Coal seam gas extraction radius measurement system and measurement method

Abstract

The present invention provides a coal seam gas extraction radius measurement system and method, which relates to the field of gas extraction technology. The system includes a flow guide pipe, a handheld measuring instrument and a host. The flow guide pipe is connected between a confluence pipe and a grid-connected rubber pipe of a gas extraction system. A flow sensor and a methane concentration sensor are also arranged in the flow guide pipe. The host includes a display, a keyboard, an integrated circuit and a power supply, etc. The method for completing the gas extraction radius measurement using the system includes: determining a measurement area, calculating a pre-extraction rate that meets the standard, dividing an investigation section in the measurement area, constructing a test borehole, connecting the confluence pipe and the extraction pipeline through a grid-connected rubber pipe after sealing the test boreholes in each investigation section, collecting flow and methane concentration data, calculating the gas pre-extraction rate, and measuring the extraction radius at each moment. The system and method solve the technical problem of accurately and efficiently measuring the coal seam gas extraction radius, and provide guidance for the reasonable arrangement of gas extraction boreholes in coal mines.

Description

Technical Field

[0001] The present invention relates to the technical field of gas extraction, and in particular to a coal seam gas extraction radius measurement system and a method for measuring the coal seam gas extraction radius by using the system. Background Art

[0002] As one of the five major disasters in coal mines, gas disasters have always been the top priority of coal mine safety production work. At present, coal mines have implemented a comprehensive gas control strategy of "protecting as much as possible and extracting as much as possible" to deal with gas disasters. Pre-extraction of coal seam gas is an important measure for coal mine gas control.

[0003] The extraction radius is an important basis for the arrangement of gas extraction drilling holes, and directly affects the gas extraction effect of pre-extraction drilling holes. If the spacing between extraction drilling holes is too large, it is difficult to meet the extraction standards and it is easy to form extraction blind spots; if the spacing is too small, it is easy to cause unnecessary waste of manpower and material resources. my country's current "Coal Mine Safety Regulations" clearly stipulate that parameters such as the extraction radius should be measured in high-gas mines, but there is no unified standard for the measurement of coal seam gas extraction radius in coal mines, and the measurement methods of the extraction radius are also inconsistent. With the increasing depth of coal mining in my country, the number of high-gas mines and outburst mines will continue to increase. The research on the measurement technology of coal seam gas extraction radius will inevitably become the research focus of the domestic academic community, and it is also urgent to formulate industry or national standards that effectively guide the direct measurement of the size of the coal seam gas extraction radius on site in coal mines.

[0004] At present, the methods for investigating the extraction radius of coal seams are mainly divided into three types: theoretical calculation, numerical simulation, and direct on-site measurement. Among them, theoretical calculation and numerical simulation analysis methods can easily and quickly determine the size of the extraction radius, and can provide certain guidance for the reasonable arrangement of extraction boreholes. However, in the process of establishing theoretical calculation models and numerical simulation analysis, it is often assumed that the coal seam is an isotropic medium, ignoring the anisotropic characteristics of coal. However, the actual occurrence state of underground coal seams presents typical anisotropic characteristics, and the structural anisotropy of coal seams has a significant impact on the extraction effect; in addition, the applicable conditions of the calculation model are too idealized, and the selection of calculation parameters is relatively difficult. Therefore, it is difficult to accurately characterize the fluid-solid coupling process between the coal body and gas around the extraction borehole, resulting in a large difference between the actual extraction effect on site and the results of theoretical calculation and numerical simulation analysis. The current direct determination methods of coal seam gas extraction radius in underground coal mines mainly include four categories: gas pressure reduction method, gas content reduction method, gas extraction flow method, and tracer gas method. Although the gas pressure reduction method is more commonly used, its field operability is poor, especially there are problems such as difficulty in measuring pressure in the coal seam, which makes it difficult for this method to reflect the real situation of coal seam gas extraction; the gas tracer method has a complex operation process, and what it actually measures is the extraction influence radius, which cannot well guide the coal seam gas extraction work in underground coal mines; the gas content reduction method and the gas extraction flow method are relatively easy to operate, especially the gas extraction flow method uses extraction data to solve the size of the coal seam gas extraction radius, which can reflect the real extraction situation of the actual extraction boreholes in the underground, but the determination and calculation methods and operation steps need to be further optimized and improved, and the implementation process also needs to be further standardized. Therefore, it is necessary to further explore more reliable and practical methods for direct determination of extraction radius, and give specific field determination processes, so as to better guide the reasonable arrangement of extraction boreholes in underground coal mines. Summary of the invention

