Self-adaptive hole protection and sealing device and method for gas extraction drilling in soft coal seam

Abstract

The application discloses a self-adaptive hole protection and hole sealing device and method for gas extraction drilling in soft coal seams, the device comprising a sectional screen pipe, an active hole protection assembly and a hole sealing assembly, the active hole protection assembly comprising a multi-section center hollow rod, a cable and a dynamic hole protection support array, the dynamic hole protection support array comprising a supporting unit radially extending and retracting along the multi-section center hollow rod, the supporting unit being used for actively supporting the hole wall and real-time self-adaptive adjustment of the supporting force. The application solves the defects of static passive sealing and separation of hole protection and hole sealing through a dynamic sensing-active regulation-coupled sealing closed loop mechanism. The network distributed electric push rod carries a sensor to real-time monitor the hole wall changes, independently adjust the supporting force and realize real-time dynamic hole protection; the automatic liquid supplementing cavity cooperates with the double back pressure valve to automatically maintain the sealing pressure. The hole protection-hole sealing two-way coupling linkage not only can realize dynamic sensing and real-time self-adaptive adjustment, always maintain the effective sealing of the hole, but also can realize the organic unity of the active hole protection and the hole sealing.

Description

Technical Field

[0001] This invention relates to the field of underground gas extraction technology in coal mines, and in particular to an adaptive borehole protection and sealing device and method for gas extraction boreholes in soft coal seams. Background Technology

[0002] Soft, low-permeability coal seams account for a high proportion of outburst-prone mines in my country. These coal seams are characterized by their soft and brittle texture, low permeability, and high gas content.

[0003] Currently, underground borehole gas extraction is an effective means of preventing and controlling gas disasters. However, due to the combined effects of deep ground stress and mining activities, pre-extraction boreholes face challenges in borehole protection and sealing. Boreholes are prone to large deformations, collapses, and sealing failures, severely impacting gas control effectiveness and even leading to gas exceedances and other disasters. Existing sealing measures are mostly static and passive, which are difficult to adapt to the dynamic changes in mining stress. They often fail during the service life of the borehole due to the formation of new fractures, causing continuous air leakage and a decrease in extraction concentration, thus restricting the extraction effect.

[0004] Meanwhile, existing technologies typically treat borehole protection and sealing as independent processes, failing to achieve synergy and unity between the two in a dynamic process. Therefore, this invention aims to solve the problems of difficult borehole formation and easy seal failure caused by mining disturbances in soft coal seams, and is particularly suitable for support and sealing operations of gas drainage boreholes in soft coal seams with severe mining disturbances. Summary of the Invention

[0005] This invention provides an adaptive borehole protection and sealing device and method for gas drainage boreholes in soft coal seams, to solve the technical problems of difficult borehole formation and easy sealing failure caused by mining disturbance in soft coal seams in the prior art. This invention can not only achieve dynamic sensing and real-time adaptive adjustment to maintain effective borehole sealing at all times, but also achieve the organic unity of active borehole protection and sealing.

[0006] In view of the above technical problems, embodiments of the present invention provide an adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams, comprising:

[0007] A segmented screen pipe is a through pipe body formed by a first screen pipe, at least one second screen pipe and a third screen pipe connected coaxially in sequence. The pipe wall of the segmented screen pipe has multiple evenly distributed vent holes. Free gas desorbed in the borehole enters the interior of the segmented screen pipe through the vent holes under the action of extraction negative pressure, and is extracted by the gas extraction pipe connected to the outside of the extraction borehole.

[0008] The sealing assembly is threaded onto the first screen tube and is used to perform a hydraulic expansion seal on the drilled hole.

[0009] Active hole protection assembly, including:

[0010] The multi-segment hollow central rod is a hollow rod formed by a first central rod, multiple second central rods and a third central rod connected coaxially in sequence. The multi-segment hollow central rod is coaxially arranged in the tube hole of the segmented screen tube, and the first central rod, the second central rod and the third central rod correspond to the first screen tube, the second screen tube and the third screen tube in axial position, respectively.

