Hydrophobic pressure reduction method for soft sandstone aquifer

Abstract

The invention discloses a dewatering and depressurizing method for a soft sandstone aquifer, and belongs to the field of coal mine water prevention and control. The method comprises the following steps: S1, acquiring basic data of a soft sandstone aquifer and characterization parameters of the damage degree of overlying strata above a roof; s2, determining a hydrophobic target aquifer; s3, after excavation of the mining roadway of the working face is completed and before coal seam mining operation is conducted, drainage holes are constructed, advanced drainage is conducted on the drainage target aquifer, and primary drainage of the drainage target aquifer is completed; and S4, coal seam stoping operation is conducted, in the coal seam mining process, the water guiding fracture zone develops, the water-containing soft sandstone fracture of the hydrophobic target water-containing layer communicates with the water guiding fracture zone above the goaf, water flows into the goaf through the water guiding fracture zone, and drainage of the secondary hydrophobic target water-containing layer is completed. According to the method, drainage and depressurization effects of the soft sandstone aquifer can be improved through combination of double ways, and the problems of water inrush and sand inrush risks existing in safe mining of coal resources under soft sandstone are solved.

Description

Technical Field

[0001] This invention belongs to the field of coal mine water control, specifically relating to a method for hydrophobic and pressure-reducing soft sandstone aquifers. Background Technology

[0002] In recent years, with the continuous improvement of coal mining technology and the gradual reduction of shallow coal reserves, most mines have shifted their operations to deeper areas. However, deep, highly confined aquifers have become a major constraint on coal mining. This is especially true in areas near aeolian oxidation zones or where the strata are relatively young, characterized by soft lithology, poor cementation, and low compressive strength. During the mining process, the aquifers in the roof of the coal seam are highly water-rich, and under certain confined water pressure, the aquifers in the roof pose a threat of water inrush and sand collapse.

[0003] Currently, the main method for dewatering and reducing pressure in aquifers under the roof is static dewatering, which involves drilling drainage boreholes in the roof to achieve this goal. However, in soft sandy aquifers under the roof, it is generally impossible to completely drain the aquifer to a non-dripping state during the dewatering process. This is mainly due to factors such as lateral recharge, or the aquifer being located within a water-conducting fracture zone. Therefore, the risk of water inrush and sand collapse still exists during the working face mining process. Summary of the Invention

[0004] Based on the above-mentioned technical problems, this invention proposes a method for hydrophobic depressurization of soft sandstone aquifers.

[0005] The technical solution adopted in this invention is:

[0006] A method for hydrophobic depressurization of soft sandstone aquifers includes the following steps:

[0007] S1. Obtain basic data on the soft sandstone aquifer and parameters characterizing the degree of damage to the overlying strata above the top plate;

[0008] S2. Based on the basic data from S1 and the parameters characterizing the degree of overburden damage, the hydrophobic target aquifer is determined.

[0009] S3. After the working face roadway is excavated and before the coal seam mining operation, drainage holes are constructed based on the location of the target aquifer to drain water in advance. Water in the target aquifer is discharged along the drainage holes to complete one drainage of the target aquifer.

[0010] S4. Coal seam mining operations are carried out. During the coal seam mining process, water-conducting fracture zones develop. The water-bearing soft sandstone fractures of the target aquifer are connected with the water-conducting fracture zone above the goaf, allowing water to flow into the goaf through the water-conducting fracture zone, thus completing the secondary drainage of the target aquifer.

[0011] Preferably, in step S1: the basic data of the soft sandstone aquifer include the aquifer permeability coefficient, water inflow, aquifer thickness, and soft sandstone disintegration; the parameters characterizing the degree of overburden damage include the height of the water-conducting fracture zone and the height of the collapse zone.

[0012] Preferably, step S2 includes the following steps:

[0013] S21. Based on the height of the water-conducting fracture zone, the height of the caving zone, the aquifer permeability coefficient, the water inflow, and the aquifer thickness, all soft sandstone aquifers within the range of the height of the water-conducting fracture zone and the caving zone are selected.

[0014] S22. Analyze the impact of mining operations on the soft sandstone aquifer.

[0015] S23. Select soft sandstone aquifers within the set influence range as hydrophobic target aquifers.

[0016] Preferably, step S3 includes the following steps:

[0017] S31. Construct drainage holes above the roof of the working face in the working face mining roadway in the direction of working face advancement; the drainage holes include a main hole and several branch holes, with the branch holes connected to the end of the main hole;

[0018] S32. Insert a sleeve into the main hole, with both ends of the sleeve open. Install a flange on the outer end of the sleeve and set a gate.

