CN110985105A - Coal seam gas extraction radius measuring system and measuring method - Google Patents
Coal seam gas extraction radius measuring system and measuring method Download PDFInfo
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Abstract
The invention provides a system and a method for measuring coal seam gas extraction radius, which relate to the technical field of gas extraction, wherein the system comprises a guide pipe, a handheld measuring instrument and a host, wherein the guide pipe is connected between a bus 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 guide pipe, and the host comprises a display, a keyboard, an integrated circuit, a power supply and the like; the method for completing the measurement of the gas extraction radius by using the system comprises the following steps: determining a measurement area, calculating the pre-extraction rate reaching the standard, dividing investigation sections in the measurement area, constructing test drill holes, connecting a collecting pipe and an extraction pipeline through a grid-connected rubber pipe after the test drill holes of each investigation section are sealed, acquiring flow and methane concentration data, calculating the gas pre-extraction rate, and determining the extraction radius at each moment. The system and the method solve the technical problem of accurately and efficiently measuring the coal seam gas extraction radius, and provide guidance for reasonable arrangement of the coal mine underground gas extraction drill hole.
Description
Technical Field
The invention relates to the technical field of gas extraction, in particular to a system for measuring the gas extraction radius of a coal seam and a method for measuring the gas extraction radius of the coal seam by using the system.
Background
The gas disaster is one of five major disasters of a coal mine and is always the central importance of the safety production work of the coal mine. At present, aiming at gas disasters, a coal mine implements a gas comprehensive treatment strategy of 'guaranteeing the gas and exhausting the gas completely', and pre-exhausting coal seam gas is an important measure for coal mine gas treatment.
The extraction radius is an important basis for arranging the gas extraction drill hole, and directly influences the gas extraction effect of the pre-extraction drill hole. The arrangement distance of the extraction drill holes is too large, extraction is not easy to reach the standard, and an extraction blind area is easy to form; the spacing is too small, which easily causes unnecessary waste of manpower and material resources. The parameters such as extraction radius and the like of a high gas mine are definitely specified in the current coal mine safety regulation in China, but no unified standard exists for measuring the gas extraction radius of an underground coal seam of a coal mine, and the measuring methods of the extraction radius are inconsistent. With the increasing coal mining depth in China, the number of high gas mines and outburst mines is increasing continuously, the research on the coal seam gas extraction radius determination technology is bound to become the research focus of the national academia, and an industry or a national standard for effectively guiding the coal mine site to directly determine the coal seam gas extraction radius is also needed to be formulated urgently.
At present, the coal seam gas extraction radius investigation method mainly comprises three types of theoretical calculation, numerical simulation and field direct measurement. The theoretical calculation and numerical simulation analysis method can conveniently and quickly determine the size of the extraction radius, can provide certain guidance for reasonable arrangement of the extraction drill hole, but the theoretical calculation model establishment and the numerical simulation analysis process mostly assume that a coal bed is an isotropic medium, ignores the anisotropic characteristic of coal, and the actual occurrence state of the underground coal bed presents typical anisotropic characteristics, and the structural anisotropy of the coal bed has obvious influence on the extraction effect; in addition, the applicable conditions of the calculation model are too ideal, and the calculation parameters are difficult to select. Therefore, the fluid-solid coupling process of the coal body and the gas around the extraction drill hole is difficult to accurately represent, and the difference between the actual extraction effect on site and the theoretical calculation and numerical simulation analysis results is large. The existing method for directly measuring the gas extraction radius of the coal seam under the coal mine mainly comprises 4 types, namely a gas pressure reduction method, a gas content reduction method, a gas extraction flow method, a tracer gas method and the like, wherein although the gas pressure reduction method is commonly used, the field operability is poor, the problems that the pressure measurement of the coal seam is difficult and the like exist particularly, and the method is difficult to reflect the real condition of the gas extraction of the coal seam; the gas tracing method has a complex operation process, and the measured actual extraction influence radius cannot well guide the gas extraction work of the coal seam under the coal mine; the operability of a gas content reduction method and a gas extraction flow method is relatively strong, particularly, the gas extraction flow method solves the size of the coal seam gas extraction radius by using extraction data, and can reflect the real extraction condition of an underground actual extraction borehole, but the measurement and calculation method and the operation steps need to be further optimized and perfected, and the implementation process needs to be further standardized. Therefore, a more reliable and practical extraction radius direct measurement method needs to be further explored, and a specific field measurement flow is given, so that reasonable arrangement of the underground coal mine extraction drill holes can be better guided.
Disclosure of Invention
The invention provides a system and a method for measuring the coal seam gas extraction radius, and aims to accurately and efficiently measure the coal seam gas extraction radius and analyze the extraction state of an extraction borehole in real time.