[0011] The cable is arranged in the hollow channel of the multi-segment central hollow pole and is used for power supply and signal transmission;

[0012] A dynamic borehole support array is installed circumferentially on the first central rod, each of the second central rods, and the third central rod. The dynamic borehole support array includes support units that extend and retract radially along the multi-segmented central hollow rod. These support units actively support the borehole wall and adaptively adjust the support force in real time. Each support unit includes four drive motors and four electric push rods installed circumferentially on the multi-segmented central hollow rod. The output shaft of each drive motor is connected to a corresponding electric push rod. The ends of the electric push rods are equipped with integrated sensors for real-time monitoring of borehole wall deformation, displacement, and pressure signals.

[0013] The first screen tube, the second screen tube, and the third screen tube each have four rectangular grooves evenly distributed along the circumference on their tube walls.

[0014] The electric push rod passes through the rectangular groove and extends and retracts radially along the multi-segment central hollow rod under the drive of the drive motor to abut against the borehole wall and achieve active adaptive support of the borehole wall.

[0015] Optionally, the active hole protection assembly further includes a fixed support rod, through which the first central rod is installed inside the hole of the first screen tube.

[0016] Optionally, the sealing assembly includes a sealing capsule, an injection tube communicating with the inner cavity of the sealing capsule, a drain tube communicating with the inner cavity of the sealing capsule via a connecting pipe, an automatic replenishment chamber communicating with the injection tube, a first back pressure valve installed on the connecting pipe, and a second back pressure valve installed on the drain tube.

[0017] Optionally, the automatic fluid replenishment chamber includes a power chamber and a fluid replenishment chamber, which are separated into two independent chambers by a flexible diaphragm. The power chamber is used to store high-pressure gas, and the fluid replenishment chamber stores high-pressure liquid for replenishing high-pressure liquid into the sealed capsule.

[0018] Optionally, the sealing capsule includes a capsule body with an installation channel, both ends of which are provided with rigid interfaces, and each rigid interface is provided with an internal thread;

[0019] The first screen tube is provided with a sealing joint that matches the installation channel, and the sealing joint is provided with an external thread that matches the internal thread.

[0020] Optionally, the sealing joint of the first screen tube is also covered with a rough texture.

[0021] Optionally, it also includes a screen, which is disposed at the end of the first screen tube near the bottom of the borehole on the segmented screen tube.

[0022] Optionally, the internal pressure of the sealing capsule after effective sealing by liquid injection expansion is set as P, the preset pressure threshold of the first back pressure valve is set as P1, the preset pressure threshold of the second back pressure valve is set as P2, and the pressure of the power chamber is set as threshold P3; wherein, P2=P=P3>P1.

[0023] This invention also provides an adaptive borehole protection and sealing method for gas drainage boreholes in soft coal seams. The method utilizes the aforementioned adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams, and includes the following steps:

[0024] S1. Determine the length of the segmented screen pipe and the multi-segmented central hollow rod according to the depth of the extraction borehole, as well as the number of the second central rod and the second screen pipe, assemble the adaptive borehole protection and sealing device for the gas extraction borehole in the soft coal seam, and lower it to the predetermined position of the extraction borehole.

[0025] S2, Initial sealing of the borehole by liquid expansion: High-pressure liquid is injected into the sealing capsule through the injection pipe to make it expand. When the pressure inside the sealing capsule reaches the opening pressure P2 of the second back pressure valve, the drain pipe opens to overflow and the injection stops. The expanded sealing capsule fits against the borehole wall to complete the initial sealing of the borehole.

[0026] S3. Active support for borehole protection: Power is supplied to the drive motor via cable. The drive motor is started to drive the electric push rod to extend outward radially through the rectangular slot until the end of the electric push rod abuts against the borehole wall. Based on the pressure signal fed back by the integrated sensor, the drive continues to drive until the set pressure is reached and the push rod displacement is locked. The drive motor then enters the pressure holding mode, so that the support unit of the dynamic borehole protection support array continuously provides the designed support force to complete the borehole protection work of the extraction borehole.

[0027] S4. Adaptive dynamic control: During the gas extraction process, when the borehole wall of the soft coal seam deforms due to mining, the integrated sensor on the electric push rod will feed back the displacement and pressure data monitored in real time to the control system; the control system independently controls each drive motor, so that the corresponding electric push rod adaptively adjusts the support force on the borehole wall, realizing adaptive adjustment and active protection of the borehole shape.

