A tail water recharge system of a middle-deep geothermal well and a working method thereof

Abstract

The application provides a tail water recharge system of a middle-deep geothermal well and a working method, and relates to the field of tail water recharge. The tail water recharge system comprises a recharge well hole, a plurality of well pipe segments and a well pipe adjusting device, the plurality of well pipe segments are sequentially inserted into the recharge well hole; the well pipe segment comprises an outer pipe body and an inner sleeve, the inner sleeve is rotationally installed in the outer pipe body, the outer pipe body is in circumferential sealing cooperation with the inner sleeve, the pipe wall of the outer pipe body is provided with a first through hole, the pipe wall of the inner sleeve is provided with a second through hole, and the well pipe segment has a closed state and a conducting state; the well pipe adjusting device comprises a driving host, a transmission rod and a pipe clamp, the transmission rod is in transmission connection with the driving host, and the transmission rod extends along the axis direction of the well pipe segment; the pipe clamp is installed at the end of the transmission rod, the pipe clamp is in axial sliding sealing and circumferential clamping cooperation with the inner sleeve, and the pipe clamp is further provided with a pressure sensor. The real recharge layer and the pressure water-bearing layer can be effectively determined, so that the conducting or closing of each well pipe segment can be flexibly adjusted.

Description

Technical Field

[0001] This invention relates to the field of tailwater reinjection technology, and in particular to a tailwater reinjection system and working method for a medium-deep geothermal well. Background Technology

[0002] With the continuous exploitation and use of geothermal energy, the groundwater level will decrease year by year, reducing the fluid pressure in the geothermal reservoir and making it difficult to produce heat stably in the long term. Geothermal reinjection refers to injecting geothermal wastewater or surface water into the geothermal reservoir, which plays an important role in maintaining the reservoir pressure and restoring heat production capacity.

[0003] For example, Chinese invention patent application CN113153223A, published on July 23, 2021, discloses a construction method for sandstone-type water-producing geothermal wells and reinjection wells. Specifically, it discloses that the water-producing geothermal well utilizes the aquifers of all aquifer groups in the geothermal reservoir. By measuring the pressure in each aquifer of the aquifer group through the water-producing geothermal well, when the reinjection well is constructed, the reinjection layer of the reinjection well is set in the aquifer with low groundwater pressure and high permeability, while blind pipes are used in other aquifers. This prevents water in the high-pressure aquifer from flowing into the low-pressure, high-permeability aquifer through the reinjection well. The water reinjected through the reinjection well quickly enters the aquifer where the reinjection layer is located, resulting in fast reinjection speed and large reinjection volume. The distance from the reinjection well to the water-producing geothermal well is 2 / 3 of the radius of influence of the water-producing geothermal well, which ensures both the reinjection volume and prevents groundwater reinjection heat breakthrough.

[0004] The existing construction methods for sandstone-type geothermal wells and reinjection wells involve calculating the water pressure outside each aquifer and the pressure inside the pipe based on the flow rate between each adjacent aquifer, and then determining the reinjection aquifer.

[0005] However, due to the different geological structures in different regions, the water flow measured by the flow probe may not be the actual flow between adjacent aquifers, and the depth of each aquifer is difficult to determine. In the absence of a determination of the actual recharge layer and aquifer, it cannot be ensured that the water inlet section of the well casing corresponds to the actual recharge layer after the casing is installed, resulting in low tailwater recharge efficiency. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a tailwater reinjection system and operating method for medium-deep geothermal wells. This system solves the problem that the depth of each aquifer is difficult to determine, and that in the absence of a clear reinjection layer and aquifer, it cannot be guaranteed that the water inlet section of the well casing corresponds to the actual reinjection layer, resulting in low tailwater reinjection efficiency.

[0007] The technical solution of the tailwater reinjection system for medium-deep geothermal wells of the present invention is as follows:

[0008] The tailwater reinjection system of a medium-deep geothermal well includes a reinjection wellbore, multiple well pipe segments, and a well pipe adjustment device. The multiple well pipe segments are sequentially inserted into the reinjection wellbore, and the multiple well pipe segments are detachably connected and have the same structure.

