A self-repairing system for sealing fractures and a self-repairing method

Abstract

The present application relates to the technical field of gas extraction in the well, and discloses a hole sealing and fissure self-repairing hole sealing system, which comprises a grouting pipe, a gas extraction pipe, an outer plugging bag, an inner plugging bag, cement, an expanded polymer and a steam generator arranged in a pre-formed borehole. The system injects high-temperature water vapor into the gas extraction pipe to activate the expanded polymer, and the steam injection amount, the fissure opening and the expanded polymer ratio are accurately controlled to ensure that the expanded polymer can fully expand and effectively plug the fissure. After being activated by high temperature, the compressive strength of the expanded polymer is greatly reduced, and the expanded polymer will not cause secondary damage to the surrounding of the hole sealing section, thereby ensuring that the extraction negative pressure of the gas is effectively converted into the flow kinetic energy in the gas extraction process. In addition, the high-temperature water vapor can further promote the desorption of coal seam gas, convert the adsorbed gas into free gas, and ultimately improve the concentration of gas extraction in the borehole, which is worth popularizing.

Description

Technical Field

[0001] This invention belongs to the field of underground gas extraction technology in coal mines, specifically relating to a self-repairing system and method for sealing cracks. Background Technology

[0002] Pre-drainage of coal seam gas through boreholes is an important measure to prevent gas disasters. However, cracks are prone to form around the borehole sealing section, leading to gas leakage and seriously affecting the gas drainage effect. The underground gas drainage effect is directly affected by the quality of the borehole sealing. Therefore, effectively improving the quality of borehole sealing is of great significance to improving the gas drainage effect.

[0003] Borehole sealing is a crucial step in pre-draining coal seam gas. A well-sealed gas drainage borehole ensures a continuous flow of gas into the borehole under negative pressure, achieving efficient gas extraction. Currently, to guarantee the sealing quality of gas drainage boreholes, existing borehole sealing technologies need to comprehensively consider both internal and external leakage issues. Pressurized grouting is currently the most widely used sealing method in underground coal mines, with cement-based materials being the commonly used grouting material. However, traditional cement materials suffer from low early strength and easy shrinkage due to water loss. This can lead to internal leakage between the sealing material itself, the gas drainage pipeline, and the borehole wall, as well as external leakage caused by regenerating fractures in the already sealed surrounding rock.

[0004] Therefore, a new type of self-repairing system and method for sealing cracks is needed to solve the problems of traditional sealing technology, improve gas extraction efficiency, and ensure safe production in mines. Summary of the Invention

[0005] The purpose of this invention is to provide a self-repairing system and method for sealing cracks that is simple in structure, easy to operate, has a good sealing effect, and improves gas extraction efficiency.

[0006] The present invention adopts the following technical solution: a self-repairing system for sealing cracks, comprising a grouting pipe, a gas extraction pipe, an outer sealing bag, an inner sealing bag, and a steam generator. The outer and inner sealing bags are both located in pre-drilled holes. The borehole between the outer and inner sealing bags is the sealing section. The grouting pipe and the gas extraction pipe pass through the outer and inner sealing bags in sequence and extend to the bottom of the borehole. The part of the gas extraction pipe extending to the bottom of the hole has a screen pipe structure. The inner end of the grouting pipe is sealed. The grouting pipe is equipped with one-way valves located inside the outer and inner sealing bags. The grouting pipe is also equipped with a burst valve located between the outer and inner sealing bags. The water inlet of the steam generator is connected to the underground water supply pipeline of the coal mine, and the gas outlet of the steam generator is connected to the outer end of the gas extraction pipe through a rubber hose joint.

[0007] Sealing grout is injected into the outer sealing bag, the inner sealing bag, and the sealing section through grouting pipes. The sealing grout is a uniformly mixed cement grout and expanding polymer.