A coal seam gas extraction radius measuring system comprises a flow guide pipe, a handheld measuring instrument and a host, wherein the flow guide pipe is connected between a collecting pipe and a grid-connected rubber pipe of the gas extraction system, and a flow sensor and a methane concentration sensor are arranged in the flow guide pipe; the host comprises a display, a keyboard, an integrated circuit and a power supply, wherein the display and the keyboard are respectively connected with the integrated circuit board, the flow sensor and the methane concentration sensor are also respectively connected with the integrated circuit board, and the power supply comprises a storage battery and an electricity utilization interface; and data is wirelessly transmitted between the handheld measuring instrument and the host.
Preferably, the section of the draft tube is circular, the diameter of the draft tube is 80 mm-200 mm, and the length of the draft tube is more than 200 mm; the guide pipe is arranged between a collecting pipe and a grid-connected rubber pipe of the gas extraction system in a straight and straight manner.
Preferably, the host is also provided with a data transmission serial port, and the data transmission serial port is connected with the underground looped network; and the electric interface is connected with an underground intrinsic safety power line.
It is also preferred that the handheld meter collects data records of flow rate and methane concentration from the host computer.
The method for measuring the coal seam gas extraction radius is provided by combining the use of the gas extraction radius measuring system, in order to realize the accurate measurement of the coal seam gas extraction radius and shorten the measurement period, and the specific technical scheme is as follows.
A coal seam gas extraction radius measuring method utilizes the gas extraction radius measuring system, and comprises the following steps:
the method comprises the following steps: selecting a measuring area, wherein at least one measuring area is selected from each horizontal area, each mining area and each geological unit to determine the gas extraction radius;
step two: calculating the gas pre-extraction rate up to the standard, including calculating the gas pre-extraction rate up to the standard of a non-outburst coal seam and an outburst coal seam;
step three: dividing the measurement area into n investigation sections, and presetting the coal seam gas extraction radius as R1、R2……RnIn each investigation section, measuring boreholes are arranged with a borehole spacing of 2R1、2R2……2RnMeasuring the original reserves of the coal bed gas in the sections in the drilling construction process;
step four: the hole sealing and the grid connection of the test drill holes are carried out, the measurement drill holes in the same investigation section are connected with the same flow guide pipe through a grid connection rubber pipe, and the flow guide pipe is connected to a collecting pipe of a gas extraction system;
step five: continuously acquiring data of flow and methane concentration in the flow guide pipe, fitting the function relation of the attenuation change of the gas flow of the drill hole along with time, calculating the total pure quantity of the gas extracted by the drill hole in the extraction time t and the actual gas pre-extraction rate of each investigation section, and obtaining the pre-extraction time t when each investigation section reaches the standard gas pre-extraction rate1、t2……tnAnd a pre-pumping time t1、t2……tnThe extraction radius is R1、R2……Rn。
Preferably, the gas pre-extraction rate reaches η0The calculation of (2) is specifically:
wherein, WC'YM for investigating the standard residual gas content of the coal seam in the section3/t；
To investigate the average original gas content, m, of the coal seam in a section3/t；
Calculating the original reserves Q of the coal bed gas in each investigation sectionOriginal sourceThe method specifically comprises the following steps:
wherein S is the planar area of the investigation section, m2(ii) a h is the thickness of the coal seam in the investigation section, m; gamma is the volume weight of coal in the investigation section, t/m3；
And will η0、QOriginal sourceThe calculated result is input into the gas extraction radius measuring system through a keyboard.
Further preferably, in the calculation of the standard gas pre-extraction rate of the non-outburst coal seam, the standard residual gas content W of the coal seam in the section is consideredC'YIs calculated as:
WC'Y＝Wj'+WCC
wherein, Wj' in order to reach the standard, the gas amount can be desorbed, m3/t；WCCThe residual gas content m of the coal under the standard atmospheric pressure3/t；
Residual gas content W of coal under standard atmospheric pressureCCIs calculated as:
wherein a and b are adsorption constants; a. thedAsh content of coal,%; madWater content of coal,%; pi is the porosity of the coal, m3/m3(ii) a Gamma is the volume weight of coal, t/m3。
Preferably, 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 section is consideredC'YThe determination specifically comprises the following steps:
W′CY＝min(Wj'+WCC，WCR)
in the formula, WCRM is the gas content at the initial outburst depth of the outburst coal seam3T; when the gas pressure at the initial outburst depth of the outburst coal seam is unknown, the value is 8m3T; when the outburst coal seam beginsWhen the gas pressure at the projection depth is known, WCRIs calculated as follows:
wherein a and b are adsorption constants; a. thedAsh content of coal,%; madWater content of coal,%; pi is the porosity of the coal, m3/m3(ii) a Gamma is the volume weight of coal, t/m3；PCRThe relative gas pressure at the initial outburst depth of the outburst coal seam is MPa; paThe standard atmospheric pressure is 0.101325 MPa.
