A dynamic sealing device and method for coal seam gas extraction hole

Abstract

The present invention records a dynamic sealing device for coal seam gas extraction holes, including a first expansion unit, a second expansion unit and a closed chamber. The first expansion unit and the second expansion unit are fixedly connected by a connecting rod, and can synchronously advance or retreat along the gas extraction hole; the first expansion unit and the second expansion unit can expand after grouting, and can closely fit the hole wall of the gas extraction hole; the first expansion unit, the second expansion unit and the gas extraction hole constitute a closed chamber, and the closed chamber is used to store slurry; after the first expansion unit, the second expansion unit and the closed chamber are grouting, a solid-liquid-solid sealing plugging structure can be formed in the gas extraction hole. The sealing device recorded in the present invention can achieve multiple enhanced sealing effects under different extraction cycles, and can also adjust the length of the sealing device according to the needs of the extraction effect, and can solve the problem of increased air leakage intensity caused by the synchronous deformation of the sealing device with the drilled coal rock after one sealing.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining outburst prevention and control, and in particular to a dynamic sealing device and method for coal seam gas extraction holes. Background Art

[0002] At present, hydraulic permeability enhancement technology has become a commonly used permeability enhancement and enhanced extraction technology for protruding coal seams in my country, such as hydraulic fracturing, hydraulic slitting and hydraulic punching. However, after the low-permeability coal seam is enhanced, the key to efficient extraction of coal seam gas lies in whether the gas extraction borehole can remain stable and unobstructed and efficiently sealed.

[0003] Common problems that cause gas extraction borehole obstruction include borehole slag blockage, borehole collapse and deformation, and borehole twisting and shrinkage. Obstruction of gas extraction boreholes is not conducive to gas extraction and migration, and may even cause damage to the extraction pipeline. The sealing quality of gas extraction boreholes is directly related to gas extraction concentration and effective extraction time. Affected by the coal rock aquifer and the fracture zone around the borehole, if the sealing quality of gas extraction boreholes is generally substandard, the effect of gas extraction is difficult to guarantee. Especially when sealing the bedding boreholes, the coal rock mass is more likely to develop fractures due to the disturbance of mining, so high-quality sealing is particularly critical.

[0004] In order to improve the sealing quality of gas extraction boreholes, researchers at home and abroad have developed a large number of new sealing materials based on the commonly used two-blocking and one-injection sealing method. Commonly used sealing materials include polyurethane, cement slurry, or cement-based composite materials, sodium silicate polymers, etc. The research and development focus of researchers is mainly on the prepared materials should have properties such as impermeability, density, pressure resistance, deformation resistance, and the ability to fit the hole wall. However, due to the performance limitations of the material itself, such as easy cracking after solidification, poor fluidity, non-recyclability, high cost, and complex procedures, it is still difficult for gas extraction boreholes to achieve economic feasibility, long-term stability, and high-concentration gas extraction. At the same time, the sealing mode of gas extraction boreholes often belongs to one-time hole formation, and the sealing position is relatively fixed and difficult to reuse. If the coal body around the extraction borehole is deformed in the later stage, the sealing effect will be greatly reduced.

[0005] Therefore, in order to further improve the sealing quality of gas extraction boreholes, there is an urgent need for a sealing device and method that can dynamically and real-time autonomously enhance the sealing effect based on different extraction cycles and can be reused. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a dynamic sealing device for coal seam gas extraction drilling.

[0007] The technical solution of the present invention is:

[0008] A dynamic sealing device for a coal seam gas extraction hole comprises a first expansion unit, a second expansion unit and a closed chamber; the first expansion unit and the second expansion unit are fixedly connected by a connecting rod and can synchronously advance or retreat along the gas extraction hole; the first expansion unit and the second expansion unit can expand after being injected with slurry, and can closely fit the hole wall of the gas extraction hole; the first expansion unit, the second expansion unit and the gas extraction hole constitute the closed chamber, and the closed chamber is used to store slurry; after the grouting of the first expansion unit, the second expansion unit and the closed chamber is completed, a solid-liquid-solid sealing and plugging structure can be formed in the gas extraction hole.

[0009] Furthermore, the second expansion unit is provided in plurality; adjacent second expansion units are connected by connecting rods and form a closed chamber with the gas extraction hole; after grouting of the first expansion unit, the second expansion unit and the closed chamber is completed, a plurality of continuous solid-liquid-solid sealing structures can be formed in the gas extraction hole.

[0010] Furthermore, the first expansion unit includes a first expansion bladder and a first slurry inlet pipe, one end of the first slurry inlet pipe is connected to the grouting equipment, and the other end extends into the first expansion bladder for injecting slurry into the first expansion bladder.

