A protection device and method for coal seam gas pre-extraction drilling hole

Abstract

This invention discloses a protective device and method for pre-drainage boreholes in coal seams. The protective main body, consisting of a protective front component, a protective rear component, and a multi-chamber self-expanding support bladder, is housed within an internal cavity. A mooring line passes through a mooring fixing buckle and connects to a first mooring hole. One end of a quick-connect steel wire connects to a winch and passes over a fixed pulley; the other end connects to a second mooring hole. This invention achieves remote winch pushing at the borehole opening via a built-in fixed pulley in the drill rod delivery system, making operation convenient and reliable. It provides precise protection against stuck drill bits and abnormal areas such as blowouts, saving material costs. Simultaneous operation is possible during drill retraction without secondary drilling, and the device can be flexibly deployed at any position within the borehole, offering strong applicability. The central through-hole with a cross-shaped structure preserves the gas channel, minimizing impact on extraction. The graded tensile strength design ensures automatic triggering of the entire process of automatic anchoring, deployment, reaction, and unanchoring, ensuring safety and efficiency.

Description

Technical Field

[0001] This invention relates to the field of prevention and control of coal seam gas pre-drainage borehole collapse, and in particular to a protective device and method for coal seam gas pre-drainage boreholes. Background Technology

[0002] With the continuous increase in coal mining depth, ground stress and engineering disturbances are constantly intensifying, significantly increasing the risk of gas accidents. The fundamental way to prevent gas disasters is to implement pre-drainage of coal seams. However, pre-drainage boreholes are highly susceptible to deformation and collapse under complex ground stress fields and mining influences, severely damaging the borehole structural stability, causing blockage of gas flow channels, significantly reducing the effective drainage range and duration, and directly affecting the gas pre-drainage effect. How to effectively prevent borehole instability and collapse, and strengthen the control of gas drainage borehole structural stability, has become a pressing technical problem for the industry. To address this issue, scholars both domestically and internationally have developed various borehole protection techniques and methods.

[0003] The existing technologies mainly include the following four categories: (1) Dragging-type casing protection technology: When drilling encounters severe blowouts and the drill rod cannot continue drilling, the drill rod needs to be withdrawn, and a special variable-diameter drill bit and casing are replaced. At the same time, the drill rod and casing are manually sent to the bottom of the hole. After restarting drilling, the drilling is slowed down, and the casing is dragged to the blowout area section by section using the ratchet mechanism at the drill bit to achieve hole protection. This technology has a complex process flow, relies on a large amount of manual operation, and has high construction costs and low efficiency. (2) Filling and protecting the hole for gas extraction method: Cast-in-place foamed lightweight soil is used as the filling support material. The process of "drilling and drilling - withdrawing the drill and filling - sealing the hole and extracting" is followed. After drilling is completed, foamed lightweight soil is injected to prevent hole collapse. Although this method has a certain effect, a large amount of filling material seriously blocks the gas flow channel, and the actual extraction effect is questionable and difficult to guarantee. (3) Full-length screen pipe protection technology: After drilling is completed and the drill rod is withdrawn, a large-diameter hollow drill rod and an openable drill bit need to be lowered back to the bottom of the hole. Then, the screen pipe is lowered into the borehole through the inner hole of the drill rod. After the screen pipe is in place, it is pushed axially to open the fixing device and anchor the screen pipe. Finally, the drill rod is withdrawn to leave the screen pipe in the whole hole. Although this technology can achieve full-hole protection, it has problems such as large equipment investment, low construction efficiency, and long operation cycle. (4) Drilling and screen integrated drilling and extraction technology: During the drilling process, the screen pipe is pre-placed inside the drill rod. The drill rod and screen pipe are alternately replaced as the drill rod advances. After the drill bit reaches the predetermined position, the screen pipe fixing device passes out from the drill bit and is fixed to the hole wall. After the drill rod is withdrawn, the screen pipe is left in the hole. Compared with the full-length screen pipe technology, this method eliminates the secondary drilling step, but it still faces the disadvantages of high equipment investment, low construction efficiency, and poor economy.

[0004] In summary, existing technologies generally suffer from common problems such as complex processes, high costs, low efficiency, blockage of gas channels, or inability to achieve precise gas control, making it difficult to meet the actual engineering needs of gas pre-drainage boreholes in deep mines. Therefore, there is an urgent need to develop a pre-drainage borehole protection device and method that is simple in structure, easy to operate, and low in cost, to achieve precise positioning and targeted prevention of borehole collapse areas, thereby effectively improving the efficiency and safety of coal mine gas extraction. Summary of the Invention

[0005] This invention provides a protective device and method for coal seam gas pre-drainage boreholes to solve the problems of existing coal seam gas pre-drainage borehole protection technologies being complex, costly, inefficient, and unable to achieve precise prevention and control of borehole collapse areas. It provides a convenient, efficient, economical and practical device and method to achieve targeted support for unstable sections of the borehole, thereby improving drainage efficiency while ensuring unobstructed gas drainage channels.

