Coal seam large-area gas content gridding detection method

Abstract

A coal seam large-area gas content gridding detection method comprises the steps that a working face needing to be detected is selected, and the specific area range of the detection working face is delimited; drilling construction parameters are designed according to the specific area range needing to be detected, and gas extraction drilling holes in the coal seam are constructed according to the design parameters; performing continuous fixed-point sampling on different depth positions of the same drill hole to form gridding sampling points among different drill holes, and measuring the gas content of the obtained coal sample; based on the gas content measurement result of each sampling point, drawing a gas content contour map in the detection area range; and dynamically adjusting gas extraction measures in combination with a gas content contour map to avoid a gas extraction blank zone. The gas content of the coal seam in front of the working face can be measured while drilling, advanced large-area refined detection of the gas content distribution rule is achieved, and the problems that according to a traditional method, the number of measuring points is small, measurement cannot be conducted while drilling and sampling are conducted, and the abnormal occurrence condition of the gas content of the coal seam of the mining working face cannot be mastered in time are solved.

Description

Technical Field

[0001] The present invention relates to a coal seam gas content detection method, in particular to a large-area coal seam gas content grid detection method, belonging to the technical field of regional coal seam gas content detection. Background Art

[0002] Coal seam gas distribution in high-gas and outburst mines is complex and diverse, presenting a serious threat of gas outbursts and gas emissions. Coal seam gas content is a key indicator for all gas disaster prevention and control measures, including coal and gas outburst hazard assessment, gas emission volume prediction, and gas extraction design. It also serves as fundamental data for mine gas reserve assessment and plays an irreplaceable role.

[0003] Transparency in coal seam gas content is a technical prerequisite for precise gas extraction and gas risk identification. Existing methods rely on a small number of gas parameter points, resulting in incomplete coverage. Coal seam gas content distribution relies on data calculation and fitting, resulting in unreliable results that fail to truly reflect local gas anomalies and ultimately prevent the precise, transparent measurement of gas parameters. Summary of the Invention

[0004] The purpose of the present invention is to provide a grid-based detection method for large-area gas content in coal seams. This method can measure the gas content in the coal seam ahead of the working face while drilling, realize advanced large-area refined detection of the gas content distribution law, and solve the problem that the traditional method has few measuring points, cannot sample and measure while drilling, and cannot timely grasp the abnormal distribution of gas content in the coal seam of the mining working face.

[0005] To achieve the above objectives, the present invention provides a method for detecting gas content in a large area of a coal seam using a grid system, comprising the following steps:

[0006] ① Select the working surface to be detected and define the specific area of the detection working surface;

[0007] ② Design drilling construction parameters for the specific area that needs to be detected, and construct gas extraction drilling holes in this coal seam according to the designed parameters;

[0008] ③ Conduct continuous fixed-point sampling at different depths of the same gas extraction borehole to form a grid of sampling points between different gas extraction boreholes and measure the gas content of the coal samples;

[0009] ④ Based on the gas content measurement results of each grid sampling point, draw a gas content contour map within the detection area;

[0010] ⑤ Combined with the gas content contour map, dynamically adjust the gas extraction measures to avoid gas extraction blank zones.

[0011] The number of gas extraction boreholes in step ② of the present invention can be calculated by formula (1), where the effective extraction radius needs to refer to the historical data of the mine. The final number of gas extraction boreholes should be rounded down to n1 and n2 and be between the two values:

[0012]

[0013] Where: n1 and n2 are the number of gas extraction boreholes;

[0014] L is the strike length of the detection area, m;

[0015] H is the average thickness of the coal seam at the working face, m;

[0016] K is the gas extraction drilling overlap coefficient;

[0017] R is the effective extraction radius, m;

[0018] D is the diameter of the gas extraction borehole, m;

[0019] r is the maximum spacing between gas extraction boreholes, m.

[0020] The continuous fixed-point sampling in step ③ of the present invention can adopt a spiral slag removal drill rod or a low-negative pressure continuous sampling device. During the sampling process, it is required not to withdraw the drill or replace the drill rod. The single sampling time is not more than 5 minutes, the single sampling mass is not less than 200g, and the sampling interval is generally not more than 50m.

[0021] In step ③ of the present invention, the coal seam gas content is determined by a direct method. The coal seam gas content is divided into four parts: sampling loss amount V1, direct desorption amount V2, crushing desorption amount V3, and non-desorbable amount V4.

[0022] The sampling loss V1 is calculated by the square root t model, which satisfies formula (2):

[0023]

[0024] Where: V t is the direct desorption amount corresponding to different time t, ml;

[0025] K is the model parameter;

[0026] t0 is the sampling time, s;

[0027] V1 is the sampling loss, ml.