[0005] In order to accurately and efficiently determine the coal seam gas extraction radius and analyze the extraction status of the extraction borehole in real time, the present invention provides a coal seam gas extraction radius measurement system and method, and the specific technical scheme is as follows.

[0006] A coal seam gas extraction radius measurement system comprises a guide tube, a handheld measuring instrument and a host computer. The guide tube is connected between a confluence pipe and a grid-connected rubber tube of a gas extraction system. A flow sensor and a methane concentration sensor are arranged in the guide tube. The host computer comprises a display, a keyboard, an integrated circuit and a power supply. The display and the keyboard are respectively connected to the integrated circuit board. The flow sensor and the methane concentration sensor are also respectively connected to the integrated circuit board. The power supply comprises a battery and a power interface. Data is transmitted wirelessly between the handheld measuring instrument and the host computer.

[0007] Preferably, the cross section of the flow guide pipe is circular, the diameter of the flow guide pipe is 80 mm to 200 mm, and the length of the flow guide pipe is greater than 200 mm; the flow guide pipe is installed straightly between the collector pipe and the grid-connected rubber pipe of the gas extraction system.

[0008] It is also preferred that the host is also provided with a data transmission serial port, which is connected to the underground ring network; and the electrical interface is connected to the underground intrinsically safe power line.

[0009] It is also preferred that the handheld meter collects data records of flow rate and methane concentration from the host computer.

[0010] In combination with the use of the above-mentioned gas extraction radius measurement system, in order to achieve accurate measurement of the coal seam gas extraction radius and shorten the measurement cycle, a coal seam gas extraction radius measurement method is provided, and the specific technical solution is as follows.

[0011] A method for measuring the radius of coal seam gas extraction, using the above-mentioned gas extraction radius measurement system, comprises the following steps:

[0012] Step 1: Select the measurement area, including selecting at least one measurement area in each level, each mining area and each geological unit to determine the gas extraction radius;

[0013] Step 2: Calculate the gas pre-extraction rate that meets the standards, including calculating the gas pre-extraction rate that meets the standards for non-outburst coal seams and outburst coal seams;

[0014] Step 3: Divide the measurement area into n investigation sections, and preset the coal seam gas extraction radius as R1, R2...R n , set up measurement boreholes in each survey section, with the borehole spacing being 2R1, 2R2...2R n During the drilling process, the original reserves of coal seam gas in the section are also measured;

[0015] Step 4: Test the sealing and grid connection of the boreholes. Connect the measuring boreholes in the same survey section to the same flow guide pipe through the grid-connected rubber pipe, and the flow guide pipe is connected to the manifold of the gas extraction system.

[0016] Step 5: Continuously collect data on flow rate and methane concentration in the diversion pipe, fit the functional relationship of borehole gas flow rate attenuation with time, and calculate the total pure amount of gas extracted from the borehole within the extraction time t, as well as the actual gas pre-extraction rate of each investigation section, and obtain the pre-extraction time t1, t2...t2 for each investigation section to reach the standard gas pre-extraction rate n , and the pre-pumping time is t1, t2...t n The extraction radius is R1, R2...R n .

[0017] Preferably, the calculation of the qualified gas pre-extraction rate η0 is specifically as follows:

[0018]

[0019] Among them, W C ' Y To investigate the residual gas content of coal seams in the section, m 3 / t; The average original gas content of coal seams in the investigated section, m 3 / t;

[0020] Calculate the original reserves Q of coal seam gas in each survey section 原 , specifically:

[0021]

[0022] Where S is the plane area of ​​the investigated section, m 2 ; h is the thickness of the coal seam in the investigated section, m; γ is the bulk density of the coal in the investigated section, t / m 3 ;

[0023] And η0, Q 原 The calculation results are input into the gas extraction radius measurement system through the keyboard.