[0006] In view of the above technical problems, embodiments of the present invention provide a protective device for coal seam gas pre-drainage boreholes, comprising:

[0007] The protective front component includes a bullet-shaped hollow shell portion, a first sidewall connected to the hollow shell portion, a second sidewall connected to the hollow shell portion and disposed opposite to the first sidewall, a corner member, and a first vent hole penetrating the hollow shell portion; a corner groove is provided on the sidewall of the hollow shell portion, and the corner member is rotatably installed in the corner groove;

[0008] The protective rear component includes a third sidewall and a fourth sidewall that are detachably engaged and connected to opposite ends of the first sidewall and the second sidewall, forming a storage cavity; it also includes a connecting base plate that is laterally connected between the third sidewall and the fourth sidewall, a second vent hole disposed at the center of the connecting base plate, and a first tethering hole disposed at the edge of the connecting base plate;

[0009] A multi-chamber self-expanding support bladder is bonded inside the receiving cavity;

[0010] The drill rod delivery system includes a rod body with a built-in cavity, a top rod disposed within the built-in cavity, a tether fixing buckle, a fixed pulley, a tethering line, and a quick-connect steel wire; the top rod is provided with a second tethering hole;

[0011] The protective body, consisting of the protective front component, the protective rear component, and the multi-chamber self-expanding support bladder, is placed inside the built-in cavity. The tethering line passes through the tethering fixing buckle and is connected to the first tethering hole. One end of the quick-connect steel wire is connected to the winch and passes around the fixed pulley. The other end of the quick-connect steel wire is connected to the second tethering hole.

[0012] Optionally, the hollow housing portion is further provided with a shaft hole and a rotating shaft passing through the shaft hole, and the corner piece is rotatably installed in the corner groove by a torsion spring.

[0013] Optionally, the third sidewall is engaged between the first end of the first sidewall and the first end of the second sidewall via a meshing member; the fourth sidewall is also engaged between the second end of the first sidewall and the second end of the second sidewall via a meshing member.

[0014] The engaging member includes a boss and a groove adapted to the boss. Each end of the first sidewall, the second sidewall, the third sidewall, and the fourth sidewall is provided with a boss and a groove.

[0015] Optionally, the multi-chamber self-expanding support bladder includes a cross-shaped bladder body, a third vent hole located at the center of the bladder body, and four expansion filling cavities evenly distributed around the third vent hole.

[0016] Each of the expansion filling cavities is provided with a polyol flexible storage cavity and an isocyanate flexible storage cavity disposed opposite to the polyol flexible storage cavity.

[0017] Optionally, the bag body is composed of an outer layer of fireproof cloth that is permeable to water but impermeable to slurry and an inner layer of fragile flexible material that is impermeable to water.

[0018] Optionally, the end of the push rod away from the second tethering hole is further provided with a round head for pushing the protective body, the diameter of the round head being larger than the diameter of the second vent hole; the fixed pulley is installed in the built-in cavity through a pulley shaft;

[0019] The upper end of the rod is also equipped with an openable drill bit.

[0020] Optionally, the tensile strength of the polyol flexible reservoir is equal to that of the isocyanate flexible reservoir;

[0021] The bonding strength between the multi-chamber self-expanding support bladder and the receiving cavity is greater than the fracture strength of the tethering line after it is connected to the first tethering hole, the tensile strength of the polyol flexible storage cavity / isocyanate flexible storage cavity, and the meshing friction between the protective front component and the protective rear component.

[0022] Optionally, the tether is made of elastic and strong plastic, and the tether is set with a preset strength threshold, which breaks after the preset strength threshold is reached.

[0023] The present invention also provides a protection method for coal seam gas pre-drainage boreholes, which uses the above-mentioned protection device for coal seam gas pre-drainage boreholes and includes the following steps:

[0024] S1. Attach the front and rear ends of the cross-shaped bag body to the storage cavity composed of the protective front part and the protective rear part to assemble the protective body, and place the protective body in the built-in cavity of the conveying drill rod; connect one end of the quick-connect steel wire to the winch, and insert the other end into the built-in cavity, turn it through the fixed pulley, and fix it to the second tethering hole of the top rod; connect the tethering line between the tethering fixing buckle and the first tethering hole of the protective rear part; install the round head to the left side of the rod body to complete the assembly work;

[0025] S2. Install the conveyor drill rod containing the protective body as the first drilling drill rod on the drilling rig, and carry out drilling operations according to the drilling parameters; as the drilling operation progresses, connect a quick-connect steel wire inside each additional ordinary drill rod until the drilling operation is completed; during the drilling operation, record the depth of stuck drill and blowout.

[0026] S3. After drilling is completed, start the drill retraction operation; use the drilling rig to pull out the drill rods one by one, and disconnect one quick-connect steel wire for each ordinary drill rod removed; continue retracting the drill until the drill reaches the recorded abnormal depth or the location of the structural zone detected in the previous geological survey. At this time, stop retracting the drill and prepare to lower the protective body.

[0027] S4. Connect the winch to the outer end of the remaining quick-connect steel wire at the orifice. Rotate the winch to retrieve the quick-connect steel wire. The quick-connect steel wire moves towards the orifice. The transmission direction is changed by the fixed pulley in the rod body, so that the top rod moves towards the connecting base plate of the protective rear part until the round head is in complete contact with the connecting base plate.

[0028] S5. Continue to rotate the winch to tighten the quick-connect steel wire. The push rod pushes the entire protective body towards the drill bit until the openable drill bit, the protective body, and the push rod are completely pressed together. Further increase the rotation force of the winch until the push rod thrust exceeds the friction of the openable drill bit. The openable drill bit is opened, and the protective front part is pushed out to deliver the drill rod. When the corner groove is fully exposed in the borehole, the corner piece is driven to rotate around the shaft under the action of the torsion spring 6. The tip of the corner piece pops out from the corner groove and contacts the borehole wall.

[0029] S6. Continue to rotate the winch, and the push rod will continue to push the protective body into the borehole until the winch can no longer rotate. At this time, part of the protective body will enter the borehole from the conveying drill rod.