[0019] S33. After the casing in the main control is completely fixed and the gate is installed, continue drilling upwards to drill several branch holes, which pass through the overburden aquifer.

[0020] S34. After drilling to the soft sandstone aquifer at the top, a screen pipe is placed in, with both ends of the screen pipe open and screen holes evenly distributed on the pipe wall.

[0021] S35. Repeat steps S31 to S34, constructing drainage holes at intervals of 100 to 120 meters.

[0022] Preferably, the main sections of the plurality of branch holes are arranged in parallel, and the ends of the branch holes are connected to the ends of the main holes through skew sections.

[0023] The beneficial technical effects of the present invention are as follows:

[0024] 1. This invention identifies target aquifers by acquiring basic data of soft sandstone aquifers and characterizing parameters of the degree of damage to the overlying strata above the roof. Based on the location of the target aquifer, it conducts pre-drainage construction to perform the first aquifer dewatering and pressure reduction operation. Subsequently, coal seam mining operations are carried out, and the water in the aquifer is discharged along the mining-induced fractures and the boreholes to achieve a second dewatering and pressure reduction. This invention can improve the dewatering and pressure reduction effect of soft sandstone aquifers, thereby solving the problem of safe and efficient coal mining under soft sandstone to a certain extent. Furthermore, it provides a theoretical basis for mining in aquifer areas with soft sandstone geological characteristics.

[0025] 2. This invention is based on the construction of drainage holes before coal seam mining and the drainage of water again through the diffusion of mining-induced fractures during coal seam mining. By combining the two approaches, the drainage and pressure reduction effect of soft sandstone aquifers can be improved, which can solve the problems of water inrush and sand collapse risks in the safe mining of coal resources under soft sandstone to a certain extent.

[0026] 3. This invention uses a main hole and several branch holes to form a drainage hole, which drains the aquifer in the form of a water collection corridor. Multiple drainage branch holes are combined to form a long and wide drainage zone, which can solve the problem of unevenness of soft sandstone aquifers. At the same time, multiple drainage branch holes can penetrate the water-blocking fault, connecting multiple closed hydrogeological units to achieve large-scale drainage. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0028] Figure 1 This is a schematic flowchart of the hydrophobic depressurization method for soft sandstone aquifers according to the present invention;

[0029] Figure 2 This is a schematic diagram illustrating the structural principle of the drainage holes in the construction of this invention. Detailed Implementation

[0030] like Figure 1 As shown, a method for hydrophobic depressurization of a soft sandstone aquifer includes the following steps:

[0031] S1. Obtain basic data on the soft sandstone aquifer and parameters characterizing the degree of damage to the overlying strata above the top plate.

[0032] The basic data for the soft sandstone aquifer include aquifer permeability coefficient, water yield, aquifer thickness, and soft sandstone disintegration. The parameters characterizing the degree of overlying rock damage include the height of the water-conducting fracture zone and the height of the caving zone.

[0033] S2. Based on the fundamental data from S1 and the parameters characterizing the degree of overlying strata damage, the hydrophobic target aquifer is determined. Specifically, this includes the following steps:

[0034] S21. Based on the height of the water-conducting fracture zone, the height of the caving zone, the aquifer permeability coefficient, the water inflow, and the aquifer thickness, screen out all soft sandstone aquifers within the range of the height of the water-conducting fracture zone and the caving zone.

[0035] S22. Analyze the impact of mining operations on the soft sandstone aquifer.

[0036] S23. Select soft sandstone aquifers within the set influence range as hydrophobic target aquifers.

[0037] S3. After the working face roadway excavation is completed and before coal seam mining operations begin, drainage holes are constructed based on the location of the target aquifer to pre-drain water from the target aquifer. Water from the target aquifer is discharged along the drainage holes, completing one drainage operation of the target aquifer. Specifically, this includes the following steps:

[0038] S31. Construct drainage holes above the roof of the working face's retreat roadway, facing the direction of the working face's advance. For example... Figure 2 As shown, the drainage hole includes a main hole 1 and several branch holes 2, with the branch holes 2 connected to the end of the main hole 1.

[0039] S32. Insert a sleeve into the main hole 1, with both ends of the sleeve open. Install a flange on the outer end of the sleeve and set a gate.

[0040] S33. After the casing in the main borehole is completely fixed and the gate is installed, continue drilling upwards to create several branch boreholes 2, which pass through the overlying aquifer. The main sections of the several branch boreholes 2 are arranged in parallel, and the ends of the branch boreholes 2 are connected to the end of the main borehole 1 through the slant section 3.