[0009] The well casing segment includes an outer casing and an inner casing. The inner casing is rotatably installed in the outer casing. The outer casing and the inner casing are circumferentially sealed together. The outer casing has a first through hole in its wall and the inner casing has a second through hole in its wall.

[0010] The well casing segment has a closed state and a conductive state. In the closed state, the first through hole and the second through hole are offset, and in the conductive state, the first through hole and the second through hole are opposite to each other.

[0011] The well casing adjustment device includes a drive unit, a transmission rod, and a pipe clamp. The drive unit is located at the upper part of the reinjection well hole, and the transmission rod is connected to the drive unit in a transmission manner. The transmission rod extends along the axial direction of the well casing segment.

[0012] The pipe clamp is installed at the end of the transmission rod. The pipe clamp is axially slidingly sealed and circumferentially locked with the inner sleeve, so as to drive the inner sleeve to rotate through the transmission rod. The pipe clamp is also equipped with a pressure sensor, which is used to detect the water pressure in the pipe.

[0013] Furthermore, both the outer tube and the inner sleeve are steel round tubes. One end of the outer tube is provided with a reduced diameter section, and the other end of the outer tube is provided with an inner retaining edge. Both the reduced diameter section and the inner retaining edge protrude from the inner wall of the outer tube. The inner sleeve is rotatably installed between the reduced diameter section and the inner retaining edge.

[0014] Furthermore, the outer tubes of two adjacent well pipe segments are threaded together, the outer wall of the reduced diameter segment is provided with external threads, and the inner wall of the other end of the outer tube is provided with internal threads. The internal threads of the well pipe segment mate with the external threads of the adjacent well pipe segment.

[0015] Furthermore, the outer wall of the inner sleeve is also bonded with a rubber liner, which is interference-fitted with the inner wall of the outer tube. The interference between the rubber liner and the outer tube is any size between 2mm and 12mm.

[0016] Furthermore, the inner wall of the inner sleeve is provided with a funnel-shaped groove, the opening direction of the funnel-shaped groove is arranged along the circumferential direction of the inner sleeve, and the opening side of the funnel-shaped groove is smoothly connected to the inner wall of the inner sleeve; the groove depth of the funnel-shaped groove gradually increases in the opposite direction of its opening.

[0017] Furthermore, the tube clamp includes a main disc body and at least two top pins. The main disc body has at least two radial holes inside, and the top pins are movably installed in the corresponding radial holes.

[0018] The radial hole is also provided with a compression spring that cooperates with the top pin, so as to drive the top pin to protrude out of the outer peripheral surface of the tube clamp and engage with the horn-shaped countersunk groove.

[0019] Furthermore, the tube clamp also includes an elastic sealing ring, which is disposed outside the main disc body and slides and seals with the inner sleeve; the elastic sealing ring is also provided with a top pin through hole corresponding to the radial hole, so that the top pin can extend through the top pin through hole into the trumpet-shaped groove.

[0020] Furthermore, the pressure sensor is installed on the main plate, and the sensing surface of the pressure sensor is located on the lower side of the main plate. The pressure sensor is electrically connected to a data processor, which is used to receive the water pressure signal emitted by the pressure sensor, so that ground personnel can adjust the state of the well pipe segment according to the water pressure change.

[0021] The technical solution for the working method of the tailwater reinjection system of the medium-deep geothermal well of the present invention is as follows:

[0022] The working method of the tailwater reinjection system of the above-mentioned medium-deep geothermal well includes the following steps:

[0023] S1. Connect multiple well pipe segments sequentially and run them into the reinjection well hole until the first well pipe segment reaches the bottom of the reinjection well hole;

[0024] S2. Install a well pipe adjustment device at the wellhead position, connect the corresponding number of transmission rods according to the depth of the reinjection well hole, and install a pipe clamp at the end of the first transmission rod;

[0025] S3. Insert the pipe clamp into the well to the depth corresponding to the first well pipe segment, and use the pressure sensor to detect the water pressure in the first well pipe segment;

[0026] S4. After the water pressure stabilizes, start the drive unit and drive the inner casing of the first well pipe segment to rotate through the pipe clamp, so that the first well pipe segment switches between the closed state and the open state, and obtains the water pressure change in real time.