[0024] It is further preferred that, in the calculation of the gas pre-extraction rate of the non-outburst coal seam, the residual gas content W of the coal seam in the inspection section that meets the standard is C ' Y The calculation is:

[0025] W C ' Y =W j '+W CC

[0026] Among them, W j ' is the desorbable gas volume that meets the standard, m 3 / t;W CC is the residual gas content of coal at standard atmospheric pressure m 3 / t;

[0027] Residual gas content of coal at standard atmospheric pressure W CC The calculation is:

[0028]

[0029] In the formula, a and b are adsorption constants; A d is the ash content of coal, %; M ad is the moisture content of coal, %; π is the porosity of coal, m 3 / m 3 ; γ is the bulk density of coal, t / m 3 .

[0030] It is further preferred that, in the calculation of the standard gas pre-extraction rate of the outburst coal seam, the standard residual gas content W of the coal seam in the inspection section is C ' Y The specific determination is:

[0031] W′ CY =min(W j '+W CC , W CR )

[0032] Where W CR To highlight the gas content at the depth of coal seam outburst, m 3 / t; when the gas pressure at the outburst depth of the outburst coal seam is unknown, the value is 8m 3 / t; When the gas pressure at the outburst depth of the outburst coal seam is known, W CR The calculation of is as follows:

[0033]

[0034] In the formula, a and b are adsorption constants; A d is the ash content of coal, %; M ad is the moisture content of coal, %; π is the porosity of coal, m 3 / m 3 ; γ is the bulk density of coal, t / m 3 ;P CR is the relative gas pressure at the depth of coal seam outburst, MPa; P a For standard atmospheric pressure, take 0.101325Mpa.

[0035] It is further preferred that in step 3, the average original gas content of the coal seam in each investigated section is calculated Specifically:

[0036]

[0037] Among them, W 原i is the original gas content measured in the i-th borehole in the investigation section, m 3 / t; n is the number of measured boreholes in the survey section;

[0038] Calculate the original reserves Q of coal seam gas in each survey section 原 , specifically:

[0039]

[0040] Where S is the plane area of ​​the investigated section, m 2 ; h is the thickness of the coal seam in the investigated section, m; γ is the bulk density of the coal in the investigated section, t / m 3 .

[0041] Further preferably, in step 5, the functional relationship of the borehole gas flow rate attenuation over time is specifically:

[0042] q t =q0e -αt

[0043] Among them, q t is the total pure amount of gas extracted from the boreholes in the investigated section at time t, m 3 / d; q0 is the total pure amount of initial gas extraction from the boreholes in the investigated section, m 3 / d; α is the scalar attenuation coefficient of borehole gas extraction in the investigated section, d -1 ; t is the drilling gas extraction time, d; the fitting of the functional relationship of the borehole gas flow rate attenuation change with time, if the fitting correlation coefficient is less than 0.8, then the data of the flow rate and methane concentration of this group are discarded;

[0044] While fitting the functional relationship of the borehole gas flow rate attenuation over time, the total pure amount of borehole gas extraction Q in the investigated section is also calculated. c , specifically:

[0045]

[0046] According to the total pure amount Q of gas extracted from the boreholes in the survey area c and the original reserves of coal seam gas Q in each investigated section 原 Calculate the actual gas pre-extraction rate η of each investigated section at time t t , specifically:

[0047]

[0048] Comparison of the actual gas pre-extraction rate η of each investigated section t and the qualified gas pre-extraction rate η0, determine the gas extraction radius of the coal seam.

