Accurate pressure relief and permeability increase rapid coal uncovering method for extremely complex coal seam

Abstract

The invention discloses an extremely complex coal seam accurate pressure relief and permeability increasing rapid coal uncovering method, which comprises the following steps of: constructing a crossing hole in a gas control roadway as a main area outburst prevention measure, constructing a bedding hole and a mechanical cave-making hole in a main haulage roadway drill site to carry out accurate pressure relief and permeability increasing gas control on a coal seam, and carrying out fixed-point hole sealing and accurate pre-pumping on the mechanical cave-making hole. A coal uncovering area is controlled through an omnibearing gridding outburst prevention measure which takes mechanical cave forming as a main part, takes layer penetrating drilling as an auxiliary part and takes precise pressure relief and permeability improvement, the targets of zero overrun and zero early warning are achieved in the coal uncovering period, and rapid and safe coal uncovering is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of rapid coal uncovering, and in particular relates to a rapid coal uncovering method for precise pressure relief and permeability enhancement in extremely complex coal seams. Background Art

[0002] Guizhou Songhe Coal Industry Development Co., Ltd., the 122 return air tunnel in the second mining area will uncover the 32# coal seam in front. The uncovering of the 32# coal seam is pseudo-inclined coal uncovering. The 32# coal seam is located in the Emeishan basalt. There is a layer of 300mm coal gangue in the uncovering area: black-gray, blocky, with bauxite spots, high carbon content on the top, high coal seam sealing index, high gas pressure, high gas content, strong adsorption, extremely complex coal seam conditions, long coal uncovering time span, and difficult coal uncovering gas control. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for rapid coal uncovering with precise pressure relief and permeability enhancement in extremely complex coal seams, so as to quickly uncover coal in pseudo-inclined coal seams with complex coal seam conditions, achieve the target coal seam gas extraction effect, and improve coal uncovering efficiency.

[0004] The technical solution adopted by the present invention is a method for rapid coal uncovering with precise pressure relief and permeability enhancement in extremely complex coal seams. The method is to construct through-layer drilling in the gas control tunnel as the main area anti-blowout measure, construct along-layer drilling and mechanical hole-making drilling in the drilling yard of the transport tunnel to precisely relieve pressure and increase permeability of the coal seam for gas control, and precisely pre-drain the mechanical hole-making drilling holes at fixed points.

[0005] Furthermore, the drilling distance along the layer is 6m, the drilling distance through the layer is 5m, and the anti-burst measures drilling holes are designed in groups every 5m from the gas control tunnel, with a total of 246 holes designed, with a hole diameter of 120mm.

[0006] Furthermore, after the drilling construction of the anti-blowout measures in the interlayer area is completed, according to the realistic sketch during the excavation of the transport tunnel, mechanical hole-making and permeability-enhancing drilling holes are constructed in the area where there is gangue in the drilling yard of the transport tunnel, and the drilling hole is located in the middle part of the gangue.

[0007] Furthermore, 9 mechanical burrowing holes were constructed in the drilling site of the transport tunnel. The diameter of the mechanical burrowing holes was 500mm, and the holes were drilled throughout the process. The spacing between the final holes of the burrowing holes was 10m, which met the extraction radius of 5m in half a month. After the drilling construction was completed, the fixed-point sealing technology was used to seal the burrowing holes to the burrowing section, and the gas in the coal-excavating area of ​​the return air tunnel was accurately pre-extracted.

[0008] Furthermore, after the construction drilling is completed, the mechanical hole drilling pipe is immediately lowered, the sliding pipe section is lowered to the outside of the control contour line of the coal seam to be uncovered and "two blocking and one injection" is used, and the screen pipe section is lowered to the control contour line of the coal seam to be uncovered.