[0028] The direct desorption amount V2 and the crushing desorption amount V3 are measured simultaneously in the well, and the non-desorption amount V4 is calculated by formula (3):

[0029]

[0030] Where: a is the Langmuir adsorption constant of coal sample;

[0031] b is the Langmuir adsorption constant of coal sample;

[0032] A d is the ash content of the coal sample;

[0033] M ad is the moisture content of the coal sample;

[0034] π is the porosity of the coal sample;

[0035] γ is the apparent density of the coal sample.

[0036] The isoline diagram of gas content in step ④ of the present invention has an isoline interval of no more than 0.5m. 3 / t.

[0037] Compared with the existing technology, the present invention is a method for detecting gas content in a large area of a coal seam. First, the working face to be detected is selected, and then a specific area range is delineated for the working face. Drilling construction parameters are designed for the specific area range to be detected, and the gas extraction boreholes of the coal seam are constructed according to the designed parameters. A spiral slag discharge drill rod or a low-negative pressure continuous sampling device is used to perform continuous fixed-point sampling at different depths of the same borehole, so that a grid of sampling points is formed between different boreholes, and the gas content of the coal samples taken is measured. Based on the gas content measurement results of each sampling point, a gas content contour map within the detection area is drawn. Combined with the gas content contour map, the gas extraction measures are dynamically adjusted to avoid gas extraction blank zones. The present invention can measure the gas content of the coal seam ahead of the working face while drilling, and realize the advanced large-area refined detection of the gas content distribution law. It solves the problems of the traditional method of having few measurement points, not being able to sample and measure while drilling, and not being able to timely grasp the abnormal occurrence of coal seam gas content in the mining working face. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a detection flow chart of the present invention;

[0039] Figure 2 This is a case study of the gridded gas content detection points in a specific embodiment of the present invention;

[0040] Figure 3 This is a contour map of gas content in a case study of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings.

[0042] like Figure 1 As shown, a grid-based method for detecting gas content in a large area of a coal seam includes the following steps:

[0043] ① Select the working surface to be detected and define the specific area of the detection working surface;

[0044] ② Design drilling construction parameters for the specific area that needs to be detected, and construct gas extraction drilling holes in this coal seam according to the designed parameters;

[0045] ③ Conduct continuous fixed-point sampling at different depths of the same gas extraction borehole to form a grid of sampling points between different gas extraction boreholes and measure the gas content of the coal samples;

[0046] ④ Based on the gas content measurement results of each grid sampling point, draw a gas content contour map within the detection area;

[0047] ⑤ Combined with the gas content contour map, dynamically adjust the gas extraction measures to avoid gas extraction blank zones.

[0048] The number of gas extraction boreholes in step ② of the present invention can be calculated by formula (1), where the effective extraction radius needs to refer to the historical data of the mine. The final number of gas extraction boreholes should be rounded down to n1 and n2 and be between the two values:

[0049]

[0050] Where: n1 and n2 are the number of gas extraction boreholes;

[0051] L is the strike length of the detection area, m;

[0052] H is the average thickness of the coal seam at the working face, m;

[0053] K is the gas extraction drilling overlap coefficient;

[0054] R is the effective extraction radius, m;

[0055] D is the diameter of the gas extraction borehole, m;

[0056] r is the maximum spacing between gas extraction boreholes, m.

[0057] The continuous fixed-point sampling in step ③ of the present invention can adopt a spiral slag removal drill rod or a low-negative pressure continuous sampling device. During the sampling process, it is required not to withdraw the drill or replace the drill rod. The single sampling time is not more than 5 minutes, the single sampling mass is not less than 200g, and the sampling interval is generally not more than 50m.

[0058] In step ③ of the present invention, the coal seam gas content is determined by a direct method. The coal seam gas content is divided into four parts: sampling loss amount V1, direct desorption amount V2, crushing desorption amount V3, and non-desorbable amount V4.

[0059] The sampling loss V1 is calculated by the square root t model, which satisfies formula (2):

[0060]

[0061] Where: V t is the direct desorption amount corresponding to different time t, ml;

[0062] K is the model parameter;

[0063] t0 is the sampling time, s;

[0064] V1 is the sampling loss, ml.

[0065] The direct desorption amount V2 and the crushing desorption amount V3 are measured simultaneously in the well, and the non-desorption amount V4 is calculated by formula (3):

[0066]

[0067] Where: a is the Langmuir adsorption constant of coal sample;

[0068] b is the Langmuir adsorption constant of coal sample;

[0069] A d is the ash content of the coal sample;

[0070] M ad is the moisture content of the coal sample;

[0071] π is the porosity of the coal sample;

[0072] γ is the apparent density of the coal sample.

[0073] The isoline diagram of gas content in step ④ of the present invention has an isoline interval of no more than 0.5m. 3 / t.

[0074] Example

[0075] The following is an example of detecting the gas content in a large area of a working face in a mine in Shanxi. The specific steps are as follows:

[0076] ① A coal mining face in a Shanxi mine was selected. The strike length of the face is 1560m, the average thickness of the coal seam is 3m, and the dip length of the face is 150m. The specific detection range is from the entrance of the return air lane of the face to 200m in the direction of the cut eye.