[0028] S5. Automatic liquid replenishment to maintain sealing: When the internal pressure P of the sealing capsule drops due to drilling deformation and falls below the preset pressure P1 of the first back pressure valve, the liquid replenishment chamber replenishes high-pressure liquid to the sealing capsule through the first back pressure valve under the high-pressure gas drive of the power chamber until the internal pressure P of the sealing capsule recovers to P2. When the drain pipe opens to overflow, the automatic liquid replenishment process terminates, and the dynamic real-time sealing operation is completed.

[0029] This invention addresses the systemic flaw of separating static passive sealing from borehole protection and sealing, achieving adaptive maintenance throughout the entire borehole lifecycle through a closed-loop mechanism of dynamic sensing, active control, and collaborative sealing. Specifically, this invention integrates a network-distributed dynamic borehole support array with a pressure-feedback sealing component into a cohesive whole.

[0030] On the one hand, the integrated sensors carried by the circumferentially distributed electric actuators can monitor the displacement and pressure changes of the borehole wall in real time. The control system independently adjusts the output of each drive motor based on the feedback data, enabling the electric actuators to precisely adjust the support force, transforming the traditional "one-time support" into "real-time dynamic borehole protection," effectively suppressing the gradual deformation and local collapse of the borehole wall caused by mining stress. On the other hand, when the internal pressure of the sealing capsule decreases due to borehole deformation, the automatic liquid replenishment chamber can automatically replenish liquid under the high-pressure gas drive of the power chamber. Combined with the pressure balance logic of the dual back pressure valve (P2=P=P3>P1), the sealing pressure is always maintained within the set range, solving the problems of continuous air leakage and extraction concentration decay caused by the generation of new fractures. This "hole protection-sealing" bidirectional coupling control mechanism transforms the two from independent links into a mutually supportive and synergistic system. The stable borehole wall morphology ensures the integrity of the sealing interface, while the long-term sealing provides a stable mechanical boundary for the borehole protection structure. Thus, under the complex geological conditions of strong mining in soft coal seams, it achieves a technological leap from "passively responding to failure" to "actively maintaining stability," significantly extending the effective service cycle of the borehole and significantly improving the efficiency and safety of gas extraction. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the overall structure of the adaptive hole protection and sealing device for gas extraction boreholes in soft coal seams according to an embodiment of the present invention.

[0033] Figure 2This is a cross-sectional view of the overall structure of the adaptive borehole protection and sealing device for gas extraction boreholes in soft coal seams according to an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram of the segmented screen tube in one embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the working state of the adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to an embodiment of the present invention.

[0036] Figure 5 This is a schematic diagram of the installation structure of the integrated sensor in one embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of the sealing assembly in one embodiment of the present invention;

[0038] Figure 7 This is a cross-sectional view of the overall structure of the sealing assembly in one embodiment of the present invention;

[0039] Figure 8 This is a cross-sectional view of the installation structure of the first sieve tube and the sealing capsule in one embodiment of the present invention.

[0040] The reference numerals in the accompanying drawings are as follows:

[0041] 1-Sealing assembly, 11-Sealing capsule, 111-Installation channel, 112-Capsule body, 113-Internal thread, 12-Injection pipe, 13-Drainage pipe, 14-Automatic replenishment chamber, 141-Power chamber, 142-Flexible diaphragm, 143-Replenishment chamber, 15-First back pressure valve, 16-Second back pressure valve, 17-Connecting pipe, 2-Active sealing assembly, 21-Multi-segment central hollow rod, 211-First central rod, 212-Secondary back pressure valve 213-Third center rod, 22-Cable, 23-Dynamic hole support array, 231-Drive motor, 232-Electric push rod, 233-Integrated sensor, 24-Fixed support rod, 3-Segmented screen tube, 31-First screen tube, 311-Sealing joint, 312-External thread, 32-Second screen tube, 33-Third screen tube, 34-Rectangular groove, 4-Ventilation hole, 5-Drilled wall, 6-Rough texture, 7-Screen. Detailed Implementation

[0042] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0043] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] like Figures 1 to 4 As shown, an embodiment of the present invention provides an adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams, comprising:

[0046] The segmented screen pipe 3 is a through pipe body formed by a first screen pipe 31, at least one second screen pipe 32 and a third screen pipe 33 connected coaxially in sequence. Multiple evenly distributed vent holes 4 are opened on the pipe wall of the segmented screen pipe 3. The free gas desorbed in the borehole enters the interior of the segmented screen pipe 3 through the vent holes 4 under the action of the extraction negative pressure, and is extracted by the gas extraction pipe connected to the outside of the extraction borehole.