[0009] Compared with the existing technology, the beneficial effect of the present invention is that it controls the coal uncovering area through a full-scale grid-based anti-burst measure with mechanical hole drilling as the main method, interlayer drilling as the auxiliary method, and precise pressure relief and permeability enhancement. After the implementation of this technology, the extraction volume of the hole drilling hole in the return air lane increased by 82.15%, and the maximum K1 value during coal uncovering was 0.22mL / g·min 1 / 2 , the maximum drill cuttings volume is 2.6kg / m; during the coal uncovering period, the goal of "zero overlimit and zero warning" is achieved to ensure fast and safe coal uncovering. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Flowchart of a method for precise pressure relief and permeability enhancement in extremely complex coal seams for rapid coal uncovering;

[0011] Figure 2 This is a cross-sectional diagram of the drilling for anti-blowout construction in the return air tunnel area;

[0012] Figure 3 The drilling plan for the anti-blowout measures in the 32# coal seam area is revealed for the 122 return air tunnel;

[0013] Figure 4 Schematic diagram of drilling and opening for mechanical cavitation and permeability enhancement measures;

[0014] Figure 5 Schematic diagram of drilling design for mechanical cavitation and permeability enhancement measures;

[0015] Figure 6 Schematic diagram of drilling design cross section for mechanical cavitation and permeability enhancement measures

[0016] Figure 7 Schematic diagram of fixed-point sealing;

[0017] Figure 8 This is a schematic diagram of small-section excavation. DETAILED DESCRIPTION

[0018] The present invention will be further explained below with reference to the accompanying drawings to facilitate better understanding by those skilled in the art.

[0019] Example 1

[0020] like Figure 1-8 As shown, the present invention provides a method for rapid coal uncovering with precise pressure relief and permeability enhancement in extremely complex coal seams. The method comprises the following steps: constructing through-layer drilling in the gas control tunnel as the main regional anti-blowout measure; constructing along-layer drilling and mechanical hole-making drilling in the drilling yard of the transport tunnel to precisely relieve pressure and enhance permeability of the coal seam for gas control; and precisely pre-extracting the mechanical hole-making drilling holes by fixed-point sealing.

[0021] Specifically, the designed drilling distance for in-layer drilling is 6m, and the drilling distance for through-layer drilling is 5m, which at least meets the requirement of 3.04m for the extraction radius for 3 months; the anti-burst measures drilling holes in the return air main tunnel area are designed with one group every 5m from the gas control tunnel, with a total of 246 holes designed, with a hole diameter of 120mm.

[0022] Because there is one layer of interbedded gangue in the coal seam and a 300mm thick interbedded gangue in the roof, the kaolinite mudstone softens when it comes into contact with water after the through-layer drilling hole passes through the coal seam, causing blockage of the drill hole and screen pipe, affecting the extraction effect. Therefore, after the drilling construction of the through-layer area is completed, in order to ensure that each layer of coal can be accurately controlled, according to the realistic sketch during the excavation of the transport tunnel, a mechanical hole is constructed in the area with interbedded gangue in the drilling site of the transport tunnel, and the drilling hole is located in the middle of the interbedded gangue.

[0023] Furthermore, nine mechanical cavitation holes were constructed in the transport tunnel drilling site. The diameter of the mechanical cavitation holes was 500mm, and the holes were drilled throughout the entire process. The spacing between the holes was 10m, meeting the extraction radius of 5m in half a month. After the drilling construction, the fixed-point sealing technology was used to seal the holes to the cavitation section, and accurately pre-extract gas from the coal uncovering area of ​​the return air tunnel. The mechanical cavitation drilling parameters are shown in Table 2:

[0024] Table 1 Mechanical cavitation drilling parameters

[0025]

[0026] When sealing the hole, the insufficient sealing depth will lead to inaccurate pre-extraction rate and extraction measurement in the evaluation unit. In order to improve the pre-extraction accuracy within the control range of the coal seam to be exposed, the mechanical hole drilling is immediately lowered after the drilling is completed. The pipe section is lowered to the outside of the control contour line of the coal seam to be exposed and "two blocking and one injection" is used (the manufacturer's customized bag belt is used for sealing the hole). The screen pipe section is lowered to the control contour line of the coal seam to be exposed, so as to achieve fixed-point sealing and only pre-extract gas from the coal seam within the evaluation, so that the pre-extraction amount within the control range of the coal seam to be exposed is more accurate, thereby achieving accurate pre-extraction.