[0030] Remove the winch at the borehole opening and continue the drill retraction operation. Use the drilling rig to pull out the next ordinary drill rod and remove a quick-connect steel wire. At this time, the drill rods from beginning to end gradually move towards the borehole opening as the drill retraction proceeds. Because the corner piece of the protective front part is in close contact with the borehole wall, the protective front part is firmly fixed in place under the action of tension.

[0031] S7. As the drill retraction proceeds, the drill rod moves further toward the borehole opening, and the protective body gradually enters the borehole completely; the tethering line connected to the bottom first tethering hole on the connecting base plate of the protective rear component gradually extends and tightens.

[0032] As the drill continues to retract, the protective front component remains firmly fixed in place under the action of the corner component, while the protective rear component moves toward the borehole with the conveying drill rod under the tension of the tie line, causing the protective front component and the protective rear component to gradually separate, allowing the multi-chamber self-expanding support bladder to stretch and unfold.

[0033] After retracting the drill bit a certain distance, under the continuous pulling of the tether line, when the tension exceeds the tensile strength of the polyol flexible reservoir and the isocyanate flexible reservoir, the polyol flexible reservoir and the isocyanate flexible reservoir rupture. The polyol and isocyanate are mixed in the expansion filling cavity and undergo an addition polymerization reaction to generate polyurethane. The volume expands rapidly until it fills the expansion filling cavity. At this time, the irregularly shaped expansion bag is formed and begins to support the borehole wall.

[0034] As the drill continues to retract, the protective front component is fixed in place by the corner component, the multi-chamber self-expanding support bladder is filled and shaped and loses its extensibility, and the protective rear component separates from the multi-chamber self-expanding support bladder.

[0035] As the drill continues to retract, the tether line is stretched until it breaks. At this point, the protective body, consisting of the front protective component, the multi-chamber self-expanding support bladder, and the rear protective component, remains inside the hole, thus completing the borehole protection.

[0036] S8. Continue to use the drilling rig to pull out the drill rods one by one. For each ordinary drill rod removed, disconnect a quick-connect steel wire until the conveyor drill rod is also removed and drilled, thus completing the complete drilling protection operation.

[0037] This invention features a sophisticated yet simple structure. Remote pushing of the drill pipe to the borehole is achieved via a built-in fixed pulley. The purely mechanical linkage not only ensures convenient operation but also guarantees the reliability and safety of downhole operations. Its protection mechanism is highly targeted: precise point support is provided for stuck drill, blowout anomaly areas, or geological structural zones, significantly reducing material consumption and construction costs compared to full-hole casing technology.

[0038] In this invention, the multi-chamber self-expanding support bladder adopts a composite design of a fireproof outer layer and a fragile flexible inner layer. Its water-permeable but grout-impermeable properties ensure gas flow while preventing coal dust intrusion. The structure, placed within the receiving chamber, can also be flexibly adjusted in size to adapt to different borehole diameters and protection length requirements. The construction process is innovatively advanced, embedding the protection operation into the drill retraction process, eliminating the need for secondary drill rod insertion, significantly saving time and manpower. Furthermore, it can be repeatedly deployed at any depth in the borehole, making it highly adaptable. The cross-shaped bladder structure of the multi-chamber self-expanding support bladder, combined with the design of a third vent, maximizes the preservation of extraction channels while the polyurethane expansion and compaction of the borehole wall, minimizing the impact on gas outbursts. Crucially, the system achieves fully automated triggering of the entire sequence of "anterior chamber anchoring - posterior chamber separation - bag deployment - chemical reaction - device detachment" through tensile strength gradient configuration (bag bonding strength > tether line fracture strength > reservoir rupture strength > front and rear chamber meshing friction). The entire process requires no manual downhole intervention, combining a high level of automation with inherent safety characteristics, resulting in significant comprehensive benefits and outstanding engineering promotion value. Attached Figure Description

[0039] 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.

[0040] Figure 1 This is a schematic diagram of the structure of the protective front component in one embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the hollow shell portion of the protective front component in one embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the structure of the protective rear component in one embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the structure of the protective rear component in another embodiment of the present invention;

[0044] Figure 5 This is a partial structural schematic diagram of a multi-chamber self-expanding support bladder in one embodiment of the present invention;

[0045] Figure 6 This is a schematic diagram of the overall structure of the multi-chamber self-expanding support bladder in one embodiment of the present invention;

[0046] Figure 7 This is a schematic diagram of the conveying drill rod in one embodiment of the present invention;

[0047] Figure 8This is a schematic diagram of the top rod in one embodiment of the present invention;

[0048] Figure 9 This is a schematic diagram of the installation structure of the tether fixing buckle and the fixed pulley in one embodiment of the present invention;

[0049] Figure 10 This is a schematic diagram of the structure of a fixed pulley in one embodiment of the present invention;

[0050] Figure 11 This is a schematic diagram illustrating the state changes of the protective device for coal seam gas pre-drainage boreholes during use, according to an embodiment of the present invention.