[0008] The expandable polymer is a temperature-controlled expandable sealant. Temperature-controlled expandable sealants are activated at temperatures above 90°C and begin to expand, exhibiting shape memory properties. The specific preparation steps for the temperature-controlled expandable sealant are as follows: (1) Pour oligomer monomers, crosslinking agents and catalysts in a weight ratio of 100: 40 ~ 50: 0.2 ~ 3 into a container and stir to mix evenly; the oligomer monomers include any one or more of 4,5-epoxytetrahydrophthalic acid diglycidyl ester, phenolic epoxy resin, resorcinol diglycidyl ether, and tetrahydrophthalic acid dimethyl ester epoxy resin; the crosslinking agent is any one or more of diethylenetriamine, dicyandiamide, and m-phenylenediamine; (2) Pour the mixture into the mold and cure it at 60-90°C for 1-4 hours, then at 100-140°C for 1-4 hours; (3) Cool to room temperature and demold. Place the sample in a 100℃ oil bath for 4-6 min and then pressurize it for 8-12 min using a hot compression molding device. (4) After cooling and unloading the external force, a polymer memory board is formed, and then temperature-controlled expansion sealant with different particle sizes is obtained by crushing and granulation.

[0009] The outer circumference of the gas extraction pipe is equipped with a heat-conducting structure located in the sealing section; the grouting pipe is equipped with clamps that contact the inner and outer sides of the outer and inner sealing bags respectively.

[0010] A self-repairing method for fractures in gas drainage boreholes, comprising the following steps: (The method utilizes the aforementioned self-repairing system for sealing fractures to repair the fractures in the gas drainage boreholes.) S1. Drilling operation at a predetermined depth at a pre-set location in the coal mine. After drilling is completed, observe the opening of cracks in the inner wall around the borehole. S2. After ensuring that the borehole structure is intact and unobstructed, install the grouting pipe, gas extraction pipe, outer sealing bag and inner sealing bag, and reserve the specified length of the grouting pipe and gas extraction pipe outside the borehole inlet. S3. Inject the prepared sealing grout into the outer and inner sealing bags through the grouting pipe. The sealing grout is first injected into the outer and inner sealing bags through two one-way valves. After the outer and inner sealing bags expand, they come into close contact with the borehole wall. When the grouting pressure exceeds the opening pressure of the rupture valve, the rupture valve is opened, and the grout is injected into the sealing section through the grouting pipe. When the grout fills the entire sealing section and the grouting pressure is stable, close the valves on the grouting pump and grouting pipe to complete the sealing of the extraction borehole. S4. After sealing the borehole, gas extraction operations are carried out through the outer port of the gas extraction pipe. S5. During the gas extraction process, when cracks are generated around the sealing section due to stress, and a portable gas concentration detector detects a significant drop in the gas extraction concentration, a cylindrical steam generator is installed at the outer port of the gas extraction pipe. S6. Turn on the steam generator and inject high-temperature steam into the borehole through the gas extraction pipe. The high-temperature steam heats the gas extraction pipe, and the heat-conducting structure on the outer circumference of the gas extraction pipe conducts heat to the sealing slurry in the sealing section. When the temperature of the expanding polymer in the sealing slurry is higher than 90°C, the expanding polymer is activated. After the expanding polymer fully expands, it effectively seals the fracture. The steam injection volume, fracture opening, and expanding polymer ratio are precisely controlled. After the steam injection is completed, the steam generator is removed for repeated use next time.

[0011] The proportion of expanded polymer in the cement slurry after uniform mixing with expanded polymer in step S3 is tracked and investigated based on the crack characteristics, which is applicable to different geological conditions and stress environments. When the crack opening is within 2 mm × 1 mm, use an expanded polymer with a weight ratio of 2% and a particle size of 0.18–0.45 mm + a weight ratio of 2% and a particle size of 0.45–0.90 mm. When the crack opening is within 3 mm × 2 mm, use an expanded polymer with a particle size of 0.18–0.45 mm (1% by weight), a particle size of 0.45–0.90 mm (2% by weight), and a particle size of 0.90–2.00 mm (2% by weight). When the crack opening is within 4 mm × 3 mm, use an expanded polymer with a particle size of 0.18–0.45 mm (1% by weight), a particle size of 0.45–0.90 mm (3% by weight), and a particle size of 0.90–2.00 mm (3% by weight).