[0027] The 122 return air tunnel of Guizhou Songhe Coal Industry Development Co., Ltd. is a dedicated return air system for the 1380 level in the second mining area. The 32# coal seam will be uncovered in front of this working face. The 32# coal seam is 3 meters thick and has an average inclination of 28°. There is no mining work on the 122 return air tunnel to the west. The 122 transport return air tunnel is located below it, and the 122 transport tunnel is located to the south. The original gas pressure of the coal seam is 2.84MPa; the original gas content of the coal seam is 12.28m 3 / t; coal seam permeability coefficient 0.07066m 2 / MPa2.d; coal seam strength coefficient 0.25; a 300mm thick layer of mudstone in the middle of the coal seam: black-gray, massive, with bauxite spots, and a high carbon content at the top. The coal seam is extremely complex, with long coal mining time spans and difficult coal mining gas control. See Table 2 for the lithology of the top and bottom slabs of the coal-bearing interlayer in the 122 return air lane:

[0028] Table 2 Lithology of the roof and floor of the coal-bearing interlayer in the 122 return air tunnel

[0029]

[0030] 246 construction holes were drilled in the 122 gas treatment tunnel, and 9 were drilled using mechanical cavitation. A comparison of conventional and mechanical cavitation extraction yields under similar geological conditions is shown in Table 3.

[0031] Table 3 Statistics of gas extraction volume from common boreholes and hole-making boreholes

[0032]

[0033]

[0034] The total extraction volume from ordinary boreholes was calculated to be 82518.78m by automatic metering device. 3 The total amount of drilling and extraction is 10047.4m 3 The total extraction volume of the hole-making drilling holes is increased by 82.15% compared with the ordinary drilling holes.

[0035] The average gas concentration in the main pipe of the mechanically drilled boreholes in the 122 main transport tunnel over 50 days was 8.4%, while the average gas concentration in conventional boreholes was 7.01%. The extraction concentration in the main pipe of the mechanically drilled boreholes was 4.59 times higher than that in conventional boreholes, with the maximum gas concentration reaching 30%. The maximum gas concentration in a single borehole was 72%, with a minimum of 26%, representing a maximum increase of 70% compared to that in a single conventional borehole. A comparison of gas concentrations in the main pipes of conventional and mechanically drilled boreholes is shown in Table 4.

[0036] Table 4 Comparison of gas concentration in common drilling and hole drilling mains

[0037]

[0038] The maximum K1 value from the beginning of coal mining to the coal seam mining in the 122 main transport tunnel is 0.42mL / g·min1 / 2 , the amount of cuttings is 3.2kg / m, and the minimum value is 0.28mL / g·min 1 / 2 , cuttings volume is 2.0kg / m, average K1 value is 0.34mL / g·min 1 / 2The drilling cuttings volume is 2.5 kg / m; the maximum K1 value from the start of coal mining to the coal seam area of ​​122 return air lane is 0.22 mL / g·min 1 / 2 , the amount of cuttings is 2.6kg / m, and the minimum value is 0.06mL / g·min 1 / 2 , cuttings volume is 1.8kg / m, average K1 value is 0.13mL / g·min 1 / 2 The drilling cuttings volume was 2.2 kg / m; the coal uncovering area of ​​122 return air tunnel was significantly smaller than that of 122 transport tunnel. The maximum K1 decreased by 0.36 mL / g·min during the excavation period. 1 / 2 The overall average decrease was 0.21 mL / g·min 1 / 2 The average reduction rate was 33.4%. The maximum reduction in drill cuttings was 1.4 kg / m, and the overall average reduction was 0.3 kg / m, with an average reduction rate of 88%. The statistical table of regional verification during the tunneling period is shown in Table 5.

[0039] Table 5 Statistics of regional verification during tunneling

[0040]

[0041]

[0042] The 122 transport tunnel and the 122 return air tunnel share similar geological conditions. Both tunnels operate in a pseudo-inclined manner, with a 12° inclination between the coal seam and the tunnel. Located in the 32# coal seam, the 122 transport tunnel took 114 days from initial regional verification to coal seam removal. The 122 return air tunnel has a designed cross-section of 5.3m x 3.5m. Due to the large cross-section, significant roof pressure was exerted during coal removal. The 122 return air tunnel employed a reduced cross-section (3m x 2m) to remove the coal seam before expanding it. This took 60 days. Currently, Guizhou Songhe Coal Industry Development Co., Ltd. is employing a precise pressure relief and permeability enhancement technology for rapid coal removal in extremely complex coal seams. This technology has reduced coal removal time by 54 days and increased coal removal efficiency by 52% compared to the 122 return air tunnel, which uses a smaller cross-section. This has enabled the 122 return air tunnel to safely and quickly remove the coal seam.

