Method for regulating sealing of borehole during gas extraction

Abstract

The application discloses a drilling hole sealing regulation method in a gas extraction process, which comprises the following steps: installing a hole sealing and pressure supplementing device to an extraction pipe and pushing it into a drilling hole from back to front; injecting water into the hole sealing and pressure supplementing device; injecting grout into the hole sealing and pressure supplementing device to complete the first hole sealing; extracting gas in the drilling hole through the extraction pipe; in the gas extraction process, when the gas extraction concentration is detected to be reduced, water is injected to supplement pressure; the gas extraction is continued, and if the gas extraction concentration is detected to be reduced, the water injection and pressure supplementing step is repeated. The application reduces the cost while ensuring the sealing effect, is safe and reliable, the grout injected during the hole sealing has better anti-shrinkage and lower permeability, so that the hole sealing section between two capsules has a longer sealing effect; through real-time monitoring of parameters such as the pressure and gas concentration in the drilling hole, liquid is injected into the rubber pipe in real time to supplement pressure and enhance the sealing property of the drilling hole, so that the safe and efficient production of the mine is ensured.

Description

Technical Field

[0001] This invention belongs to the field of mining engineering technology, specifically relating to a method for controlling borehole sealing during gas extraction. Background Technology

[0002] As coal mining depth and intensity increase, the gas content and emission rate in coal seams become increasingly serious, making gas drainage a crucial means of ensuring safe coal mine production. However, traditional borehole sealing methods often result in reduced gas drainage effectiveness in the later stages of drilling due to the formation of gas leakage channels caused by peri-hole fissures.

[0003] In existing technologies, sealing gas drainage boreholes typically employs a "two-plug-one-injection" method, using a gas bag and grouting material to form a sealing section. However, due to factors such as negative pressure during borehole extraction and mining disturbances, cracks easily appear on the outer circumference of the borehole wall, leading to gas leakage and consequently affecting gas extraction efficiency. To address this issue, this invention develops a borehole sealing control method based on the traditional "two-plug-one-injection" method. This method achieves continuous and effective sealing of the borehole during gas extraction, thereby improving gas extraction efficiency. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems in the prior art, the present invention provides a method for controlling the sealing performance of boreholes during gas extraction, which is easy to operate, allows for multiple adjustments to the sealing, has a good sealing effect, and is highly reliable.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for controlling borehole sealing during gas drainage, comprising the following steps:

[0006] S1. Install the sealing and pressure-repairing device onto the extraction pipe and push it into the borehole from back to front.

[0007] S2. Inject water into the sealing and pressurizing device. Stop injecting water when the water injection pressure is not less than the predetermined grouting and sealing pressure P.

[0008] S3. Next, grout is injected into the sealing and pressure replenishing device. When the grouting pressure reaches the grouting sealing pressure P, the first sealing is completed.

[0009] S4. Extract gas from the borehole through the extraction pipe;

[0010] S5. During the gas extraction process, if a decrease in gas extraction concentration is detected, water is injected into the sealing and pressurizing device to replenish pressure in accordance with step S2. When the gas concentration is detected to rise and return to the original state, water injection and pressurization are stopped.

[0011] S6. Continue gas extraction. If a decrease in gas extraction concentration is detected, repeat step S5.

[0012] The sealing and pressurizing device includes a front bladder and a rear bladder arranged at intervals on the extraction pipe. A grouting pipe parallel to the extraction pipe is provided between the front bladder and the rear bladder. The grouting pipe is equipped with a front one-way valve located in the front bladder, a rear one-way valve located in the rear bladder, and a burst valve located between the front bladder and the rear bladder. The device is characterized in that the extraction pipe is also equipped with a radial expander located between the front bladder and the rear bladder, and the rear end of the radial expander is connected to an injection pipeline passing through the rear bladder.

[0013] The radial expander includes a rubber tube coaxially disposed outside the extraction tube. A rigid thin tube is fixedly disposed on the inner circle of the rubber tube. The inner circles of the front and rear sides of the rigid thin tube are respectively provided with central supports that are sleeved on the extraction tube. The wall of the rubber tube is a double-layer structure with a sealed cavity. Several slurry permeable holes that are open inward and outward along the radial direction are provided on the rubber tube and the rigid thin tube. The rear end of the rubber tube is provided with an injection port that is connected to the front end of the injection pipeline.

[0014] The central support includes a positioning ring fitted onto the extraction pipe. The positioning ring is threaded with a top screw that presses against the extraction pipe. Three support rods are evenly arranged on the outer circle of the positioning ring along the circumferential direction. The length of each support rod is along the radial direction of the positioning ring. The outer end of the support rod is fixedly connected to the inner circle of the rigid thin tube.

