Gas extraction drill hole sealing system and method

Abstract

The invention discloses a gas extraction drill hole sealing system and method, and the system comprises a bag assembly which comprises an inner bag and an outer bag, and the inner bag and the outer bag are respectively disposed on the inner side and the outer side of a drill hole to form a hole sealing space; the hole sealing pipe is arranged in the extending direction of the drill hole and arranged in the coal seam, the grouting pump is configured to pump the sodium silicate solution in the sodium silicate solution storage tank into the hole sealing pipe, and the sodium silicate solution flows into the coal seam through the hole sealing pipe; the carbon dioxide conveying assembly and the gas injection pipe are arranged in the extending direction of the drill hole and penetrate through the inner bag and the outer bag, the gas injection pump is configured to pump carbon dioxide gas in the carbon dioxide storage tank into the gas injection pipe, and the carbon dioxide gas is discharged into the hole sealing space through the gas injection pipe; the extraction pipe assembly comprises an extraction pipe, and the extraction pipe penetrates into the inner side of the hole sealing space and is configured to extract gas located in the drill hole; and the air exhaust assembly comprises an air exhaust pipe and is configured to form a negative pressure environment in the hole sealing space.

Description

Technical Field

[0001] This invention relates to the field of sealing boreholes in gas drainage, and more particularly to a sealing system and method for gas drainage boreholes. Background Technology

[0002] Coal is my country's dominant energy source, occupying a primary position in the primary energy production and consumption structure. my country's robust demand for coal has led to a rapid shift in coal mining towards deeper mines, consequently increasing the difficulty of gas control. However, coal gas is not only a hazard that easily causes coal mine accidents, but it is also a usable, efficient, and clean energy source. Therefore, achieving efficient coal mine gas extraction is of great significance for gas disaster control and resource utilization.

[0003] As a major factor affecting gas drainage efficiency, borehole sealing in gas drainage drilling is still hampered by current sealing methods, which suffer from long material curing times, high costs, and ineffective pore sealing. This proposed method aims to solve these problems, effectively improve gas drainage efficiency and safety, and can be applied to borehole sealing operations in coal mine gas drainage drilling. Summary of the Invention

[0004] This solution addresses the problems and needs raised above by proposing a gas extraction borehole sealing system and sealing method. Due to the adoption of the following technical features, it can achieve the above-mentioned technical objectives and bring about several other technical benefits.

[0005] One object of the present invention is to provide a gas drainage borehole sealing system, comprising: The bag assembly, including an inner bag and an outer bag, is placed inside and outside the borehole, respectively, to form a sealing space. At least one sodium silicate delivery assembly includes: a sodium silicate solution storage tank, a grouting pump, and a sealing pipe connected in sequence, wherein the sealing pipe is arranged along the extension direction of the borehole and placed in the coal seam, and the grouting pump is configured to pump sodium silicate solution from the sodium silicate solution storage tank into the sealing pipe and flow from the sealing pipe into the coal seam; A carbon dioxide delivery assembly includes: a carbon dioxide storage tank, an injection pump, and an injection pipe connected in sequence, wherein the injection pipe is arranged along the extension direction of the borehole and passes through the inner bladder and the outer bladder, and the injection pump is configured to pump carbon dioxide gas from the carbon dioxide storage tank into the injection pipe and discharge it into the sealing space through the injection pipe. The extraction tube assembly includes an extraction tube and an extraction pump connected thereto. The extraction tube is sequentially inserted into the outer bladder and the inner bladder to a borehole inside the inner bladder. The extraction pump is configured to extract methane gas located in the borehole. An air extraction assembly includes an air extraction pipe and an air extraction pump connected thereto, wherein the air extraction pipe extends into the sealed space and the air extraction pump is configured to create a negative pressure environment within the sealed space. Sodium silicate is used as a sealing material. It reacts with carbon dioxide to generate silica colloid, which solidifies to form a sealant, thereby sealing the coal seam where the pore space is located.