[0011] Furthermore, a stop valve is provided on the first slurry inlet pipe.

[0012] Furthermore, the second expansion unit includes a second expansion bladder, a second slurry inlet pipe and a slurry outlet pipe; one end of the second slurry inlet pipe passes through the first expansion bladder, extends into the interior of the second expansion bladder, and a grouting port is opened inside the second expansion bladder; the other end of the second slurry inlet pipe is connected to a grouting device for injecting slurry into the second expansion bladder.

[0013] Furthermore, a stop valve and a one-way valve are provided on the second slurry inlet pipe, and the one-way valve is provided close to the end surface of the second expansion bag; and a one-way valve is provided on the slurry outlet pipe.

[0014] Furthermore, the second slurry inlet pipe is configured as a segmented threaded connection, each segment of the slurry inlet pipe is connected via a connecting joint, and a grouting port is provided in the corresponding second expansion bag.

[0015] Furthermore, the connecting rod is made of nylon plastic or aluminum alloy, and its length is set to 1.5m-2m, and its two ends are threadedly connected to the first expansion unit and the second expansion unit.

[0016] Furthermore, the first expansion bladder and the second expansion bladder are both made of a slightly elastic material; in the un-grouted state, their length is set to 1m-1.5m, their thickness is set to 5mm-10mm, and the gap between their outer wall and the inner wall of the gas extraction hole is ≦10mm.

[0017] A method for dynamically sealing a coal seam gas extraction hole comprises the following steps:

[0018] S1, using a drill pipe to push the sealing device to a set position in the gas extraction hole;

[0019] S2, opening the stop valve, and using a grouting device to inject grout into the first expansion bag and the second expansion bag, so that the first expansion bag and the second expansion bag expand and fit tightly with the wall of the gas extraction hole, thereby forming a solid blockage for the coal body fissures;

[0020] The one-way valve of the second expansion unit is opened, and the slurry is injected into the closed chamber to form a liquid plugging on the coal body fissures, thereby forming a multi-stage solid-liquid-solid sealing structure in the gas extraction hole;

[0021] After the grouting pressure of the grouting pump reaches the set pressure, the pressure is stabilized for a period of time, and then the stop valve is closed;

[0022] S3, manually stretch the gas extraction pipe line to check whether the sealing device is loose, and if it is not loose, the sealing operation is completed.

[0023] S4, performing gas extraction operation through gas extraction equipment, and based on the gas extraction effect, repeating the grouting operation of step S2 regularly or timely to supplement the slurry in the sealing device.

[0024] Furthermore, before starting step S1, the number of second expansion units to be used is determined according to the depth of the gas extraction hole, and the gas extraction pipe and the second slurry inlet pipe are connected to the required length using connecting joints.

[0025] 12. A method for dynamically sealing coal seam gas extraction holes according to claim 10, characterized in that, in step S1, the set position is the distance between the second expansion bladder located at the bottom of the gas extraction hole and the orifice of the gas extraction hole, wherein the through-layer drilling is ≧6m, and the in-layer drilling is ≧10m.

[0026] Furthermore, in step S2, the grouting pressure of the grouting pump is ≥ 3 MPa, and the pressure stabilization time is ≥ 20 min.

[0027] Furthermore, the slurry injected into the first expansion bladder bag and the second expansion bladder bag is made of a non-coagulating material.

[0028] The beneficial effects of the present invention are:

[0029] The sealing device described in the present invention can not only achieve multiple enhanced sealing effects under different extraction cycles, but also can adjust the sealing device and length in time according to the extraction effect needs, that is, if the gas extraction drilling hole sealing position has a hole collapse, deformation and other problems that are not conducive to efficient sealing, it is helpful to solve the problem of increased leakage intensity in the later period caused by the deformation of the borehole coal body after the first sealing. In addition, the sealing device described in the present invention can be used repeatedly, that is, if the gas extraction drilling hole meets the gas extraction volume requirements, the sealing device can be completely taken out to seal other gas extraction drilling holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : A schematic structural diagram of a sealing device in an exemplary embodiment of the present invention;

[0031] Figure 2 : A schematic structural diagram of a sealing device provided with a plurality of second expansion units in an exemplary embodiment of the present invention.