[0047] The sealing assembly 1 is threaded onto the first screen tube 31 and is used to perform a hydraulic expansion seal on the drilled hole.

[0048] Active hole protection assembly 2 includes:

[0049] The multi-segment hollow central rod 21 is a hollow rod formed by a first central rod 211, multiple second central rods 212 and a third central rod 213 connected coaxially in sequence. The multi-segment hollow central rod 21 is coaxially arranged in the tube hole of the segmented screen tube 3, and the first central rod 211, the second central rod 212 and the third central rod 213 correspond to the first screen tube 31, the second screen tube 32 and the third screen tube 33 in axial position, respectively.

[0050] Cable 22 is arranged in the hollow channel of the multi-segment central hollow pole 21 and is used for power supply and signal transmission.

[0051] A dynamic borehole support array 23 is installed circumferentially on the first central rod 211, each of the second central rods 212, and the third central rod 213, respectively. The dynamic borehole support array includes support units that extend and retract radially along the multi-segment central hollow rod 21. The support units are used to actively support the borehole wall 5 and adaptively adjust the support force in real time. The support units include four drive motors 231 and four electric push rods 232 installed circumferentially on the multi-segment central hollow rod 21. The output shaft of each drive motor 231 is connected to a corresponding electric push rod 232. An integrated sensor 233 is installed at the end of the electric push rod 232 for real-time monitoring of the deformation displacement and pressure signal of the borehole wall 5.

[0052] The first screen tube 31, the second screen tube 32 and the third screen tube 33 each have four rectangular grooves 34 that are evenly distributed in the circumferential direction on their tube walls.

[0053] The electric push rod 232 passes through the rectangular slot 34 and extends and retracts radially along the multi-segment central hollow rod 21 under the drive of the drive motor 231, so as to abut against the borehole wall 5 and realize active adaptive support for the borehole wall 5.

[0054] Understandably, the lengths of the segmented screen tube 3 and the multi-segmented hollow central rod 21, as well as the number of second central rods 212 and second screen tubes 32, are all determined by the depth of the extraction borehole. That is, the lengths of the segmented screen tube 3 and the multi-segmented hollow central rod 21 can be freely adjusted by the borehole depth; the length of the segmented screen tube 3 can be achieved by increasing the number of second screen tubes 32, and the length of the multi-segmented hollow central rod 21 can be achieved by increasing the number of second central rods 212.

[0055] Understandably, by uniformly arranging four sets of drive motors 231-electric push rods 232 around the first screen tube 31, the second screen tube 32, and the third screen tube 33 to form a distributed active support network, the drive motors 231 installed around the multi-segment central hollow rod 21 drive the electric push rods 232 to extend and retract radially. The sensors integrated at the ends of the electric push rods 232 can monitor the deformation displacement and pressure signals of the borehole wall 5 in real time, so that the push rods can accurately abut against and actively and adaptively support the borehole wall 5, effectively preventing the collapse and deformation of the borehole in soft coal seams, ensuring the smooth and stable flow of the gas extraction channel, and improving the efficiency and safety of gas extraction.

[0056] In one embodiment, such as Figure 1 and Figure 2As shown, the active hole protection assembly 2 also includes a fixed support rod 24, and the first central rod 211 is installed in the hole of the first screen tube 31 through the fixed support rod 24.