[0006] In addition, the gas drainage borehole sealing system and sealing method according to the present invention may also have the following technical features: In one example of the present invention, the invention further includes: a pressure sensor located in the sealing space; when sodium silicate solution is injected into the coal seam, the pressure sensor is configured to determine whether the sodium silicate solution has been sufficiently injected into the coal seam based on the pressure data inside the sealing space; when carbon dioxide is injected into the sealing space, the pressure sensor is configured to determine whether the silica gel has been cured based on the pressure data inside the sealing space; wherein, when the pressure data detected by the pressure sensor is stable, the silica gel has been cured.

[0007] In one example of the present invention, the sodium silicate delivery assembly comprises a plurality of such assemblies, which are spaced apart along the circumferential direction of the borehole.

[0008] In one example of the invention, in two adjacent sodium silicate delivery assemblies, the crack range radiated by one sodium silicate delivery assembly overlaps with the crack range radiated by the other sodium silicate delivery assembly.

[0009] In one example of the present invention, the sodium silicate delivery assembly is located close to the borehole, and the radial distance between the assembly and the borehole is no more than 0.5m.

[0010] In one example of the present invention, The sealing tube has multiple liquid passage holes, which are spaced apart along the length of the sealing tube, with the distance between two adjacent liquid passage holes not greater than 20mm, and the inner diameter of each liquid passage hole not less than 5mm. The air injection pipe has multiple air vents, which are spaced apart along the length of the air injection pipe. The distance between two adjacent air vents is no more than 20 mm, and the inner diameter of each air vent is no less than 5 mm.

[0011] In one example of the present invention, the chemical reaction formula for sealing the coal seam where the sealing space is located is as follows: CO2+Na2SiO3+H2O→H2SiO3+Na2CO3 In the formula, H2SiO3 is solid silicone used to fill the gaps in the drilled hole (210).

[0012] In one example of the invention, the sodium silicate solution is composed of a mixture of sodium silicate and water.

[0013] Another object of the present invention is to provide a sealing method for a gas extraction borehole sealing system as described above, comprising the following steps: S10: Borehole pretreatment: Determine the borehole diameter and depth according to the extraction needs and actual site conditions, clean the rock powder and accumulated water in the borehole, and ensure that the borehole wall is dry; S20: Inflation tube installation: After the inner and outer bladders are arranged to form a sealing space, insert the inflation tube into the sealing space and preliminarily seal the gap between the inflation tube and the outer bladder with gauze or rubber ring. S30: Sealing pipe installation: Sealing pipes are arranged in a ring around the gas extraction borehole. The radius of the ring arrangement is determined according to the actual geological conditions on site. The gap between the sealing pipe and the corresponding installation hole wall is initially sealed with gauze or rubber ring. S40: Installation of extraction tube and air extraction tube: The extraction tube is sequentially inserted into the outer bag and the inner bag to the drilled hole inside the inner bag; the air extraction tube is inserted into the sealing space; wherein, the gap between the extraction tube and the outer bag, the inner bag and the air extraction tube and the outer bag are initially sealed with gauze or rubber ring. S50: Sodium silicate solution injection: Start the grouting pump and the air pump to inject sodium silicate solution into the coal seam from the sealing pipe. At the same time, the air pump extracts the gas in the sealing space to form a negative pressure environment. Under the dual action of the negative pressure state of the sealing space and the grouting pressure, the sodium silicate solution enters the sealing space through the surrounding cracks. Based on the pressure data in the sealing space, it is determined whether the sodium silicate solution has been injected sufficiently. S60: Carbon dioxide injection: Start the air injection pump and introduce high-concentration carbon dioxide into the sealing space. Confirm whether curing is complete based on the pressure data in the sealing space. When the pressure stabilizes, it indicates that curing is complete. S70: Gas Extraction: After the chemical reaction of the coal seam where the sealing space is located is completed, the gas in the borehole located inside the sealing space is extracted by the extraction pipe assembly.