[0051] The reference numerals in the accompanying drawings are as follows:

[0052] 1-Protective front component, 11-Hollow shell section, 111-Corner groove, 112-Shaft hole, 113-Rotating shaft, 12-First side wall, 13-Second side wall, 14-Corner component, 15-First vent hole, 2-Protective rear component, 21-Third side wall, 22-Fourth side wall, 23-Connecting base plate, 24-Second vent hole, 25-First tethering hole, 26-Storage cavity, 3-Multi-chamber self-expanding support bladder, 31-Bag body, 32- 33-Third vent hole, 331-Polyol flexible storage cavity, 332-Isocyanate flexible storage cavity, 4-Delivery drill rod, 41-Internal cavity, 42-Rod body, 43-Top rod, 431-Second tether hole, 432-Round head, 44-Tether fixing buckle, 45-Fixed pulley, 46-Tethering line, 47-Quick-connect steel wire, 48-Pulley shaft, 49-Opening and closing drill bit, 5-Windlass, 6-Torsion spring, 7-Boss, 8-Groove. Detailed Implementation

[0053] 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.

[0054] 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.

[0055] 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.

[0056] like Figures 1 to 11 As shown, an embodiment of the present invention provides a protective device for coal seam gas pre-drainage boreholes, comprising:

[0057] The protective front component 1 includes a bullet-shaped hollow shell portion 11, a first side wall 12 connected to the hollow shell portion 11, a second side wall 13 connected to the hollow shell portion 11 and disposed opposite to the first side wall 12, a corner component 14, and a first vent hole 15 penetrating the hollow shell portion 11; a corner groove 111 is provided on the side wall of the hollow shell portion 11, and the corner component 14 is rotatably installed in the corner groove 111.

[0058] The protective rear component 2 includes a third sidewall 21 and a fourth sidewall 22 that are detachably engaged and connected to the opposite ends of the first sidewall 12 and the second sidewall 13, forming a storage cavity 26; it also includes a connecting base plate 23 that is laterally connected between the third sidewall 21 and the fourth sidewall 22, a second vent 24 disposed at the center of the connecting base plate 23, and a first tethering hole 25 disposed at the edge of the connecting base plate 23.

[0059] The multi-chamber self-expanding support bladder 3 is bonded inside the receiving cavity 26.

[0060] The conveying drill rod 4 includes a rod body 42 with an internal cavity 41, a top rod 43 disposed in the internal cavity 41, a tether fixing buckle 44, a fixed pulley 45, a tethering line 46, and a quick-connect steel wire 47; a second tethering hole 431 is provided on the top rod 43.

[0061] The protective body, consisting of the protective front component 1, the protective rear component 2, and the multi-chamber self-expanding support bladder 3, is placed in the internal cavity 41. The tethering line 46 passes through the tethering fixing buckle 44 and is connected to the first tethering hole 25. One end of the quick-connect steel wire 47 is connected to the winch 5 and passes around the fixed pulley 45. The other end of the quick-connect steel wire 47 is connected to the second tethering hole 431.

[0062] Understandably, the protective front component 1 and the protective rear component 2 are mainly made of polyoxymethylene material, and the first vent 15 and the second vent 24 facilitate gas (methane) flow. The bullet-shaped hollow shell part 11 and the rotatable corner part 14 of the protective front component 1 are designed to be firmly fixed to the borehole wall after entering the borehole, effectively preventing the device from shifting. The protective rear component 2 is connected to the protective front component 1 by a separable meshing connection. With the multi-chamber self-expanding support bladder 3, the front chamber can be fixed, the rear chamber can be separated, and the bladder can automatically expand to support the borehole wall during the drill retraction process. This ensures both the accuracy of the borehole protection and the smooth flow of methane. The components such as the top rod 43, the tie line 46, and the quick-connect steel wire 47 built into the conveying drill rod 4 realize the remote and precise lowering and fixing of the protective device through mechanical linkage, which greatly improves the work efficiency and safety. The overall structure is compact, easy to operate, and low in cost.

[0063] In one embodiment, such as Figure 1 and Figure 2 As shown, the hollow housing part 11 is also provided with a shaft hole 112 and a rotating shaft 113 passing through the shaft hole 112. The corner piece 14 is rotatably installed in the corner groove 111 by a torsion spring 6. Understandably, through the cooperation of the rotating shaft 113 and the torsion spring 6, the corner piece 14 is elastically rotated and installed in the corner groove 111. When the protective front piece 1 is pushed out of the inner cavity 41 and the corner groove 111 is exposed to the drill hole, the torsion spring 6 releases its elastic force to drive the corner piece 14 to automatically rotate and pop out around the rotating shaft 113. The tip of the corner piece 14 penetrates the hole wall to form a mechanical anchor.

[0064] In one embodiment, such as Figures 1 to 4As shown, the third sidewall 21 is engaged between the first end of the first sidewall 12 and the first end of the second sidewall 13 via a meshing member; the fourth sidewall 22 is also engaged between the second end of the first sidewall 12 and the second end of the second sidewall 13 via a meshing member. The meshing member includes a boss 7 and a groove 8 adapted to the boss 7. Each end of the first sidewall 12, the second sidewall 13, the third sidewall 21, and the fourth sidewall 22 is provided with one of the aforementioned bosses 7 and one of the aforementioned grooves 8. Understandably, the separable meshing connection between the protective front component 1 and the protective rear component 2 is achieved through the interlocking (non-forced connection) of the boss 7 and the groove 8. This provides sufficient radial constraint force during the device transport stage, ensuring that the multi-chamber self-expanding support bladder 3 is stably stored and smoothly lowered in the receiving cavity 26. At the same time, it forms a controllable weak link during drill retraction. The meshing friction force is designed to be lower than the bladder's adhesive strength and the breaking strength of the tether line 46, ensuring that the protective front component 1 and the protective rear component 2 can separate in a predetermined order under subsequent tensile force, thereby triggering the stretching and chemical reaction of the multi-chamber self-expanding support bladder 3. This symmetrically distributed double-sided meshing method ensures balanced force and smooth separation. Meanwhile, the standardized boss 7 and groove 8 structure facilitates modular assembly.

