Wavy directional drilling and grouting reconstruction method for rock stratum with complex fracture structure

Abstract

This invention discloses a method for wavy directional drilling and grouting modification of complex fractured rock strata. First, by analyzing the overburden structure of the coal seam roof, permeable windows in the key water-resistant layer are identified. Second, by analyzing the overburden structure of the coal seam roof, the spatial structure of the weathered and normal bedrock layers in the window area is identified. Third, the height of the caving zone and fracture zone formed by coal seam mining in the permeable window area is predicted. Fourth, the relationship between the mining-induced water-conducting fractures and the exposed weathered bedrock layer in the window area is analyzed to identify areas where grouting can be used to treat the permeable window. Fifth, based on the identified areas where grouting can be used, wavy directional boreholes are designed on the surface in the weathered bedrock layer of the window area. Sixth, the wavy directional boreholes are drilled and grouting is carried out to create an artificially reconstructed water-blocking layer in the permeable window area, thereby reducing water inflow from the roof of the coal mining face and protecting groundwater resources.

Description

Technical Field

[0001] This invention relates to the technical field of mine water control and groundwater resource protection, and in particular to a method for wavy directional drilling and grouting modification of complex fractured rock strata. Background Technology

[0002] In the Yushen, Yuheng, and Shenfu coal mining areas of the western Jurassic coalfield, the main coal seams mined are the Yan'an Formation of the Jurassic system. During the deposition of the overlying strata, weathering geological processes have resulted in the formation of a 10-30m weathered bedrock layer with well-developed weathering fissures on the top surface of the normal bedrock layer. The low-permeability soil layers of the Tertiary Baode Formation and Lishi Formation at the top of the weathered bedrock layer are key water-blocking layers that protect the groundwater of the loose aquifers near the surface. This "coal-bedrock-weather-soil-sand" stratigraphic structure forms a typical hydrogeological structure of the mining area, with "coal below and water above, and coal and water coexisting". However, the key water-controlling strata were subjected to geological erosion (such as wind erosion and rainwater erosion) during the deposition process, resulting in unstable deposition thickness and range. They were missing in large areas in the Shenfu mining area and in local areas in the Yushen and Yuheng mining areas, forming typical permeable "skylights". This led to a close hydraulic connection between the Jurassic weathered bedrock aquifer and the near-surface Quaternary loose aquifer (Salawusu Formation, aeolian sand, etc.).

[0003] In the Yushen and other medium-deep coal seam mining areas, mining-induced water-conducting fractures (the sum of caving zones and fissure zones) easily breach the normal bedrock layer and develop into the weathered bedrock aquifer. In areas lacking critical aquitard layers or with water-blocking windows, hydraulically connected groundwater from the weathered bedrock aquifer and near-surface water-rich loose aquifers enters the mining space, generally causing severe roof water hazards and groundwater loss from loose aquifers. For example, many production mines in the Yushen mining area have normal water inflow rates exceeding 1000 m³ / h, and the water level in the near-surface water-supplying aquifer (Quaternary loose aquifer) continues to decline. In recent years, the problems of large-scale water inflow from mine roof aquifers and groundwater loss have become extremely prominent, significantly impacting mine safety and water resource protection.

[0004] To improve the water-blocking capacity of rock strata, grouting is typically used to fill and modify the fissures in the coal seam overburden. In existing technologies, the weathered bedrock layer is usually used as the receiving layer, and vertical boreholes are used to grout and modify this layer, transforming the weathered bedrock aquifer into a relatively impermeable layer to control the leakage of groundwater in the loose aquifers near the surface in areas with missing soil layers and open spaces. However, this method has problems such as large drilling volume, many ineffective drilling steps, and a low drilling rate for vertical fissures in the receiving rock strata (the probability of fissures revealed by the borehole), resulting in poor grouting effect. Summary of the Invention

[0005] The purpose of this invention is to provide a method for wavy directional drilling and grouting modification of complex fractured rock strata, so as to solve the problems of large drilling volume, many ineffective drilling steps, and poor grouting effect in the existing technology.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for wavy directional drilling and grouting modification of complex fractured rock strata includes the following steps:

[0008] Step 1: Analyze the overburden structure of the coal seam that requires drilling and grouting, and determine its hydrogeological structure;

[0009] Step 2: Based on the hydrogeological structure obtained in Step 1, determine the permeable skylight area formed due to the lack of its aquitard layer, and at the same time determine the thickness of the weathered bedrock in the permeable skylight area and predict the height of the mining-induced water-conducting fractures formed by coal seam mining.