Preferably, in the third step, the average original gas content of the coal seam of each investigation section is calculated
The method specifically comprises the following steps:
wherein, WOriginal iM original gas content measured for the ith measurement borehole in the investigation section3T; n is the number of the measured drill holes in the investigation section;
calculating the original reserves Q of the coal bed gas in each investigation sectionOriginal sourceThe method specifically comprises the following steps:
wherein S is the planar area of the investigation section, m2(ii) a h is the thickness of the coal seam in the investigation section, m; gamma is the volume weight of coal in the investigation section, t/m3。
Further preferably, in the fifth step, the function relationship of the attenuation change of the borehole gas flow along with the time is specifically as follows:
qt＝q0e-αt
wherein q istFor the investigation of the total purity of the drilled gas extraction in the section at the time t, m3/d；q0For investigating the total purity m of initial gas extraction drilled in a section3α is the pure quantity attenuation coefficient of the drilling gas extraction in the investigation section, d-1(ii) a t is the time for extracting gas in the drill hole, d; fitting a functional relation of the drill hole gas flow along with the time attenuation change, and discarding the data of the group of flow and methane concentration if the fitting correlation coefficient is less than 0.8;
the method is characterized in that the total pure quantity Q of the gas extraction of the drill hole in the investigation section is calculated while the fitting of the function relation of the gas flow of the drill hole along with the time attenuation change is carried outcThe method specifically comprises the following steps:
measuring total purity Q of drilled gas extraction according to investigation sectioncAnd original reserves Q of coal bed gas in each investigation sectionOriginal sourceCalculating the actual gas pre-extraction rate η of each section under investigation at time ttThe method specifically comprises the following steps:
comparing the actual gas pre-extraction rates η of the respective investigation sectionstAnd the pre-extraction rate η of gas reaching the standard0And determining the gas extraction radius of the coal seam.
The system has the advantages that the system collects the gas of the measuring drill holes by using the guide pipe, measures the flow and the methane concentration in real time by arranging the flow sensor and the methane concentration sensor, records the monitoring result by using the host, and processes and analyzes the monitoring data; the handheld measuring instrument can collect monitoring information from the host computer, so that offline measurement can be realized; the method for measuring the gas extraction radius by using the coal seam gas extraction radius measuring system simplifies the step of measuring the extraction radius, is more convenient to operate, shortens the measuring period, and enables the measuring result to better accord with the actual engineering.
Drawings
FIG. 1 is a schematic diagram of a coal seam gas extraction radius measurement system;
FIG. 2 is a schematic diagram of the internal connection of a coal seam gas extraction radius measurement system;
FIG. 3 is a schematic diagram of a connection structure of a coal seam gas extraction radius measurement system;
FIG. 4 is a schematic view of the layout of the survey boreholes in the bedding parallel survey section;
FIG. 5 is a schematic view of the layout of the survey borehole in the cross-layer investigation section;
in the figure: 1-a flow guide pipe, 11-a flow sensor, 12-a methane concentration sensor, 2-a host, 21-a display, 22-a keyboard, 23-a power supply, 24-an integrated circuit, 25-a data transmission serial port, 26-an electric interface, 3-a handheld measuring instrument, 4-a collecting pipe and 5-a grid-connected rubber pipe; 6-inspecting the roadway; 7-coal body; 8-boundary condition drilling; 9-measurement area.
Detailed Description
Referring to fig. 1 to 5, embodiments of a system and a method for measuring a coal seam gas extraction radius according to the present invention are as follows.
In order to solve the problems that in the measurement of the gas extraction radius, a theoretical calculation model does not accord with the anisotropic characteristics of coal, and the engineering matching is poor; the calculation of numerical simulation is over simplified, so that the difference from the actual value is large; in direct measurement, the gas pressure reduction method has poor operability, the gas tracing method has complex process, the measurement and calculation methods of the gas content reduction method and the gas extraction flow method are inaccurate, the measurement period is long, and the like.