[0015] The inlet end of the injection pipeline is connected to a storage tank, and an injection pump, valve and pressure gauge are installed sequentially along the liquid flow direction on the injection pipeline.

[0016] The specific process of step S2 is as follows: open the valve, start the injection pump, and inject clean water into the rubber tube through the injection pipeline. The rubber tube expands when water is injected inside, and the outer circle of the rubber tube is tightly pressed against the inner wall of the borehole. When the injection pressure is not less than the predetermined grouting and sealing pressure P, close the injection pump and the valve.

[0017] The specific process of step S3 is as follows: grout is injected into the front and rear sluice bags through the grouting pipe. After the front and rear sluice bags are filled with grout, the grouting pressure is increased to reach the bursting pressure P1 of the bursting valve (e.g., 1.5 MPa-2 MPa). Then the bursting valve is opened, and the grout is injected into the borehole between the front and rear sluice bags. The grout is injected into the cracks in the borehole wall through the grouting hole on the rubber tube. When the grouting pressure reaches the grouting sealing pressure P, the first sealing is completed.

[0018] The specific process of step S5 is as follows: During the gas extraction process, when a decrease in gas extraction concentration is detected, the valve on the injection pipeline is opened, the injection pump is started, and clean water is injected into the rubber tube again. The rubber tube continues to expand, and the outer circle of the rubber tube further presses against and seals the inner wall of the borehole. When the injection pressure reaches the set pressure replenishment and sealing pressure P2 and is maintained for a period of time, when the gas concentration is detected to rise and return to its original state, the injection pump and valve are closed.

[0019] The slurry is made by uniformly mixing environmentally friendly sealing material and water in a 1:1 mass ratio;

[0020] The environmentally friendly sealing material is made up of the following raw materials in the following weight ratio: 700-800 parts silicate cement, 30-50 parts superabsorbent resin, 30-50 parts coal gangue powder, 30-50 parts quick-setting agent and 30-50 parts expansion agent; the particle size of all raw materials is 80-200 mesh.

[0021] By weight percentage, the superabsorbent polymer is a mixture of 75% sodium polyacrylate, 24% polyacrylic acid, 0.7% SiO2 and 0.3% Al2(SO4)3.

[0022] The silicate cement is grade 42.5 ordinary silicate cement;

[0023] Coal gangue powder is made from crushed coal gangue produced during coal mining.

[0024] By adopting the above technical solution, compared with the prior art, the present invention has the following technical effects:

[0025] (1) Improve sealing effect: By setting a rubber tube between the front and rear bladder bags for dynamic pressure sealing, the leakage caused by cracks around the borehole can be effectively reduced and the gas extraction efficiency can be improved.

[0026] (2) The positioning ring inside the radial expander is fixedly connected to the extraction pipe with a set screw, so as to avoid axial movement of the radial expander when it is installed into the borehole.

[0027] (3) When using it, first inject liquid into the rubber tube to expand the rubber tube and press the outer circle of the rubber tube against the inner wall of the borehole. Then, grout is injected. After grouting, the grout fills the inner circle space of the rubber tube and supports the rigid thin tube. This ensures that the rubber tube can only expand radially outward when it expands. At the same time, the grout is injected into the cracks in the inner wall of the borehole through the liquid permeation hole on the rubber tube. Since the liquid injection pressure in the rubber tube is not less than the predetermined grouting sealing pressure P, the grout will not cover the outer circle of the rubber tube. Even after the grout solidifies, the reliability of the rubber tube can be ensured to be repressurized and expanded again.

[0028] (4) The rigid thin tube is designed to facilitate the fixed connection with the support rod, ensure that the rubber tube remains in an extended state when installed into the borehole, and provide support for the expansion of the rubber tube, so that the rubber tube can only expand outward in the radial direction.

[0029] (5) Using coal gangue in environmentally friendly sealing materials achieves comprehensive utilization of industrial solid waste. Adding an expanding agent to the environmentally friendly sealing material allows for expansion during solidification, avoiding cement shrinkage and providing active support to the borehole wall. This prevents shrinkage in the sealing section from forming leakage channels and reduces gas leakage during gas extraction. Adding superabsorbent resin to the environmentally friendly sealing material reduces its permeability, enhances its sealing properties, and improves the sealing effect. Furthermore, the proportions of various raw materials in the environmentally friendly sealing material can be adjusted to achieve more combination options.