[0012] The working principle and technical effect of this invention using the above technical solution are as follows: Cement slurry containing expanding polymer is pre-injected into the gas extraction borehole. The expanding polymer expands after being activated by high temperature, thus achieving the effect of preventing stress-induced cracks around the borehole sealing section and causing a significant drop in gas extraction concentration. A detachable cylindrical steam generator is installed at the outer end of the gas extraction pipe. This steam generator features rapid installation and disassembly. High-temperature steam is injected into the borehole through the gas extraction pipe via the steam generator. Heat conduction activates the expanding polymer inside the outer sealing bag, the inner sealing bag, and the sealing section. The steam injection volume is precisely controlled according to the crack opening and the expanding polymer ratio to ensure expansion. The polymer can fully expand and effectively seal the fractures. After the high-temperature steam injection is completed, the steam generator is removed for recycling. The compressive strength of the expanded polymer is greatly reduced after being activated by high temperature. After expansion, it will not cause secondary damage to the surrounding area of ​​the sealing section, thus ensuring that the negative pressure of gas extraction is effectively converted into the flow kinetic energy during the gas extraction process. In addition, the high-temperature water vapor injected into the borehole can further promote the desorption of coal seam gas, turning adsorbed gas into free gas, thus ensuring that the negative pressure of gas extraction is effectively converted into the flow kinetic energy during the gas extraction process, ultimately achieving an increase in the gas extraction concentration in the borehole. This invention has broad application prospects and significant economic and social value. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention during normal gas drainage; Figure 2 This is a schematic diagram of the connection structure between a detachable cylindrical steam generator and a gas extraction pipe.

[0014] Figure 3 This is a schematic diagram of the self-healing mechanism of cracks during the operation of the present invention. Detailed Implementation

[0015] The present invention will now be described clearly and completely with reference to the accompanying drawings and embodiments: like Figures 1 to 3As shown, a self-repairing system for sealing cracks according to the present invention includes a grouting pipe 3, a gas extraction pipe 1, an outer sealing bag 4, an inner sealing bag 5, and a steam generator 2. The outer sealing bag 4 and the inner sealing bag 5 are both located within a pre-drilled borehole 7. The borehole 7 between the outer sealing bag 4 and the inner sealing bag 5 is the sealing section. The grouting pipe 3 and the gas extraction pipe 1 sequentially pass through the outer sealing bag 4 and the inner sealing bag 5 and extend into the bottom of the borehole 7. The extraction pipe 1 has a screen pipe structure at the bottom of the hole. The inner port of the grouting pipe 3 is sealed. The grouting pipe 3 is equipped with a one-way valve 9 located inside the outer sealing bag 4 and the inner sealing bag 5. The grouting pipe 3 is equipped with a burst valve 10 located between the outer sealing bag 4 and the inner sealing bag 5. The water inlet of the steam generator 2 is connected to the underground water supply pipeline of the coal mine. The gas outlet of the steam generator 2 is connected to the outer port of the gas extraction pipe 1 through a rubber hose joint 11.

[0016] Sealing grout 6 is injected into the outer sealing bag 4, the inner sealing bag 5, and the sealing section through the grouting pipe 3. The sealing grout 6 is a uniformly mixed cement grout 14 and expanding polymer (SDP) 12.

[0017] Expandable polymer 12 is a temperature-controlled expandable sealant. Temperature-controlled expandable sealants are activated at temperatures above 90°C and begin to expand, exhibiting shape memory properties. The specific preparation steps for the temperature-controlled expandable sealant are as follows: (1) Pour oligomer monomers, crosslinking agents and catalysts in a weight ratio of 100: 40 ~ 50: 0.2 ~ 3 into a container and stir to mix evenly; the oligomer monomers include any one or more of 4,5-epoxytetrahydrophthalic acid diglycidyl ester, phenolic epoxy resin, resorcinol diglycidyl ether, and tetrahydrophthalic acid dimethyl ester epoxy resin; the crosslinking agent is any one or more of diethylenetriamine, dicyandiamide, and m-phenylenediamine; (2) Pour the mixture into the mold and cure it at 60-90°C for 1-4 hours, then at 100-140°C for 1-4 hours; (3) Cool to room temperature and demold. Place the sample in a 100℃ oil bath for 4-6 min and then pressurize it for 8-12 min using a hot compression molding device. (4) After cooling and unloading the external force, a polymer memory board is formed, and then temperature-controlled expansion sealant with different particle sizes is obtained by crushing and granulation.

[0018] The outer circumference of the gas extraction pipe 1 is provided with a heat-conducting structure 13 located in the sealing section; the grouting pipe 3 is provided with clamps 8 that contact the inner and outer sides of the outer sealing bag 4 and the inner sealing bag 5 respectively.