[0049] The beneficial effect of the present invention is that it provides a coal seam gas extraction radius measurement system, which uses a diversion pipe to collect the gas from the measuring borehole, sets a flow sensor and a methane concentration sensor to measure the flow and methane concentration in real time, uses a host to record the monitoring results, and processes and analyzes the monitoring data; a handheld measuring instrument can collect monitoring information from the host, thereby realizing offline measurement; a method for measuring the gas extraction radius using the coal seam gas extraction radius measurement system simplifies the steps of extraction radius measurement, makes operation more convenient, shortens the measurement cycle, and the measurement results are more in line with engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the composition of the coal seam gas extraction radius measurement system;

[0051] Figure 2 It is a schematic diagram of the internal connection of the coal seam gas extraction radius measurement system;

[0052] Figure 3 It is a schematic diagram of the connection structure of the coal seam gas extraction radius measurement system;

[0053] Figure 4 This is a schematic diagram of the layout of measurement boreholes in the bedding parallel survey section;

[0054] Figure 5 It is a schematic diagram of the layout of measurement drilling holes in the layer-penetrating investigation section;

[0055] In the figure: 1- flow guide pipe, 11- flow sensor, 12- methane concentration sensor, 2- host, 21- display, 22- keyboard, 23- power supply, 24- integrated circuit, 25- data transmission serial port, 26- power interface, 3- handheld measuring instrument, 4- manifold, 5- grid-connected rubber pipe; 6- investigation tunnel; 7- coal body; 8- boundary condition drilling hole; 9- measurement area. DETAILED DESCRIPTION

[0056] Combination Figures 1 to 5 As shown, the specific implementation methods of a coal seam gas extraction radius measurement system and measurement method provided by the present invention are as follows.

[0057] In order to solve the shortcomings in gas extraction radius measurement, such as the theoretical calculation model does not conform to the anisotropic characteristics of coal and has poor engineering matching; the numerical simulation calculation is too simplified, resulting in a large difference from the actual situation; in direct measurement, the gas pressure reduction method has poor operability, the gas tracer method has complex process, the gas content reduction method and the gas extraction flow method have inaccurate measurement and calculation methods, and the measurement period is long, the present invention combines the use of a coal seam gas extraction radius measurement system to provide an accurate and efficient measurement method.

[0058] A coal seam gas extraction radius measurement system specifically includes a flow guide tube 1, a handheld measuring instrument 3 and a host 2. The flow guide tube is connected between the confluence pipe 4 and the grid-connected rubber tube 5 of the gas extraction system. A flow sensor 11 and a methane concentration sensor 12 are arranged in the flow guide tube 1 to measure the flow rate and methane concentration of the gas. The host includes a display 21, a keyboard 22, an integrated circuit 24 and a power supply 23. The display 21 and the keyboard 22 are respectively connected to the integrated circuit board 24. The flow sensor 11 and the methane concentration sensor 12 are also respectively connected to the integrated circuit board 24. The power supply 23 includes a battery and an electrical interface 26. The electrical interface 26 can be an external power supply / charging shared interface to ensure that the host can monitor online and offline. Data is transmitted wirelessly between the handheld measuring instrument 3 and the host 2, specifically, data can be transmitted through Bluetooth or other wireless transmission technologies. The handheld measuring instrument 3 collects data records of flow rate and methane concentration from the host 2, so that offline monitoring data can be collected. The cross section of the flow guide pipe 1 is circular, and the diameter of the flow guide pipe is 80mm to 200mm. The commonly used diameters are 80mm, 100mm, 120mm, 150mm, 180mm, 200mm and other specifications. It can also be processed and customized according to actual needs; the length of the flow guide pipe is greater than 200mm. The flow guide pipe 1 is installed flatly between the confluence pipe 4 and the grid-connected rubber pipe 5 of the gas extraction system to ensure the accuracy of the flow and methane concentration measurement. The host 2 is also provided with a data transmission serial port, which is connected to the underground ring network; the electrical interface 26 is connected to the underground intrinsically safe power line. A coal seam gas extraction radius measurement system uses a flow guide pipe to collect gas from the measuring borehole, and measures the flow and methane concentration in real time by setting a flow sensor and a methane concentration sensor. The host records the monitoring results and processes and analyzes the monitoring data; the handheld measuring instrument can collect monitoring information from the host, so that offline measurement can be achieved.

[0059] In combination with the use of the above-mentioned gas extraction radius measurement system, in order to achieve accurate measurement of the coal seam gas extraction radius and shorten the measurement period, the present invention also provides a coal seam gas extraction radius measurement method.