[0027] S5. If the water pressure detected increases when the first well section is adjusted from a closed state to a conductive state, it indicates that the formation where the first well section is located is a pressure aquifer; if the water pressure detected decreases or remains unchanged when the first well section is adjusted from a closed state to a conductive state, it indicates that the formation where the first well section is located is a reinjection layer.

[0028] S6. Based on the formation conditions of the first well section, if it is a pressure aquifer, adjust the first well section to a closed state; if it is a reinjection layer, adjust the first well section to a conductive state.

[0029] S7. Repeat the operation from bottom to top to adjust all well casing segments to the corresponding state, remove the pipe clamp, and finally remove the well casing adjustment device.

[0030] Furthermore, in step S1, the required well pipe segments are first adjusted to a closed state on the ground, and then the well pipe segments are connected in sequence after the adjustment is completed; the length of the transmission rod is equal to the length of the well pipe segment, and the thread locking direction of the well pipe segment is the same as the locking direction of the pipe clamp.

[0031] Beneficial Effects: The tailwater reinjection system of this medium-deep geothermal well adopts a design consisting of a reinjection wellbore, multiple well casing segments, and a well casing adjustment device. Multiple well casing segments are sequentially connected and inserted into the reinjection wellbore. Each well casing segment includes an outer casing and an inner casing. The inner casing is rotatably fitted into the outer casing. The well casing segment can switch between a closed state and a connected state through the cooperation of a first through-hole in the outer casing and a second through-hole in the inner casing. When the first and second through-holes are aligned, the reinjection wellbore and the internal space of the well casing segment are connected, allowing tailwater to be reinjected into the formation. When the first and second through-holes are misaligned, the reinjection wellbore and the internal space of the well casing segment are isolated, thus preventing water from the pressurized aquifer from entering the well casing segment.

[0032] Furthermore, the well casing adjustment device is designed with a drive unit, a transmission rod, and a pipe clamp. The drive unit is located at the top of the reinjection well, and the transmission rod extends along the axis of the well casing segment, connecting the drive unit and the pipe clamp. First, multiple well casing segments are lowered into the reinjection well. Then, the pipe clamp is inserted into the well casing segment. The pipe clamp and the inner casing slide axially and lock circumferentially, sealing the bottom well casing segment and creating a sealed space. A pressure sensor is used to detect the water pressure inside the bottom well casing segment. Once the water pressure stabilizes, the drive unit is activated, and the pipe clamp rotates the inner casing of the bottom well casing segment, switching the bottom well casing segment between a closed and open state, allowing real-time monitoring of water pressure changes.

[0033] If adjusting the bottom well casing segment from a closed to a conductive state results in an increase in detected water pressure, it indicates that the formation where the bottom well casing segment is located is a pressure aquifer. If adjusting the bottom well casing segment from a closed to a conductive state results in a decrease or no change in detected water pressure, it indicates that the formation where the bottom well casing segment is located is a reinjection layer. If it is a pressure aquifer, adjust the bottom well casing segment to a closed state; if it is a reinjection layer, adjust the bottom well casing segment to a conductive state. Then, repeat the operation from bottom to top until all well casing segments are adjusted to the corresponding states, and then remove the casing clamp.

[0034] Each pipe section of the tailwater reinjection system of this medium-deep geothermal well has an adjustable double-layer pipe structure. The water pressure change at the bottom of the pipe clamp determines whether the well pipe section is in a pressure aquifer. This effectively identifies the actual reinjection layer and the pressure aquifer, allowing for flexible adjustment of the opening or closing of each well pipe section. This ensures that the well pipe opening corresponds to the actual reinjection layer after the pipe is installed, improving the efficiency and reliability of tailwater reinjection. Attached Figure Description

[0035] Figure 1 This is a cross-sectional schematic diagram of the tailwater reinjection system in a specific embodiment of the tailwater reinjection system of the medium-deep geothermal well of the present invention.