[0019] A self-repairing method for fractures in gas drainage boreholes, comprising the following steps: (The method utilizes the aforementioned self-repairing system for sealing fractures to repair the fractures in the gas drainage boreholes.) S1. Drill hole 7 at a predetermined depth at a pre-set location in the coal mine. After drilling hole 7 is completed, observe the crack opening on the inner wall around drilling hole 7. S2. After ensuring that the structure of borehole 7 is intact and unobstructed, install grouting pipe 3, gas extraction pipe 1, outer sealing bag 4 and inner sealing bag 5, and reserve a specified length of grouting pipe 3 and gas extraction pipe 1 outside the inlet of borehole 7. S3. The prepared sealing grout 6 is injected into the outer sealing bag 4 and the inner sealing bag 5 through the grouting pipe 3. The sealing grout 6 is first injected into the outer sealing bag 4 and the inner sealing bag 5 through two one-way valves 9. After the outer sealing bag 4 and the inner sealing bag 5 expand, they come into close contact with the borehole wall 7. When the grouting pressure exceeds the opening pressure of the rupture valve 10, the rupture valve 10 is opened, and the grout is injected into the sealing section through the grouting pipe 3. When the grout fills the entire sealing section and the grouting pressure is stable, the valves on the grouting pump and the grouting pipe 3 are closed to complete the sealing of the extraction borehole 7. S4. After sealing the borehole, gas extraction is carried out through the outer port of the gas extraction pipe 1 to the borehole 7. S5. During the gas extraction process, when cracks are generated around the sealing section due to stress, and a portable gas concentration detector detects a significant drop in the gas extraction concentration, a cylindrical steam generator 2 is installed at the outer port of the gas extraction pipe 1. S6. Turn on the steam generator 2 and inject high-temperature steam into the borehole 7 through the gas extraction pipe 1. The high-temperature steam heats the gas extraction pipe 1, and the heat-conducting structure 13 on the outer circle of the gas extraction pipe 1 conducts heat to the sealing slurry 6 in the sealing section. When the temperature of the expanding polymer 12 in the sealing slurry 6 is higher than 90°C, the expanding polymer 12 is activated. After the expanding polymer 12 fully expands, it effectively seals the crack. The steam injection volume, the crack opening 15, and the ratio of expanding polymer 12 are precisely controlled. After the steam injection is completed, the steam generator 2 is removed for repeated use next time.

[0020] The proportion of expanded polymer 12 in the cement slurry 14 after uniform mixing with expanded polymer 12 in step S3 is investigated based on the crack characteristics, and is applicable to different geological conditions and stress environments. When the crack 15 opening is within 2 mm × 1 mm, use 2% by weight of expanded polymer 12 with a particle size of 0.18 to 0.45 mm + 2% by weight of expanded polymer 12 with a particle size of 0.45 to 0.90 mm. When the crack 15 opening is within 3 mm × 2 mm, use an expanded polymer 12 with a particle size of 0.18 to 0.45 mm (1% by weight), a particle size of 0.45 to 0.90 mm (2% by weight), and a particle size of 0.90 to 2.00 mm (2% by weight). When the crack 15 opening is within 4 mm × 3 mm, use an expanded polymer 12 with a particle size of 0.18–0.45 mm (1% by weight), a particle size of 0.45–0.90 mm (3% by weight), and a particle size of 0.90–2.00 mm (3% by weight).

[0021] The above embodiments are for illustrative purposes only and are not intended to limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A self-healing system for sealing cracks, characterized in that: The system includes a grouting pipe, a gas extraction pipe, an outer sealing bag, an inner sealing bag, and a steam generator. Both the outer and inner sealing bags are located in pre-drilled holes. The borehole between the outer and inner sealing bags is the sealing section. The grouting pipe and the gas extraction pipe pass through the outer and inner sealing bags in sequence and extend into the bottom of the borehole. The part of the gas extraction pipe that extends to the bottom of the hole has a screen pipe structure. The inner end of the grouting pipe is sealed. The grouting pipe is equipped with one-way valves located inside the outer and inner sealing bags. The grouting pipe is also equipped with a burst valve located between the outer and inner sealing bags. The water inlet of the steam generator is connected to the underground water supply pipeline of the coal mine, and the gas outlet of the steam generator is connected to the outer end of the gas extraction pipe through a rubber hose joint. Sealing grout is injected into the outer sealing bag, the inner sealing bag, and the sealing section through grouting pipes. The sealing grout is a uniformly mixed cement grout and expanding polymer. Expandable polymer is a temperature-controlled expandable sealant. It is activated at temperatures above 90°C and begins to expand, exhibiting shape memory properties. The outer circumference of the gas extraction pipe is equipped with a heat-conducting structure located in the sealing section.

