Elastic bending joint type coal mine underground casing device and construction method

Abstract

The present application provides a kind of elastic bending section type coal mine casing device underground, comprising: a plurality of head-to-tail connection casing body, each casing body includes elastic member, sealing portion, first joint, second joint, first joint, second joint is located at the both ends of elastic member, sealing portion is arranged on the surface of elastic member and covers elastic member, the both ends of sealing portion are connected with first joint and second joint respectively, two casing bodies connected adjacently are connected by first joint and second joint, elastic member 2 is used as the framework structure of casing body, sealing portion 3 is arranged on the surface of elastic member 2 to seal elastic member 2, which plays the role of water isolation and pressure resistance, the casing body has certain flexibility in axial direction, and can be lowered into along the long distance of curved borehole;It has enough compressive strength in radial direction, can withstand hole wall surrounding rock stress, water pressure, gas pressure and the like, the elastic members of the casing bodies arranged adjacently are connected by first joint 1 and second joint 5, and the working efficiency of casing in raise hole is improved.

Description

Technical Field

[0001] This invention belongs to the field of underground gas extraction in coal mines, specifically relating to an elastic bend type underground casing device and its construction method. Background Technology

[0002] Pre-drainage of gas through underground drilling is a fundamental method for gas control in coal mines. In recent years, directional long-bore drilling technology has become one of the important means of regionalized gas control in coal mines. Based on the characteristics of the borehole structure, directional drilling generally consists of three parts: the casing section, the transition section, and the target formation section. The casing section is located at the borehole opening and requires casing to be lowered for sealing. It is fundamental to ensuring large-scale adjustment of the borehole trajectory, control of high-pressure water and gas, and protection of fractured formations. The casing should be lowered into place according to design specifications and dimensions. Currently, the casing lowering depth is generally 9–30 m, and can reach over 100 m in special cases. This requires the casing to have sufficient radial strength to withstand high-pressure water and gas, and sufficient axial length to meet the requirements of long-distance casing lowering.

[0003] While ordinary seamless steel casings possess sufficient pressure-bearing strength, their excessive rigidity makes them prone to jamming against the borehole wall when encountering bends, hindering long-distance installation. Furthermore, long-distance installation of ordinary seamless steel casings also incurs drawbacks such as high construction costs and heavy labor demands. Therefore, a new type of casing is urgently needed that can enable long-distance installation in bends, solving the problem of the difficulty in turning with ordinary seamless steel casings and improving gas extraction efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an elastic bendable underground casing device and construction method for coal mines, thereby solving the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A flexible bend type underground casing device for coal mines includes: multiple casing bodies connected end to end in sequence. Each casing body includes an elastic element, a sealing part, a first joint, and a second joint. The first joint and the second joint are located at both ends of the elastic element. The sealing part is located on the surface of the elastic element and covers the elastic element. The two ends of the sealing part are respectively connected to the first joint and the second joint. Two adjacent casing bodies are connected to each other through the first joint and the second joint.

[0007] Preferably, the elastic element is a spring, and the sealing part is a rubber layer. The rubber layer covers the spring and seals it. When the spring is in a free state, the rubber layer located between two adjacent spring coils sinks to form a free part. The outer normal of the free part points to the inside of the spring. When the spring is compressed in a tight state, the length of the free part is zero and the depth is 3mm to 20mm. When the spring is stretched to its maximum elastic deformation, the length of the free part is 6mm to 40mm and the depth is zero.

[0008] Preferably, the thickness of the sealing part is 20 mm, it is bonded to the elastic element with high-strength resin adhesive, the elastic modulus of the sealing part is 1 MPa to 10 MPa, and the density is 1 kg / m³. 3 .

[0009] Preferably, the flexible bend type underground casing device for coal mines further includes: an inner liner, which is sleeved inside the elastic element and engages with the elastic element to enhance the radial support force of the elastic element.

[0010] Preferably, the flexible bend type underground casing device for coal mines further includes: a guide part connected to the second connector, the guide part including an oscillator connector, a shell, balls, an inner shell, a guide head, and a return spring, the oscillator connector being matched and connected to the second connector, the inner shell being sleeved inside the shell, balls being provided at the connection between the shell and the inner shell, one end of the inner shell being connected to the shell through a return spring, and the other end being provided with a guide head extending out of the shell.

[0011] Preferably, the flexible bend-type underground casing device for coal mines further includes: a conversion joint (including a connecting part and a third joint and a fourth joint with two connecting ends), the third joint is used to connect with the drill pipe, and the fourth joint is used to connect with the first joint.