[0060] A method for measuring the radius of coal seam gas extraction, using the above-mentioned gas extraction radius measurement system, comprises the following steps:

[0061] Step 1: Select the measurement area, including selecting at least one measurement area in each level, each mining area and each geological unit to determine the gas extraction radius. Specifically, the number of measurement areas is determined according to the number of mine levels, mining areas and geological units. Generally, at least one measurement area should be selected for each level, mining area and geological unit to determine the extraction radius. The coal seam and gas storage conditions in the selected measurement area should be representative, and should have the wind, water, electricity and other construction conditions required for construction drilling, as well as the conditions for sealing the extraction drilling and grid-connected extraction. There should be no large faults, fissures and other structures in and near the measurement area.

[0062] Step 2: Calculate the gas pre-extraction rate that meets the standards, including calculating the gas pre-extraction rate that meets the standards for non-outburst coal seams and outburst coal seams.

[0063] The calculation of the standard gas pre-extraction rate η0 is as follows:

[0064]

[0065] Among them, W′ CY To investigate the residual gas content of coal seams in the section, m 3 / t; The average original gas content of coal seams in the investigated section, m 3 / t; the qualified residual gas content of coal seams in the survey section can be determined based on a comprehensive survey of the purpose of mine gas extraction and the actual daily production situation, or determined by calculation, among which the calculation of qualified residual gas content of coal seams in the survey section of non-outburst coal seams is different from that of qualified residual gas content of coal seams in the survey section of outburst coal seams.

[0066] The original coal seam gas reserves Q in each investigated section are also calculated. 原 , specifically:

[0067]

[0068] Where S is the plane area of ​​the investigated section, m 2 ; h is the thickness of the coal seam in the investigated section, m; γ is the bulk density of the coal in the investigated section, t / m 3 ;

[0069] After the calculation is completed, η0, Q 原 The calculation results are input into the gas extraction radius measurement system through the keyboard.

[0070] Furthermore, in the calculation of the gas pre-extraction rate that meets the standard in non-outburst coal seams, the residual gas content W′ that meets the standard in the coal seams in the investigation section is CY The calculation is:

[0071] W′ CY =W j '+W CC

[0072] Among them, W j ' is the desorbable gas volume that meets the standard, m 3 / t, its value can be determined according to the standard of coal mine gas extraction specification; W CC is the residual gas content of coal at standard atmospheric pressure m 3 / t;

[0073] Residual gas content of coal at standard atmospheric pressure W CC The calculation is:

[0074]

[0075] In the formula, a and b are adsorption constants; A d is the ash content of coal, %; M ad is the moisture content of coal, %; π is the porosity of coal, m 3 / m 3 ; γ is the bulk density of coal, t / m 3 .

[0076] Furthermore, in the calculation of the gas pre-extraction rate of coal seams that meet the standard, the desorbable gas content index of coal and the gas pre-extraction prevention effect should be comprehensively determined, and the residual gas content W of the coal seams that meet the standard in the section should be examined. C ' Y The specific determination is:

[0077] W′ CY =min(W j '+W CC , W CR )

[0078] Where W CR To highlight the gas content at the depth of coal seam outburst, m 3 / t; when the gas pressure at the outburst depth of the outburst coal seam is unknown, the value is 8m 3 / t; When the gas pressure at the outburst depth of the outburst coal seam is known, W CR The calculation of is as follows:

[0079]

[0080] In the formula, a and b are adsorption constants; A d is the ash content of coal, %; M ad is the moisture content of coal, %; π is the porosity of coal, m 3 / m 3 ; γ is the bulk density of coal, t / m 3 ;P CR is the relative gas pressure at the depth of coal seam outburst, MPa; P aFor standard atmospheric pressure, take 0.101325Mpa.

[0081] Step 3: Divide the measurement area into n investigation sections, and preset the coal seam gas extraction radius as R1, R2...R n , set up measurement boreholes in each survey section, with the borehole spacing being 2R1, 2R2...2R n During the drilling process, the original reserves of coal seam gas in the section are also measured.