2. The self-healing system for sealing cracks according to claim 1, characterized in that: The specific preparation steps for temperature-controlled expansion sealant are as follows: (1) Pour oligomer monomers, crosslinking agents and catalysts in a weight ratio of 100:40~50:0.2~3 into a container and stir to mix evenly; the oligomer monomers include any one or more of 4,5-epoxytetrahydrophthalic acid diglycidyl ester, phenolic epoxy resin, resorcinol diglycidyl ether, and tetrahydrophthalic acid dimethyl ester epoxy resin; the crosslinking agent is any one or more of diethylenetriamine, dicyandiamide, and m-phenylenediamine; (2) Pour the mixture into the mold and cure it at 60~90℃ for 1~4 hours, then at 100~140℃ for 1~4 hours; (3) Cool to room temperature and demold. Place the sample in a 100°C oil bath for 4-6 minutes, and then pressurize and hold for 8-12 minutes using a hot compression molding device. (4) After cooling and unloading the external force, a polymer memory board is formed, and then temperature-controlled expansion sealant with different particle sizes is obtained by crushing and granulation.

3. The self-healing system for sealing cracks according to claim 2, characterized in that: The grouting pipe is equipped with clamps that contact the inner and outer sides of the outer and inner sealing bags, respectively.

4. A method for self-repairing fractures in gas drainage boreholes, wherein the method uses the self-repairing system for sealing fractures as described in claim 3 to repair fractures in gas drainage boreholes, characterized in that: The steps are as follows: S1. Drilling operation at a predetermined depth at a pre-set location in the coal mine. After drilling is completed, observe the opening of cracks in the inner wall around the borehole. S2. After ensuring that the borehole structure is intact and unobstructed, install the grouting pipe, gas extraction pipe, outer sealing bag and inner sealing bag, and reserve the specified length of the grouting pipe and gas extraction pipe outside the borehole inlet. S3. Inject the prepared sealing grout into the outer and inner sealing bags through the grouting pipe. The sealing grout is first injected into the outer and inner sealing bags through two one-way valves. After the outer and inner sealing bags expand, they come into close contact with the borehole wall. When the grouting pressure exceeds the opening pressure of the rupture valve, the rupture valve is opened, and the grout is injected into the sealing section through the grouting pipe. When the grout fills the entire sealing section and the grouting pressure is stable, close the valves on the grouting pump and grouting pipe to complete the sealing of the extraction borehole. S4. After sealing the borehole, gas extraction operations are carried out through the outer port of the gas extraction pipe. S5. During the gas extraction process, when cracks are generated around the sealing section due to stress, and a portable gas concentration detector detects a significant drop in the gas extraction concentration, a cylindrical steam generator is installed at the outer port of the gas extraction pipe. S6. Turn on the steam generator and inject high-temperature steam into the borehole through the gas extraction pipe. The high-temperature steam heats the gas extraction pipe, and the heat-conducting structure on the outer circumference of the gas extraction pipe conducts heat to the sealing slurry in the sealing section. When the temperature of the expanding polymer in the sealing slurry is higher than 90°C, the expanding polymer is activated. After the expanding polymer fully expands, it effectively seals the fracture. The steam injection volume, fracture opening, and expanding polymer ratio are precisely controlled. After the steam injection is completed, the steam generator is removed for repeated use next time.

5. The self-repairing method for gas drainage borehole fractures according to claim 4, characterized in that: The proportion of expanded polymer in the cement slurry after uniform mixing with expanded polymer in step S3 is tracked and investigated based on the crack characteristics, which is applicable to different geological conditions and stress environments. When the crack opening is within 2mm×1mm, use an expanded polymer with a weight ratio of 2% and a particle size of 0.18-0.45mm and a weight ratio of 2% and a particle size of 0.45-0.90mm. When the crack opening is within 3mm×2mm, use an expanded polymer with a particle size of 0.18-0.45mm (1% by weight), 0.45-0.90mm (2% by weight), and 0.90-2.00mm (2% by weight). When the crack opening is within 4mm×3mm, use an expanded polymer with a particle size of 0.18-0.45mm at a weight ratio of 1%, 0.45-0.90mm at a weight ratio of 3%, and 0.90-2.00mm at a weight ratio of 3%.

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