[0012] Preferably, the flexible bend type underground casing device for coal mines further includes: multiple PVC pipes, spaced apart between each casing body and matched and connected to the casing body. When the borehole trajectory curvature is ≥0.3° / m, the casing body connection combination is selected to facilitate the turning of the entire borehole section. When the borehole trajectory curvature is ≤0.3° / m, the PVC pipes and the casing body are spaced apart and connected in a combination.

[0013] A method for constructing a flexible bend type underground casing in coal mines, wherein when the borehole trajectory curvature is ≥0.3° / m, a combination method for connecting the casing body is selected. The method includes the following steps.

[0014] Step 1: Determine the diameter of the casing body according to the drilling type and construction requirements.

[0015] Step 2: Lower the casing. Install the guide on the second joint of the first casing body. Connect the first joint of the first casing to the second joint of the second casing body. Push the guide into the hole along the orifice. Similarly, connect the third, fourth, fifth, etc., in sequence, lowering as you connect, until the lowering depth meets the construction requirements. If the lowering process is obstructed or the casing is too deep to be pushed manually, proceed to step 3.

[0016] Step 3: Select the size of the adapter according to the casing body. The third connector of the adapter is connected to the drill pipe, and the fourth connector is connected to the first connector of the casing body. For each additional casing, use the drilling rig feed force to send the casing body into the hole until the target hole depth is reached. Control the feed speed when the drilling rig feeds in to allow the spring body to fully release its energy and prevent damage from exceeding the elastic limit.

[0017] Step 4: After the last casing body is lowered, the drill rig clamp is used to reverse the drill head to remove the drill rod and adapter, and then the borehole device is installed and the hole is sealed.

[0018] When the borehole trajectory curvature is ≤0.3° / m, a combination of PVC pipe and casing body with alternating connection is selected. In step 2 of this method, the PVC pipe and casing body are inserted alternately, and the other steps are the same as when the borehole trajectory curvature is ≥0.3° / m.

[0019] Compared with the prior art, the present invention has the following technical effects.

[0020] (I) The casing device of the present invention uses an elastic element as the skeleton structure of the casing body, and a sealing part is provided on the surface of the elastic element to seal the elastic element, which plays a role in water isolation and pressure resistance. The casing body has a certain degree of flexibility in the axial direction, which can be lowered long distances along curved boreholes; it has sufficient compressive strength in the radial direction, which can withstand the stress of the surrounding rock of the borehole wall and water pressure, air pressure, etc. The elastic elements of adjacent casing bodies are connected by threads through the first joint and the second joint, which can effectively solve the problem that ordinary steel seamless casings cannot be lowered long distances due to excessive rigidity, and improve the working efficiency of casing in the borehole.

[0021] (II) The casing body of the casing device of the present invention is made of rubber layer to form the outer wall of the casing, which has a good sealing effect. It is not only inexpensive in terms of material cost, but also lightweight and easy to transport, which greatly reduces the on-site construction cost and the labor intensity of workers. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention.

[0023] Figure 2 This is the present invention. Figure 1 A magnified view of part A.

[0024] Figure 3 This is a schematic diagram of the guide portion of the present invention.

[0025] Figure 4 This is a schematic diagram of the adapter of the present invention.

[0026] Figure 5 This is a schematic diagram of the PVC pipe structure of the present invention.

[0027] Figure 6 This is a diagram showing the application of the device of the present invention in drilling.

[0028] Figure 7 This is a diagram showing the application of the device of the present invention in drilling.

[0029] The meanings of the labels in the diagram are as follows: 1-First connector, 2-Elastic element, 3-Sealing part, 4-High-strength resin adhesive, 5-Second connector, 6-Inner liner tube, 7-Converter connector, 8-PVC pipe, 71-Third connector, 72-Fourth connector, 73-Connecting part, 91-Oscillator connector, 92-Outer shell, 93-Ball bearing, 94-Inner shell, 95-Guide head, 96-Reset spring.

[0030] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0031] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0032] The directional terms used in this document, such as “length,” “radial,” “horizontal,” and “vertical,” correspond to the specific directions on the paper in the accompanying drawings or the corresponding directions in the space shown in the drawings.

[0033] Example 1:

[0034] A flexible bendable underground casing device for coal mines, such as Figure 1-5 As shown, it includes: multiple sleeve bodies connected end to end. Each sleeve body includes an elastic element 2, a sealing part 3, a first connector 1, and a second connector 5. The first connector 1 and the second connector 5 are located at both ends of the elastic element 2. The sealing part 3 is located on the surface of the elastic element 2 and covers the elastic element 2. The two ends of the sealing part 3 are respectively connected to the first connector 1 and the second connector 5. Two adjacent sleeve bodies are connected to each other through the first connector 1 and the second connector 5.