[0057] Understandably, by rigidly connecting the first central rod 211 and the first screen tube 31 with the fixed support rod 24, the coaxial positioning and integrated fixation of the multi-segment central hollow rod 21 and the segmented screen tube 3 are achieved, which effectively prevents the multi-segment central hollow rod 21 from shifting, shaking or axially moving in the borehole, and ensures that the electric push rod 232 of the dynamic hole protection support array 23 can be accurately aligned with the rectangular groove 34 and stably extend to abut against the borehole wall 5, which significantly improves the overall structural rigidity and anti-disturbance capability of the device.

[0058] In one embodiment, such as Figure 6 and Figure 7 As shown, the sealing assembly 1 includes a sealing capsule 11, an injection tube 12 communicating with the inner cavity of the sealing capsule 11, a drain tube 13 communicating with the inner cavity of the sealing capsule 11 via a connecting pipe 17, an automatic replenishment chamber 14 communicating with the injection tube 12, a first back pressure valve 15 installed on the connecting pipe 17, and a second back pressure valve 16 installed on the drain tube 13.

[0059] Understandably, through the coordinated operation of the injection pipe 12, the discharge pipe 13, the first back pressure valve 15, and the second back pressure valve 16, a pressure self-feedback dynamic balance system is constructed between the sealing capsule 11, the automatic replenishment chamber 14, and the connecting pipe 17: when the internal pressure P of the sealing capsule 11 drops to the preset pressure threshold P1 of the first back pressure valve 15 due to borehole deformation, automatic replenishment is performed; when the internal pressure P of the sealing capsule 11 exceeds the preset pressure threshold P2 of the second back pressure valve 16, overflow occurs through the second back pressure valve 16, thereby maintaining the sealing pressure within the set range. This achieves full-cycle adaptive sealing and long-term dynamic sealing without manual intervention, effectively solving the problems of sealing failure and gas leakage caused by mining deformation in soft coal seams.

[0060] In one embodiment, such as Figure 6 and Figure 7 As shown, the automatic fluid replenishment chamber 14 includes a power chamber 141 and a fluid replenishment chamber 143. The power chamber 141 and the fluid replenishment chamber 143 are separated into two independent chambers that are not connected to each other by a flexible diaphragm 142. The power chamber 141 is used to store high-pressure gas, and the fluid replenishment chamber 143 stores high-pressure liquid and is used to replenish high-pressure liquid into the sealed capsule 11.

[0061] Understandably, the automatic replenishment chamber 14 separates the power chamber 141 from the replenishment chamber 143 through a flexible diaphragm 142. The high-pressure gas in the power chamber 141 drives the high-pressure liquid in the replenishment chamber 143 to replenish the sealing capsule 11, thereby achieving dynamic maintenance of the sealing pressure. At the same time, the sealing capsule 11 is made of friction-resistant, antistatic, and highly elastic rubber material, the flexible diaphragm 142 is made of oil-resistant and low-permeability membrane, and the segmented screen tube 3 is made of high-strength and deformation-resistant tube. This gives the device excellent antistatic safety, wear resistance, fatigue resistance, and structural stability, effectively solving the problems of aging, leakage, and instability of traditional sealing devices in humid, highly corrosive, and strongly disturbed coal mine environments, and ensuring long-term dynamic sealing and protection effects.

[0062] In one embodiment, such as Figure 3 and Figure 7 As shown, the sealing capsule 11 includes a capsule body 112 with an installation channel 111. Both ends of the installation channel 111 are provided with rigid interfaces, and internal threads 113 are provided on the rigid interfaces.

[0063] The first screen tube 31 is provided with a sealing joint 311 that matches the installation channel 111, and the sealing joint 311 is provided with an external thread 312 that matches the internal thread 113.

[0064] Understandably, the rigid internal threads 113 at both ends of the installation channel 111 of the sealing capsule 11 and the external threads 312 of the sealing joint 311 of the first screen tube 31 form a rigid threaded connection, which reliably connects the flexible sealing capsule 11 to the rigid first screen tube 31. This not only preserves the high elastic sealing performance of the capsule, but also significantly enhances the structural strength and anti-slip capability, effectively preventing the sealing capsule 11 from shifting or falling off during high-pressure liquid injection. At the same time, it realizes detachable and quick assembly, which is convenient for on-site installation and subsequent maintenance, and greatly improves the overall sealing reliability, structural stability and engineering applicability of the device.