[0036] Figure 2 This is a cross-sectional schematic diagram of a well pipe segment in a specific embodiment of the tailwater reinjection system for a medium-deep geothermal well according to the present invention;

[0037] Figure 3 This is a top view of the pipe clamp in a specific embodiment of the tailwater reinjection system for a medium-deep geothermal well according to the present invention.

[0038] In the diagram: 1-Recharge wellbore, 2-Well casing segment, 20-Rubber liner, 21-Outer casing, 210-First through hole, 211-Reduced diameter section, 212-Inner flange, 213-External thread, 22-Inner casing, 220-Second through hole, 221-Flare-shaped groove, 3-Well casing adjustment device, 30-Well casing frame, 31-Drive host, 32-Transmission rod, 33-Casing clamp, 330-Main disc, 331-Top pin, 332-Compression spring, 333-Elastic sealing ring, 34-Pressure sensor, 35-Solenoid valve. Detailed Implementation

[0039] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0040] Specific embodiment 1 of the tailwater reinjection system for medium-deep geothermal wells of the present invention, as follows: Figures 1 to 3As shown, the tailwater reinjection system of a medium-deep geothermal well includes a reinjection wellbore 1, multiple well pipe segments 2, and a well pipe adjustment device 3. The multiple well pipe segments 2 are sequentially inserted into the reinjection wellbore 1. The multiple well pipe segments 2 are detachably connected and have the same structure. The well pipe segment 2 includes an outer pipe body 21 and an inner sleeve 22. The inner sleeve 22 is rotatably installed in the outer pipe body 21. The outer pipe body 21 and the inner sleeve 22 are circumferentially sealed. The pipe wall of the outer pipe body 21 has a first through hole 210, and the pipe wall of the inner sleeve 22 has a second through hole 220.

[0041] The well casing segment 2 has a closed state and a connected state. In the closed state, the first through hole 210 and the second through hole 220 are staggered, and in the connected state, the first through hole 210 and the second through hole 220 are opposite to each other. The well casing adjustment device 3 includes a drive host 31, a transmission rod 32 and a pipe clamp 33. The drive host 31 is located at the upper part of the reinjection well hole 1. The transmission rod 32 is connected to the drive host 31 and extends along the axial direction of the well casing segment 2. The pipe clamp 33 is installed at the end of the transmission rod 32. The pipe clamp 33 is axially slidingly sealed and circumferentially locked with the inner casing 22 so as to drive the inner casing 22 to rotate through the transmission rod 32. The pipe clamp 33 is also equipped with a pressure sensor 34, which is used to detect the water pressure in the pipe.

[0042] The tailwater reinjection system of this medium-deep geothermal well adopts a design consisting of a reinjection wellbore 1, multiple well pipe segments 2, and a well pipe adjustment device 3. The multiple well pipe segments 2 are sequentially connected and inserted into the reinjection wellbore 1. Each well pipe segment 2 includes an outer pipe body 21 and an inner casing 22. The inner casing 22 is rotatably fitted into the outer pipe body 21. The well pipe segment 2 can switch between a closed state and a connected state through the cooperation of a first through-hole 210 of the outer pipe body 21 and a second through-hole 220 of the inner casing 22. When the first through-hole 210 and the second through-hole 220 are aligned, the internal space of the reinjection wellbore 1 and the well pipe segment 2 is open, allowing tailwater to be reinjected into the formation. When the first through-hole 210 and the second through-hole 220 are misaligned, the internal space of the reinjection wellbore 1 and the well pipe segment 2 is isolated, thereby preventing water from the pressurized aquifer from entering the well pipe segment 2.

[0043] Furthermore, the well casing adjustment device 3 is designed with a drive unit 31, a transmission rod 32, and a pipe clamp 33. The drive unit 31 is located at the upper part of the reinjection well 1, and the transmission rod 32 extends along the axial direction of the well casing segment 2, connecting the drive unit 31 and the pipe clamp 33. First, multiple well casing segments 2 are lowered into the reinjection well 1. Then, the pipe clamp 33 is inserted into the well casing segment 2. The pipe clamp 33 and the inner casing 22 are axially sliding and circumferentially locking, forming a sealed space at the bottom of the well casing segment 2. A pressure sensor is used to detect the water pressure inside the bottom well casing segment 2. After the water pressure stabilizes, the drive unit 31 is started, and the pipe clamp 33 drives the inner casing 22 of the bottom well casing segment 2 to rotate, switching the bottom well casing segment 2 between a closed state and a conductive state, thus acquiring real-time information on water pressure changes.

