Method for determining construction position of fracturing-grouting modified curtain

Abstract

The invention discloses a fracturing-grouting modified curtain construction position determination method, which comprises the following steps of: checking and cleaning a mine water filling source, determining the layer position and height of curtain construction, analyzing by combining a sedimentary environment and a sedimentary facies of a rock stratum, determining a water source supply channel, and determining a lateral influence distance of a water guide crack zone. The method comprises the steps of determining the width of a protection coal pillar and the width of a curtain according to a coal seam mining mode and the water pressure of an aquifer, carrying out hydraulic fracturing simulation, predicting the extension length and the width of a crack, determining slurry proportioning parameters, comprehensively considering the water source supply direction, the lateral influence distance of a water guide crack zone and the protection coal pillar, and determining the center position of the curtain. Evaluating the water interception effect of the curtain; according to the method, crack development, hydrostatic pressure, coal pillar mechanical characteristics and slurry diffusion rules are considered while the curtain position is set, it is guaranteed that the subsequently constructed curtain has good stability and durability, a basis is provided for subsequent adjustment and optimization, and safe production of a coal mine is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine water hazard control methods and relates to a method for determining the construction position of a fracturing-grouting modified curtain. Background Art

[0002] With the increasing requirements for safe and green mining in coal mines, coal mine water prevention and control work is gradually shifting from process management to source prevention. Among them, curtain water interception technology has become a research hotspot due to its environmental protection, high efficiency and low cost.

[0003] During coal mining, the existence of low-injectability aquifers poses a great challenge to groundwater prevention and control work. Traditional modified curtain construction methods are difficult to achieve continuous curtains, while grouting after fracturing can better achieve curtain construction in low-injectability rock formations. However, when determining the curtain construction position under the fracturing-grouting process, the existing technology does not fully consider the rock formation characteristics, the extension law of the fracturing cracks and the diffusion characteristics of the slurry, resulting in a lack of effective support for the reasonable determination of the curtain position. Therefore, there is an urgent need for a modified curtain construction position determination method for the fracturing-grouting process. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for determining the construction position of a fracturing-grouting modified curtain, which solves the problem that the construction position of the modified curtain in the fracturing-grouting process is based solely on experience without fully considering the rock formation characteristics, the extension law of the fracturing cracks and the diffusion characteristics of the slurry.

[0005] The technical solution adopted by the present invention is a method for determining the construction position of a fracturing-grouting modified curtain, comprising the following steps: Step 1: Find out the source of water for mine filling and determine the layer and height of the curtain construction; Step 2: Analyze the sedimentary environment and sedimentary facies of the rock formation to determine the water supply channel; Step 3: Determine the lateral impact distance of the water-conducting fracture zone; Step 4: Determine the width of the protective coal pillar based on the coal seam mining method and the water pressure of the aquifer; Step 5: Determine the width of the curtain; Step 6: Conduct hydraulic fracturing simulation to predict the fracture extension length and width; Step 7: Determine the slurry ratio parameters; Step 8: Determine the center position of the curtain by comprehensively considering the water supply direction, the lateral impact distance of the water-conducting fracture zone, and the protective coal pillar; Step 9: Evaluate the curtain's water-blocking effectiveness.

[0006] The present invention is also characterized in that: Step 1 is carried out as follows: Step 1.1: Conduct geological exploration, hydrogeological survey, water level correlation analysis and water quality tracing to identify the source of mine water; Step 1.2: Set the curtain construction layer in the second aquifer, and extend the top and bottom of the curtain to the first aquiclude and the second aquiclude respectively. The height of the curtain entering the first aquiclude and the height of the second aquiclude are both not less than 10m. Step 1.3, calculate the curtain construction height h :

[0007] in, h 1 is the thickness of the second aquifer, m; h 2 is the distance the curtain enters the first waterproof layer, m; h 3 is the distance the curtain enters the second waterproof layer, m.

[0008] Step 2 is carried out as follows: Step 2.1, determine the source and direction of aquifer recharge through regional groundwater flow field analysis; Step 2.2: Draw a contour map of the sand body thickness of the water-filled aquifer, a contour map of the sand-to-ground ratio of the aquifer, and a stratigraphic profile within the water-conducting fracture zone. Analyze the sedimentary environment and sedimentary facies characteristics. Combined with the recharge direction of the aforementioned water-filled source, determine the channel for strip seepage and determine whether the curtain takes the form of full or partial closure. If the seepage channel is planar, the curtain takes the form of full closure; if the seepage channel is strip-shaped, the curtain takes the form of partial closure.