[0014] In one example of the present invention, the specific process of the chemical reaction for sealing the coal seam where the sealing space is located in step S70 is as follows: S71: Sodium silicate first undergoes a hydrolysis reaction in aqueous solution to produce sodium hydroxide, as shown in the following reaction: S72: The generated sodium hydroxide makes the solution alkaline. Subsequently, CO2 is passed through, and the reaction is as follows: 2NaOH + CO2 → Na2CO3 + H2O S73: The generated sodium hydroxide neutralizes the sodium silicate, causing the sodium silicate hydrolysis equilibrium to shift continuously to the right, promoting further dissociation of silicate ions into silicic acid, i.e.: CO2+Na2SiO3+H2O→H2SiO3+Na2CO3.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This technical solution utilizes readily available and inexpensive carbon dioxide and sodium silicate, which can further improve the economic benefits of mines. The fluidity of the sodium silicate solution, combined with the negative pressure environment within the borehole, allows for effective sealing covering of most fractures around the borehole, making it suitable for complex geological conditions with highly developed fractures. The reaction between sodium silicate and carbon dioxide can solidify within one hour, effectively shortening the sealing time and improving work efficiency. Furthermore, the chemicals and byproducts used in the sealing process are non-toxic and non-hazardous, ensuring worker safety and preventing environmental pollution of the coal seam during construction.

[0016] The preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, so as to facilitate an understanding of the features and advantages of the invention. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0018] Figure 1 This is a schematic diagram of a gas extraction borehole sealing system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of a borehole according to an embodiment of the present invention; Figure 3 This is a flowchart of a sealing method for a gas extraction borehole sealing system according to an embodiment of the present invention.

[0019] List of reference numerals in the attached diagram: Sealing system 100; Bag assembly 10; Inner pouch 11; 12 outer pouches; Sealing space A; Sodium silicate delivery assembly 20; Sodium silicate solution storage tank 21; Grouting pump 22; Sealing tube 23; Fluid passage 231; First shut-off valve 24; Carbon dioxide delivery assembly 30; Carbon dioxide storage tank 31; Air pump 32; Inflation tube 33; Vent hole 331; Second shut-off valve 34; Extraction tube assembly 40; Extraction tube 41; Pressure sensor 50; Fixed sleeve 60; Coal seam 200; Drill hole 210; Crack 220. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0022] According to a first aspect of the present invention, a gas extraction borehole sealing system 100 is provided, such as... Figure 1 and Figure 2 As shown, it includes: The pouch assembly 10 includes an inner pouch 11 and an outer pouch 12, which are respectively placed inside and outside the borehole 210 to form a sealing space A; At least one sodium silicate delivery assembly 20 includes: a sodium silicate solution storage tank 21, a grouting pump 22, and a sealing pipe 23 connected in sequence, wherein the sealing pipe 23 is arranged along the extension direction of the borehole 210 and placed in the coal seam 200, and the grouting pump 22 is configured to pump the sodium silicate solution in the sodium silicate solution storage tank 21 to the sealing pipe 23, and flow from the sealing pipe 23 to the coal seam 200; The carbon dioxide delivery assembly 30 includes: a carbon dioxide storage tank 31, an injection pump 32, and an injection pipe 33 connected in sequence. The injection pipe 33 is arranged along the extension direction of the borehole 210 and passes through the inner bag 11 and the outer bag 12. The injection pump 32 is configured to pump carbon dioxide gas from the carbon dioxide storage tank 31 into the injection pipe 33, and discharge it from the injection pipe 33 into the sealing space A. The carbon dioxide storage tank 31 contains high-purity CO2 (purity ≥ 99%).

[0023] The extraction pipe assembly 40 includes an extraction pipe 41 and an extraction pump (not shown in the figure) connected thereto. The extraction pipe 41 is sequentially inserted through the outer bag 12 and the inner bag 11 to a borehole 210 inside the inner bag 11. The extraction pump is configured to extract methane gas located in the borehole 210. It is understood that an extraction container is connected to the extraction pump to contain the methane gas. The air extraction assembly 70 includes an air extraction pipe 71 and an air extraction pump (not shown in the figure) connected thereto. The air extraction pipe 71 extends into the sealed space A, and the air extraction pump is configured to create a negative pressure environment in the sealed space A. It is understood that an air extraction container is connected to the air extraction pump to contain the gas extracted from the air extraction space A. Sodium silicate is used as a sealing material. It reacts with carbon dioxide to generate silica colloid, which solidifies to form a sealant, thereby sealing the coal seam 200 where the sealing space A is located.

