A method for determining a coal seam gas extraction radius based on a coal seam gas content

Abstract

A kind of coal seam gas extraction radius determination method based on coal seam gas content, coal seam original gas content determination: when construction extraction borehole, the coal seam gas content determined before extraction is recorded as: W0 0 , record time is t0 moment;Residual gas content determination after extraction: after extraction after t time, at the distance of r0 and r1 from the center of borehole, arrange gas content determination radial borehole, determine residual gas content after extraction of coal seam at t j Moment is recorded as: W0 j , W1 j ;Residual gas content distribution model determination after extraction: based on the determined residual coal seam gas content parameter after extraction, determine the distribution model of residual gas content of coal seam after extraction;Extraction radius calculation: according to the requirement of actual extraction rate, the extraction radius at t moment is calculated from the distribution model of residual gas content.The present application can solve the problems of complex process, inaccurate manual reading and inaccurate calculation model in the process of coal seam gas extraction radius determination, and improve the accuracy of coal seam gas extraction radius determination.

Description

Technical Field

[0001] This invention relates to a method for determining the gas extraction radius of a coal seam, specifically a method for determining the gas extraction radius of a coal seam based on the gas content of the coal seam, belonging to the technical field of coal mine gas extraction radius parameter determination. Background Technology

[0002] Coal seam gas hazards are a major safety hazard in coal mines, and the prevention and utilization of coal seam gas is one of the important tasks for safe and efficient coal mining. In the process of coal seam gas prevention and utilization, the extraction radius measurement technology is a key technology used to determine the layout of gas extraction boreholes and evaluate the extraction effect. Gas diffusion in coal seams has a certain range, and the extraction radius refers to the effective range of the gas extraction borehole's influence on the diffusion of coal seam gas. Accurate measurement of the extraction radius can determine the rational layout of gas extraction boreholes to achieve the goals of efficient gas extraction, reducing coal mine gas concentration, and preventing coal seam gas explosions.

[0003] Common methods for measuring gas drainage radius include theoretical calculation methods and practical measurement methods. Theoretical calculation methods, based on mathematical models and fluid dynamics principles, estimate the drainage radius by calculating the distance and time of gas diffusion. Practical measurement methods, on the other hand, determine the drainage radius by collecting field data, such as the output of gas drainage boreholes and gas concentration distribution, and then analyzing and evaluating this data.

[0004] Currently, the technology for measuring the extraction radius faces the following difficulties. First, the diffusion process of coal seam gas is complex and is affected by factors such as coal seam structure, gas permeability, and adsorption and desorption of coal seam gas. Second, on-site data acquisition and processing need to be accurate and reliable, taking into account factors such as coal mine geological conditions and the performance of gas extraction equipment. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the coal seam gas extraction radius based on the coal seam gas content, which can solve the problems of complex procedures, inaccurate manual readings, and imprecise calculation models in the process of determining the coal seam gas extraction radius, thereby improving the accuracy of coal seam gas extraction radius determination.

[0006] To achieve the above objectives, this invention provides a method for determining the gas extraction radius of a coal seam based on its gas content. The calculation of the gas extraction radius is divided into three steps: determining the initial gas content of the coal seam, determining the residual gas content after extraction, determining the distribution function of the residual gas content after extraction, and calculating the extraction radius. The specific determination steps are as follows:

[0007] ① Determination of original gas content in coal seams: The gas content of the coal seam before extraction, as measured during the drilling of extraction boreholes, is recorded as: W0 0 The recording time is t0.

[0008] ② Determination of residual gas content after extraction: After extraction for time t, radial boreholes for gas content determination are arranged at distances r0 and r1 from the borehole center, and the residual gas content is measured at time t. j The residual gas content of the coal seam after extraction at a given time is recorded as: W1 j ;

[0009] ③ Determination of residual gas content distribution function after extraction: Based on the residual gas content parameters after coal seam extraction measured in step ②, determine the residual gas content distribution model after coal seam extraction;

[0010] ④ Calculation of extraction radius: Based on the actual extraction rate requirements, the extraction radius at time t is calculated using the coal seam residual gas content distribution model in step ③.