[0032] Explanation of symbols

[0033] 1-first expansion unit, 11-first expansion bag, 12-first slurry inlet pipe;

[0034] 2-second expansion unit, 21-second expansion bag, 22-second pulp inlet pipe, 23-slurry outlet pipe 23;

[0035] 3-Stop valve;

[0036] 4- One-way valve;

[0037] 5-Sealed chamber;

[0038] 6-Connecting rod;

[0039] 7-Gas extraction pipe. DETAILED DESCRIPTION

[0040] The present invention is described in detail below by way of embodiments in conjunction with the accompanying drawings.

[0041] The present invention discloses a dynamic sealing device for a coal seam gas extraction hole, comprising a first expansion unit 1, a second expansion unit 2, a sealed chamber 5 and a gas extraction pipe 7.

[0042] The first expansion unit 1 includes: a first expansion bladder 11 and a first slurry inlet pipe 12 .

[0043] One end of the first slurry inlet pipe 12 is connected to the grouting equipment, and the other end extends into the first expansion bag 11 for injecting slurry into the first expansion bag 11 .

[0044] The first slurry inlet pipe 12 is provided with a stop valve 3, which further controls the slurry pressure inside the first expansion bladder 11 by controlling and regulating the slurry flow in the pipe.

[0045] The second expansion unit 2 includes: a second expansion bag 21 , a second slurry inlet pipe 22 , and a slurry outlet pipe 23 .

[0046] One end of the second slurry inlet pipe 22 passes through the first expansion bag 11 and extends into the second expansion bag 21 , and a grouting port is opened in the second expansion bag 21 .

[0047] The other end of the second slurry inlet pipe 22 is connected to the grouting equipment and is provided with a stop valve 3 for injecting slurry into the second expansion bag 21 .

[0048] Furthermore, the second slurry inlet pipe 22 is provided with a one-way valve 4 near the end surface of the second expansion bag 21 to prevent the slurry in the pipe from flowing back.

[0049] One end of the slurry outlet pipe 23 extends into the second expansion bladder 21, and the other end extends into the closed chamber 5. Under pressure, part of the slurry in the second expansion bladder 21 can flow into the closed chamber 5 from the slurry outlet pipe 23.

[0050] The slurry outlet pipe 23 is provided with a one-way valve 4, under the control of the one-way valve 4, the slurry in the pipe can be prevented from flowing back.

[0051] The first expansion unit 1 , the second expansion unit 2 and the gas extraction hole constitute a closed chamber 5 , and the closed chamber 5 is used to store the slurry flowing out of the second expansion bag 21 .

[0052] The first expansion unit 1 and the second expansion unit 2 are connected and fixed by a connecting rod 6, so that the first expansion unit 1 and the second expansion unit 2 can move forward or backward synchronously in the gas extraction hole. Specifically, the connecting rod 6 is used to connect the expansion bag of the first expansion unit 1 and the expansion bag of the second expansion unit 2.

[0053] The connecting rod 6 is made of a corrosion-resistant material with a certain mechanical strength, such as nylon plastic or aluminum alloy.

[0054] One end of the gas extraction pipe 7 is connected to the gas extraction equipment, and the other end passes through the first expansion unit 1 and the second expansion unit 2 in sequence, and then extends to the bottom of the gas extraction hole.

[0055] In this embodiment:

[0056] Open the grouting equipment and the stop valve 3, and inject slurry into the first expansion bag 11 and the second expansion bag 21 through the first slurry inlet pipe 12 and the second slurry inlet pipe 22 respectively; under the action of the slurry pressure, the expansion bag expands and fits tightly to the inner wall of the gas extraction hole to form a solid sealing structure; open the one-way valve 4 of the second expansion unit 2, and inject slurry into the closed chamber 5 to form a liquid sealing structure. Thus, the device forms a solid-liquid-solid sealing structure in the gas extraction hole.

[0057] After the expansion bag is expanded, it fits tightly to the inner wall of the gas extraction hole, which means that there is no gap between the outer wall of the expansion bag and the inner wall of the gas extraction hole, and the gas can be prevented from passing through. By setting the grouting pressure, a certain slurry pressure value is maintained in the expansion bag, and the purpose of the operation can be achieved.

[0058] In the above embodiments, it is preferred that:

[0059] 1. The length of the connecting rod 6 is set to 1.5m-2m, and an external thread is set at both ends of the connecting rod. The expansion bags corresponding to the two ends are provided with matching threaded holes on their end faces. The connecting rod 6 is fixedly connected with the expansion bags through threads.

[0060] 2. The number of second expansion units 2 can be multiple according to actual production requirements, and adjacent second expansion units 2 are also fixedly connected by connecting rods 6.