[0024] The sealing principle of the sealing system 100 is as follows: Sodium silicate conveying assembly 20 feeds sodium silicate into coal seam 200, while carbon dioxide conveying assembly 30 injects carbon dioxide into sealing space A. During this process, sodium silicate first undergoes a hydrolysis reaction in aqueous solution to produce sodium hydroxide, as shown in the following reaction: The generated sodium hydroxide makes the solution alkaline. CO2 is then introduced, and the reaction is as follows: 2NaOH + CO2 → Na2CO3 + H2O. The generated sodium hydroxide neutralizes the pH, continuously shifting the sodium silicate hydrolysis equilibrium to the right, promoting further dissociation of silicate ions into silicic acid: CO2 + Na2SiO3 + H2O → H2SiO3 + Na2CO3. The resulting silicic acid (H2SiO3) is a weak acid that is sparingly soluble in water. In solution, it initially exists as a single molecule. As the concentration increases, it undergoes a condensation reaction, agglomerating to form a flocculent precipitate, i.e., silicic acid gel. The silicic acid gel subsequently hardens through dehydration and shrinkage, transforming into a solid gel that tightly fills the 210mm borehole gap, achieving gas sealing.

[0025] The sealing system utilizes readily available and inexpensive carbon dioxide and sodium silicate, which can further improve the economic efficiency of the mine. Through the fluidity of the sodium silicate solution and the negative pressure environment within borehole 210, the sealing effect can cover most of the surrounding fractures 220, making it suitable for complex geological conditions such as highly developed fractures 220. The reaction between sodium silicate and carbon dioxide can solidify within one hour, effectively shortening the sealing time and improving work efficiency. The chemicals and byproducts used in the sealing process are non-toxic and non-hazardous, ensuring the safety of workers and preventing environmental pollution of the coal seam 200 during construction.

[0026] In one example of the present invention, it further includes: a pressure sensor 50 located in the sealing space A; when sodium silicate solution is injected into the coal seam 200, the pressure sensor 50 is configured to determine whether the sodium silicate solution has been sufficiently injected into the coal seam 200 based on pressure data inside the sealing space A; when carbon dioxide is injected into the sealing space A, the pressure sensor 50 is configured to determine whether the silica gel has been cured based on pressure data inside the sealing space A; wherein, when the pressure data detected by the pressure sensor 50 is stable, the silica gel has been cured. For example, a pressure sensor 50 is fixedly installed on the extraction pipe 41 and connected to an external display, thereby transmitting the pressure data within the sealing space A to the display in real time, facilitating the operation of the sealing system 100. The pressure sensor 50 is arranged on the surface of the extraction pipe 41 inside the gas extraction borehole to monitor its internal pressure, thereby determining whether the sodium silicate solution has been sufficiently injected.

[0027] In one example of the present invention, the sodium silicate delivery assembly 20 includes a plurality of components, which are spaced apart along the circumferential direction of the borehole 210; by providing a plurality of sodium silicate delivery assemblies 20, the sealing efficiency of the coal and rock around the borehole 210 can be greatly improved.

[0028] In one example of the present invention, in two adjacent sodium silicate delivery assemblies 20, the range of the fissure 220 radiated by one sodium silicate delivery assembly 20 overlaps with the range of the fissure 220 radiated by the other sodium silicate delivery assembly 20. In short, among the multiple sodium silicate delivery assemblies 20 arranged circumferentially, the radiation range of sodium silicate delivered to the coal seam 200 by each sealing pipe 23 overlaps with the radiation range of the adjacent sealing pipe 23, thereby effectively sealing the coal seam 200 around the borehole 210.