[0082] According to the previous extraction experience of the mine or neighboring mines, several expected coal seam gas extraction radius sizes are determined, and the preset coal seam gas extraction radius is R1, R2...R n , the selected measurement area is divided into n investigation sections, and the measurement boreholes in each investigation section are arranged at intervals of 2R1, 2R2, ..., 2R n The design and construction process of the drilling hole is the same as that of the daily extraction drilling hole in the mine. The borehole diameter and length are consistent with the parameters of the daily extraction drilling hole in the mine, but they should meet the relevant requirements of the coal mine gas extraction specification. The number of measurement boreholes in each survey section in the survey area shall not be less than 9, and at least 2 boundary condition boreholes shall be constructed on both sides of each survey section. The spacing between boundary condition boreholes is consistent with the spacing between boreholes in each survey section. Figures 4 to 5 As shown, the in-layer arrangement is to arrange drill holes along the coal seam in the coal seam tunnel, and the through-layer arrangement is to arrange drill holes in the rock tunnel or coal seam tunnel to the adjacent coal seam.

[0083] Furthermore, the average original gas content of coal seams in each investigated section was calculated. Specifically:

[0084]

[0085] Among them, W 原i is the original gas content measured in the i-th borehole in the investigation section, m 3 / t; n is the number of measured boreholes in the survey section;

[0086] Calculate the original reserves Q of coal seam gas in each survey section 原 , specifically:

[0087]

[0088] Where S is the plane area of ​​the investigated section, m 2 ; h is the thickness of the coal seam in the investigated section, m; γ is the bulk density of the coal in the investigated section, t / m 3 .

[0089] Step 4: Test the sealing and grid connection of the boreholes. Connect the measuring boreholes in the same survey section to the same guide pipe through the grid-connected rubber tube, and the guide pipe is connected to the manifold of the gas extraction system.

[0090] After the test drilling construction is completed, the borehole sealing work should be completed within 24 hours. The sealing process is the same as the sealing process of the daily extraction drilling in the mine. The materials and parameters used for sealing are consistent with the daily extraction drilling in the mine, but they should meet the standard requirements of the coal mine gas extraction specification. After the test drilling sealing work is completed, the grid connection work should be completed within 24 hours, and the extraction drilling holes in the same inspection section should be connected to the same manifold. The outlet of the manifold is connected to the diversion pipe of the coal seam gas extraction radius measurement system, and then connected to the pipeline of the coal seam gas extraction system through the grid-connected rubber pipe.

[0091] Step 5: Continuously collect data on flow rate and methane concentration in the diversion pipe, fit the functional relationship of borehole gas flow rate attenuation with time, and calculate the total pure amount of gas extracted from the borehole within the extraction time t, as well as the actual gas pre-extraction rate of each investigation section, and obtain the pre-extraction time t1, t2...t2 for each investigation section to reach the standard gas pre-extraction rate n , and the pre-pumping time is t1, t2...t n The extraction radius is R1, R2...R n .

[0092] After the measuring borehole is connected to the coal seam gas extraction radius measurement system, the system continuously collects the extraction mixed flow and methane concentration of the manifold in each survey section, and displays them in real time on the display screen of the host to determine the size of the coal seam gas extraction radius. The measurement time can be set through the keyboard on the host, but it should be based on the coal seam gas content and permeability coefficient. In principle, when the coal seam gas content is ≥8m 3 / t, the observation time shall not be less than 60 days. When the gas content of coal seam is less than 8m 3 / t, the observation time shall not be less than 30d.

[0093] The display screen on the main unit of the coal seam gas extraction radius measurement system can display the daily extraction volume (m 3 / d) is the vertical axis of the curve. After the set observation time is reached, the coal seam gas extraction radius measurement and analysis system automatically fits the observation results to obtain the functional relationship between the borehole gas flow rate and the attenuation of time. When the fitting correlation coefficient is less than 0.8, the system automatically prompts "the fitting degree is low, it is recommended to discard this group of data."