[0010] Step 3: Analyze the relationship between the thickness of weathered bedrock in the permeable skylight area and the height of mining-induced water-conducting fractures obtained in Step 2, and determine all groutable skylight areas;

[0011] Step 4: Among all the groutable skylight areas identified in Step 3, select one groutable skylight area and design a directional drilling structure with a wavy shape that has a gentle undulation on the cross-section and a height-to-width ratio of less than 1:2.

[0012] Step 5: Grouting is performed on the wavy directional boreholes designed in Step 4 to form a grouting modification layer;

[0013] Step 6: Among all the groutable skylight areas identified in Step 3, select the areas that have not yet been grouted and repeat Steps 4 and 5 until all groutable skylight areas have been grouted.

[0014] Step 2 is implemented through the following sub-steps:

[0015] Step a:

[0016] Step a1: Identify the hydrogeological structure in Step 1 and determine the permeable skylight area;

[0017] Step a2: Identify the thickness of weathered bedrock in the permeable skylight area in step a1;

[0018] Step b:

[0019] Step b1: Identify the hydrogeological structure in Step 1, and predict the height of the caving zone and the fracture zone based on the thickness of the main coal seam.

[0020] Step b2: Determine the height of the mining-induced water-conducting fracture by summing the height of the caving zone and the fracture zone in step b1.

[0021] In step a1, sections with a critical waterproof layer thickness of ≤5m are identified as permeable skylight areas;

[0022] Step 3 is implemented through the following sub-steps:

[0023] Step 31: Analyze the relationship between the thickness of weathered bedrock in the permeable window area and the height of the mining-induced water-conducting fractures obtained in steps a2 and b2.

[0024] Step 32: Subtract the height of the mining-induced water-conducting fractures from the thickness of the weathered bedrock in the permeable skylight area to obtain the thickness of the residual weathered bedrock layer in the permeable skylight area.

[0025] Step 33: Define the sections with a residual weathered bedrock thickness > 5m in the permeable skylight area as groutable skylight areas, and determine all groutable skylight areas;

[0026] Step 4 is implemented through the following sub-steps:

[0027] Step 41: Among all the groutable skylight areas determined in step 33, select one groutable skylight area, expand the groutable skylight area outward, and designate the expanded area as the drilling and grouting modification area.

[0028] Step 42: Design multiple wavy directional boreholes within the drilling and grouting modification zone;

[0029] In step 41, extend outwards by 30-50m along the perimeter of the groutable skylight area;

[0030] In step 42, the center baselines of each wavy directional borehole are arranged in parallel with a spacing of 15-30m.

[0031] The design center baseline for wavy directional boreholes is set at a point 1 / 2 times the thickness of the residual weathered bedrock strata in the permeable window zone below the top of the weathered bedrock aquifer. The wave amplitude width is 3-5 times the thickness of the residual weathered bedrock strata in the permeable window zone, and the wave amplitude height is 2 / 3 times the thickness of the residual weathered bedrock strata in the permeable window zone. The peaks and troughs of adjacent wavy directional boreholes are complementary.

[0032] The present invention also has the following features:

[0033] Furthermore, step 5 is specifically implemented through the following sub-steps:

[0034] Step 51: During the wavy directional drilling process in Step 4, inject fly ash-based slurry and stop the injection when the injection pressure reaches the specified value;

[0035] Step 52: After stopping the injection, continue drilling along the wavy directional section, and circulate the grouting through the wavy directional borehole to fill the cracks in the weathered bedrock layer, until the designed final hole is reached and the grouting is finally completed, forming a grouting modification layer.

[0036] Furthermore, in step 51, the injection is stopped when the injection pressure is >1 MPa.

[0037] Furthermore, during the drilling of the wavy directional section, grouting was carried out according to the principle of grouting whenever leakage occurred.

[0038] Compared with the prior art, the present invention has the following technical effects:

[0039] (I) The method of wavy directional drilling and grouting modification for complex fractured rock strata of the present invention adopts wavy directional drilling and grouting modification to form a cross-sectional staggered directional borehole arrangement pattern. While revealing vertical fractures, it also reveals multiple sets of near-horizontal fractures multiple times, overcoming the problems of large drilling workload, many ineffective advances, and insufficient reliability of grouting modification.

