to the first vertical section (11); The reflux well (2) has a second vertical section (21) and a heat exchange path extension section; the upper end of the heat exchange path extension section is connected to the bottom of the second vertical section (21); the horizontal distance between any part of the heat exchange path extension section except the upper end and the first vertical section (11) is greater than the horizontal distance between the upper end of the heat exchange path extension section and the first vertical section (11); the end of the heat exchange docking section (12) facing away from the first vertical section (11) is connected to the heat exchange path extension section; Both the inlet well (1) and the return well (2) are equipped with reinforced casings (3); The docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells also includes a support component (4) and multiple partition components (5). The support member (4) and the plurality of the partition members (5) are all located inside the reinforced casing (3) within the return well (2); The support member (4) extends along the axial direction of the corresponding reinforcing sleeve (3) and is located in the middle of the reinforcing sleeve (3); a plurality of partitions (5) are located in the gap between the support member (4) and the inner wall of the reinforcing sleeve (3), the plurality of partitions (5) are spaced apart circumferentially, and the partitions (5) are respectively connected to the support member (4) and the corresponding reinforcing sleeve (3); the support member (4) and the plurality of partitions (5) together divide the interior of the reinforcing sleeve (3) into a plurality of independent fluid channels (31). The number of heat exchange docking sections (12) is multiple, and at least one of the multiple heat exchange docking sections (12) has two ends connected to the middle area of ​​the first vertical section (11) and the middle area of ​​the heat exchange path extension section, respectively. The plurality of fluid channels (31) include at least one first flow channel (311) and at least one second flow channel (312); the top of the first flow channel (311) is connected to the first heat exchange section (121), and the upper and lower ends of the first flow channel (311) are closed; The support member (4) is an inner tube, the lower end of the support member (4) is closed, and the lower end side wall of the support member (4) is provided with a through hole (41) that communicates with the first flow channel (311).

2. The docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells according to claim 1, characterized in that: The heat exchange path extension includes a first extension (22) and a second extension (23); the horizontal distance between the first extension (22) and the first vertical section (11) gradually increases from top to bottom; The top of the second extension section (23) is connected to the bottom of the first extension section (22); at least one of the heat exchange docking sections (12) is connected to the bottom of the second extension section (23).

3. The docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells according to claim 2, characterized in that: The first extended segment (22) is straight, and the angle α between it and the horizontal plane satisfies: 70°≤α≤80°.

4. The docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells according to claim 1, characterized in that: The separator (5) is elongated and extends in a spiral direction.

5. The docking well structure for enhancing the heat exchange efficiency of medium-deep geothermal wells according to claim 1, characterized in that: The separator (5) is a heat-conducting metal component, and the surface of the separator (5) has protrusions.

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