[0029] In one example of the present invention, the sodium silicate delivery assembly 20 is disposed close to the borehole 210, and the radial distance between the assembly and the borehole 210 is no more than 0.5m.

[0030] This distance is located within the effective fracture zone formed by the combustion and explosion. Sodium silicate can directly penetrate and fill the fracture channels created by the combustion and explosion, while maximizing the use of the negative pressure environment created by extraction. In one example of the present invention, The sealing tube 23 is provided with a plurality of liquid passage holes 231, which are spaced apart along the length of the sealing tube 23, and the distance between two adjacent liquid passage holes 231 is not greater than 20mm, and the inner diameter of each liquid passage hole 231 is not less than 5mm. The air injection pipe 33 has a plurality of air vents 331, which are spaced apart along the length of the air injection pipe 33, and the distance between two adjacent air vents 331 is no more than 20mm, and the inner diameter of each air vent 331 is no less than 5mm.

[0031] By opening liquid passage holes 231 and air passage holes 331 on the sealing pipe 23 and the air injection pipe 33 respectively, the uniformity of sodium silicate solution injected into the coal seam 200 and the uniformity of carbon dioxide injected into the sealing space A can be greatly improved, thereby greatly improving the sealing efficiency.

[0032] In one example of the present invention, the chemical reaction formula for sealing the coal seam 200 where the sealing space A is located is as follows: CO2+Na2SiO3+H2O→H2SiO3+Na2CO3 In the formula, H2SiO3 is solid silicone used to fill the gaps in the drilled hole (210).

[0033] Specifically, the chemical reaction described herein proceeds as follows: Sodium silicate first undergoes a hydrolysis reaction in aqueous solution to produce sodium hydroxide, as shown in the following reaction: The generated sodium hydroxide makes the solution alkaline. Subsequently, CO2 is passed through, and the reaction is as follows: 2NaOH + CO2 → Na2CO3 + H2O The resulting sodium hydroxide neutralizes the sodium silicate, causing the hydrolysis equilibrium of sodium silicate to shift further to the right, promoting the further dissociation of silicate ions into silicic acid, i.e.: CO2+Na2SiO3+H2O→H2SiO3+Na2CO3.

[0034] The generated silicic acid (H2SiO3) is a weak acid that is sparingly soluble in water. It initially exists in solution as a single molecule, and as the concentration increases, it undergoes a condensation reaction, agglomerating to form a flocculent precipitate, namely silicic acid gel.

[0035] The silica gel gradually hardens through dehydration and shrinkage, transforming into a solid gel that tightly fills the gap in borehole 210, thus achieving gas sealing.

[0036] In one example of the invention, the sodium silicate solution is composed of a mixture of sodium silicate and water.

[0037] In one example of the present invention, a fixing sleeve 60 is further included, which is sleeved on the sealing tube 23 or the injection tube 33 or the extraction tube 71 or the extraction tube 41, and connected between the sealing tube 23 and the wall of the corresponding mounting hole or between the injection tube 33, the extraction tube 71, the extraction tube 41 and the outer bag 12, configured to seal and fix the gap between the sealing tube 23 and the wall of the corresponding mounting hole or between the injection tube 33, the extraction tube 71, the extraction tube 41 and the outer bag 12.

[0038] For example, the fixing sleeve 50 is a flange structure, which fixes the sealing pipe 23, the gas injection pipe 33, the extraction pipe 41, and the extraction pipe 71. By setting the fixing sleeve 60, the sealing pipe 23 can be fixed in the coal seam 200, and the gas injection pipe 33, the extraction pipe 41, and the extraction pipe 71 can be fixed on the outer bag 12, which helps to stabilize the sealing pipe 23, the gas injection pipe 33, the extraction pipe 41, and the extraction pipe 71.

[0039] In one example of the present invention, the sodium silicate conveying assembly 20 further includes a first on / off valve 24 disposed on the sealing pipe 23 and configured to control the on / off of sodium silicate solution between the sodium silicate solution tank and the coal seam 200; In one example of the present invention, the carbon dioxide delivery assembly 30 further includes a second on / off valve 34 disposed on the gas injection pipe 33 and configured to control the on / off of carbon dioxide from the carbon dioxide tank and the sealing space A.