[0040] (II) The method of wavy directional drilling and grouting modification of complex fractured rock strata of the present invention forms an artificial water-blocking layer in the permeable skylight area by wavy directional drilling and coordinated grouting modification on the construction surface, thereby reducing the water inflow of the roof of the coal mining face and protecting groundwater resources. It is suitable for large-scale industrial use and promotion. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the borehole cross-section arrangement for wavy directional grouting treatment of the groutable skylight area in the method of the present invention;

[0042] Figure 2 This is a schematic diagram of the wavy directional drilling grouting method of the present invention;

[0043] Figure 3 This is a schematic diagram of the borehole layout for wavy directional grouting treatment of the groutable skylight area in the method of the present invention;

[0044] Figure 4 This is a schematic diagram of a typical hydrogeological structure in this invention. Detailed Implementation

[0045] This invention provides a method for wavy directional drilling and grouting modification of complex fractured rock strata, comprising the following steps:

[0046] Step 1: Analyze the overburden structure of the coal seam that requires drilling and grouting, and determine its hydrogeological structure.

[0047] Step 2: Based on the hydrogeological structure obtained in Step 1, determine the permeable skylight area formed due to the absence of its impermeable layer, and simultaneously determine the thickness M of the weathered bedrock in the permeable skylight area.风基 It is also estimated that the height of the water-conducting fractures caused by coal seam mining will be higher.

[0048] Step 3: Analyze the relationship between the thickness of weathered bedrock in the permeable skylight area and the height of mining-induced water-conducting fractures obtained in Step 2, and determine all skylight areas that can be grouted.

[0049] Step 4: Among all the groutable skylight areas identified in Step 3, select one groutable skylight area and design a directional drilling structure with a wavy shape that has a gentle undulation on the cross-section and a height-to-width ratio of less than 1:2.

[0050] Step 5: Grouting modification is performed on the wavy directional boreholes designed in Step 4 to form a grouting modification layer.

[0051] Step 6: Among all the groutable skylight areas identified in Step 3, select the areas that have not yet been grouted and repeat Steps 4 and 5 until all groutable skylight areas have been grouted.

[0052] By adopting wavy directional drilling and grouting modification, a cross-sectional directional drilling design pattern was formed. While exposing vertical fractures, multiple sets of near-horizontal fractures were exposed multiple times, ensuring sufficient exposure of the rock strata in all directions. This overcame the problems of insufficient reliability of grouting modification caused by large drilling volume and many ineffective advances.

[0053] As a preferred option, in step 2, based on its hydrogeological structure, the thickness M of the weathered bedrock in the permeable skylight area is determined through steps a and b, respectively. 风基 and the height of the water-conducting fissure.

[0054] Step a: Identify the hydrogeological structure from Step 1, determine the permeable skylight area, and identify the thickness M of the weathered bedrock in the permeable skylight area. 风基。

[0055] Step b: Identify the hydrogeological structure in Step 1, and based on the thickness of the main coal seam, predict the height of the caving zone and the height of the fracture zone respectively, and determine the sum of the height of the caving zone and the height of the fracture zone in Step b1 as the height of the mining-induced water-conducting fracture.

[0056] As a preferred approach, in the third step, firstly, by plotting value lines, the relationship between the thickness of weathered bedrock in the permeable window area and the height of the mining-induced water-conducting fractures obtained in steps a2 and b2 is analyzed. Secondly, the thickness of the residual rock layer (M) is obtained by subtracting the height of the mining-induced water-conducting fractures from the thickness of the weathered bedrock in the permeable window area. 残 ( ) Value line map. Finally, sections with residual rock layer thickness > 5m were designated as groutable skylights, thus identifying all groutable skylights and making the identification of groutable skylights more accurate.

[0057] As a preferred option, in the fourth step, one groutable window area is selected from all groutable window areas, and this groutable window area is expanded outwards, with the expanded area designated as the drilling and grouting modification zone; for example... Figures 1 to 3 As shown, wavy directional boreholes are designed within the drilling and grouting modification zone.

[0058] In a further preferred embodiment, in the fourth step, the center baselines of each wavy directional borehole are arranged in parallel with a spacing of 15-30m.

[0059] 1 / 2 M below the top of the weathered bedrock 残 The baseline of the wavy directional drilling design is 3-5 times the M. 残 For amplitude width, 2 / 3 times M 残 The amplitude height; where the peaks and troughs of adjacent wavy directional boreholes are complementary.