[0043] In summary, the method for precise pressure relief and permeability enhancement of extremely complex coal seams provided by the present invention has the following advantages:

[0044] 1) Under the same geological environment, the extraction volume of the hole-making borehole and the ordinary borehole with the same extraction volume and extraction days were compared. The total extraction volume of the hole-making borehole was 10047.4mm 3 The total amount of conventional drilling extraction is 82517m 3 The total extraction volume of the hole-making drilling is increased by 82.15% compared with the ordinary drilling;

[0045] 2) The average gas concentration in the main pipe of the mechanical cavitation drilling in the 122 transport tunnel is 8.4%. The concentration of gas extracted by the cavitation drilling is 70% higher than that of the ordinary drilling.

[0046] 3) The maximum decrease of K1 during the excavation of the 122 return air tunnel was 0.36 mL / g·min compared with that during the excavation of the 122 transport tunnel. 1 / 2 The overall average decrease was 0.21 mL / g·min 1 / 2 , with an average reduction rate of 33.4%; the maximum reduction in cuttings was 1.4kg / m, and the overall average reduction was 0.3kg / m, with an average reduction rate of 88%;

[0047] 4) Under the same geological conditions, the coal mining efficiency of the 122 return air tunnel is 54% higher than that of the 122 transport tunnel;

[0048] 5) Comparisons in tunneling efficiency, gas extraction concentration, gas extraction volume, K1 value, and drill cuttings volume demonstrate that the precise pressure relief and permeability enhancement technology for rapid coal mining in extremely complex coal seams is of great significance for gas control in basalt coal interlayers with high gas content, high pressure, high sealing index, high ground stress, low permeability, and strong adsorption in inclined coal seams. This technology can make up for the shortcomings in gas control in pseudo-inclined coal seams and provide a theoretical basis for similar projects in the future.

[0049] The above-described embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit and principles of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for rapid coal uncovering in extremely complex coal seams with precise pressure relief and permeability enhancement, characterized by: This method is to construct through-layer drilling in the gas control tunnel as the main area anti-blowout measure, construct along-layer drilling and mechanical hole-making drilling in the transportation tunnel drilling site to accurately relieve the pressure and increase the permeability of the coal seam for gas control, and accurately pre-extract the mechanical hole-making drilling holes by sealing them at fixed points.

2. The method for rapid coal uncovering by precise pressure relief and permeability enhancement in extremely complex coal seams according to claim 1 is characterized in that: The drilling distance along the layer is 6m, the drilling distance through the layer is 5m, and the anti-burst measures drilling holes are designed in groups every 5m from the gas control tunnel, with a total of 246 holes designed, with a hole diameter of 120mm.

3. The method for rapid coal uncovering by precise pressure relief and permeability enhancement in extremely complex coal seams according to claim 1 is characterized in that: After the drilling construction of the anti-blowout measures in the interlayer area is completed, according to the realistic sketch during the excavation of the transport tunnel, mechanical hole-making and permeability-enhancing drilling holes are constructed in the area where there is gangue in the drilling yard of the transport tunnel, and the drilling hole is located in the middle part of the gangue.

4. The method for rapid coal uncovering by precise pressure relief and permeability enhancement in extremely complex coal seams according to claim 3 is characterized in that: Nine mechanical burrowing holes were constructed in the drilling yard of the transport tunnel. The diameter of the mechanical burrowing holes was 500mm, and the holes were drilled throughout the process. The spacing between the final holes was 10m, which met the extraction radius of 5m in half a month. After the drilling construction was completed, the fixed-point sealing technology was used to seal the burrowing holes to the burrowing section, and the gas in the coal-excavating area of ​​the return air tunnel was accurately pre-extracted.

5. The method for rapid coal uncovering by precise pressure relief and permeability enhancement in extremely complex coal seams according to claim 4 is characterized in that: Immediately after the construction drilling is completed, the pipe is lowered into the mechanical hole drilling hole, the sliding pipe section is lowered to the outside of the control contour line of the coal seam to be uncovered and the "two blocking and one injection" method is used, and the screen pipe section is lowered to the control contour line of the coal seam to be uncovered.

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