[0030] In summary, this invention reduces costs while ensuring sealing performance, is safe and reliable, and the grout injected during grouting and sealing has better anti-shrinkage properties and lower permeability, thus enabling a longer-lasting sealing effect in the sealing section between the two bags. By real-time monitoring of parameters such as pressure and gas concentration inside the borehole, real-time injection of liquid into the rubber tube enhances the sealing performance of the borehole, ensuring safe and efficient mine production. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the sealing and pressure-repairing device in this invention;

[0032] Figure 2 yes Figure 1 Schematic diagram of the end face structure of the rubber expansion tube. Detailed Implementation

[0033] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0034] like Figure 1 and Figure 2 As shown, the borehole sealing control method in the gas extraction process of the present invention includes the following steps:

[0035] S1. Install the sealing and pressure-repairing device onto the extraction pipe 1 and push it into the borehole 21 from back to front.

[0036] The sealing and pressurizing device includes a front bladder 3 and a rear bladder 2 spaced apart on the extraction pipe 1. A grouting pipe 4 parallel to the extraction pipe 1 is provided between the front bladder 3 and the rear bladder 2 (the grout tank, grouting pump, pressure gauge, grouting valve and other components connected to the inlet of the grouting pipe 4 are not shown in the figure). The grouting pipe 4 is provided with a front one-way valve 6 located in the front bladder 3, a rear one-way valve 5 located in the rear bladder 2, and a burst valve 7 located between the front bladder 3 and the rear bladder 2. The feature is that the extraction pipe 1 is also provided with a radial expander located between the front bladder 3 and the rear bladder 2. The rear end of the radial expander is connected to an injection pipeline 8 that passes through the rear bladder 2.

[0037] The radial expander includes a rubber tube 9 coaxially disposed outside the extraction pipe 1. A rigid thin tube 10 is fixedly disposed on the inner circle of the rubber tube 9. The inner circles of the front and rear sides of the rigid thin tube 10 are respectively provided with central supports 11 sleeved on the extraction pipe 1. The tube wall of the rubber tube 9 is a double-layer structure with a sealed cavity. Several slurry permeation holes 12 that are radially permeable inside and outside are provided on the rubber tube 9 and the rigid thin tube 10. The rear end of the rubber tube 9 is provided with an injection port 13 connected to the front end of the injection pipeline 8.

[0038] The central support 11 includes a positioning ring 14 fitted onto the extraction pipe 1. The positioning ring 14 is threaded with a top screw 15 that presses against the extraction pipe 1. Three support rods 16 are evenly arranged on the outer circle of the positioning ring 14 along the circumferential direction. The length of each support rod 16 is along the radial direction of the positioning ring 14. The outer end of the support rod 16 is fixedly connected to the inner circle of the rigid thin tube 10.

[0039] The inlet end of the injection pipeline 8 is connected to the storage tank 17. The injection pipeline 8 is equipped with an injection pump 18, a valve 19 and a pressure gauge 20 in sequence along the liquid flow direction.

[0040] S2. Open valve 19, start injection pump 18, and inject clean water into rubber tube 9 through injection pipeline 8. The rubber tube 9 expands with water injection, and the outer circle of rubber tube 9 is tightly pressed against the inner wall of borehole 21. When the injection pressure is not less than the predetermined grouting sealing pressure P, close injection pump 18 and valve 19.

[0041] S3. Grout is injected into the front bag 3 and the rear bag 2 through the grouting pipe 4. After the front bag 3 and the rear bag 2 are filled with grout, the grouting pressure is increased to reach the bursting pressure P1 of the bursting valve 7 (e.g., 1.5Mpa-2Mpa). Then the bursting valve 7 is opened, and the grout is injected into the borehole 21 between the front bag 3 and the rear bag 2. The grout is injected into the cracks in the wall of the borehole 21 through the grouting hole 12 on the rubber tube 9. When the grouting pressure reaches the grouting sealing pressure P, the first sealing is completed.

[0042] S4. Extract gas from borehole 21 through extraction pipe 1;

[0043] S5. During the gas extraction process, when a decrease in gas extraction concentration is detected, open valve 19 on injection pipeline 8, start injection pump 18, and inject clean water into rubber tube 9 again. Rubber tube 9 continues to expand, and the outer circle of rubber tube 9 further presses against the inner wall of borehole 21 to seal. When the injection pressure reaches the set pressure replenishment and sealing pressure P2 and is maintained for a period of time, when the gas concentration is detected to rise and return to the original state, close injection pump 18 and valve 19.

[0044] S6. Continue gas extraction. If a decrease in gas extraction concentration is detected, repeat step S5.

[0045] The slurry mentioned in step S3 is made by uniformly mixing environmentally friendly sealing material and water in a 1:1 mass ratio;

[0046] The environmentally friendly sealing material is made up of the following raw materials in the following weight ratio: 700-800 parts silicate cement, 30-50 parts superabsorbent resin, 30-50 parts coal gangue powder, 30-50 parts quick-setting agent and 30-50 parts expansion agent; the particle size of all raw materials is 80-200 mesh.