[0035] In this embodiment, the casing device uses an elastic element 2 as the skeleton structure of the casing body. A sealing part 3 is provided on the surface of the elastic element 2 to seal the elastic element 2, which serves to prevent water leakage and resist pressure. The casing body has a certain degree of flexibility in the axial direction, which can be lowered long distances along curved boreholes. It has sufficient compressive strength in the radial direction, which can withstand the stress of the surrounding rock of the borehole wall and water pressure, air pressure, etc. The elastic elements of adjacent casing bodies are connected by threads through the first joint 1 and the second joint 5, which can effectively solve the problem that ordinary steel seamless casings cannot be lowered long distances due to excessive rigidity, and improve the working efficiency of casing in the borehole.

[0036] The elastic element 2 is connected to the first connector 1 and the second connector 5 by welding.

[0037] In a preferred embodiment, the elastic element 2 is a spring, and the sealing part 3 is a rubber layer. The rubber layer covers the spring and seals it. When the spring is in a free state, the rubber layer between two adjacent spring coils sinks to form a free part. The outer normal of the free part points to the inside of the spring. When the spring is compressed in a tight state, the length of the free part is zero and the depth is 20mm. When the spring is stretched to its maximum elastic deformation, the length of the free part is 40mm and the depth is zero.

[0038] The spring is readily available, and the elastomer and rubber layer are easily combined to form a casing body suitable for use in drilling. The advantage of this structure is that it ensures good sealing and water resistance regardless of whether the casing is in a bent or natural state, or whether it is on the compressed or tensile side during bending. The spring pitch is 40mm. When the spring is compressed in a tight position, the rubber layer depth is half the pitch, i.e., 20mm, and the free part length is zero. When the spring is stretched to its maximum elastic deformation, the free part length is 40mm, and the depth is zero.

[0039] In a preferred embodiment, the sealing part 3 has a thickness of 20mm and is bonded to the elastic element 2 with high-strength resin adhesive 4. The elastic modulus of the sealing part 3 is 1MPa to 10MPa. Its advantage lies in the sufficient elastic modulus to withstand the radial pressure exerted on the portion between the spring sections, specifically including the pressure of the surrounding rock, formation water pressure, and gas pressure. The density is 1kg / m³. 3 The advantage is that it can reduce the weight of the casing while meeting the strength requirements, making it easier to handle and reducing the labor intensity of workers.

[0040] As a preferred embodiment, the flexible bend type underground casing device for coal mines further includes: an inner liner 6, which is sleeved inside the elastic member 2 and cuts into the elastic member 2, and is used to enhance the radial support force of the elastic member. The inner liner 6 has the same material, structure, and function as the conduit used in electrical engineering, and has a certain rigidity in the radial direction and a certain flexibility in the axial direction.

[0041] In this embodiment, the inner side of the spring body is a liner tube, which can increase the radial stiffness of the device, improve the radial support strength of the casing body, and further enhance the support stability of the device in drilling.

[0042] As a preferred embodiment, the flexible bend type underground casing device for coal mines further includes: a guide section connected to the second connector 5. The guide section includes an oscillator connector 91, a housing 92, a ball bearing 93, an inner housing 94, a guide head 95, and a return spring 96. The oscillator connector 91 is matched and connected to the second connector 5. The inner housing 94 is sleeved inside the housing 92. A ball bearing is provided at the connection between the housing 92 and the inner housing. One end of the inner housing 94 is connected to the housing 92 through the return spring 96, and the other end is provided with a guide head 95, which extends out of the housing.

[0043] In this embodiment, the return spring axis of the guide part coincides with the axis of the sleeve body. The front section of the guide head is designed as an arc-shaped blunt head. When the device passes through the curved hole section, the guide head is deflected by the lateral force of the hole wall. As the guide head moves, it gradually enters the straight hole section. Under the action of the return spring, the guide head automatically returns to the correct position. In addition, the blunt head is less likely to hit the hole wall and can "run along the wall". The guide part of this embodiment adopts a shuttle-shaped oscillator. At the same time, the shuttle shape can adapt to the bending of the hole wall to a greater extent and can play a guiding role for the sleeve under the curved hole wall from 5° to 45°.

[0044] As a preferred embodiment, the flexible bend type underground casing device for coal mines further includes: a conversion joint 7, including a connecting part 73 and a third joint 71 and a fourth joint 72 with two connecting ends. The third joint 71 is used to connect with the drill pipe, and the fourth joint 72 is used to connect with the first joint 1.