[0065] Furthermore, by adjusting the length and diameter of each sidewall (which can be set according to requirements), it can be adapted to different borehole diameters and protection lengths, significantly improving the versatility and construction reliability of the device.

[0066] In one embodiment, such as Figure 5 and Figure 6 As shown, the multi-chamber self-expanding support bladder 3 includes a cross-shaped bladder body 31, a third vent 32 located at the center of the bladder body 31, and four expansion filling cavities 33 evenly distributed around the third vent 32. Each expansion filling cavity 33 contains a polyol flexible storage cavity 331 and an isocyanate flexible storage cavity 332 disposed opposite to the polyol flexible storage cavity 331.

[0067] Understandably, the front and rear ends of the multi-chamber self-expanding support bladder 3 are bonded together with the receiving cavity 26, which is composed of the protective front component 1 and the protective rear component 2, by adhesive. This cavity possesses a certain tensile strength, exceeding the upper limit of the tether line 46. The tether line 46 is made of elastic plastic, possessing a certain strength but prone to breakage after being stretched to a certain extent. The tether fixing buckle 44, the fixed pulley 45, and the pulley shaft 48 are all made of high-strength alloy steel, using the same material as the rod body 42 to prevent breakage. Once the polyol flexible storage cavity 331 and the isocyanate flexible storage cavity 332 are damaged, their contents immediately mix and undergo an addition polymerization reaction to generate polyurethane, which fills and expands the filling cavity 33. Ultimately, the multi-chamber self-expanding support bladder 3 expands into a "cross" shape, tightly fitting the borehole wall to prevent borehole instability and collapse.

[0068] In one embodiment, such as Figure 5 and Figure 6 As shown, the bag body 31 is composed of an outer layer of fireproof cloth that is permeable to water but impermeable to slurry and an inner layer of fragile flexible material that is impermeable to water. Understandably, both the polyol flexible storage cavity 331 and the isocyanate flexible storage cavity 332 are made of fragile flexible material that is impermeable to water.

[0069] In one embodiment, such as Figures 7 to 10 As shown, the end of the push rod 43 away from the second tethering hole 431 is also provided with a round head 432 for pushing the protective body. The diameter of the round head 432 is larger than the diameter of the second vent hole 24. The fixed pulley 45 is installed in the built-in cavity 41 through the pulley shaft 48. The upper end of the rod body 42 is also provided with an openable drill bit 49. Understandably, the diameter of the round head 432 at the end of the push rod 43 is larger than the diameter of the second vent hole 24, which ensures that the push rod 43 can accurately apply force when pushing the protective body and will not accidentally enter the storage cavity 26, thus ensuring operational stability. The fixed pulley 45 is firmly installed in the built-in cavity 41 of the conveying drill rod 4 through the pulley shaft 48, which effectively changes the force direction of the quick-connect steel wire 47, realizes the function of remotely controlling the movement of the push rod 43 at the orifice, and improves the convenience and safety of operation.

[0070] In one embodiment, the polyol flexible reservoir 331 and the isocyanate flexible reservoir 332 have the same tensile strength.

[0071] The bonding strength between the multi-chamber self-expanding support bladder 3 and the receiving cavity 26 is greater than the fracture strength after the tethering line 46 is connected to the first tethering hole 25, the tensile strength of the polyol flexible storage cavity 331 / isocyanate flexible storage cavity 332, and the meshing friction between the protective front component 1 and the protective rear component 2.

[0072] Understandably, this allows the protective front component 1 and protective rear component 2 to separate first under tension during the drill retraction process. Then, the multi-chamber self-expanding support bladder 3 deploys, followed by the rupture of the polyol flexible storage chamber 331 and the isocyanate flexible storage chamber 332. Finally, the tethering line 46 breaks, and the coal seam gas pre-drainage borehole protection device is accurately lowered to the designated location. The above setup constructs a tensile strength gradient chain (bonding strength between the multi-chamber self-expanding support bladder 3 and the receiving chamber 26 > breaking strength of the tethering line 46 > tensile strength of the storage chamber > meshing friction force between the front and rear chambers), achieving precise timing control of the separation and chemical reaction of each component during drill retraction. The graded tensile design automatically completes the entire sequence of "separation-deployment-reaction-anchoring" without external control, avoiding human error, ensuring the accuracy of the timing and spatial location of the chemical reaction, and significantly improving the reliability and success rate of deep hole fixed-point protection.

[0073] In one embodiment, such as Figure 11 As shown, the tether line 46 is made of elastic and strong plastic, and the tether line 46 is set with a preset strength threshold, which breaks after being reached. Understandably, the design of the tether line 46, made of elastic and strong plastic and with a preset strength threshold, achieves precise mechanical control during the deployment of the protective device: during the drill retraction phase, the elastic properties allow the tether line 46 to undergo controllable deformation as the drill rod retracts, maintaining the dynamic connection between the protective body and the conveying drill rod 4; the timely breakage of the tether line 46 when the tension reaches the preset threshold ensures that after the multi-chamber self-expanding support bladder 3 is fully deployed at the designated position, the protective body can promptly detach from the conveying drill rod 4 and remain inside the hole.