[0044] If adjusting the bottom well casing segment 2 from a closed state to a conductive state results in an increase in detected water pressure, it indicates that the formation where the bottom well casing segment 2 is located is a pressure aquifer. If adjusting the bottom well casing segment 2 from a closed state to a conductive state results in a decrease or no change in detected water pressure, it indicates that the formation where the bottom well casing segment 2 is located is a reinjection layer. If it is a pressure aquifer, adjust the bottom well casing segment 2 to a closed state; if it is a reinjection layer, adjust the bottom well casing segment 2 to a conductive state. Then, repeat the operation from bottom to top until all well casing segments 2 are adjusted to the corresponding states, and then remove the pipe clamp 33. Each pipe section of this reinjection well system is an adjustable double-layer pipe structure. The water pressure change at the bottom of the pipe clamp 33 determines whether the well pipe section 2 is in a pressure aquifer. This effectively identifies the actual reinjection layer and the pressure aquifer, allowing for flexible adjustment of the well pipe section 2 to be open or closed. This ensures that the well pipe's through-hole corresponds to the actual reinjection layer after the pipe is installed, improving the efficiency and reliability of tailwater reinjection.

[0045] In this embodiment, both the outer tube 21 and the inner sleeve 22 are steel round tubes. One end of the outer tube 21 is provided with a reduced diameter section 211, and the other end is provided with an inner flange 212. Both the reduced diameter section 211 and the inner flange 212 protrude from the inner wall of the outer tube 21. The inner sleeve 22 is rotatably installed between the reduced diameter section 211 and the inner flange 212. Specifically, the outer tubes 21 of two adjacent well pipe segments 2 are threaded together. The outer wall of the reduced diameter section 211 is provided with an external thread 213, and the inner wall of the other end of the outer tube 21 is provided with an internal thread. The internal thread of the well pipe segment 2 mates with the external thread 213 of the adjacent well pipe segment 2. During the tubing process, the well pipe segments 2 are sequentially threaded together and gradually lowered into the well. The outer tubes 21 of each well pipe segment 2 are connected to form a whole tube, while the inner sleeves 22 of each well pipe segment 2 can rotate independently, allowing different well pipe segments 2 to be flexibly adjusted to a conductive or closed state.

[0046] As a further preferred embodiment, a rubber liner 20 is also bonded to the outer wall of the inner sleeve 22. The rubber liner 20 is interference-fitted with the inner wall of the outer tube 21, and the interference between the rubber liner 20 and the outer tube 21 is any size between 2mm and 12mm. Since both the outer tube 21 and the inner sleeve 22 are steel round tubes, if they were directly sealed together, the processing difficulty and cost would be too high. By setting the rubber liner 20 on the outer wall of the inner sleeve 22, the gap between the outer tube 21 and the inner sleeve 22 is eliminated, resulting in good sealing performance and low manufacturing cost.

[0047] The inner sleeve 22 has a flared groove 221 on its inner wall. The opening of the flared groove 221 is along the circumference of the inner sleeve 22, and the opening side of the flared groove 221 is smoothly connected to the inner wall of the inner sleeve 22. The depth of the flared groove 221 gradually increases in the opposite direction to its opening. Figure 1 As shown, the funnel-shaped sinker 221 is funnel-shaped in the circumferential unfolded plane of the inner casing 22. During the insertion of the pipe clamp 33 into the well, the pipe clamp 33 slides axially with the inner wall of the inner casing 22. When it enters the well to the position corresponding to the funnel-shaped sinker 221, the pipe clamp 33 is rotated in the opposite direction of the opening and clamped into the funnel-shaped sinker 221. As the depth of the funnel-shaped sinker 221 gradually increases, the pipe clamp 33 and the funnel-shaped sinker 221 form a reliable clamping engagement, which can further drive the inner casing 22 to rotate synchronously to adjust the conduction or closure state.