[0060] The center baselines of each wavy directional borehole are arranged in parallel, and the "peaks" and "troughs" of adjacent wavy directional boreholes are designed to complement each other, forming a directional borehole arrangement pattern with staggered and complementary profiles. While revealing vertical fractures, multiple sets of near-horizontal fractures are revealed multiple times.

[0061] As a preferred option, grouting modification is performed on one of the wavy directional boreholes. During the drilling of the wavy directional borehole, fly ash-based grout is injected, and the injection is stopped when the injection pressure reaches the specified value. After the injection is stopped, drilling continues along the wavy directional section, and grouting is circulated through the wavy directional borehole to fill the fissures in the weathered bedrock layer, achieving the design target and finally completing the grouting, improving the grouting effect, reducing the amount of work, and forming a grouting modification layer.

[0062] Further optimized, during the drilling of the wavy directional section, grouting is carried out according to the principle of grouting every leak. The grout is selected according to conventional methods, and a fly ash-based grout with clay, cement and fly ash as the base is adopted to further improve the grouting effect.

[0063] This completes the grouting modification layer. This water interception and drainage method, which targets concentrated water inflow channels in the roof of coal seams using a combination of surface wavy directional drilling and grouting modification, solves the problems of water waste caused by traditional drilling and drainage methods, as well as low coal resource recovery rates and inefficiencies in coal mining techniques such as height-restricted mining. It overcomes the problems of low drilling efficiency for vertical fractures and low drilling efficiency for near-horizontal fractures in near-horizontal directional drilling, as well as insufficient reliability of grouting modification. During wavy directional drilling, the drilling rate of complex rock structure fractures can be significantly improved, and the reliability of grouting reinforcement of the injected rock layer can be significantly enhanced. This has practical significance for achieving efficient prevention and control of water hazards in coal seams and coordinated protection of water resources.

[0064] As a preferred option, in step a, sections with a critical waterproof layer thickness ≤ 5m are identified as permeable skylight areas. (When the thickness is less than 5m, the grouting modification layer thickness is insufficient to achieve a water-blocking effect. When the residual thickness is 0, the weathered bedrock modification layer after grouting treatment is easily damaged by mining-induced water-conducting fissures and cannot play a water-blocking role).

[0065] As a preferred option, in the fourth step, the contour lines of the groutable skylight area are extended outward by 30-50m to further improve the coverage of the treatment area, ensure the treatment effect, and increase the safety factor.

[0066] As a preferred option, in the fifth step, the injection is stopped when the injection pressure is >1MPa to ensure that the pressure does not exceed the specified index.

[0067] As a preferred option, in the second step, the heights of the caving zone and the fracture zone are estimated using the corresponding tables in the "Specifications for Coal Pillar Retention and Coal Mining in Buildings, Water Bodies, Railways and Main Shafts". The corresponding tables are as follows:

[0068]

[0069] in:

[0070] The formula is used to calculate the cumulative thickness of the main coal seam. The application range is 1 to 3 meters for a single seam and a cumulative thickness not exceeding 15 meters.

[0071] The height of the collapse zone;

[0072] Hl is the height of the fracture zone;

[0073] The height of the water-conducting fracture zone during mining.

[0074] The method for wavy directional drilling and grouting modification of complex fractured rock strata of the present invention, taking a burial depth of 100m, a grouting layer thickness of 30m, and a grouting zone width of 300m as an example, can reduce the ineffective drilling footage by more than 80% compared with vertical drilling and by more than 30% compared with near-horizontal directional drilling, and can improve the overall grouting modification efficiency by more than 50%.

[0075] The grout diffusion distance in a vertical borehole is generally 15m. Taking a grouting zone with a width of 300m as an example, 10 boreholes with a spacing of 30m are needed to complete the full coverage grouting of this section. The ineffective drilling depth in the non-grouting section reaches 10 holes. 100m / hole = 1000m, while wavy directional drilling only requires the construction of one hole, and the ineffective footage is only 100m of drilling work in the vertical section. Therefore, wavy directional drilling significantly reduces ineffective footage, and the greater the burial depth of the grouting layer, the more significant the reduction in ineffective footage.

[0076] Compared to near-horizontal directional drilling, where the vertical diffusion distance of grout is generally 5m, taking a grouting layer thickness of 30m as an example, it would require drilling three horizontal boreholes at a vertical spacing of 10m to expose a 30m thick horizontal fracture group. In contrast, wavy directional drilling generally only requires drilling one hole to penetrate and expose a 30m thick horizontal fracture group, completing the grouting modification. The amount of drilling work can be reduced by more than 30%.