[0074] This invention also provides a protection method for coal seam gas pre-drainage boreholes, which employs the aforementioned protection device for coal seam gas pre-drainage boreholes during operation, such as... Figure 11 As shown, it includes the following steps:

[0075] S1. Attach the front and rear ends of the cross-shaped bag body 31 to the storage cavity 26 composed of the protective front part 1 and the protective rear part 2 to assemble the protective body, and place the protective body in the built-in cavity 41 of the conveying drill rod 4; connect one end of the quick-connect steel wire 47 to the winch 5, and insert the other end into the built-in cavity 41, turn it through the fixed pulley 45, and fix it in the second tethering hole 431 of the top rod 43; connect the tethering line 46 between the tethering fixing buckle 44 and the first tethering hole 25 of the protective rear part 2; install the round head 432 to the left side of the rod body 42 to complete the assembly.

[0076] S2. Drilling: Install the conveyor drill rod 4 containing the protective body as the first drilling drill rod on the drilling machine, and carry out drilling operations according to the drilling parameters; as the drilling operation proceeds, connect a quick-connect steel wire 47 inside each additional ordinary drill rod until the drilling operation is completed; during the drilling operation, record the depth of abnormal conditions such as stuck drill and blowout.

[0077] S3. Drill Retraction: After drilling is completed, start the drill retraction operation; use the drilling rig to pull out the drill rods one by one, and disconnect a quick-connect steel wire 47 for each ordinary drill rod removed; continue to retract the drill until the drill reaches the depth of the recorded abnormal state or the location of the structural zone detected in the previous geological survey. At this time, stop retracting the drill and prepare to lower the protective main body.

[0078] S4. Lowering the protective body: After retracting the drill to the specified depth, connect the winch 5 to the outer end of the remaining quick-connect steel wire 47 at the borehole opening. Rotate the winch 5 to retrieve the quick-connect steel wire 47. The quick-connect steel wire 47 moves towards the borehole opening. The transmission direction is changed by the fixed pulley 45 in the rod body 42, so that the top rod 43 moves towards the connecting base plate 23 of the protective rear part 2 until the round head 432 is in complete contact with the connecting base plate 23.

[0079] S5. Continue to rotate the winch 5 to tighten the quick-connect steel wire 47. The push rod 43 pushes the entire protective body towards the drill bit until the openable drill bit 49, the protective body, and the push rod 43 are completely pressed together. Further increase the rotational force of the winch 5 until the thrust of the push rod 43 exceeds the friction of the openable drill bit 49. The openable drill bit 49 is opened, and the protective front part 1 is pushed out to deliver the drill rod 4. When the corner groove 111 is fully exposed in the borehole, the corner piece 14 is driven to rotate around the shaft 113 under the action of the torsion spring 6. The tip of the corner piece 14 pops out from the corner groove 111 and contacts the borehole wall.

[0080] S6. Continue to rotate the winch 5, and the push rod 43 continues to push the protective body into the borehole until the winch 5 can no longer rotate. At this time, part of the protective body enters the borehole from the conveying drill rod 4.

[0081] Remove the winch 5 at the borehole opening and continue the drill retraction operation. Use the drilling rig to pull out the next ordinary drill rod and remove a quick-connect steel wire 47. At this time, the drill rods from beginning to end gradually move towards the borehole opening as the drill retraction proceeds. Because the corner piece 14 of the protective front piece 1 is in close contact with the borehole wall, it firmly fixes the protective front piece 1 in place like a barb under the action of tension.

[0082] S7. Drilling protection: As the drill is withdrawn, the drill rod moves further toward the borehole opening, and the protection body gradually enters the borehole completely; the tether line 46 connected to the bottom first tether hole 25 on the connecting base plate 23 of the protection rear component 2 gradually extends and tightens.

[0083] As the drill continues to retract, the protective front piece 1 remains firmly fixed in place under the action of the corner piece 14, while the protective rear piece 2 moves toward the borehole with the conveying drill rod 4 under the tension of the tie line 46, causing the protective front piece 1 and the protective rear piece 2 to gradually separate, allowing the multi-chamber self-expanding support bladder 3 to stretch and unfold.

[0084] After the drill continues to retract a certain distance, under the continuous pulling of the tether line 46, when the tension exceeds the tensile strength of the polyol flexible storage cavity 331 and the isocyanate flexible storage cavity 332, the polyol flexible storage cavity 331 and the isocyanate flexible storage cavity 332 rupture. The polyol and isocyanate are mixed in the expansion filling cavity 33 and undergo an addition polymerization reaction to generate polyurethane. The volume expands rapidly until it fills the expansion filling cavity 33. At this time, the irregular expansion bladder (multi-chamber self-expanding support bladder 3) is formed and begins to support the borehole wall.

[0085] As the drill continues to retract, the protective front component 1 is fixed in place by the corner component 14, the multi-chamber self-expanding support bladder 3 is filled and shaped and loses its extensibility, and the protective rear component 2 separates from the multi-chamber self-expanding support bladder 3.

[0086] As the drill continues to retract, the tether line 46 is stretched until it breaks. At this point, the protective body consisting of the protective front component 1, the multi-chamber self-expanding support bladder 3, and the protective rear component 2 remains inside the hole, thus completing the drilling protection.

[0087] S8. Continue to use the drilling rig to pull out the drill rods one by one. For each ordinary drill rod removed, disconnect a quick-connect steel wire 47 until the conveying drill rod 4 is also removed and drilled, thus completing the complete drilling protection operation.