[0011] The methods for determining the gas content before coal seam extraction in step ① and the residual gas content after extraction in step ② of this invention are both direct underground measurement methods, and the sampling depth should always be kept consistent when measuring the gas content.

[0012] In step ③ of this invention, the distribution model of the residual gas content in the coal seam after extraction is as follows:

[0013] W i j =d·lnr i +k (1)

[0014] In the formula: For extraction t j At time r, the distance from the borehole center is i The residual gas content at the location, m 3 / t;

[0015] d and k are constants related to the coal's structure.

[0016] in k = W1 j -d·lnr1;

[0017] In step ④ of this invention, the extraction radius is calculated to obtain the extraction radius r under specific extraction time and extraction rate conditions. The calculation formula is as follows:

[0018]

[0019] In the formula: r is the borehole extraction radius after extraction time t, in meters;

[0020] η is the designed coal seam gas extraction rate.

[0021] The formula for calculating the gas extraction rate η in step ④ of this invention is as follows:

[0022]

[0023] In the formula: W c To ensure the extraction of residual gas content meets standards, m 3 / t.

[0024] Compared with existing technologies, this invention divides the gas (coalbed methane) content measurement into three parts: underground gas content measurement technology based on coalbed methane content; and gas extraction radius calculation into three parts: initial coalbed methane content measurement, residual gas content measurement after extraction, determination of the residual gas content distribution model after extraction, and extraction radius calculation. It considers the redistribution of coalbed methane during extraction and establishes a distribution model for the residual gas content after extraction, which better reflects the actual situation of gas content changes during extraction and is feasible and progressive. This invention can solve the problems of complex procedures, inaccurate manual readings, and imprecise calculation models in the process of determining the coalbed methane extraction radius, thus improving the accuracy of coalbed methane extraction radius measurement. Attached Figure Description

[0025] Figure 1 This is a flowchart of the present invention;

[0026] Figure 2 This is a mine 3 in an embodiment of the present invention. # Schematic diagram of the layout of extraction holes and content holes at measuring point No. 1 in the coal seam return air roadway. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figures 1-2 As shown, a method for determining the gas extraction radius of a coal seam based on its gas content is presented. The calculation of the gas extraction radius is divided into three steps: determining the initial gas content of the coal seam, determining the residual gas content after extraction, determining the distribution model of the residual gas content after extraction, and calculating the extraction radius. The specific measurement steps are as follows:

[0029] ① Determination of original gas content in coal seams: The gas content of the coal seam before extraction, as measured during the drilling of extraction boreholes, is recorded as follows: The recording time is time t0;

[0030] ② Determination of residual gas content after extraction: After extraction for time t, radial boreholes for gas content determination are arranged at distances r0 and r1 from the center of the borehole, and the residual gas content is measured at time t. j The residual gas content of the coal seam after extraction at a given time is recorded as: W1 j ;

[0031] ③ Determination of the distribution function of residual gas content after extraction: Based on the residual gas content parameters after coal seam extraction measured in step ②, the distribution model of residual gas content after coal seam extraction is determined.

[0032] ④ Calculation of extraction radius: Based on the actual extraction rate requirements, the extraction radius at time t is calculated using the distribution model of residual gas content in the coal seam from step ③.

[0033] The methods for determining the gas content before coal seam extraction in step ① and the residual gas content after extraction in step ② are both the existing direct underground measurement methods. The sampling depth should always be kept consistent when determining the gas content before coal seam extraction in step ① and the residual gas content after extraction in step ②.

[0034] In step ③, the distribution model of the residual gas content in the coal seam after extraction is as follows:

[0035] W i j =d·lnr i +k (1)

[0036] In the formula: For extraction t j At time r, the distance from the borehole center is i The residual gas content at the location, m 3 / t;

[0037] d and k are constants related to the coal quality structure.