[0065] In one embodiment, such as Figure 8 As shown, the sealing joint 311 of the first screen tube 31 is also covered with a rough texture 6.

[0066] Understandably, the rough texture significantly increases the friction coefficient between the inner wall of the sealing capsule 11 and the first screen tube 31, forming a double-fixed structure between the expanded sealing capsule 11 and the first screen tube 31, which combines a threaded rigid connection with a tight frictional bond on the rough surface. This effectively prevents the axial slippage or circumferential rotation of the sealing capsule 11 during high-pressure hydraulic expansion sealing, significantly improving the structural stability and sealing durability of the sealing assembly 1 under conditions of strong mining and large deformation in soft coal seams. It also avoids sealing failure and gas leakage caused by displacement of the sealing capsule 11, ensuring long-term dynamic sealing effect.

[0067] In one embodiment, such as Figure 1 and Figure 3 As shown, the adaptive borehole protection and sealing device for the gas extraction borehole in the soft coal seam also includes a screen 7, which is set at the end of the first screen 31 near the bottom of the borehole on the segmented screen 3.

[0068] Understandably, by setting an adjustable mesh screen 7 at the port of the first screen tube 31 at the bottom of the hole of the segmented screen tube 3, the broken coal particles generated by stress release during the drilling process of soft coal seam are effectively intercepted from entering the screen tube, thus avoiding the blockage of the vent hole 4 and the jamming failure of the multi-segmented central hollow rod 21 and the electric push rod 232.

[0069] In one embodiment, the internal pressure of the sealing capsule 11 after effective sealing by liquid injection expansion is set as P, the preset pressure threshold of the first back pressure valve 15 is set as P1, the preset pressure threshold of the second back pressure valve 16 is set as P2, and the pressure threshold of the power chamber 141 is set as P3; wherein, P2=P=P3>P1.

[0070] This invention also provides an adaptive borehole protection and sealing method for gas drainage boreholes in soft coal seams, utilizing the aforementioned adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams for borehole protection and sealing, such as... Figure 4 As shown, it includes the following steps:

[0071] S1. Determine the lengths of the segmented screen pipe 3 and the multi-segmented central hollow rod 21 according to the depth of the drainage borehole, as well as the number of the second central rod 212 and the second screen pipe 32. Assemble the adaptive borehole protection and sealing device for the gas drainage borehole in the soft coal seam and lower it to the predetermined position of the drainage borehole.

[0072] Understandably, based on the depth of the extraction borehole, the required lengths of the screen pipe and center rod are determined, and the first screen pipe 31, the second screen pipe 32, the third screen pipe 33...the nth screen pipe (if more screen pipes exist) are connected sequentially by threads to form a segmented screen pipe 3; simultaneously, the first center rod 211, the second center rod 212, the third center rod 213...the nth center rod (if more center rods exist) with support units are connected sequentially by threads to form a multi-segmented hollow center rod 21; the support units on the connected center rods correspond one-to-one with the rectangular slots 34 on the screen pipe wall; then the screen 7 is installed at the port of the segmented screen pipe 3 located at the bottom of the extraction borehole. The assembled segmented screen pipe 3 is connected to the sealing capsule 11 in the sealing assembly 1 by threads, and then the entire protective hole and sealing device is placed at the predetermined position in the extraction borehole.

[0073] S2. Initial sealing via liquid expansion: High-pressure liquid is injected into the sealing capsule 11 through the injection pipe 12 to cause it to expand. When the internal pressure of the sealing capsule 11 reaches the opening pressure P2 of the second back pressure valve 16, the drain pipe 13 opens to overflow, stopping the injection. The expanded sealing capsule 11 fits against the borehole wall 5 to complete the initial sealing of the borehole. At this time, both ends of the expanded sealing capsule 11 are rigidly connected to the first screen tube 31 of the segmented screen tube 3 via threads, and the middle part is tightly bonded to the rough texture 6 of the sealing joint 311 on the first screen tube 31 by means of surface friction.

