Environment-friendly clay-containing cement-based mixture and method for sealing gas drilling hole using the same

Abstract

The application discloses a clay-containing cement-based environment-friendly mixture and a gas drilling hole sealing method thereof, which is prepared by mixing the following raw materials in a proportion by weight: 700-800 parts of Portland cement, 30-50 parts of superabsorbent resin, 30-50 parts of coal gangue powder, 30-50 parts of a quick-setting agent and 30-50 parts of a clay expanding agent. The environment-friendly mixture is mixed with water in a mass ratio of 1:1, and is used as a sealing grouting medium after being uniformly stirred. The application has the following advantages: (1) the coal gangue is used as the sealing material, thereby realizing comprehensive utilization of industrial solid waste; (2) the clay expanding agent is added into the material, so that the material expands while being solidified, the problem of cement shrinkage is avoided, the drilling hole wall can be actively supported, the shrinkage of the sealing section is prevented from forming a gas leakage channel, and the gas leakage amount in the gas extraction process is reduced; and (3) the superabsorbent resin is added into the material, so that the permeability of the sealing material is reduced, the sealing property of the material is enhanced, and the sealing effect is improved.

Description

Technical Field

[0001] This invention belongs to the field of coal mine gas extraction technology, specifically relating to an environmentally friendly clay-cement based mixture and its method for sealing gas boreholes. Background Technology

[0002] Borehole sealing is a crucial step in pre-draining coal seam gas. A well-sealed borehole ensures that the negative pressure from the extraction process provides a continuous driving force for the coal seam gas to flow into the borehole, thereby achieving efficient gas extraction. In addition to coal seam conditions and sealing parameters, the sealing material is one of the most important factors determining the quality of the sealing.

[0003] Traditional cement materials suffer from defects such as low early strength and easy shrinkage due to water loss. This leads to air leakage within the borehole, between the sealing material itself, the extraction pipeline, and between the sealing material and the borehole wall. Furthermore, it causes regeneration of fractures in the already sealed surrounding rock, resulting in external air leakage. To address these defects, research has focused on improving the performance of cement sealing materials by adding reagents with specific properties, such as early-strength agents, clay expansion agents, and nanomaterials. Additives with different functions show significant advantages in improving the performance of sealing cement. However, in the later stages of coal mine gas extraction, disturbances in the surrounding coal and rock mass can cause further cracking in the sealing material, between the sealing material and the borehole wall, and between the slurry and coal (rock) mass around the borehole. As these fractures develop further, a large amount of outside air leaks into the borehole under negative pressure, causing a significant decrease in the extracted concentration. Summary of the Invention

[0004] Based on the above analysis, the present invention provides an environmentally friendly clay-cement based mixture and its method for sealing gas boreholes, which solves the problems of water loss and shrinkage of existing cement sealing materials and the easy generation of cracks in the later stage of extraction.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: a clay-cement based environmentally friendly mixture, which is made by mixing raw materials in the following weight ratio: 700-800 parts of silicate cement, 30-50 parts of superabsorbent resin, 30-50 parts of coal gangue powder, 30-50 parts of quick-setting agent and 30-50 parts of clay expansion agent.

[0006] All raw materials have a particle size of 80-200 mesh.

[0007] 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.

[0008] The silicate cement is ordinary silicate cement of grade 42.5.

[0009] Coal gangue powder is made from crushed coal gangue produced during coal mining.

[0010] A clay-cement-based environmentally friendly mixture is used in a gas borehole sealing method. The environmentally friendly sealing material is mixed with water at a mass ratio of 1:1 and stirred evenly before being used as a sealing grouting medium.

[0011] Compared with currently used sealing materials, the present invention has the following advantages by adopting the above technical solution: (1) Coal gangue was used as a sealing material, realizing the comprehensive utilization of industrial solid waste.

[0012] (2) Adding clay expansion agent to the sealing material can expand while solidifying, avoiding the problem of cement shrinkage. It can play an active support role for the borehole wall, prevent the sealing section from shrinking and forming a gas leakage channel, and reduce the amount of gas leakage during the gas extraction process.

[0013] (3) Adding superabsorbent resin to the material can reduce the permeability of the sealing material, enhance the sealing performance of the material, and improve the sealing effect.