[0048] In this embodiment, the tube clamp 33 includes a main disc 330 and at least two top pins 331. The main disc 330 has at least two radial holes inside, and the top pins 331 are movably installed in the corresponding radial holes. A compression spring 332 is also provided in the radial holes to cooperate with the top pins 331, driving the top pins 331 to protrude from the outer circumferential surface of the tube clamp 33 and engage with the flared grooves 221. Specifically, four radial holes are provided, circumferentially spaced about the center of the main disc 330. The four top pins 331 are distributed at a 90° central angle. Correspondingly, two flared grooves 221 are symmetrically provided at the center of the inner wall of the inner sleeve 22. When two of the top pins 331 of the tube clamp 33 engage with the corresponding flared grooves 221, the inner sleeve 22 can be rotated in the opposite direction of the opening.

[0049] The pipe clamp 33 also includes an elastic sealing ring 333, which is located outside the main disc 330 and slides in a sealing fit with the inner casing 22. The elastic sealing ring 333 also has a top pin through hole corresponding to the radial hole, allowing the top pin 331 to extend through the top pin through hole into the funnel-shaped groove 221. The elastic sealing ring 333 eliminates the gap between the pipe clamp 33 and the inner casing 22, ensuring that a bottom-sealed space can be constructed in the pipe space below the pipe clamp 33, facilitating accurate detection of water pressure within the bottom well casing segment 2.

[0050] Additionally, a pressure sensor 34 is mounted on the main panel 330, with its sensing surface located on the lower side of the main panel 330. The pressure sensor 34 is electrically connected to a data processor (not shown in the figure). The data processor receives water pressure signals from the pressure sensor 34, allowing surface personnel to adjust the state of the well casing segment 2 based on water pressure changes. Furthermore, the main panel 330 is also equipped with a solenoid valve 35. The data processor is electrically connected to the solenoid valve 35. During the insertion of the pipe clamp 33 into the well, the solenoid valve 35 is opened to allow water in the pipe to be discharged upwards. When the pipe clamp 33 is fully inserted into the well, the solenoid valve 35 is closed to seal the inner casing 22, forming a sealed space at the bottom.

[0051] The working method of the tailwater reinjection system of the above-mentioned medium-deep geothermal wells includes the following steps:

[0052] S1. Connect multiple well pipe segments 2 sequentially and run them into the reinjection wellbore 1 until the first well pipe segment reaches the bottom of the reinjection wellbore 1. The first well pipe segment refers to the bottommost well pipe segment. In step S1, first adjust all the required well pipe segments 2 to a closed state on the ground. Specifically, the first through hole 210 of the inner casing 22 and the second through hole 220 of the outer casing 21 are offset in opposite directions to a set angle, for example, 30°. The offset angle between the inner and outer casings of each well pipe segment 2 is the same. After adjustment, connect the well pipe segments 2 sequentially with threads. Furthermore, the length of the transmission rod 32 is equal to the length of the well pipe segment 2. The standard length of both the well pipe segment 2 and the transmission rod 32 is 10m. The thread locking direction of the well pipe segment 2 is the same as the locking direction of the pipe clamp 33.

[0053] S2. A well pipe frame 30 of the well pipe adjusting device 3 is erected at the wellhead position, and a drive unit 31 is installed. A corresponding number of transmission rods 32 are connected according to the depth of the reinjection well 1, and a pipe clamp 33 is installed at the end of the first transmission rod. The first transmission rod refers to the transmission rod located at the lowest end. In this embodiment, the depth of the medium-deep geothermal well is 300m, which means that thirty well pipe segments 2 are required to reach the bottom of the reinjection well 1. Correspondingly, thirty transmission rods 32 are needed to rotate the first well pipe segment through the transmission rods 32 and the pipe clamp 33.