[0047] By weight percentage, the superabsorbent polymer is a mixture of 75% sodium polyacrylate, 24% polyacrylic acid, 0.7% SiO2 and 0.3% Al2(SO4)3.

[0048] The silicate cement is grade 42.5 ordinary silicate cement;

[0049] Coal gangue powder is made from crushed coal gangue produced during coal mining.

[0050] The above embodiments illustrate the basic principles and features of the present invention, but are merely preferred embodiments and are not limited to these embodiments. Those skilled in the art, inspired by this patent, can make many modifications and improvements without departing from the spirit and scope of the claims, all of which fall within the scope of protection of the present invention. Therefore, the scope of this patent and its protection should be determined by the appended claims.

Claims

1. A method for controlling borehole sealing during gas drainage, characterized in that: Includes the following steps: S1. Install the sealing and pressure-replenishing device onto the extraction pipe and push it into the borehole from back to front; the sealing and pressure-replenishing device includes a front bladder and a rear bladder that are spaced apart on the extraction pipe. A grouting pipe parallel to the extraction pipe is provided between the front bladder and the rear bladder. The grouting pipe is provided with a front one-way valve located in the front bladder, a rear one-way valve located in the rear bladder, and a burst valve located between the front bladder and the rear bladder. The extraction pipe is also provided with a radial expander located between the front bladder and the rear bladder. The rear end of the radial expander is connected to an injection pipeline that passes through the rear bladder. The radial expander includes a rubber tube coaxially disposed outside the extraction tube. A rigid thin tube is fixedly disposed on the inner circle of the rubber tube. The inner circles of the front and rear sides of the rigid thin tube are respectively provided with central supports that are sleeved on the extraction tube. The wall of the rubber tube is a double-layer structure with a sealed cavity. Several slurry permeable holes with radial direction are provided on the rubber tube and the rigid thin tube. The rear end of the rubber tube is provided with an injection port connected to the front end of the injection pipeline. The inlet end of the injection pipeline is connected to a storage tank. An injection pump, a valve and a pressure gauge are sequentially disposed on the injection pipeline along the liquid flow direction. S2. Open the valve and start the injection pump to inject clean water into the rubber tube through the injection pipeline. The rubber tube expands as water is injected inside, and the outer circle of the rubber tube is tightly pressed against the inner wall of the borehole. When the injection pressure is not less than the predetermined grouting and sealing pressure P, close the injection pump and valve. S3. Inject grout into the front and rear sluice bags through the grouting pipe. After the front and rear sluice bags are filled with grout, continue to increase the grouting pressure. When the rupture pressure P1 of the rupture valve is reached, the rupture valve opens and the grout is injected into the borehole between the front and rear sluice bags. The grout is injected into the cracks in the borehole wall through the grouting hole on the rubber tube. When the grouting pressure reaches the grouting sealing pressure P, the first sealing is completed. S4. Extract gas from the borehole through the extraction pipe; S5. During the gas extraction process, when a decrease in gas extraction concentration is detected, open the valve on the injection pipeline, start the injection pump, and inject clean water into the rubber tube again. The rubber tube continues to expand, and the outer circle of the rubber tube further presses against and seals the inner wall of the borehole. When the injection pressure reaches the set pressure replenishment and sealing pressure P2 and is maintained for a period of time, and when the gas concentration is detected to rise and return to its original state, close the injection pump and valve. S6. Continue gas extraction. If a decrease in gas extraction concentration is detected, repeat step S5.

2. The method for controlling borehole sealing during gas extraction according to claim 1, characterized in that: The central support includes a positioning ring fitted onto the extraction pipe. The positioning ring is threaded with a top screw that presses against the extraction pipe. Three support rods are evenly arranged on the outer circle of the positioning ring along the circumferential direction. The length of each support rod is along the radial direction of the positioning ring. The outer end of the support rod is fixedly connected to the inner circle of the rigid thin tube.

3. The method for controlling borehole sealing during gas extraction according to claim 1, characterized in that: The slurry is made by uniformly mixing environmentally friendly sealing material and water in a 1:1 mass ratio; The environmentally friendly sealing material is made up of the following raw materials in the following weight ratio: 700-800 parts silicate cement, 30-50 parts superabsorbent resin, 30-50 parts coal gangue powder, 30-50 parts quick-setting agent and 30-50 parts expansion agent; the particle size of all raw materials is 80-200 mesh.

4. The method for controlling borehole sealing during gas extraction according to claim 3, characterized in that: By weight percentage, the superabsorbent polymer is a mixture of 75% sodium polyacrylate, 24% polyacrylic acid, 0.7% SiO2 and 0.3% Al2(SO4)3. The silicate cement is grade 42.5 ordinary silicate cement; Coal gangue powder is made from crushed coal gangue produced during coal mining.

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