[0041] S34. After drilling to the soft sandstone aquifer at the top, a screen pipe is placed in, with both ends of the screen pipe open and screen holes evenly distributed on the pipe wall.

[0042] S35. Repeat steps S31 to S34, constructing drainage holes at intervals of 100 to 120 meters.

[0043] S4. Coal seam mining operations are carried out. During the coal seam mining process, water-conducting fracture zones develop. The water-bearing soft sandstone fractures of the target aquifer are connected with the water-conducting fracture zone above the goaf, allowing water to flow into the goaf through the water-conducting fracture zone, thus completing the secondary drainage of the target aquifer.

[0044] This invention identifies target aquifers by acquiring basic data of soft sandstone aquifers and parameters characterizing the degree of damage to the overlying strata above the roof. Based on the location of these target aquifers, it conducts pre-drainage operations to reduce pressure and water levels in the aquifer for the first stage. Coal seam mining then commences, with water from the aquifer draining along mining-induced fractures and through boreholes to achieve a second stage of depressurization and drainage. This invention improves the depressurization and drainage effect of soft sandstone aquifers, thereby addressing, to some extent, the issue of safe and efficient coal mining under soft sandstone. Furthermore, it provides a theoretical basis for mining in aquifer areas with soft sandstone geological characteristics.

[0045] This invention uses a main hole and several branch holes to form a drainage hole, which drains the aquifer in the form of a water collection corridor. Multiple drainage and collection branch holes are combined to form a long and wide drainage zone, which can solve the problem of unevenness of soft sandstone aquifers. At the same time, multiple drainage and collection branch holes can penetrate the water-blocking fault, connecting multiple closed hydrogeological units and realizing large-scale drainage.

[0046] For any parts not mentioned above, existing technologies can be adopted or referenced.

[0047] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for hydrophobic depressurization of soft sandstone aquifers, characterized in that... Includes the following steps: S1. Obtain basic data on the soft sandstone aquifer and parameters characterizing the degree of damage to the overlying strata above the top plate; S2. Based on the basic data from S1 and the parameters characterizing the degree of overburden damage, the hydrophobic target aquifer is determined. S3. After the working face roadway is excavated and before the coal seam mining operation, drainage holes are constructed based on the location of the target aquifer to drain water in advance. Water in the target aquifer is discharged along the drainage holes to complete one drainage of the target aquifer. S4. Coal seam mining operations are carried out. During the coal seam mining process, water-conducting fracture zones develop. The water-bearing soft sandstone fractures of the target aquifer are connected with the water-conducting fracture zone above the goaf, allowing water to flow into the goaf through the water-conducting fracture zone, thus completing the secondary drainage of the target aquifer.

2. The method for hydrophobic depressurization of a soft sandstone aquifer according to claim 1, characterized in that, In step S1: the basic data of the soft sandstone aquifer include the aquifer permeability coefficient, water inflow, aquifer thickness, and soft sandstone disintegration; the parameters characterizing the degree of overburden damage include the height of the water-conducting fracture zone and the height of the collapse zone.

3. The method for hydrophobic depressurization of a soft sandstone aquifer according to claim 2, characterized in that, Step S2 includes the following steps: S21. Based on the height of the water-conducting fracture zone, the height of the caving zone, the aquifer permeability coefficient, the water inflow, and the aquifer thickness, all soft sandstone aquifers within the range of the height of the water-conducting fracture zone and the caving zone are selected. S22. Analyze the impact of mining operations on the soft sandstone aquifer. S23. Select soft sandstone aquifers within the set influence range as hydrophobic target aquifers.

4. The method for hydrophobic depressurization of a soft sandstone aquifer according to claim 1, characterized in that, Step S3 includes the following steps: S31. Construct drainage holes above the roof of the working face in the working face mining roadway in the direction of working face advancement; the drainage holes include a main hole and several branch holes, with the branch holes connected to the end of the main hole; S32. Insert a sleeve into the main hole, with both ends of the sleeve open. Install a flange on the outer end of the sleeve and set a gate. S33. After the casing in the main control is completely fixed and the gate is installed, continue drilling upwards to drill several branch holes, which pass through the overburden aquifer. S34. After drilling to the soft sandstone aquifer at the top, a screen pipe is placed in, with both ends of the screen pipe open and screen holes evenly distributed on the pipe wall. S35. Repeat steps S31 to S34, constructing drainage holes at intervals of 100 to 120 meters.

5. The method for hydrophobic depressurization of a soft sandstone aquifer according to claim 1, characterized in that, The main sections of the several branch holes are arranged in parallel, and the ends of the branch holes are connected to the ends of the main holes through the slant section.

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