[0054] S3. Insert the pipe clamp 33 into the well to the depth corresponding to the first well pipe segment, and use the pressure sensor 34 to detect the water pressure in the first well pipe segment. During insertion, the solenoid valve 35 of the pipe clamp 33 opens to allow water in the pipe to be discharged upwards, ensuring the smooth downward movement of the pipe clamp 33 in the well. After reaching the set depth, the solenoid valve 35 is closed, and the elastic sealing ring 333 seals with the inner wall of the inner casing 22, ensuring that the space below the pipe clamp 33 is a bottom-sealed space.

[0055] S4. After the water pressure stabilizes, start the drive unit 31. The pipe clamp 33 will rotate the inner casing of the first well pipe segment, switching the first well pipe segment between a closed and open state to monitor water pressure changes in real time. Water pressure stabilization here means that after closing the solenoid valve 35, the bottom water pressure no longer fluctuates significantly. A continuous increase or decrease in water pressure should also be considered as water pressure stabilization. In actual operation, wait 3 to 10 seconds after closing the solenoid valve 35 before starting the drive unit 31.

[0056] S5. If the water pressure increases when the first well pipe segment is adjusted from a closed state to a conductive state, it indicates that the formation where the first well pipe segment is located is a pressure aquifer; if the water pressure decreases or remains unchanged when the first well pipe segment is adjusted from a closed state to a conductive state, it indicates that the formation where the first well pipe segment is located is a reinjection layer. Specifically, the rotational angular velocity of the transmission rod 32 is less than 3° / s. During the rotation, the torque load of the drive host 31 is detected in real time. If the torque load changes abruptly, it indicates that the pipe clamp 33 is engaged with the inner casing 22. Then, rotating forward at a set angle of 30° will adjust the first well pipe segment to a conductive state. Continuing to rotate 10° to 80° will put the first well pipe segment in a closed state. Rotating to 90° will achieve the next conductive state.

[0057] S6. Based on the formation conditions of the first well casing segment, if it is a pressure aquifer, adjust the first well casing segment to a closed state; if it is a reinjection layer, adjust the first well casing segment to a conductive state.

[0058] S7. Repeat the operation from bottom to top to adjust all well casing segments to the corresponding state, remove the pipe clamp 33, and finally remove the well casing adjustment device 3.

[0059] The specific implementation of the working method of the tailwater reinjection system of the medium-deep geothermal well of the present invention is the same as the specific implementation of the working method of the tailwater reinjection system of the deep geothermal well in the specific implementation of the tailwater reinjection system of the medium-deep geothermal well of the present invention, and will not be repeated here.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A tailwater reinjection system for a medium-deep geothermal well, characterized in that, It includes a reinjection wellbore, multiple well pipe segments, and a well pipe adjustment device. The multiple well pipe segments are sequentially inserted into the reinjection wellbore. The multiple well pipe segments are detachably connected and have the same structure. The well casing segment includes an outer casing and an inner casing. The inner casing is rotatably installed in the outer casing. The outer casing and the inner casing are circumferentially sealed together. The outer casing has a first through hole in its wall and the inner casing has a second through hole in its wall. The well casing segment has a closed state and a conductive state. In the closed state, the first through hole and the second through hole are offset, and in the conductive state, the first through hole and the second through hole are opposite to each other. The well casing adjustment device includes a drive unit, a transmission rod, and a pipe clamp. The drive unit is located at the upper part of the reinjection well hole, and the transmission rod is connected to the drive unit in a transmission manner. The transmission rod extends along the axial direction of the well casing segment. The pipe clamp is installed at the end of the transmission rod. The pipe clamp is axially slidingly sealed and circumferentially locked with the inner sleeve, so as to drive the inner sleeve to rotate through the transmission rod. The pipe clamp is also equipped with a pressure sensor, which is used to detect the water pressure in the pipe.

2. The tailwater reinjection system for medium-deep geothermal wells according to claim 1, characterized in that, Both the outer tube and the inner sleeve are steel round tubes. One end of the outer tube is provided with a reduced diameter section, and the other end of the outer tube is provided with an inner retaining edge. Both the reduced diameter section and the inner retaining edge protrude from the inner wall of the outer tube. The inner sleeve is rotatably installed between the reduced diameter section and the inner retaining edge.