[0074] S3. Active borehole protection: Power is supplied to the drive motor 231 via cable 22, along with control signals from the control system. The drive motor 231 is activated to drive the electric push rod 232 radially through the rectangular slot 34 until its end abuts against the borehole wall 5. Based on the pressure signal from the integrated sensor 233, the drive continues until the set pressure is reached, at which point the push rod displacement is locked. The drive motor 231 then enters a pressure-holding mode, ensuring the dynamic borehole protection support array continuously provides the designed support force, thus completing the borehole protection work. The control system can be a control system from existing technologies.

[0075] S4. Adaptive dynamic control: During the gas extraction process, when the borehole wall 5 of the soft coal seam is deformed due to mining, the integrated sensor 233 on the electric push rod 232 will feed back the displacement and pressure data monitored in real time to the control system; the control system independently controls each drive motor 231, so that the corresponding electric push rod 232 adaptively adjusts the support force on the borehole wall 5, thereby realizing adaptive adjustment and active protection of the borehole shape.

[0076] S5. Automatic liquid replenishment to maintain sealing: When the internal pressure P of the sealing capsule 11 drops due to drilling deformation and falls below the preset pressure P1 of the first back pressure valve 15, the system pressure balance is broken. At this time, the replenishment chamber 143, driven by the high-pressure gas in the power chamber 141, replenishes high-pressure liquid to the sealing capsule 11 through the first back pressure valve 15 until the internal pressure P of the sealing capsule 11 is restored to P2. When the drain pipe 13 opens to overflow, the automatic liquid replenishment process terminates, and the dynamic real-time sealing operation is completed.

[0077] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams, characterized in that, include: The segmented screen pipe (3) is a through pipe body formed by a first screen pipe (31), at least one second screen pipe (32) and a third screen pipe (33) connected coaxially in sequence. Multiple evenly distributed vent holes (4) are opened on the pipe wall of the segmented screen pipe (3). The free gas desorbed in the borehole enters the interior of the segmented screen pipe (3) through the vent holes (4) under the action of the extraction negative pressure, and is extracted by the gas extraction pipe connected to the outside of the extraction borehole. The sealing assembly (1) is threaded onto the first screen tube (31) and is used to perform a hydraulic expansion seal on the borehole; Active hole protection assembly (2), comprising: The multi-segment hollow central rod (21) is a hollow rod formed by a first central rod (211), multiple second central rods (212) and a third central rod (213) connected coaxially in sequence. The multi-segment hollow central rod (21) is coaxially arranged in the tube hole of the segmented screen tube (3). The first central rod (211), the second central rod (212) and the third central rod (213) correspond to the first screen tube (31), the second screen tube (32) and the third screen tube (33) in axial position, respectively. Cable (22) is arranged in the hollow channel of the multi-segment central hollow pole (21) for power supply and signal transmission; The dynamic hole protection support array (23) is installed in the circumference of the first central rod (211), each of the second central rods (212) and the third central rod (213), respectively. The dynamic hole protection support array includes a support unit that extends and retracts radially along the multi-segment central hollow rod (21). The support unit is used to actively support the borehole wall (5) and adaptively adjust the support force in real time. The support unit includes four drive motors (231) and four electric push rods (232) installed around the multi-segment central hollow rod (21). The output shaft of each drive motor (231) is connected to a corresponding electric push rod (232). The end of each electric push rod (232) is equipped with an integrated sensor (233) for real-time monitoring of the deformation displacement and pressure signal of the borehole wall (5). The first screen tube (31), the second screen tube (32) and the third screen tube (33) are each provided with four rectangular grooves (34) evenly distributed in the circumferential direction on their tube walls. The electric push rod (232) passes through the rectangular slot (34) and extends radially along the multi-segment central hollow rod (21) under the drive of the drive motor (231) to abut against the borehole wall (5) and achieve active adaptive support of the borehole wall (5).

2. The adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to claim 1, characterized in that, The active hole protection assembly (2) also includes a fixed support rod (24), and the first central rod (211) is installed in the hole of the first screen tube (31) through the fixed support rod (24).

3. The adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to claim 2, characterized in that, The sealing assembly (1) includes a sealing capsule (11), an injection tube (12) communicating with the inner cavity of the sealing capsule (11), a drain tube (13) communicating with the inner cavity of the sealing capsule (11) via a connecting pipe (17), an automatic replenishment chamber (14) communicating with the injection tube (12), a first back pressure valve (15) installed on the connecting pipe (17), and a second back pressure valve (16) installed on the drain tube (13).