[0009] In step 3, the development height and collapse angle of the water-conducting fracture zone are determined through geophysical exploration, numerical simulation, and downhole drilling exploration, and the lateral impact distance of the water-conducting fracture zone is calculated:

[0010] in, L 1 is the lateral impact distance of the water-conducting fracture zone, m; H li is the development height of the water-conducting fracture zone, m; α is the collapse angle, °; thus determining the development range of the water-conducting fracture zone.

[0011] In step 4, the width of the protective coal pillar is calculated by comprehensively considering the coal seam thickness or mining height, the actual water head value of the aquifer, and the tensile strength of the coal:

[0012] in, L 2 is the width of the protective coal pillar, m; K is the safety factor, ranging from 2 to 5; M 1 is the coal seam thickness or mining height, m;p is the actual water head value, Pa; K p is the tensile strength of coal, MPa; the width of the protective coal pillar is adjusted to be no less than 20m by adjusting the safety factor.

[0013] Calculate the width of the curtain in step 5:

[0014] in, is the width of the curtain, m; is the average permeability coefficient of the curtain, ; is the permissible per-width infiltration, ; is the water level difference between inside and outside the curtain, m.

[0015] In step 6, the compressive strength, tensile strength, elastic modulus and Poisson's ratio of the rock are tested. Combined with the horizontal stress difference of the formation and the ratio of vertical stress to horizontal stress, the fracturing pressure of 15MPa-80MPa and the pressure of 5m 3 / h-30m 3 / h fracturing flow rate is substituted into the numerical simulation software to predict the extension length and width of the fracturing crack.

[0016] In step 7, gangue, cement, and PAM anti-dispersant are selected as slurry materials based on the extension length and width of the fracturing cracks. Gangue accounts for 5%-30% by weight, PAM anti-dispersant accounts for 1%-3% by weight, and the rest is cement. After testing, the slurry is mixed so that the slurry fills the cracks, and the effective filling range of the slurry in the cracks is calculated: L y =L-L3 Among them, L y is the effective filling range of the slurry in the crack, m; L is the extension length of the fracturing crack, m; L3 is the length of the crack that cannot be filled by the slurry, m.

[0017] In step 8, the distance between the center of the curtain and the boundary of the goaf is calculated by the width of the protective coal pillar, the lateral impact distance of the water-conducting fracture zone, and the extension length of the fracturing crack: L z =L1+L2+L Among them, L z is the distance between the center of the curtain and the boundary of the goaf, m; thus determining the center of the curtain.

[0018] In step 9, water volume monitoring in the goaf and water level monitoring in the underground aquifer are carried out. By comparing the monitoring data, the construction effect of the curtain is verified: The fully enclosed curtain is qualified when the water volume after the curtain is closed does not exceed 60% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; The construction of the partially enclosed curtain is qualified when the water volume after the curtain is constructed does not exceed 30% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; If the water cutoff effect of the curtain does not meet expectations, the water cutoff effect can be improved by changing the curtain form, increasing the fracturing pressure, increasing the diffusion range of the slurry, and optimizing the curtain position.

[0019] The beneficial effects of the present invention are: The present invention adopts the combined analysis of water levels and the tracing of water quality to comprehensively determine the water source for filling, and combines the sedimentary phase analysis to determine the seepage channel of the injectable sandstone layer, thereby determining the construction layer and height of the curtain; the position of the curtain is determined by mining crack exploration, calculation of the width of the anti-waterproof coal pillar, verification of the fracturing crack and testing of the effective filling range of the slurry; while setting the curtain position, the development of cracks, hydrostatic pressure, mechanical characteristics of the coal pillar and the law of slurry diffusion are taken into consideration to ensure that the subsequently constructed curtain has good stability and durability, and realizes the logical and scientific step-by-step deep determination of the construction position of the fracturing grouting modified curtain, and through the monitoring of the crack expansion and the water volume in the goaf and the water level of the underground aquifer, the construction effect of the modified curtain can be verified in time, providing a basis for subsequent adjustment and optimization, and ensuring the safe production of the coal mine. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of the present invention; Figure 2 It is a modified curtain construction positioning diagram in the present invention; Figure 3 This is a diagram of the modified curtain fracturing grouting process of the present invention; Figure 4 This is a diagram of the construction and monitoring of the modified curtain in the present invention.