[0038] in k = W1 j -d·lnr1.

[0039] In step ④, the extraction radius is calculated to obtain the extraction radius r under specific extraction time and extraction rate conditions. The calculation formula is as follows:

[0040]

[0041] In the formula: r is the borehole extraction radius after extraction time t, in meters;

[0042] η is the designed coal seam gas extraction rate.

[0043] The formula for calculating the gas extraction rate η mentioned in step ④ is as follows:

[0044]

[0045] In the formula: W c To ensure the extraction of residual gas content meets standards, m 3 / t

[0046] Example:

[0047] This embodiment is for a certain mine. #The arrangement of measuring point No. 1 in the coal seam return air roadway, before gas drainage in a certain gas drainage face of a certain mine, involves arranging drainage boreholes as required, and determining the gas content measurement positions with the drainage boreholes as the center. This includes the following steps:

[0048] ① The gas content of the coal seam before extraction, as measured during the drilling of the extraction borehole, is recorded as follows: The recording time is t0 = 0d. The current design gas extraction rate requirement is η = 30%. The target residual gas content W is obtained according to the gas extraction rate calculation formula. c It is 6.12m 3 / t;

[0049] ② Determination of residual gas content after extraction: After extraction for t1 = 20 days, boreholes were drilled at center distances r0 = 1m and r1 = 2m to determine the residual gas content of the coal seam after extraction. This residual gas content was recorded as follows:

[0050] ③ Determine the relevant constants of coal quality structure based on the residual coal seam gas content parameters measured in step ②: k = 5.33, the residual gas content distribution model after extraction is:

[0051]

[0052] ④ Calculate the extraction radius by substituting the results from steps ① and ③ into the formula:

[0053]

[0054] The residual gas content W that meets the design extraction target after 20 days of extraction was calculated. c It is 6.12m 3 Under the / t condition, the extraction radius is 1.86m.

Claims

1. A method for determining the coal seam gas extraction radius based on coal seam gas content, characterized in that, The calculation of the gas extraction radius is divided into three parts: determination of the initial gas content of the coal seam, determination of the residual gas content after extraction, determination of the distribution function of the residual gas content after extraction, and calculation of the extraction radius. The specific determination steps are as follows: ① Initial gas content determination of coal seam: The gas content of the coal seam before extraction, as measured during the drilling of extraction boreholes, is recorded as follows: The recording time is time; ② Determination of residual gas content after extraction: After... After time extraction, at a distance from the center of the borehole and Radial boreholes for gas content measurement were drilled at the location. The residual gas content of the coal seam after extraction at a given time is recorded as: , ; ③ Determination of residual gas content distribution function after extraction: Based on the residual gas content parameters after coal seam extraction measured in step ②, determine the residual gas content distribution model after coal seam extraction; ④ Calculation of extraction radius: Based on the actual extraction rate requirements, the residual gas content distribution model after coal seam extraction in step ③ is used to calculate the extraction radius. The sampling radius at any given moment; In step ③, the distribution model of residual gas content after coal seam extraction is as follows: （1） In the formula: For sampling At that moment, the distance from the borehole center was The residual gas content at the location, m 3 / t; , Let be a constant related to the coal's structure, where: ， ； Step ④ involves calculating the extraction radius to determine the extraction radius under specific extraction time and extraction rate conditions. The calculation formula is: （2） In the formula: For the process t The borehole extraction radius after time extraction, in meters; The designed coal seam gas extraction rate.

2. The method for determining the coal seam gas extraction radius based on coal seam gas content according to claim 1, characterized in that, The methods for determining the gas content before coal seam extraction in step ① and the residual gas content after extraction in step ② are both direct underground measurement methods, and the sampling depth should always be consistent when measuring the gas content.

3. The method for determining the coal seam gas extraction radius based on coal seam gas content according to claim 1, characterized in that, The gas extraction rate mentioned in step ④ The calculation formula is: （3） In the formula: To ensure the extraction of residual gas content meets standards, m 3 / t.

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