[0061] 3. The first expansion bladder 11 and the second expansion bladder 21 are both made of slightly elastic material, such as rubber, and can expand autonomously under the action of slurry pressure. When they are installed in the gas extraction hole, they expand and fit the inner wall of the gas extraction hole under the action of grouting.

[0062] 4. The first expansion bladder 11 and the second expansion bladder 21 are set to be cylindrical. When not filled with slurry, their length is set to 1m-1.5m and their thickness is set to 5mm-10mm.

[0063] Since the aperture of the gas extraction borehole is generally between 75mm-110mm, the diameter size of the first expansion bladder 11 and the second expansion bladder 21 is set to between 65mm-100mm, that is, the gap between the outer wall of the first expansion bladder 11 and the second expansion bladder 21 and the inner wall of the gas extraction hole should be ≤10mm to meet the operational requirement of tightly fitting the inner wall of the gas extraction hole after expansion.

[0064] 5. The second slurry inlet pipe 22 can be set to a segmented threaded connection, and the number of segments is determined according to the number of the second expansion units 2. The segments of the slurry inlet pipe are connected through connecting joints; the second slurry inlet pipe 22 is sealed and connected to the corresponding second expansion bag 21, and a grouting port is set in the corresponding second expansion bag 21.

[0065] 6. The gas extraction pipe 7 can be set to be segmented threaded connection, so as to change its overall length, which is suitable for gas extraction hole operations at different depths. Each segment is connected by a connecting joint, and the gas pipe passes through each expansion bag in turn and is sealed and connected to the expansion bag.

[0066] Based on the sealing device described above, this embodiment also describes a method for dynamically sealing a coal seam gas extraction hole, comprising the following steps:

[0067] S1, according to the depth of the gas extraction hole, determine the number of the second expansion units 2, and use the connecting joints to connect the gas extraction pipe 7 and the second slurry inlet pipe 22 to the required length.

[0068] S2, using a drill rod to push the sealing device to a set position in the gas extraction hole.

[0069] S3, open the stop valve 3, use grouting equipment, such as a grouting pump, to inject grout into the first expansion bag 11 and the second expansion bag 21, so that the first expansion bag 11 and the second expansion bag 21 expand and fit tightly with the wall of the gas extraction hole, forming a solid blockage for the coal body fissures;

[0070] The one-way valve 4 of the second expansion unit 2 is opened, and the slurry is injected into the closed chamber 5 to form a liquid plugging for the coal body fissures; a multi-stage solid-liquid-solid sealing structure is formed in the gas extraction hole;

[0071] After the grouting pressure of the grouting pump reaches the set pressure, the pressure is stabilized for a period of time, and then the stop valve 3 is closed.

[0072] S4, manually stretch the gas extraction pipe 7 pipeline to check whether the sealing device is loose, and if it is not loose, the sealing operation is completed.

[0073] S5, performing gas extraction operation through gas extraction equipment, and based on the gas extraction effect, regularly or timely repeating the grouting operation of step S3 to replenish the slurry in the sealing device to enhance the sealing effect.

[0074] In the above steps:

[0075] 1. In step S2, the sealing device is pushed to the set position in the gas extraction hole, which means the distance between the second expansion bag 21 at the bottom of the borehole and the borehole opening is: ≧6m for through-layer drilling and ≧10m for along-layer drilling.

[0076] 2. In step S3, the grouting pressure of the grouting pump is ≥ 3MPa, and the pressure stabilization time is ≥ 20min.

[0077] 3. In step S5, the grouting operation of step S3 is repeated regularly or in a timely manner. The purpose is that after a long period of gas extraction operation, the coal body of the gas extraction hole will be deformed, which may easily cause the pressure of the sealing device to decrease, thereby weakening the sealing quality. Therefore, it is necessary to regularly or in a timely manner replenish slurry to the expansion bag of the sealing device to increase the slurry pressure, so as to ensure that the expansion bag fits tightly with the coal body and at the same time ensure that the coal body cracks between the expansion bags are effectively sealed.

[0078] 4. The slurry injected into the expansion bag needs to be non-coagulable, for example, made of complex polymer materials.