[0021] In the figure, 1. First aquifer, 2. First aquiclude, 3. Second aquifer, 4. Second aquiclude, 5. Mined coal seam, 6. Water accumulation area in goaf, 7. Roadway, 8. Water-conducting fracture, 9. Lateral impact area of ​​water-conducting fracture zone, 10. Protective coal pillar, 11. Fracturing fracture, 12. Fracture area where slurry cannot fill, 13. Fracture area where slurry effectively fills, 14. Modified curtain, 15. Fracturing fracture extension area, 16. Fracturing-grouting drilling hole, 17. Branch hole, 18. Fracturing construction vehicle, 19. Grouting construction vehicle, 20. Water level observation hole outside the wall, 21. Water level observation outside the wall, 22. Water level observation hole inside the wall, 23. Water level observation inside the wall, 24. Microseismic monitoring vehicle. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] A method for determining the location of a fracturing-grouting modified curtain construction comprises the following steps: Step 1: Carry out geological exploration, hydrogeological survey, water level correlation analysis and water quality tracing to find out the source of mine water filling. Set the curtain construction layer in the second aquifer, and the top and bottom of the curtain extend to the first aquiclude and the second aquiclude respectively. The height of the curtain entering the first aquiclude and the height of the second aquiclude are not less than 10m. Calculate the construction height of the curtain. h :

[0024] in, h 1 is the thickness of the second aquifer, m; h 2 is the distance the curtain enters the first waterproof layer, m; h 3 is the distance the curtain enters the second waterproof layer, m; Step 2: Determine the source and direction of aquifer recharge through regional groundwater flow field analysis. Draw contour maps of sand body thickness and sand-to-ground ratio of the water-filled aquifer, as well as stratigraphic profiles within the water-conducting fracture zone. Analyze the sedimentary environment and sedimentary facies characteristics. Combined with the recharge direction of the water-filled source, determine the channel for strip seepage and determine whether the curtain should be fully or partially closed. If the seepage channel is distributed in a planar manner, the curtain should be fully closed; if the seepage channel is strip-shaped, the curtain should be partially closed. Step 3: Determine the development height and collapse angle of the water-conducting fracture zone through geophysical exploration, numerical simulation, and downhole drilling exploration, and calculate the lateral impact distance of the water-conducting fracture zone:

[0025] in, L 1 is the lateral impact distance of the water-conducting fracture zone, m; H li is the development height of the water-conducting fracture zone, m; α is the collapse angle, °; thus determining the development range of the water-conducting fracture zone; Step 4: Calculate the width of the protective coal pillar based on the coal seam thickness or mining height, the actual water head value of the aquifer, and the tensile strength of the coal:

[0026] in, L 2 is the width of the protective coal pillar, m; K is the safety factor, ranging from 2 to 5; M 1 is the coal seam thickness or mining height, m; p is the actual water head value, Pa;K p is the tensile strength of coal, MPa; by adjusting the safety factor, the width of the protective coal pillar should be no less than 20m to ensure that the curtain has sufficient strength and water interception capacity; Step 5: Calculate the width of the curtain:

[0027] in, is the width of the curtain, m; is the average permeability coefficient of the curtain, ; is the permissible per-width infiltration, ; is the water level difference between inside and outside the curtain, m; Step 6: Test the rock's compressive strength, tensile strength, elastic modulus, and Poisson's ratio, and set a fracturing pressure of 15MPa-80MPa and a 5m 3 / h-30m 3 / h fracturing flow rate and substituted it into the numerical simulation software to predict the extension length and width of the fracturing crack; Step 7: Based on the extension length and width of the fracturing cracks, select gangue, cement, and PAM anti-dispersant as the slurry mix materials, with gangue accounting for 5%-30% by weight, PAM anti-dispersant accounting for 1%-3% by weight, and the rest being cement. After testing, mix the slurry so that it fills the cracks, and calculate the effective filling range of the slurry in the cracks: L y =L-L3 Among them, L y is the effective filling range of the slurry in the crack, m; L is the extension length of the fracturing crack, m; L3 is the length of the crack that cannot be filled by the slurry, m; Step 8: Calculate the distance between the center of the curtain and the boundary of the goaf by using the width of the protective coal pillar, the lateral impact distance of the water-conducting fracture zone, and the extension length of the fracturing crack: L z =L1+L2+L Among them, L z is the distance between the center of the curtain and the boundary of the goaf, m; thus, the center of the curtain is determined to ensure that the curtain can effectively cut off the groundwater recharge channel. The center of the curtain is located at the center of the drilling and fracturing. Step 9: Carry out water volume monitoring in the goaf and water level monitoring in the underground aquifer, and verify the construction effect of the curtain by comparing the monitoring data: The fully enclosed curtain is qualified when the water volume after the curtain is closed does not exceed 60% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; The construction of the partially enclosed curtain is qualified when the water volume after the curtain is constructed does not exceed 30% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; If the water cutoff effect of the curtain does not meet expectations, the water cutoff effect can be improved by changing the curtain form, increasing the fracturing pressure, increasing the diffusion range of the slurry, and optimizing the curtain position.