Claims

1. A method for wavy directional drilling and grouting modification of complex fractured rock strata, characterized in that, Includes the following steps: Step 1: Analyze the overburden structure of the coal seam that requires drilling and grouting, and determine its hydrogeological structure; Step 2: Based on the hydrogeological structure obtained in Step 1, determine the permeable skylight area formed due to the lack of its aquitard layer, and at the same time determine the thickness of the weathered bedrock in the permeable skylight area and predict the height of the mining-induced water-conducting fractures formed by coal seam mining. Step 3: Analyze the relationship between the thickness of weathered bedrock in the permeable skylight area and the height of mining-induced water-conducting fractures obtained in Step 2, and determine all groutable skylight areas; Step 4: Among all the groutable skylight areas identified in Step 3, select one groutable skylight area and design a directional drilling structure with a wavy shape that has a gentle undulation on the cross-section and a height-to-width ratio of less than 1:

2. Step 5: Grouting is performed on the wavy directional boreholes designed in Step 4 to form a grouting modification layer; Step 6: Among all the groutable skylight areas identified in Step 3, select the areas that have not yet been grouted and repeat Steps 4 and 5 until all groutable skylight areas have been grouted. Step 2 is implemented through the following sub-steps: Step a: Step a1: Identify the hydrogeological structure in Step 1 and determine the permeable skylight area; Step a2: Identify the thickness of weathered bedrock in the permeable skylight area in step a1; Step b: Step b1: Identify the hydrogeological structure in Step 1, and predict the height of the caving zone and the fracture zone based on the thickness of the main coal seam. Step b2: Determine the height of the mining-induced water-conducting fracture by summing the height of the caving zone and the fracture zone in step b1. In step a1, sections with a critical waterproof layer thickness of ≤5m are identified as permeable skylight areas; Step 3 is implemented through the following sub-steps: Step 31: Analyze the relationship between the thickness of weathered bedrock in the permeable skylight area and the height of the mining-induced water-conducting fractures obtained in steps a2 and b2. Step 32: Subtract the height of the mining-induced water-conducting fractures from the thickness of the weathered bedrock in the permeable skylight area to obtain the thickness of the residual weathered bedrock layer in the permeable skylight area. Step 33: Define the sections with a residual weathered bedrock thickness > 5m in the permeable skylight area as groutable skylight areas, and determine all groutable skylight areas; Step 4 is implemented through the following sub-steps: Step 41: Among all the groutable skylight areas determined in step 33, select one groutable skylight area, expand the groutable skylight area outward, and designate the expanded area as the drilling and grouting modification area. Step 42: Design multiple wavy directional boreholes within the drilling and grouting modification zone; In step 41, extend outwards by 30-50m along the perimeter of the groutable skylight area; In step 42, the center baselines of each wavy directional borehole are arranged in parallel with a spacing of 15-30m. The design center baseline for wavy directional boreholes is set at 1 / 2 times the thickness of the residual weathered bedrock strata in the permeable skylight area below the top plate of the weathered bedrock aquifer. The wave amplitude width is 3 to 5 times the thickness of the residual weathered bedrock strata in the permeable skylight area, and the wave amplitude height is 2 / 3 times the thickness of the residual weathered bedrock strata in the permeable skylight area. The wave peaks and troughs of adjacent wavy directional boreholes are complementary.

2. The method for wavy directional drilling and grouting modification of complex fractured rock strata as described in claim 1, characterized in that, Step 5 is implemented through the following sub-steps: Step 51: During the wavy directional drilling process in Step 4, inject fly ash-based slurry and stop the injection when the injection pressure reaches the specified value; Step 52: After stopping the injection, continue drilling along the wavy directional section, and circulate the grouting through the wavy directional borehole to fill the cracks in the weathered bedrock layer, until the designed final hole is reached and the grouting is finally completed, forming a grouting modification layer.

3. The method of undulating directional drilling and grouting reformation of complex fractured formation as claimed in claim 2, wherein, In step 51, the injection is stopped when the injection pressure is >1 MPa.

4. The method of undulating directional drilling and grouting reformation of complex fracture structure rock mass as claimed in claim 3, characterized in that, During the drilling of the wavy directional section, grouting is carried out according to the principle of grouting whenever leakage occurs.

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