[0045] The purpose of the adapter joint is to address situations where, during the implementation of the device in this embodiment, the strata are highly fractured, the casing body is long, or the borehole is curved, making manual pushing of the casing difficult. In such cases, a drilling rig can be used to lower the casing. Specifically, the drill rod on the drilling rig connects to the third connector 71 of the adapter joint, and the fourth connector 72 connects to the first connector 1 of the casing body. After connection, the drilling rig feeds the drill rod, driving the casing into the section of the borehole requiring protection. During the lowering process, the casing can adapt to the borehole trajectory and bend forward, effectively solving the problem of lowering long-distance, large-angle casing sections in coal mines.

[0046] Example 2:

[0047] A method for constructing flexible, bendable casing in underground coal mines. This method is selected when the borehole trajectory curvature is ≥0.3° / m. Figure 1 The diagram illustrates the combination method of the sleeve joint connection. This method is implemented using the sleeve device of the embodiment, and the actual application state is as follows. Figure 6 As shown, it includes the following steps.

[0048] Step 1: Determine the casing size. The size of flexible bendable underground casing devices in coal mines varies depending on the drilling type and construction requirements. Commonly used sizes are φ168, φ146, φ127, and φ108, corresponding to borehole diameters of φ193, φ153, φ133, and φ120. According to industry practice, the standard length of a single casing section is 1m, 2m, or 3m.

[0049] Step 2: Connect the casings and lower them into the hole. First, connect the first connector 5 of the first casing to the guide part 9. Then, connect the second connector of the first female connector 1 of the first casing to the first connector 5 of the second casing. Push them into the hole from the orifice. Similarly, connect the third, fourth, and fifth casings in sequence, lowering them as you connect, until the required depth is reached. If the lowering process is completed smoothly, proceed with the installation of the orifice device and sealing of the hole. If the lowering process is obstructed or the casing is too deep to be pushed manually, proceed to Step 3.

[0050] Step 3: Determine the size of the adapter. The adapter is used to connect the drill pipe and the casing body. Depending on the commonly used drill pipe type, the adapter sizes are φ73-108, φ73-127, φ73-146, φ89-108, φ89-127, φ89-146, φ89-168, etc.

[0051] When the drilling rig feeds the casing, the feed rate should not be too fast, and the feed force should not be too great. If necessary, it can be pulled back and forth several times to ensure that the casing extends smoothly in the borehole. Otherwise, forced feeding can easily damage the spring body and the inner liner.

[0052] Step 4: Connect the adapter. Connect the drill rod of the appropriate size to the third connector 71 of the adapter. Then connect the fourth connector 72 of the adapter to the first connector of the next casing in sequence. After each casing is added, use the drilling rig to feed it into the hole until the target hole depth is reached. When feeding the casing, the feed speed should be reasonably controlled to allow the spring body to fully release its energy and avoid exceeding the elastic limit and causing damage.

[0053] Step 5: Uncoupling the adapter. After the last casing is lowered, use the drill rig chuck to reverse the drill head and remove the drill rod and adapter, then proceed with subsequent work such as installing the borehole device and sealing the hole.

[0054] Example 3:

[0055] This embodiment provides a flexible, bendable type underground casing device for coal mines and its usage method. It is selected when the borehole trajectory curvature is ≤0.3° / m. Figure 1 The sleeve section shown is Figure 5 The diagram shows the combination method for inter-phase connection of PVC pipes; the actual application state of this method is as follows. Figure 7 As shown, it includes the following steps.

[0056] Step 1: Determine the casing size. The size of flexible bend-type underground casing devices in coal mines varies depending on the drilling type and construction requirements. Commonly used sizes are φ168, φ146, φ127, and φ108, corresponding to borehole diameters of φ193, φ153, φ133, and φ120. According to industry practice, the standard length of a single casing section is 1m, 2m, or 3m. Non-standard sizes can be designed according to actual needs.

[0057] Step 2: Lower the flexible sleeve body and PVC pipe. First, connect the first flexible sleeve section to the shuttle-shaped vibrator and push it into the hole from the orifice. Then, connect the first specially made PVC pipe to the first flexible sleeve section. Similarly, connect the second, third, and fourth pipes in sequence, lowering them as you connect, until the required depth is reached. If the lowering process is completed smoothly, proceed with subsequent work such as installing the orifice device and sealing the hole. If the lowering process encounters obstacles or the pipe is too deep to be pushed manually, proceed to Step 3.

[0058] Step 3: Determine the size of the adapter. The adapter is used to connect the drill pipe and the casing body. Depending on the commonly used drill pipe type, the adapter sizes are φ73-108, φ73-127, φ73-146, φ89-108, φ89-127, φ89-146, φ89-168, etc.