4. The adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to claim 3, characterized in that, The automatic fluid replenishment chamber (14) includes a power chamber (141) and a fluid replenishment chamber (143). The power chamber (141) and the fluid replenishment chamber (143) are separated into two independent chambers that are not connected to each other by a flexible diaphragm (142). The power chamber (141) is used to store high-pressure gas, and the fluid replenishment chamber (143) stores high-pressure liquid and is used to replenish high-pressure liquid into the sealed capsule (11).

5. The adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to claim 4, characterized in that, The sealing capsule (11) includes a capsule body (112) with an installation channel (111), both ends of the installation channel (111) are provided with rigid interfaces, and internal threads (113) are provided on the rigid interfaces. The first screen tube (31) is provided with a sealing joint (311) that matches the installation channel (111), and the sealing joint (311) is provided with an external thread (312) that matches the internal thread (113).

6. The adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to claim 5, characterized in that, The sealing joint (311) of the first screen tube (31) is also covered with a rough texture (6).

7. The adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to claim 1, characterized in that, It also includes a screen (7), which is disposed at the end of the first screen tube (31) near the bottom of the borehole on the segmented screen tube (3).

8. The adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams according to claim 4, characterized in that, The internal pressure of the sealing capsule (11) after effective sealing after liquid injection expansion is set to P, the preset pressure threshold of the first back pressure valve (15) is set to P1, the preset pressure threshold of the second back pressure valve (16) is set to P2, and the pressure threshold of the power chamber (141) is set to P3; wherein, P2=P=P3>P1.

9. An adaptive borehole protection and sealing method for gas drainage boreholes in soft coal seams, characterized in that, Using the adaptive borehole protection and sealing device for gas drainage boreholes in soft coal seams as described in any one of claims 1-8, the borehole protection and sealing process includes the following steps: S1. Determine the length of the segmented screen pipe (3) and the multi-segmented central hollow rod (21) according to the depth of the extraction borehole, and determine the number of the second central rod (212) and the second screen pipe (32), assemble the adaptive hole protection and sealing device for the gas extraction borehole of the soft coal seam, and lower it to the predetermined position of the extraction borehole. S2, initial sealing of the hole by liquid expansion: high pressure liquid is injected into the sealing capsule (11) through the injection pipe (12) to make it expand. When the pressure inside the sealing capsule (11) reaches the opening pressure P2 of the second back pressure valve (16), the drain pipe (13) opens to overflow and stops the injection. The expanded sealing capsule (11) fits against the borehole wall (5) to complete the initial sealing of the borehole. S3. Active support hole protection: Power is supplied to the drive motor (231) through the cable (22). The drive motor (231) is started to drive the electric push rod (232) to extend outward radially through the rectangular slot (34) until the end of the electric push rod (232) abuts against the borehole wall (5). According to the pressure signal fed back by the integrated sensor (233), the drive continues to drive to the set pressure and then locks the push rod displacement. The drive motor (231) switches to the pressure holding mode, so that the support unit of the dynamic hole protection support array continuously provides the design support force to complete the hole protection work of the extraction borehole. S4. Adaptive dynamic control: During the gas extraction process, when the borehole wall (5) of the soft coal seam is deformed due to mining, the integrated sensor (233) on the electric push rod (232) will feed back the displacement and pressure data monitored in real time to the control system; the control system independently controls each drive motor (231), so that the corresponding electric push rod (232) adaptively adjusts the support force on the borehole wall (5), thereby realizing adaptive adjustment and active protection of the borehole shape; S5. Automatic liquid replenishment to maintain sealing: When the internal pressure P of the sealing capsule (11) drops due to drilling deformation and is lower than the preset pressure P1 of the first back pressure valve (15), the replenishment chamber (143) replenishes high-pressure liquid to the sealing capsule (11) through the first back pressure valve (15) under the high pressure gas drive of the power chamber (141) until the internal pressure P of the sealing capsule (11) is restored to P2. When the drain pipe (13) opens to overflow, the automatic liquid replenishment process terminates and the dynamic real-time sealing work is completed.

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