[0094] Furthermore, the functional relationship of the borehole gas flow rate attenuation over time is specifically:

[0095] q t =q0e -αt

[0096] Among them, q t is the total pure amount of gas extracted from the boreholes in the investigated section at time t, m 3 / d; q0 is the total pure amount of initial gas extraction from the boreholes in the investigated section, m 3 / d; α is the scalar attenuation coefficient of borehole gas extraction in the investigated section, d -1 ; t is the drilling gas extraction time, d; the fitting of the functional relationship of the borehole gas flow rate attenuation change with time, if the fitting correlation coefficient is less than 0.8, then the data of the flow rate and methane concentration of this group are discarded;

[0097] While fitting the functional relationship of the borehole gas flow rate attenuation over time, the total pure amount of borehole gas extraction Q in the investigated section is also calculated. c , specifically:

[0098]

[0099] According to the total pure amount Q of gas extracted from the boreholes in the survey area c and the original reserves of coal seam gas Q in each investigated section 原 Calculate the actual gas pre-extraction rate η of each investigated section at time t t , specifically:

[0100]

[0101] Comparison of the actual gas pre-extraction rate η of each investigated section t and the qualified gas pre-extraction rate η0, determine the gas extraction radius of the coal seam.

[0102] The coal seam gas extraction radius measurement system automatically compares the actual gas pre-extraction rate η of each investigation section t and the gas pre-extraction rate η0, the measured drilling spacing is 2R1, 2R2...2R n The pre-extraction time t1, t2, ... t2 of each investigated section to achieve gas extraction standards n The pre-extraction time under the current extraction conditions of the mine (certain extraction hole diameter, sealing process, etc.) is also obtained as t1, t2...t n The extraction radius R1, R2, ... R n .

[0103] The method of measuring the gas extraction radius using the coal seam gas extraction radius measurement system simplifies the extraction radius measurement steps, is more convenient to operate, shortens the measurement cycle, and the measurement results are more in line with engineering practice. The coal seam gas extraction radius measurement system in this method is easy to operate and has strong practicality, which greatly shortens the measurement cycle of the coal seam gas extraction radius. It can truly reflect the gas extraction status of the mine, has simple requirements for on-site test conditions, strong applicability and practicality, and reliable measurement results. It has innovated the traditional coal seam gas pressure and content measurement principles and methods, and improved the scientificity of coal seam gas extraction drilling design and construction in underground coal mines.