[0028] Among them, the top of the mined coal seam is the second aquiclude, the second aquifer, the first aquiclude, and the first aquifer in sequence, and the second aquifer is a directly charged aquifer.

[0029] Example 1: A method for determining the location of a fracturing-grouting modified curtain construction comprises the following steps: Step 1: Find out the source of water for mine filling and determine the layer and height of the curtain construction; Step 2: Analyze the sedimentary environment and sedimentary facies of the rock formation to determine the water supply channel; Step 3: Determine the development height and collapse angle of the water-conducting fracture zone through geophysical exploration, numerical simulation, and downhole drilling exploration, and calculate the lateral impact distance of the water-conducting fracture zone:

[0030] in, L 1 is the lateral impact distance of the water-conducting fracture zone, m; H li is the development height of the water-conducting fracture zone, m; α is the collapse angle, °; thus determining the development range of the water-conducting fracture zone; Step 4: Calculate the width of the protective coal pillar based on the coal seam thickness or mining height, the actual water head value of the aquifer, and the tensile strength of the coal:

[0031] in, L 2 is the width of the protective coal pillar, m; K is the safety factor, ranging from 2 to 5; M 1 is the coal seam thickness or mining height, m; p is the actual water head value, Pa; K p is the tensile strength of coal, MPa; the width of the protective coal pillar is set to 30m by adjusting the safety factor; Step 5: Determine the width of the curtain; Step 6: Test the compressive strength, tensile strength, elastic modulus, and Poisson's ratio of the rock, and set the fracturing pressure of 15 MPa and 5 m 3 / h fracturing flow rate and substituted it into the numerical simulation software to predict the extension length and width of the fracturing crack; Step 7: Based on the extension length and width of the fracturing cracks, select gangue, cement, and PAM anti-dispersant as the slurry mix materials, with gangue accounting for 5% by weight, PAM anti-dispersant accounting for 1% by weight, and the rest being cement. After testing, mix the slurry so that it fills the cracks, and calculate the effective filling range of the slurry in the cracks: L y =L-L3 Among them, L y is the effective filling range of the slurry in the crack, m; L is the extension length of the fracturing crack, m; L3 is the length of the crack that cannot be filled by the slurry, m; Step 8: Calculate the distance between the center of the curtain and the boundary of the goaf by using the width of the protective coal pillar, the lateral impact distance of the water-conducting fracture zone, and the extension length of the fracturing crack: L z =L1+L2+L Among them, L z is the distance between the center of the curtain and the boundary of the goaf, m; thus determining the center of the curtain; Step 9: Evaluate the curtain's water-blocking effectiveness.

[0032] Example 2: A method for determining the location of a fracturing-grouting modified curtain construction comprises the following steps: Step 1: Carry out geological exploration, hydrogeological survey, water level correlation analysis and water quality tracing to find out the source of water filling the mine. Set the curtain construction layer in the second aquifer, and extend the top and bottom of the curtain to the first aquiclude and the second aquiclude respectively. The height of the curtain entering the first aquiclude and the height of the second aquiclude are both 10m. Calculate the construction height of the curtain h :

[0033] in, h 1 is the thickness of the second aquifer, m; h 2 is the distance the curtain enters the first waterproof layer, m; h 3 is the distance the curtain enters the second waterproof layer, m; Step 2: Analyze the sedimentary environment and sedimentary facies of the rock formation to determine the water supply channel; Step 3: Determine the development height and collapse angle of the water-conducting fracture zone through geophysical exploration, numerical simulation, and downhole drilling exploration, and calculate the lateral impact distance of the water-conducting fracture zone:

[0034] in, L1 is the lateral impact distance of the water-conducting fracture zone, m; H li is the development height of the water-conducting fracture zone, m; α is the collapse angle, °; thus determining the development range of the water-conducting fracture zone; Step 4: Calculate the width of the protective coal pillar based on the coal seam thickness or mining height, the actual water head value of the aquifer, and the tensile strength of the coal:

[0035] in, L 2 is the width of the protective coal pillar, m; K is the safety factor, ranging from 2 to 5; M 1 is the coal seam thickness or mining height, m; p is the actual water head value, Pa; K p is the tensile strength of coal, MPa; the width of the protective coal pillar is adjusted to be no less than 20m by adjusting the safety factor; Step 5: Calculate the width of the curtain:

[0036] in, is the width of the curtain, m; is the average permeability coefficient of the curtain, ; is the permissible per-width infiltration, ; is the water level difference between inside and outside the curtain, m; Step 6: Conduct hydraulic fracturing simulation to predict the fracture extension length and width; Step 7: Based on the extension length and width of the fracturing cracks, select gangue, cement, and PAM anti-dispersant as the slurry mix materials, with gangue accounting for 30% by weight, PAM anti-dispersant accounting for 3% by weight, and the rest being cement. After testing, mix the slurry so that it fills the cracks, and calculate the effective filling range of the slurry in the cracks: L y =L-L3 Among them, L y is the effective filling range of the slurry in the crack, m; L is the extension length of the fracturing crack, m; L3 is the length of the crack that cannot be filled by the slurry, m; Step 8: Determine the center position of the curtain by comprehensively considering the water supply direction, the lateral impact distance of the water-conducting fracture zone, and the protective coal pillar; Step 9: Evaluate the curtain's water-blocking effectiveness.

[0037] Example 3: A method for determining the location of a fracturing-grouting modified curtain construction comprises the following steps: Step 1: Carry out geological exploration, hydrogeological survey, water level correlation analysis and water quality tracing to find out the source of mine water filling. Set the curtain construction layer in the second aquifer, and extend the top and bottom of the curtain to the first aquiclude and the second aquiclude respectively. The height of the curtain entering the first aquiclude and the height of the second aquiclude are both 20m. Calculate the construction height of the curtain h :

[0038] in, h 1 is the thickness of the second aquifer, m; h 2 is the distance the curtain enters the first waterproof layer, m; h 3 is the distance the curtain enters the second waterproof layer, m; Step 2: Determine the source and direction of aquifer recharge through regional groundwater flow field analysis. Draw contour maps of sand body thickness and sand-to-ground ratio of the water-filled aquifer, as well as stratigraphic profiles within the water-conducting fracture zone. Analyze the sedimentary environment and sedimentary facies characteristics. Combined with the recharge direction of the water-filled source, determine the channel for strip seepage and determine whether the curtain should be fully or partially closed. If the seepage channel is distributed in a planar manner, the curtain should be fully closed. If the seepage channel is strip-shaped, the curtain should be partially closed. Step 3: Determine the lateral impact distance of the water-conducting fracture zone; Step 4: Determine the width of the protective coal pillar based on the coal seam mining method and the water pressure of the aquifer; Step 5: Determine the width of the curtain; Step 6: Test the rock's compressive strength, tensile strength, elastic modulus, and Poisson's ratio, and set a fracturing pressure of 80 MPa and a pressure of 30 m3 / s based on the horizontal stress difference and the ratio of vertical stress to horizontal stress. 3 / h fracturing flow rate and substituted it into the numerical simulation software to predict the extension length and width of the fracturing crack; Step 7: Determine the slurry ratio parameters; Step 8: Determine the center position of the curtain by comprehensively considering the water supply direction, the lateral impact distance of the water-conducting fracture zone, and the protective coal pillar; Step 9: Carry out water volume monitoring in the goaf and water level monitoring in the underground aquifer, and verify the construction effect of the curtain by comparing the monitoring data: The fully enclosed curtain is qualified when the water volume after the curtain is closed does not exceed 60% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; The construction of the partially enclosed curtain is qualified when the water volume after the curtain is constructed does not exceed 30% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; If the water cutoff effect of the curtain does not meet expectations, the water cutoff effect can be improved by changing the curtain form, increasing the fracturing pressure, increasing the diffusion range of the slurry, and optimizing the curtain position.

[0039] Example 4: A method for determining the location of a fracturing-grouting modified curtain construction comprises the following steps: Step 1: Carry out geological exploration, hydrogeological survey, water level correlation analysis and water quality tracing to find out the source of water filling the mine. Set the curtain construction layer in the second aquifer, and extend the top and bottom of the curtain to the first aquiclude and the second aquiclude respectively. The height of the curtain entering the first aquiclude and the height of the second aquiclude are both 10m. Calculate the construction height of the curtain h :