3. The tailwater reinjection system for medium-deep geothermal wells according to claim 2, characterized in that, The outer tubes of two adjacent well tube segments are threaded together. The outer wall of the reduced diameter segment is provided with external threads, and the inner wall of the other end of the outer tube is provided with internal threads. The internal threads of the well tube segment mate with the external threads of the adjacent well tube segment.

4. The tailwater reinjection system for medium-deep geothermal wells according to claim 1, characterized in that, The outer wall of the inner sleeve is also bonded with a rubber lining, which is interference-fitted with the inner wall of the outer tube. The interference between the rubber lining and the outer tube is any size between 2mm and 12mm.

5. The tailwater reinjection system for a medium-deep geothermal well according to claim 1, characterized in that, The inner wall of the inner sleeve is provided with a funnel-shaped groove, the opening direction of the funnel-shaped groove is set along the circumferential direction of the inner sleeve, and the opening side of the funnel-shaped groove is smoothly connected to the inner wall of the inner sleeve; the groove depth of the funnel-shaped groove gradually increases in the opposite direction of its opening.

6. The tailwater reinjection system for a medium-deep geothermal well according to claim 5, characterized in that, The tube clamp includes a main disc body and at least two top pins. The main disc body has at least two radial holes inside, and the top pins are movably installed in the corresponding radial holes. The radial hole is also provided with a compression spring that cooperates with the top pin, so as to drive the top pin to protrude out of the outer peripheral surface of the tube clamp and engage with the horn-shaped countersunk groove.

7. The tailwater reinjection system for a medium-deep geothermal well according to claim 6, characterized in that, The tube clamp also includes an elastic sealing ring, which is disposed outside the main disc and slides and seals with the inner sleeve; the elastic sealing ring is also provided with a top pin through hole corresponding to the radial hole, so that the top pin can extend through the top pin through the top pin through hole into the flared groove.

8. The tailwater reinjection system for a medium-deep geothermal well according to claim 6, characterized in that, The pressure sensor is mounted on the main body, and the sensing surface of the pressure sensor is located on the lower side of the main body. The pressure sensor is electrically connected to a data processor, which is used to receive the water pressure signal emitted by the pressure sensor so that ground personnel can adjust the state of the well pipe segment according to the water pressure change.

9. A method for operating a tailwater reinjection system using a medium-deep geothermal well as described in claim 1, characterized in that, Includes the following steps: S1. Connect multiple well pipe segments sequentially and run them into the reinjection well hole until the first well pipe segment reaches the bottom of the reinjection well hole; S2. Install a well pipe adjustment device at the wellhead position, connect the corresponding number of transmission rods according to the depth of the reinjection well hole, and install a pipe clamp at the end of the first transmission rod; S3. Insert the pipe clamp into the well to the depth corresponding to the first well pipe segment, and use the pressure sensor to detect the water pressure in the first well pipe segment; S4. After the water pressure stabilizes, start the drive unit and drive the inner casing of the first well pipe segment to rotate through the pipe clamp, so that the first well pipe segment switches between the closed state and the open state, and obtains the water pressure change in real time. S5. If the water pressure detected increases when the first well section is adjusted from a closed state to a conductive state, it indicates that the formation where the first well section is located is a pressure aquifer; if the water pressure detected decreases or remains unchanged when the first well section is adjusted from a closed state to a conductive state, it indicates that the formation where the first well section is located is a reinjection layer. S6. Based on the formation conditions of the first well section, if it is a pressure aquifer, adjust the first well section to a closed state; if it is a reinjection layer, adjust the first well section to a conductive state. S7. Repeat the operation from bottom to top to adjust all well casing segments to the corresponding state, remove the pipe clamp, and finally remove the well casing adjustment device.

10. The working method of the tailwater reinjection system of a medium-deep geothermal well according to claim 9, characterized in that, step In S1, the required well pipe segments are first adjusted to a closed state on the ground, and then the well pipe segments are connected in sequence after the adjustment is completed; the length of the transmission rod is equal to the length of the well pipe segment, and the thread locking direction of the well pipe segment is the same as the locking direction of the pipe clamp.

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