[0077] ② The effective radius R of gas extraction in the history of the mine is 2.5m, the overlap coefficient K of gas extraction boreholes is 1.2, the diameter D of gas extraction boreholes is 0.113m, and the spacing r of gas extraction boreholes is 7.5m. According to formula (1), the number of gas extraction boreholes in this coal seam should be between 26.7 and 36.7 and rounded up. Considering the spacing between boreholes and construction cost, 26 construction boreholes are finally selected, with a borehole inclination of 0°, an azimuth of 90°, and a borehole depth of 120m. The first borehole is located 5m from the entrance of the return air lane of the working face to the cutting direction.

[0078] ③Construct gas extraction boreholes in the detection area and take samples while drilling to determine the gas content of the coal seam. The sampling interval is 30m, forming a Figure 2 The gas content measurement results of the gridded detection points are shown in Table 1.

[0079] Table 1 Gas content determination results

[0080]

[0081]

[0082] ④ According to the gas content measurement data shown in Table 1, draw Figure 3 The gas content contour map of the detection area is shown, with an isovalue interval of 0.2m. 3 / t, it was found that the gas content distribution in the detection area was highly non-uniform, and there was a gas accumulation area within a certain range from the return air tunnel entrance to the cutting direction of 150m and the inclination of 100m.

[0083] ⑤ According to the gas content contour map, dynamically adjust the gas extraction measures. For gas concentration areas, the gas extraction effect can be enhanced by increasing the gas extraction time, etc., so as to avoid gas extraction gaps.

[0084] The present invention can measure the gas content of the coal seam in front of the working face while drilling, and realize the advanced and refined detection of the gas content distribution law in a large area. It solves the problems of the traditional method that there are few measuring points, it is impossible to take samples and measure while drilling, and it is impossible to timely grasp the abnormal occurrence of gas content in the coal seam of the mining working face.

Claims

1. A grid-based method for detecting gas content in a large area of a coal seam, characterized in that: The following steps are involved: ① Select the working surface to be detected and define the specific area of the detection working surface; ② Design drilling construction parameters for the specific area that needs to be detected, and construct gas extraction drilling holes in this coal seam according to the designed parameters; ③ Conduct continuous fixed-point sampling at different depths of the same gas extraction borehole to form a grid of sampling points between different gas extraction boreholes and measure the gas content of the coal samples; ④ Based on the gas content measurement results of each grid sampling point, draw a gas content contour map within the detection area; ⑤ Combined with the gas content contour map, dynamically adjust the gas extraction measures to avoid gas extraction blank zones.

2. A method for detecting gas content in a large area of a coal seam using gridding according to claim 1, characterized in that: The number of gas extraction boreholes in this coal seam in step ② is calculated by formula (1), where the effective extraction radius needs to refer to the historical data of the mine. The final number of gas extraction boreholes should be rounded down to n1 and n2 and be between the two values: Where: n1 and n2 are the number of gas extraction boreholes; L is the strike length of the detection area, m; H is the average thickness of the coal seam at the working face, m; K is the gas extraction drilling overlap coefficient; R is the effective extraction radius, m; D is the diameter of the gas extraction borehole, m; r is the maximum spacing between gas extraction boreholes, m.

3. A method for detecting gas content in a large area of a coal seam using gridding according to claim 2, characterized in that: The continuous fixed-point sampling in step ③ uses a spiral slag removal drill rod or a low-negative pressure continuous sampling device. During the sampling process, the drill must not be withdrawn or the drill rod replaced. The single sampling time must not exceed 5 minutes, the single sampling mass must not be less than 200g, and the sampling interval must not exceed 50m.

4. A method for detecting gas content in a large area of a coal seam using a grid system according to claim 3, characterized in that: Step ③ uses the direct method to determine the coal seam gas content. The coal seam gas content is divided into four parts: sampling loss amount V1, direct desorption amount V2, crushing desorption amount V3, and non-desorbable amount V4.

5. A method for detecting gas content in a large area of a coal seam using gridding according to claim 3, characterized in that: The sampling loss V1 is calculated by the square root t model, which satisfies formula (2): Where: V t is the direct desorption amount corresponding to different time t, ml; K is the model parameter; t0 is the sampling time, s; V1 is the sampling loss, ml.

6. A method for detecting gas content in a large area of a coal seam using a grid system according to claim 3, characterized in that: The direct desorption amount V2 and the crushing desorption amount V3 are measured simultaneously in the well, and the non-desorption amount V4 is calculated by formula (3): Where: a is the Langmuir adsorption constant of coal sample; b is the Langmuir adsorption constant of coal sample; A d is the ash content of the coal sample; M ad is the moisture content of the coal sample; π is the porosity of the coal sample; γ is the apparent density of the coal sample.

7. A method for detecting gas content in a large area of a coal seam using a grid system according to claim 5, characterized in that: The isoline map of gas content in step ④ has an isovalue interval of no more than 0.5m. 3 / t.

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