[0040] in, h 1 is the thickness of the second aquifer, m; h 2 is the distance the curtain enters the first waterproof layer, m; h 3 is the distance the curtain enters the second waterproof layer, m; Step 2: Determine the source and direction of aquifer recharge through regional groundwater flow field analysis. Draw contour maps of sand body thickness and sand-to-ground ratio of the water-filled aquifer, as well as stratigraphic profiles within the water-conducting fracture zone. Analyze the sedimentary environment and sedimentary facies characteristics. Combined with the recharge direction of the water-filled source, determine the channel for strip seepage and determine whether the curtain should be fully or partially closed. If the seepage channel is distributed in a planar manner, the curtain should be fully closed; if the seepage channel is strip-shaped, the curtain should be partially closed. Step 3: Determine the development height and collapse angle of the water-conducting fracture zone through geophysical exploration, numerical simulation, and downhole drilling exploration, and calculate the lateral impact distance of the water-conducting fracture zone:

[0041] in, L 1 is the lateral impact distance of the water-conducting fracture zone, m; H li is the development height of the water-conducting fracture zone, m; α is the collapse angle, °; thus determining the development range of the water-conducting fracture zone; Step 4: Calculate the width of the protective coal pillar based on the coal seam thickness or mining height, the actual water head value of the aquifer, and the tensile strength of the coal:

[0042] in, L 2 is the width of the protective coal pillar, m; K is the safety factor, ranging from 2 to 5; M1 is the coal seam thickness or mining height, m; p is the actual water head value, Pa; K p is the tensile strength of coal, MPa; the width of the protective coal pillar is set to 20m by adjusting the safety factor; Step 5: Determine the width of the curtain; Step 6: Conduct hydraulic fracturing simulation to predict the fracture extension length and width; Step 7: Determine the slurry ratio parameters; Step 8: Determine the center position of the curtain by comprehensively considering the water supply direction, the lateral impact distance of the water-conducting fracture zone, and the protective coal pillar; Step 9: Evaluate the curtain's water-blocking effectiveness.

[0043] Example 5: A method for determining the location of a fracturing-grouting modified curtain construction comprises the following steps: Step 1: Carry out geological exploration, hydrogeological survey, water level correlation analysis and water quality tracing to find out the source of mine water filling. Set the curtain construction layer in the second aquifer, and extend the top and bottom of the curtain to the first aquiclude and the second aquiclude respectively. The height of the curtain entering the first aquiclude and the height of the second aquiclude are both 15m. Calculate the construction height of the curtain h :

[0044] in, h 1 is the thickness of the second aquifer, m; h 2 is the distance the curtain enters the first waterproof layer, m; h 3 is the distance the curtain enters the second waterproof layer, m; Step 2: Analyze the sedimentary environment and sedimentary facies of the rock formation to determine the water supply channel; Step 3: Determine the development height and collapse angle of the water-conducting fracture zone through geophysical exploration, numerical simulation, and downhole drilling exploration, and calculate the lateral impact distance of the water-conducting fracture zone:

[0045] in, L 1 is the lateral impact distance of the water-conducting fracture zone, m; H li is the development height of the water-conducting fracture zone, m; α is the collapse angle, °; thus determining the development range of the water-conducting fracture zone; Step 4: Calculate the width of the protective coal pillar based on the coal seam thickness or mining height, the actual water head value of the aquifer, and the tensile strength of the coal:

[0046] in,L 2 is the width of the protective coal pillar, m; K is the safety factor, ranging from 2 to 5; M 1 is the coal seam thickness or mining height, m; p is the actual water head value, Pa; K p is the tensile strength of coal, MPa; the width of the protective coal pillar is set to 25m by adjusting the safety factor; Step 5: Determine the width of the curtain; Step 6: Test the rock's compressive strength, tensile strength, elastic modulus, and Poisson's ratio, and set a fracturing pressure of 50 MPa and a pressure of 20 m3 / s based on the horizontal stress difference and the ratio of vertical stress to horizontal stress. 3 / h fracturing flow rate and substituted it into the numerical simulation software to predict the extension length and width of the fracturing crack; Step 7: Based on the extension length and width of the fracturing cracks, select gangue, cement, and PAM anti-dispersant as the slurry mix materials, with gangue accounting for 20% by weight, PAM anti-dispersant accounting for 2% by weight, and the rest being cement. After testing, mix the slurry so that it fills the cracks, and calculate the effective filling range of the slurry in the cracks: L y =L-L3 Among them, L y is the effective filling range of the slurry in the crack, m; L is the extension length of the fracturing crack, m; L3 is the length of the crack that cannot be filled by the slurry, m; Step 8: Determine the center position of the curtain by comprehensively considering the water supply direction, the lateral impact distance of the water-conducting fracture zone, and the protective coal pillar; Step 9: Evaluate the curtain's water-blocking effectiveness.