[0040] According to a second aspect of the present invention, a sealing method for a gas extraction borehole sealing system 100 as described above is provided. Figure 3 As shown, it includes the following steps: S10: Pre-treatment of borehole 210: Determine the diameter and depth of borehole 210 according to the extraction needs and actual site conditions, clean the rock powder and accumulated water in borehole 210, and ensure that the borehole wall is dry; S20: Installation of the air injection tube 33: After the inner bag 11 and the outer bag 12 are arranged to form a sealing space A, insert the air injection tube 33 into the sealing space A, and preliminarily seal the gap between the air injection tube 33 and the outer bag 12 with gauze or rubber ring. S30: Installation of sealing pipe 23: The sealing pipe 23 is arranged in a ring around the gas extraction borehole 210. The radius of the ring arrangement is determined according to the actual geological conditions on site. The gap between the sealing pipe 23 and the hole wall of its corresponding installation hole is initially sealed with gauze or rubber ring. S40: Installation of extraction pipe 41 and extraction pipe 71: The extraction pipe 41 is sequentially inserted into the outer bag 12 and the inner bag 11 to the drill hole 210 inside the inner bag 11; the extraction pipe 71 is inserted into the sealing space A; wherein, the gaps between the extraction pipe 41 and the outer bag 12 and the inner bag 11, as well as the gap between the extraction pipe 71 and the outer bag 12, are initially sealed with gauze or rubber rings; S50: Sodium silicate solution injection: Start the grouting pump 22 and the air pump to inject sodium silicate solution into the coal seam 200 through the sealing pipe 23. At the same time, the air pump extracts the gas in the sealing space A to form a negative pressure environment. Under the dual action of the negative pressure state of the sealing space A and the grouting pressure, the sodium silicate solution enters the sealing space A through the peripheral cracks 220. Based on the pressure data in the sealing space A, it is determined whether the sodium silicate solution has been injected sufficiently. S60: Carbon dioxide injection: Start the gas injection pump 32 to introduce high-concentration carbon dioxide into the sealing space A. Based on the pressure data in the sealing space A, confirm whether the solidification is complete. When the pressure stabilizes, it indicates that the solidification is complete. This creates a sealed environment inside and outside the sealing space A, preventing leakage when extracting methane gas.

[0041] S70: Gas extraction: After the chemical reaction of sealing the coal seam 200 where the sealing space A is located is completed, the gas in the borehole 210 located inside the sealing space A is extracted by the extraction pipe assembly 40.

[0042] The sealing method utilizes readily available and inexpensive carbon dioxide and sodium silicate, which can further improve the economic benefits of the mine. Through the fluidity of the sodium silicate solution and the negative pressure environment within borehole 210, the sealing effect can cover most of the surrounding fractures 220, making it suitable for complex geological conditions such as highly developed fractures 220. The reaction between sodium silicate and carbon dioxide can solidify within one hour, effectively shortening the sealing time and improving work efficiency. The chemicals and byproducts used in the sealing process are non-toxic and non-hazardous, ensuring the safety of workers and preventing environmental pollution of the coal seam 200 during construction.

[0043] In one example of the present invention, the specific process of the chemical reaction for sealing the coal seam 200 where the sealing space A is located in step S70 is as follows: S71: Sodium silicate first undergoes a hydrolysis reaction in aqueous solution to produce sodium hydroxide, as shown in the following reaction: S72: The generated sodium hydroxide makes the solution alkaline. Subsequently, CO2 is passed through, and the reaction is as follows: 2NaOH + CO2 → Na2CO3 + H2O S73: The generated sodium hydroxide neutralizes the sodium silicate, causing the sodium silicate hydrolysis equilibrium to shift continuously to the right, promoting further dissociation of silicate ions into silicic acid, i.e.: CO2+Na2SiO3+H2O→H2SiO3+Na2CO3.