[0088] In this invention, the structure is simple and the design is reasonable. It mainly consists of five parts: a protective front component 1, a multi-chamber self-expanding support bladder 3, a protective rear component 2, a conveying drill rod 4, and a winch. After drilling is completed, the drill is retracted to the depth of abnormal conditions such as stuck drill or blowout, or to the location of the structural area detected in the previous geological exploration. The winch is then connected to tighten the quick-connect steel wire 47, which drives the top rod 43 to move forward until the top rod 43 pushes the protective body (composed of the protective front component 1, the multi-chamber self-expanding support bladder 3, and the protective rear component 2) out of the inner cavity 41 and into the borehole. At this time, the corner piece 14 in the corner groove 111 is fully opened under the action of the torsion spring 6, abutting against the borehole wall and fixing the protective front component 1 in place. As the drill continues to retract, the protective front component 1 and the protective rear component 2 gradually separate. The multi-chamber self-expanding support bladder 3 enclosed within them is stretched and expanded until the polyol flexible storage chamber 331 and the isocyanate flexible storage chamber 332 rupture. The internal polyol and isocyanate react to form polyurethane, which rapidly expands until it fills the expansion filling chamber 33. At this point, the multi-chamber self-expanding support bladder 3 takes shape and begins to support the borehole wall. As the drill continues to retract, the tethering line 46 is continuously stretched until it breaks. At this point, the protective body is left in the designated position to continuously protect the borehole. This invention has advantages such as convenient operation, strong adaptability, and significant protective effect. Its innovative multi-level mechanical control system and self-expanding support scheme, through the synergistic effect of pure mechanical linkage and chemical expansion, can achieve precise support at any position in the borehole without secondary drilling. It can be widely applied to gas drainage borehole protection projects under various complex geological conditions and has broad prospects for promotion and application.

[0089] 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. A protective device for coal seam gas pre-drainage boreholes, characterized in that, include: The protective front component (1) includes a bullet-shaped hollow shell part (11), a first side wall (12) connected to the hollow shell part (11), a second side wall (13) connected to the hollow shell part (11) and disposed opposite to the first side wall (12), a corner piece (14), and a first vent hole (15) penetrating the hollow shell part (11); a corner groove (111) is provided on the side wall of the hollow shell part (11), and the corner piece (14) is rotatably installed in the corner groove (111); The protective rear component (2) includes a third sidewall (21) and a fourth sidewall (22) that are detachably engaged and connected to the opposite ends of the first sidewall (12) and the second sidewall (13), forming a storage cavity (26); it also includes a connecting base plate (23) that is laterally connected between the third sidewall (21) and the fourth sidewall (22), a second vent hole (24) located at the center of the connecting base plate (23), and a first tethering hole (25) located at the edge of the connecting base plate (23); A multi-chamber self-expanding support bladder (3) is bonded inside the receiving cavity (26); The conveying drill rod (4) includes a rod body (42) with an internal cavity (41), a top rod (43) disposed in the internal cavity (41), a tether fixing buckle (44), a fixed pulley (45), a tether line (46) and a quick-connect steel wire (47); a second tether hole (431) is provided on the top rod (43). The protective body, consisting of the protective front component (1), the protective rear component (2), and the multi-chamber self-expanding support bladder (3), is placed in the built-in cavity (41). The tether line (46) passes through the tether fixing buckle (44) and is connected to the first tether hole (25). One end of the quick-connect steel wire (47) is connected to the winch (5) and passes around the fixed pulley (45). The other end of the quick-connect steel wire (47) is connected to the second tether hole (431).

2. The protective device for coal seam gas pre-drainage boreholes according to claim 1, characterized in that, The hollow housing part (11) is also provided with a shaft hole (112) and a rotating shaft (113) passing through the shaft hole (112). The corner piece (14) is rotatably installed in the corner groove (111) by a torsion spring (6).

3. The protective device for coal seam gas pre-drainage boreholes according to claim 2, characterized in that, The third sidewall (21) is engaged between the first end of the first sidewall (12) and the first end of the second sidewall (13) by means of a meshing component; the fourth sidewall (22) is also engaged between the second end of the first sidewall (12) and the second end of the second sidewall (13) by means of a meshing component; The engaging member includes a boss (7) and a groove (8) adapted to the boss (7). Each end of the first sidewall (12), the second sidewall (13), the third sidewall (21) and the fourth sidewall (22) is provided with a boss (7) and a groove (8).

4. The protective device for coal seam gas pre-drainage boreholes according to claim 3, characterized in that, The multi-chamber self-expanding support bladder (3) includes a cross-shaped bladder body (31), a third vent (32) located at the center of the bladder body (31), and four expansion filling cavities (33) evenly distributed around the third vent (32). Each of the expansion filling cavities (33) is provided with a polyol flexible storage cavity (331) and an isocyanate flexible storage cavity (332) disposed opposite to the polyol flexible storage cavity (331).

5. The protective device for coal seam gas pre-drainage boreholes according to claim 4, characterized in that, The bag body (31) is composed of a fireproof cloth outer layer that is permeable to water but impermeable to slurry and an inner layer of fragile flexible material that is impermeable to water.

6. The protective device for coal seam gas pre-drainage boreholes according to claim 4, characterized in that, The top rod (43) is also provided with a round head (432) for pushing the protective body at the end away from the second tethering hole (431). The diameter of the round head (432) is larger than the diameter of the second vent hole (24). The fixed pulley (45) is installed in the built-in cavity (41) through the pulley shaft (48). The upper end of the rod is also equipped with an openable drill bit (49).

7. The protective device for coal seam gas pre-drainage boreholes according to claim 6, characterized in that, The polyol flexible reservoir (331) has the same tensile strength as the isocyanate flexible reservoir (332); The bonding strength between the multi-chamber self-expanding support bladder (3) and the receiving cavity (26) is greater than the fracture strength of the tether line (46) after it is connected to the first tether hole (25) and the tensile strength of the polyol flexible storage cavity (331) / the isocyanate flexible storage cavity (332) and the meshing friction between the protective front part (1) and the protective rear part (2).