[0059] Step 4: Connect the adapter. Connect the drill rod of the appropriate size to the third connector 71 of the adapter. Then, connect the fourth connector 72 of the adapter to the next flexible casing section or PVC pipe connector in sequence. For each additional section, use the drilling rig to feed it into the hole until the target hole depth is reached. When feeding the casing, the feed speed must be properly controlled. The feed speed and force should not be too high when the drilling rig feeds the casing. If necessary, pull it back and forth several times to ensure the casing extends smoothly within the borehole. Otherwise, forced feeding can easily damage the spring body and inner liner.

[0060] Step 5: Uncoupling the adapter. After lowering the last flexible sleeve section or PVC pipe, use the drill rig chuck to reverse the drill head and remove the drill rod and adapter, then proceed with subsequent work such as installing the borehole device and sealing the hole.

Claims

1. A method for constructing a flexible, bendable type underground casing in coal mines, characterized in that, The method uses an elastic bend type underground casing device for coal mines. The elastic bend type underground casing device for coal mines includes: multiple casing bodies connected end to end in sequence. Each casing body includes an elastic element (2), a sealing part (3), a first joint (1), and a second joint (5). The first joint (1) and the second joint (5) are located at both ends of the elastic element (2). The sealing part (3) is located on the surface of the elastic element (2) and covers the elastic element (2). The two ends of the sealing part (3) are connected to the first joint (1) and the second joint (5) respectively. Two adjacent casing bodies are connected to the second joint (5) through the first joint (1). It also includes a conversion connector (7), which includes a connecting part (73) and a third connector (71) and a fourth connector (72) with the two ends of the connection. The third connector (71) is used to connect to the drill pipe, and the fourth connector (72) is used to connect to the first connector (1). It also includes a guide section, which is connected to the second connector (5). The guide section includes an oscillator connector (91), a housing (92), a ball (93), an inner housing (94), a guide head (95), and a return spring (96). The oscillator connector (91) is matched and connected to the second connector (5). The inner housing (94) is fitted inside the housing (92). A ball is provided at the connection between the housing (92) and the inner housing. One end of the inner housing (94) is connected to the housing (92) through the return spring (96), and the other end is provided with a guide head (95). The guide head extends out of the housing. When the curvature of the borehole trajectory is ≥0.3° / m, the combination method of casing body connection is selected to facilitate the turning of the entire borehole section; The steps of this method include: Step 1: Determine the diameter of the casing body according to the drilling type and construction requirements; Step 2: Lower the casing. Install the guide on the second joint (5) of the first casing body. Connect the first joint (1) of the first casing to the second joint (5) of the second casing body. Push the guide along the orifice into the hole. Similarly, connect the third, fourth and fifth casings in sequence, lowering them as you connect until the lowering depth meets the construction requirements. If the lowering process is blocked or the casing is too deep to be pushed by manpower, proceed to step 3. Step 3: Select the size of the adapter (7) according to the casing body. The third connector (71) of the adapter (7) is connected to the drill pipe, and the fourth connector (72) is connected to the first connector (1) of the casing body. For each additional casing, use the drilling rig feed force to send the casing body into the hole until the target hole depth is reached. Control the feed speed when the drilling rig feeds in so that the spring body can fully release energy to avoid exceeding the elastic limit and causing damage. Step 4: After the last casing body is lowered, the drill rig clamp is used to reverse the drill head to remove the drill rod and adapter (7), and the borehole device is installed and the hole is sealed.

2. The method for constructing flexible, bendable underground casing in coal mines as described in claim 1, characterized in that, The elastic element (2) is a spring, and the sealing part (3) is a rubber layer. The rubber layer covers the spring and seals the spring. When the spring is in a free state, the rubber layer between two adjacent spring coils sinks to form a free part. The outer normal of the free part points to the inside of the spring. When the spring is compressed in a tight state, the length of the free part is zero and the depth is 3mm to 20mm. When the spring is stretched to the maximum elastic deformation, the length of the free part is 6mm to 40mm and the depth is zero.

3. The method for constructing flexible, bent-joint underground casing in coal mines as described in claim 2, characterized in that, The sealing part (3) has a thickness of 20 mm and is bonded to the elastic element (2) with high-strength resin adhesive (4). The elastic modulus of the sealing part (3) is 1 MPa to 10 MPa, and the density is 1 kg / m³. 3 .

4. The method for constructing flexible, bendable underground casing in coal mines as described in claim 3, characterized in that, The elastic bend type underground casing device for coal mines also includes: an inner liner (6), which is sleeved inside the elastic element (2) and fits into the elastic element (2) to enhance the radial support force of the elastic element.

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