[0044] The generated silicic acid (H2SiO3) is a weak acid that is sparingly soluble in water. It initially exists in solution as a single molecule, and as the concentration increases, it undergoes a condensation reaction, agglomerating to form a flocculent precipitate, namely silicic acid gel.

[0045] The silica gel gradually hardens through dehydration and shrinkage, transforming into a solid gel that tightly fills the gap in borehole 210, thus achieving gas sealing.

[0046] The foregoing description, with reference to preferred embodiments, details exemplary implementations of the gas extraction borehole sealing system 100 and sealing method proposed in this invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of this invention, and various combinations can be made to the various technical features and structures proposed in this invention without exceeding the protection scope of this invention, which is determined by the appended claims.

Claims

1. A gas extraction borehole sealing system, characterized in that, include: The pouch assembly (10) includes an inner pouch (11) and an outer pouch (12), which are placed inside and outside the borehole (210) respectively to form a sealing space (A). At least one sodium silicate delivery assembly (20) includes: a sodium silicate solution storage tank (21), a grouting pump (22), and a sealing pipe (23) connected in sequence, wherein the sealing pipe (23) is arranged along the extension direction of the borehole (210) and placed in the coal seam (200), and the grouting pump (22) is configured to pump the sodium silicate solution in the sodium silicate solution storage tank (21) to the sealing pipe (23) and flow from the sealing pipe (23) to the coal seam (200); The carbon dioxide delivery assembly (30) includes: a carbon dioxide storage tank (31), an injection pump (32), and an injection pipe (33) connected in sequence, wherein the injection pipe (33) is arranged along the extension direction of the borehole (210) and passes through the inner bladder (11) and the outer bladder (12), and the injection pump (32) is configured to pump carbon dioxide gas in the carbon dioxide storage tank (31) into the injection pipe (33) and discharge it into the sealing space (A) through the injection pipe (33); The extraction pipe assembly (40) includes an extraction pipe (41) and an extraction pump connected thereto. The extraction pipe (41) is sequentially inserted through the outer bladder (12) and the inner bladder (11) to a borehole (210) inside the inner bladder (11). The extraction pump is configured to extract methane gas located in the borehole (210). The air extraction assembly (70) includes an air extraction pipe (71) and an air extraction pump connected thereto, the air extraction pipe (71) extending into the sealed space (A), and the air extraction pump configured to create a negative pressure environment within the sealed space (A); Sodium silicate is used as a sealing material. It reacts with carbon dioxide to generate silica colloid, which solidifies to form a seal, thereby sealing the coal seam (200) where the sealing space (A) is located.

2. The gas extraction borehole sealing system according to claim 1, characterized in that, It also includes: a pressure sensor (50) located in the sealing space (A); when sodium silicate solution is injected into the coal seam (200), the pressure sensor (50) is configured to determine whether the sodium silicate solution has been fully injected into the coal seam (200) based on the pressure data inside the sealing space (A); when carbon dioxide is injected into the sealing space (A), the pressure sensor (50) is configured to determine whether the silica gel has been cured based on the pressure data inside the sealing space (A); wherein, when the pressure data detected by the pressure sensor (50) is stable, the silica gel has been cured.

3. The gas extraction borehole sealing system according to claim 1, characterized in that, The sodium silicate delivery assembly (20) comprises a plurality of such assemblies and is spaced apart along the circumferential direction of the borehole (210).

4. The gas extraction borehole sealing system according to claim 3, characterized in that, In two adjacent sodium silicate delivery assemblies (20), the range of the fissure (220) radiated by one sodium silicate delivery assembly (20) overlaps with the range of the fissure (220) radiated by the other sodium silicate delivery assembly (20).

5. The gas extraction borehole sealing system according to claim 3, characterized in that, The sodium silicate delivery assembly (20) is located close to the borehole (210), and the radial distance between it and the borehole (210) is no more than 0.5m.