[0079] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A dynamic sealing device for coal seam gas extraction holes, characterized in that: including a first expansion unit and a second expansion unit; The first expansion unit and the second expansion unit are fixedly connected by a connecting rod and can synchronously move forward or backward along the gas extraction hole; The first expansion unit and the second expansion unit can expand after the slurry is poured, and can closely fit the hole wall of the gas extraction hole; and The first expansion unit, the second expansion unit and the gas extraction hole constitute a closed chamber, and the closed chamber is used to store slurry; After the grouting of the first expansion unit, the second expansion unit and the closed chamber is completed, a solid-liquid-solid sealing structure can be formed in the gas extraction hole; The first expansion unit comprises a first expansion bag and a first slurry inlet pipe, one end of the first slurry inlet pipe is connected to the grouting equipment, and the other end extends into the first expansion bag for injecting slurry into the first expansion bag, and a stop valve is arranged on the first slurry inlet pipe; The second expansion unit comprises a second expansion bag, a second slurry inlet pipe and a slurry outlet pipe; one end of the second slurry inlet pipe penetrates through the first expansion bag and extends into the interior of the second expansion bag, and a grouting port is provided inside the second expansion bag; the other end of the second slurry inlet pipe is connected to a grouting device for injecting slurry into the second expansion bag, and under the action of pressure, part of the slurry in the second expansion bag can flow from the slurry outlet pipe into the closed chamber; The second slurry inlet pipe is provided with a stop valve and a one-way valve, and the one-way valve is provided close to the end surface of the second expansion bag; the slurry outlet pipe is provided with a one-way valve; and the first expansion unit is not provided with a slurry outlet pipe.

2. A dynamic sealing device for coal seam gas extraction holes according to claim 1, characterized in that: The second expansion unit is provided in plurality; Adjacent second expansion units are connected by connecting rods and form a closed chamber with the gas extraction hole; After the grouting of the first expansion unit, the second expansion unit and the closed chamber is completed, a plurality of continuous solid-liquid-solid sealing structures can be formed in the gas extraction hole.

3. A dynamic sealing device for coal seam gas extraction holes according to claim 2, characterized in that: The second slurry inlet pipe is configured to be segmented threadedly connected, each segment of the slurry inlet pipe is connected via a connecting joint, and a grouting port is provided in the corresponding second expansion bag.

4. A dynamic sealing device for coal seam gas extraction holes according to claim 1 or 2, characterized in that: The connecting rod is made of nylon plastic or aluminum alloy, and its length is set to 1.5m-2m. Its two ends are threadedly connected to the first expansion unit and the second expansion unit.

5. A dynamic sealing device for coal seam gas extraction holes according to claim 1 or 2, characterized in that: The first expansion bladder and the second expansion bladder are both made of slightly elastic material; in the un-grouted state, their length is set to 1m-1.5m, their thickness is set to 5mm-10mm, and the gap between their outer wall and the inner wall of the gas extraction hole is ≦10mm.

6. A method for dynamically sealing a coal seam gas extraction hole, using the sealing device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, using a drill pipe to push the sealing device to a set position in the gas extraction hole; S2, opening the stop valve, and using a grouting device to inject grout into the first expansion bag and the second expansion bag, so that the first expansion bag and the second expansion bag expand and fit tightly with the wall of the gas extraction hole, thereby forming a solid blockage for the coal body fissures; Under the action of pressure, the one-way valve on the slurry outlet pipe of the second expansion unit opens, and the slurry is injected into the closed chamber from the slurry outlet pipe to form a liquid plugging on the coal body cracks, thereby forming at least one section of solid-liquid-solid sealing hole structure in the gas extraction hole; After the grouting pressure of the grouting pump reaches the set pressure, the pressure is stabilized for a period of time, and then the stop valve is closed; S3, manually stretching the gas extraction pipe line to check whether the sealing device is loose, and if it is not loose, the sealing operation is completed; S4, performing gas extraction operation through gas extraction equipment, and based on the gas extraction effect, repeating the grouting operation of step S2 in a timely manner to supplement the slurry in the sealing device.

7. A method for dynamically sealing a coal seam gas extraction hole according to claim 6, characterized in that: Before starting step S1, the number of second expansion units to be used is determined according to the depth of the gas extraction hole, and the gas extraction pipe and the second slurry inlet pipe are connected to the required length using a connecting joint.

8. A method for dynamically sealing a coal seam gas extraction hole according to claim 6, characterized in that: In step S1, the position is set to the distance between the second expansion bag located at the bottom of the gas extraction hole and the mouth of the gas extraction hole, wherein, if it is a through-layer drilling, the distance is ≧6m; if it is a layer-parallel drilling, the distance is ≧10m.

9. A method for dynamically sealing a coal seam gas extraction hole according to claim 6, characterized in that: In step S2, the grouting pressure of the grouting pump is ≥ 3MPa, and the pressure stabilization time is ≥ 20min.

10. A method for dynamically sealing a coal seam gas extraction hole according to claim 6, characterized in that: The slurry injected into the first expansion bladder bag and the second expansion bladder bag is made of a non-coagulating material.

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