[0047] Example 6: For example, a mine in Inner Mongolia and Shaanxi Province experienced significant water inflow from the working face after mining, and the overburden aquifers all exhibited low injectability. Through steps 1-9, the seepage channels of the injectable sandstone layers were identified, and a modified curtain was constructed to improve water interception. Two ground boreholes with a depth of 480-560m were constructed in the sandstone layer area. Transient electromagnetic and direct current geophysical exploration methods were used, combined with regional hydrological monitoring data and water chemical analysis results, to find out that the water source came from the Zhiluo Formation aquifer in the area, which is 28-40m vertically away from the coal seam roof. This water-filled aquifer is mainly replenished laterally, and the replenishment direction is from northwest to southeast. Through the sedimentary phase analysis of the sandstone layer, combined with the previous drilling and geophysical exploration results, it was determined that the water source replenishment channel is the high permeability layer in the sandstone layer. On this basis, microseismic monitoring, numerical simulation and underground measurement methods were used to determine the lateral impact distance of the water-conducting fracture zone, and its development height reached the coal seam. The coal seam mining area is 125m above the seam, the rock movement angle is 63°, and the lateral impact boundary is 21m. According to the development of the water-conducting fracture zone and the mining method of the coal seam, considering that the water pressure of the regional aquifer can reach 4.8MPa, referring to the "Detailed Rules for Water Prevention and Control in Coal Mines", the width of the protective coal pillar is determined to be 33 meters, that is, the boundary of the curtain should be 54m away from the boundary of the goaf. Taking into account the direction of water supply, the lateral impact distance of the water-conducting fracture zone and the setting of the protective coal pillar, the modified curtain boundary is set on the northwest side of the coal seam mining area, parallel to the boundary of the goaf. After exploration and analysis, the position requirements of the curtain arrangement are determined, and further core testing of the water conductivity and mechanical properties of the rock formation is carried out. Theoretical calculations and numerical simulations were carried out to determine the height of the modified curtain to be 50 meters (10 meters into each of the two aquicludes) and the width of the modified curtain to be 20 meters. Fracturing tests were carried out indoors to study the crack expansion characteristics. Combined with numerical simulations, the fracturing pressure was designed to be 20 MPa and the fracturing fluid flow rate to be 10 m³ / min. Hydraulic fracturing was implemented. During the fracturing process, the microseismic monitoring system was used to monitor the expansion of the cracks in real time, and the fracturing parameters were dynamically adjusted to ensure that the crack width had good slurry passing capacity and the connectivity of the cracks. The crack expansion monitoring and exploration verification were carried out. The drilling peek technology was used to explore and verify the cracks after hydraulic fracturing. The results showed that the development of cracks met the design requirements, and the injectability and connectivity of the sandstone layer were significantly improved. According to the development degree and width of the cracks, the mass ratio of gangue, cement and PAM anti-dispersant was determined to be 15:83:2 to form grouting slurry, which was injected into the cracks of the sandstone layer. After the construction of the modified curtain was completed, the water volume in the goaf and the water level of the underground aquifer were continuously monitored. After a period of monitoring, it was found that the water volume in the goaf was significantly reduced, with a reduction of 45%. The downward trend of the water level of the underground aquifer was effectively controlled, especially the water level difference inside and outside the modified curtain was as high as 120m, indicating that the construction effect of the modified curtain was good.

Claims

1. A method for determining the location of a fracturing-grouting modified curtain, characterized in that: The following steps are involved: Step 1: Identify the source of water for mine filling and determine the layer and height of the curtain construction; Step 2: Analyze the sedimentary environment and sedimentary facies of the rock formation to determine the water supply channel; Step 3: Determine the lateral impact distance of the water-conducting fracture zone; Step 4: Determine the width of the protective coal pillar based on the coal seam mining method and the water pressure of the aquifer; Step 5: Determine the width of the curtain; Step 6: Conduct hydraulic fracturing simulation to predict the fracture extension length and width; Step 7: Determine the slurry ratio parameters; Step 8: Determine the center position of the curtain by comprehensively considering the water supply direction, the lateral impact distance of the water-conducting fracture zone, and the protective coal pillar; Step 9: Evaluate the curtain's water-blocking effectiveness.

2. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 1, characterized in that: The step 1 is specifically performed as follows: Step 1.1: Conduct geological exploration, hydrogeological survey, water level correlation analysis and water quality tracing to identify the source of mine water; Step 1.2: Set the curtain construction layer in the second aquifer, and extend the top and bottom of the curtain to the first aquiclude and the second aquiclude respectively. The height of the curtain entering the first aquiclude and the height of the second aquiclude are both not less than 10m. Step 1.3, calculate the curtain construction height h : in, h 1 is the thickness of the second aquifer, m; h 2 is the distance the curtain enters the first waterproof layer, m; h 3 is the distance the curtain enters the second waterproof layer, m.

3. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 1, characterized in that: The step 2 is specifically performed as follows: Step 2.1, determine the source and direction of aquifer recharge through regional groundwater flow field analysis; Step 2.2: Draw the sand body thickness contour map of the water-filled aquifer, the sand-to-ground ratio contour map of the aquifer, and the stratigraphic profile within the water-conducting fracture zone. Analyze the sedimentary environment and sedimentary facies characteristics. Combined with the recharge direction of the water-filled source, determine the strip seepage channel and determine whether the curtain takes the form of full or partial closure. If the seepage channel is distributed in a planar manner, the curtain takes the form of full closure; if the seepage channel is strip-shaped, the curtain takes the form of partial closure.

4. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 1, characterized in that: In step 3, the development height and collapse angle of the water-conducting fracture zone are determined through geophysical exploration, numerical simulation, and downhole drilling exploration, and the lateral impact distance of the water-conducting fracture zone is calculated: in, L 1 is the lateral impact distance of the water-conducting fracture zone, m; H li is the development height of the water-conducting fracture zone, m; α is the collapse angle, °; thus determining the development range of the water-conducting fracture zone.

5. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 4, characterized in that: In step 4, the width of the protective coal pillar is calculated by comprehensively considering the coal seam thickness or mining height, the actual water head value of the aquifer, and the tensile strength of the coal: in, L 2 is the width of the protective coal pillar, m; K is the safety factor, ranging from 2 to 5; M 1 is the coal seam thickness or mining height, m; p is the actual water head value, Pa; K p is the tensile strength of coal, MPa; the width of the protective coal pillar is adjusted to be no less than 20m by adjusting the safety factor.

6. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 2, characterized in that: Calculate the width of the curtain in step 5: in, is the width of the curtain, m; is the average permeability coefficient of the curtain, ; is the permissible per-width infiltration, ; is the water level difference between inside and outside the curtain, m.

7. The method for determining the construction position of a fracturing-grouting modified curtain according to any one of claims 1 to 6, characterized in that: In step 6, the compressive strength, tensile strength, elastic modulus and Poisson's ratio of the rock are tested, and the fracturing pressure of 15MPa-80MPa and 5m are set according to the horizontal stress difference of the formation and the ratio of vertical stress to horizontal stress. 3 / h-30m 3 / h fracturing flow rate is substituted into the numerical simulation software to predict the extension length and width of the fracturing crack.

8. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 5, characterized in that: In step 7, gangue, cement, and PAM anti-dispersant are selected as slurry materials according to the extension length and width of the fracturing cracks, wherein the gangue accounts for 5%-30% by weight, the PAM anti-dispersant accounts for 1%-3% by weight, and the remainder is cement. After testing, the slurry is prepared so that the slurry fills the cracks, and the effective filling range of the slurry in the cracks is calculated: L y =L-L3 Among them, L y is the effective filling range of the slurry in the crack, m; L is the extension length of the fracturing crack, m; L3 is the length of the crack that cannot be filled by the slurry, m.

9. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 8, characterized in that: In step 8, the distance between the center of the curtain and the boundary of the goaf is calculated by using the width of the protective coal pillar, the lateral impact distance of the water-conducting fracture zone, and the extension length of the fracturing crack: L z =L1+L2+L Among them, L z is the distance between the center of the curtain and the boundary of the goaf, m; thus determining the center of the curtain.

10. The method for determining the construction position of a fracturing-grouting modified curtain according to claim 3, characterized in that: In step 9, water volume monitoring of the goaf and water level monitoring of the underground aquifer are carried out, and the construction effect of the curtain is verified by comparing the monitoring data: The fully enclosed curtain is qualified when the water volume after the curtain is closed does not exceed 60% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; The construction of the partially enclosed curtain is qualified when the water volume after the curtain is constructed does not exceed 30% of the water volume before the project and the water level difference between the inside and outside of the curtain is not less than 20% of the external water level; If the water cutoff effect of the curtain does not meet expectations, the water cutoff effect can be improved by changing the curtain form, increasing the fracturing pressure, increasing the diffusion range of the slurry, and optimizing the curtain position.

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