6. The gas extraction borehole sealing system according to claim 1, characterized in that, The sealing tube (23) is provided with a plurality of liquid passage holes (231), the plurality of liquid passage holes (231) are arranged at intervals along the length direction of the sealing tube (23), and the distance between two adjacent liquid passage holes (231) is not greater than 20mm, and the inner diameter of each liquid passage hole (231) is not less than 5mm; The air injection pipe (33) is provided with a plurality of air holes (331), which are spaced apart along the length of the air injection pipe (33), and the distance between two adjacent air holes (331) is not greater than 20mm, and the inner diameter of each air hole (331) is not less than 5mm.

7. The gas extraction borehole sealing system according to claim 1, characterized in that, The chemical reaction formula for sealing the coal seam (200) where the sealing space (A) is located is as follows: CO2+Na2SiO3+H2O→H2SiO3+Na2CO3 In the formula, H2SiO3 is solid silicone used to fill the gaps in the drilled hole (210).

8. The gas extraction borehole sealing system according to claim 1, characterized in that, The sodium silicate solution is composed of a mixture of sodium silicate and water.

9. A sealing method for a gas extraction borehole sealing system as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S10: Pretreatment of borehole (210): Determine the diameter and depth of borehole (210) according to the extraction needs and actual site conditions, clean the rock powder and water inside borehole (210) and ensure that the borehole wall is dry; S20: Installation of the air injection tube (33): After the inner bag (11) and outer bag (12) are arranged to form a sealing space (A), insert the air injection tube (33) into the sealing space (A) and preliminarily seal the gap between the air injection tube (33) and the outer bag (12) with gauze or rubber ring. S30: Installation of sealing pipe (23): The sealing pipe (23) is arranged in a ring around the gas extraction borehole (210). The radius of the ring arrangement is determined according to the actual geological conditions on site. The gap between the sealing pipe (23) and the hole wall of its corresponding installation hole is initially sealed with gauze or rubber ring. S40: Installation of extraction pipe (41) and extraction pipe (71): The extraction pipe (41) is sequentially inserted into the outer bag (12) and the inner bag (11) to the drill hole (210) inside the inner bag (11); the extraction pipe (71) is inserted into the sealing space (A); wherein, the gaps between the extraction pipe (41) and the outer bag (12), the inner bag (11) and the gap between the extraction pipe (71) and the outer bag (12) are initially sealed with gauze or rubber rings; S50: Sodium silicate solution injection: Start the grouting pump (22) and the air pump to inject sodium silicate solution into the coal seam (200) from the sealing pipe (23). At the same time, the air pump extracts the gas in the sealing space (A) to form a negative pressure environment. Under the dual action of the negative pressure state of the sealing space (A) and the grouting pressure, the sodium silicate solution enters the sealing space (A) through the peripheral cracks (220). Based on the pressure data in the sealing space (A), it is determined whether the sodium silicate solution has been injected sufficiently. S60: Carbon dioxide injection: Start the air injection pump (32) to introduce high concentration carbon dioxide into the sealing space (A), and confirm whether the curing is complete based on the pressure data in the sealing space (A). When the pressure stabilizes, it indicates that the curing is complete. S70: Gas extraction: After the chemical reaction of sealing the coal seam (200) where the sealing space (A) is located is completed, the gas in the borehole (210) located inside the sealing space (A) is extracted by the extraction pipe assembly (40).

10. The sealing method for the gas drainage borehole sealing system according to claim 9, characterized in that, In step S70, the specific process of the chemical reaction for sealing the coal seam (200) where the sealing space (A) is located is as follows: S71: Sodium silicate first undergoes a hydrolysis reaction in aqueous solution to produce sodium hydroxide, as shown in the following reaction: S72: The generated sodium hydroxide makes the solution alkaline. Subsequently, CO2 is passed through, and the reaction is as follows: 2NaOH + CO2 → Na2CO3 + H2O S73: The generated sodium hydroxide neutralizes the sodium silicate, causing the sodium silicate hydrolysis equilibrium to shift continuously to the right, promoting further dissociation of silicate ions into silicic acid, i.e.: CO2+Na2SiO3+H2O→H2SiO3+Na2CO3.

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