[0014] (4) The proportions of each of the raw materials in this invention can be adjusted to achieve more combination schemes. Detailed Implementation

[0015] This invention is applied to the "two-plug-one-injection" sealing process for underground gas boreholes in coal mines. The sealing sections inside the two gas bags and between the two gas bags all use the clay-cement-based environmentally friendly mixture of this invention.

[0016] The sealing material, which is a clay-cement based environmentally friendly mixture, is injected into the two bags through the grouting pipe. When the pressure reaches the set threshold (such as 1.5Mpa-2Mpa), the burst valve located between the two bags bursts, and the grouting pipe injects grout into the gap of the sealing section between the two bags, thereby sealing the extraction borehole.

[0017] (1) Example 1 The clay-cement based environmentally friendly mixture (sealing material) is made from the following raw materials in the indicated weight ratios: 700 parts silicate cement, 30 parts superabsorbent resin, 50 parts coal gangue powder, 50 parts quick-setting agent, and 50 parts clay expansion agent.

[0018] Mix the above raw materials in proportion, stir evenly, mix with water at a mass ratio of 1:1, stir, and then use for grouting.

[0019] (2) Example 2 The clay-cement based environmentally friendly mixture (sealing material) is made from the following raw materials in the indicated weight ratios: 800 parts silicate cement, 30 parts superabsorbent resin, 50 parts coal gangue powder, 50 parts quick-setting agent, and 50 parts clay expansion agent.

[0020] Mix the above raw materials in proportion, stir evenly, mix with water at a mass ratio of 1:1, stir, and then use for grouting.

[0021] (3) Example 3 The clay-cement based environmentally friendly mixture (sealing material) is made from the following raw materials in the indicated weight ratios: 700 parts silicate cement, 30 parts superabsorbent resin, 50 parts coal gangue powder, 30 parts quick-setting agent, and 50 parts clay expansion agent.

[0022] Mix the above raw materials in proportion, stir evenly, mix with water at a mass ratio of 1:1, stir, and then use for grouting.

[0023] (4) Example 4 The clay-cement based environmentally friendly mixture (sealing material) is made from the following raw materials in the indicated weight ratios: 800 parts silicate cement, 30 parts superabsorbent resin, 50 parts coal gangue powder, 30 parts quick-setting agent, and 50 parts clay expansion agent.

[0024] Mix the above raw materials in proportion, stir evenly, mix with water at a mass ratio of 1:1, stir, and then use for grouting.

[0025] (5) Example 5 The clay-cement based environmentally friendly mixture (sealing material) is made from the following raw materials in the indicated weight ratios: 800 parts silicate cement, 30 parts superabsorbent resin, 30 parts coal gangue powder, 30 parts quick-setting agent, and 50 parts clay expansion agent.

[0026] In Examples 1-5 above, the particle size of all raw materials is 80-200 mesh. By weight percentage, the superabsorbent resin is a mixture of 75% sodium polyacrylate, 24% polyacrylic acid, 0.7% SiO2, and 0.3% Al2(SO4)3. The silicate cement is ordinary silicate cement of grade 42.5. The coal gangue powder is made from crushed coal gangue produced during coal mining.

[0027] The preparation method of the above-mentioned clay-cement-based environmentally friendly mixture sealing material is as follows: the sealing raw materials are mixed in proportion and stirred evenly to obtain the sealing material.

[0028] The above-mentioned clay-cement-based environmentally friendly mixture sealing material is used for sealing gas boreholes: the sealing material is mixed with water at a mass ratio of 1:1, stirred, and then injected.

[0029] The properties of the materials obtained in Examples 1-5 above, as determined by testing, are as follows: 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 sealing gas boreholes, characterized in that: The clay-cement-based environmentally friendly mixture is mixed with water at a mass ratio of 1:1 and stirred evenly before being used as a sealing grouting medium. The clay-cement-based environmentally friendly mixture is made 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 clay expansion agent. 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. All raw materials have a particle size of 80-200 mesh.

2. The gas borehole sealing method according to claim 1, characterized in that: The silicate cement is ordinary silicate cement of grade 42.

5.

3. The gas borehole sealing method according to claim 1, characterized in that: Coal gangue powder is made from crushed coal gangue produced during coal mining.

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