[0104] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for measuring the radius of coal seam gas extraction, using a gas extraction radius measurement system, characterized in that: The system includes a flow guide tube, a handheld measuring instrument and a host. The flow guide tube is connected between the confluence pipe and the grid-connected rubber pipe of the gas extraction system. A flow sensor and a methane concentration sensor are arranged in the flow guide tube. The host includes a display, a keyboard, an integrated circuit and a power supply. The display and the keyboard are respectively connected to the integrated circuit board. The flow sensor and the methane concentration sensor are also respectively connected to the integrated circuit board. The power supply includes a battery and an electricity interface. Data is transmitted wirelessly between the handheld measuring instrument and the host. The method steps include: Step 1: Select the measurement area, including selecting at least one measurement area in each level, each mining area and each geological unit to determine the gas extraction radius; Step 2: Calculate the gas pre-extraction rate that meets the standards, including calculating the gas pre-extraction rate that meets the standards for non-outburst coal seams and outburst coal seams; The calculation of the standard gas pre-extraction rate η0 is specifically: Among them, W' CY To investigate the residual gas content of coal seams in the section, m 3 / t; The average original gas content of coal seams in the investigated section, m 3 / t; Calculate the original reserves Q of coal seam gas in each survey section 原 , specifically: Where S is the plane area of ​​the investigated section, m 2 ; h is the thickness of the coal seam in the investigated section, m; γ is the bulk density of the coal in the investigated section, t / m 3 ; And η0, Q 原 The calculation results are input into the gas extraction radius measurement system through the keyboard; In the calculation of the gas pre-extraction rate of the non-outburst coal seam, the residual gas content W' of the coal seam in the inspection section is CY The calculation is: IN' CY =W' j +W CC Among them, W' j The amount of gas that can be desorbed to meet the standard, m 3 / t;W CC is the residual gas content of coal at standard atmospheric pressure m 3 / t; Residual gas content of coal at standard atmospheric pressure W CC The calculation is: In the formula, a and b are adsorption constants; A d is the ash content of coal, %; M ad is the moisture content of coal, %; π is the porosity of coal, m 3 / m 3 ; γ is the bulk density of coal, t / m 3 ; In the calculation of the standard gas pre-extraction rate of the outburst coal seam, the standard residual gas content W' of the coal seam in the inspection section is CY The specific determination is: IN' CY =min(W' j +W CC ,IN CR ) Where W CR To highlight the gas content at the depth of coal seam outburst, m 3 / t; when the gas pressure at the outburst depth of the outburst coal seam is unknown, the value is 8m 3 / t; When the gas pressure at the outburst depth of the outburst coal seam is known, W CR The calculation of is as follows: In the formula, a and b are adsorption constants; A d is the ash content of coal, %; M ad is the moisture content of coal, %; π is the porosity of coal, m 3 / m 3 ; γ is the bulk density of coal, t / m 3 ;P CR is the relative gas pressure at the depth of coal seam outburst, MPa; P a For standard atmospheric pressure, take 0.101325Mpa; Step 3: Divide the measurement area into n survey sections, and preset the coal seam gas extraction radius as R1, R2, ... R n , set up measurement boreholes in each survey section, with the borehole spacing being 2R1, 2R2...2R n During the drilling process, the original reserves of coal seam gas in the section are also measured; In step 3, the average original gas content of coal seams in each investigated section is calculated. Specifically: Among them, W 原i is the original gas content measured in the i-th borehole in the investigation section, m 3 / t; n is the number of measured boreholes in the survey section; Calculate the original reserves Q of coal seam gas in each survey section 原 , specifically: Where S is the plane area of ​​the investigated section, m 2 ; h is the thickness of the coal seam in the investigated section, m; γ is the bulk density of the coal in the investigated section, t / m 3 ; Step 4: Test the sealing and grid connection of the boreholes. Connect the measurement boreholes in the same survey section to the same flow guide pipe through the grid-connected rubber pipe, and the flow guide pipe is connected to the manifold of the gas extraction system. Step 5: Continuously collect data on flow rate and methane concentration in the diversion pipe, fit the functional relationship of borehole gas flow rate attenuation with time, and calculate the total pure amount of gas extracted from the borehole within the extraction time t, as well as the actual gas pre-extraction rate of each investigation section, and obtain the pre-extraction time t1, t2...t2 for each investigation section to reach the standard gas pre-extraction rate n , and the pre-pumping time is t1, t2...t n The extraction radius is R1, R2...R n ; In step 5, the functional relationship of the borehole gas flow rate attenuation over time is specifically: q t =q0e -αt Among them, q t is the total pure amount of gas extracted from the boreholes in the investigated section at time t, m 3 / d; q0 is the total pure amount of initial gas extraction from the boreholes in the investigated section, m 3 / d; α is the scalar attenuation coefficient of borehole gas extraction in the investigated section, d -1 ; t is the drilling gas extraction time, d; the fitting of the functional relationship of the borehole gas flow rate attenuation change with time, if the fitting correlation coefficient is less than 0.8, then the data of the flow rate and methane concentration of this group are discarded; While fitting the functional relationship of the borehole gas flow rate attenuation over time, the total pure amount of borehole gas extraction Q in the investigated section is also calculated. c , specifically: According to the total pure amount Q of gas extracted from the boreholes in the survey area c and the original reserves of coal seam gas Q in each investigated section 原 Calculate the actual gas pre-extraction rate η of each investigated section at time t t , specifically: Comparison of the actual gas pre-extraction rate η of each investigated section t and the qualified gas pre-extraction rate η0, determine the gas extraction radius of the coal seam.

2. A method for measuring the radius of coal seam gas extraction according to claim 1, characterized in that: The cross section of the flow guide pipe is circular, the diameter of the flow guide pipe is 80mm-200mm, and the length of the flow guide pipe is greater than 200mm; the flow guide pipe is installed straightly between the collector pipe and the grid-connected rubber pipe of the gas extraction system.

3. A method for measuring the radius of coal seam gas extraction according to claim 1, characterized in that: The host is also provided with a data transmission serial port, which is connected to the underground ring network; the power interface is connected to the underground intrinsically safe power line.

4. A method for measuring the radius of coal seam gas extraction according to claim 1, characterized in that: The handheld meter collects data records of flow rate and methane concentration from the host computer.

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