8. The protective device for coal seam gas pre-drainage boreholes according to claim 7, characterized in that, The tether (46) is made of elastic and strong plastic and is set with a preset strength threshold, which breaks after the preset strength threshold is reached.

9. A protection method for coal seam gas pre-drainage boreholes, characterized in that, The operation using the protective device for coal seam gas pre-drainage boreholes as described in claim 8 includes the following steps: S1. The front and rear ends of the cross-shaped bag body (31) are glued to the storage cavity (26) composed of the protective front part (1) and the protective rear part (2) to assemble the protective body, and the protective body is placed in the built-in cavity (41) of the conveying drill rod (4); one end of the quick-connect steel wire (47) is connected to the winch (5), and the other end is inserted into the built-in cavity (41), turned by the fixed pulley (45), and fixedly connected to the second tethering hole (431) of the top rod (43); the tethering line (46) is connected between the tethering fixing buckle (44) and the first tethering hole (25) of the protective rear part (2); the round head (432) is installed on the left side of the rod body (42) to complete the assembly work; S2. Install the conveyor drill rod (4) containing the protective body as the first drilling drill rod on the drilling machine, and carry out drilling operations according to the drilling parameters. As the drilling operation progresses, connect a quick-connect steel wire (47) inside each additional ordinary drill rod until the drilling operation is completed. During the drilling operation, record the depth of the stuck drill and the blowhole. S3. After drilling is completed, start the drill retraction operation; use the drilling rig to pull out the drill rods one by one, and remove a quick-connect steel wire (47) for each ordinary drill rod removed; continue to retract the drill until the drill reaches the recorded abnormal depth or the location of the structural area detected in the previous geological survey. At this time, stop retracting the drill and prepare to lower the protective body. S4. Connect the winch (5) to the outer end of the remaining quick-connect wire (47) at the orifice. Rotate the winch (5) to retrieve the quick-connect wire (47). The quick-connect wire (47) moves towards the orifice and changes the transmission direction through the fixed pulley (45) in the rod (42). This causes the top rod (43) to move towards the connecting base plate (23) of the protective rear part (2) until the round head (432) is in complete contact with the connecting base plate (23). S5. Continue to rotate the winch (5) to tighten the quick-connect wire (47). The push rod (43) pushes the entire protective body towards the drill bit until the open-close drill bit (49), the protective body and the push rod (43) are completely pressed together. Further increase the rotation force of the winch (5) until the push rod (43) pushes the friction of the open-close drill bit (49). The open-close drill bit (49) is opened and the protective front part (1) is pushed out to deliver the drill rod (4). When the corner groove (111) is fully exposed in the borehole, the corner piece (14) is driven to rotate around the shaft (113) under the action of the torsion spring (6). The tip of the corner piece (14) pops out from the corner groove (111) and contacts the borehole wall. S6. Continue to rotate the winch (5), and the push rod (43) continues to push the protective body into the borehole until the winch (5) can no longer rotate. At this time, part of the protective body enters the borehole from the conveying drill rod (4). Remove the winch (5) at the borehole opening and continue the drilling withdrawal operation. Use the drilling machine to pull out the next ordinary drill rod and remove a quick-connect steel wire (47). At this time, the drill rods from beginning to end gradually move towards the borehole opening as the drilling withdrawal proceeds. Because the corner piece (14) of the protective front piece (1) is in close contact with the borehole wall, the protective front piece (1) is firmly fixed in place under the action of tension. S7. As the drill retraction proceeds, the drill rod moves further toward the borehole opening, and the protective body gradually enters the borehole completely; the tether line (46) connected to the bottom first tether hole (25) on the connecting base plate (23) of the protective rear part (2) gradually extends and tightens; As the drill continues to retract, the protective front part (1) remains firmly fixed in place under the action of the corner piece (14), while the protective rear part (2) moves toward the borehole with the conveying drill rod (4) under the tension of the tie line (46), so that the protective front part (1) and the protective rear part (2) gradually separate, and the multi-chamber self-expanding support bladder (3) can be stretched and expanded. After the drill continues to retract a certain distance, under the continuous pulling of the tether line (46), when the tension exceeds the tensile strength of the polyol flexible reservoir (331) and the isocyanate flexible reservoir (332), the polyol flexible reservoir (331) and the isocyanate flexible reservoir (332) rupture. The polyol and isocyanate are mixed in the expansion filling cavity (33) and undergo an addition polymerization reaction to generate polyurethane. The volume expands rapidly until it fills the expansion filling cavity (33). At this time, the irregular expansion bag is formed and begins to support the hole wall. As the drill continues to retract, the protective front piece (1) is fixed in place by the corner piece (14), the multi-chamber self-expanding support bladder (3) is filled and shaped and loses its extensibility, and the protective rear piece (2) separates from the multi-chamber self-expanding support bladder (3). As the drill continues to retract, the tether line (46) is stretched until it breaks. At this point, the protective body consisting of the protective front component (1), the multi-chamber self-expanding support bladder (3), and the protective rear component (2) remains inside the hole, thus completing the drilling protection. S8. Continue to use the drilling machine to pull out the drill rods one by one. For each ordinary drill rod removed, a quick-connect steel wire (47) is removed until the conveying drill rod (4) is also removed and drilled, thus completing the complete drilling protection operation.

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