The utility model provides a coal seam gas drainage radius measurement system specifically includes honeycomb duct 1, handheld measuring apparatu 3 and host computer 2, and the honeycomb duct is connected between collector pipe 4 and the rubber tube 5 that is incorporated into the power networks of gas drainage system, is provided with flow sensor 11 and methane concentration sensor 12 in the honeycomb duct 1 for measure the flow and the methane concentration of gas. The host machine comprises a display 21, a keyboard 22, an integrated circuit 24 and a power supply 23, wherein the display 21 and the keyboard 22 are respectively connected with the integrated circuit board 24, the flow sensor 11 and the methane concentration sensor 12 are also respectively connected with the integrated circuit board 24, the power supply 23 comprises a storage battery and an electricity utilization interface 26, and the electricity utilization interface 26 can be an external power supply/charging shared interface, so that the host machine can be monitored on line and off line. Data are wirelessly transmitted between the handheld measuring instrument 3 and the host 2, specifically, data can be transmitted through bluetooth or other wireless transmission technologies, and the handheld measuring instrument 3 collects data records of flow and methane concentration from the host 2, so that offline monitoring data can be collected. The section of the draft tube 1 is circular, the diameter of the draft tube is 80 mm-200 mm, and various specifications such as the diameter of 80mm, the diameter of 100mm, the diameter of 120mm, the diameter of 150mm, the diameter of 180mm, the diameter of 200mm and the like are commonly used, and the draft tube can be processed and customized according to actual requirements; the length of the draft tube is more than 200 mm. The flow guide pipe 1 is straightly arranged between a collecting pipe 4 and a grid-connected rubber pipe 5 of the gas extraction system, so that the accuracy of flow and methane concentration measurement is ensured. The host machine 2 is also provided with a data transmission serial port which is connected with the underground looped network; the electrical interface 26 is used to connect the downhole intrinsically safe power line. A coal seam gas extraction radius measuring system collects gas of measuring drill holes by using a flow guide pipe, measures flow and methane concentration in real time by arranging a flow sensor and a methane concentration sensor, records a monitoring result by using a host, and processes and analyzes monitoring data; the handheld measuring instrument can collect monitoring information from the host computer, so that offline measurement can be realized.
In combination with the use of the gas extraction radius measuring system, the invention also provides a method for measuring the coal seam gas extraction radius in order to realize the accurate measurement of the coal seam gas extraction radius and shorten the measurement period.
A coal seam gas extraction radius measuring method utilizes the gas extraction radius measuring system, and comprises the following steps:
the method comprises the following steps: and selecting a measuring area, wherein at least one measuring area is selected from each horizontal area, each mining area and each geological unit to determine the gas extraction radius. The method specifically comprises the steps of determining the number of measurement areas according to the number of mine levels, mining areas and geological units, generally selecting at least one measurement area for extraction radius measurement of each level, mining area and geological unit, wherein the occurrence condition of coal beds and gas in the selected measurement areas is representative, the selected measurement areas are required to have the construction conditions of wind, water, electricity and the like required by construction drilling and the conditions of extraction drilling hole sealing and grid-connected extraction, and no large faults, cracks and other structures exist in and near the measurement areas.
Step two: and calculating the gas pre-extraction rate reaching the standard, including calculating the gas pre-extraction rate reaching the standard of the non-outburst coal seam and the outburst coal seam.
Standard gas pre-extraction rate η0The calculation of (2) is specifically:
wherein, W'CYM for investigating the standard residual gas content of the coal seam in the section3/t；
To investigate the average original gas content, m, of the coal seam in a section3T; the standard-reaching residual gas content of the coal seam in the investigation section can be determined by comprehensive investigation according to the mine gas extraction purpose and the daily production actual condition, or determined by calculation, wherein the standard-reaching residual gas content of the coal seam in the investigation section of the non-outburst coal seam is different from the standard-reaching residual gas content of the coal seam in the investigation section of the outburst coal seam.
And calculating the original reserves Q of the coal bed gas in each investigation sectionOriginal sourceThe method specifically comprises the following steps:
wherein S is the planar area of the investigation section, m2(ii) a h is the thickness of the coal seam in the investigation section, m; gamma is the volume weight of coal in the investigation section, t/m3；
After the calculation is completed, η is added0、QOriginal sourceThe calculated result is input into the gas extraction radius measuring system through a keyboard.
Further, in the calculation of the standard gas pre-extraction rate of the non-outburst coal seam, the standard residual gas content W 'of the coal seam in the section is inspected'CYIs calculated as:
W′CY＝Wj'+WCC
wherein, Wj' in order to reach the standard, the gas amount can be desorbed, m3The value of the/t can be determined according to the standard of the coal mine gas drainage standard; wCCThe residual gas content m of the coal under the standard atmospheric pressure3/t；
Residual gas content W of coal under standard atmospheric pressureCCIs calculated as:
wherein a and b are adsorption constants; a. thedAsh content of coal,%; madWater content of coal,%; pi is the porosity of the coal, m3/m3(ii) a Gamma is the volume weight of coal, t/m3。
Furthermore, in the calculation of the standard gas pre-extraction rate of the outburst coal seam, the desorbable gas quantity index and the gas pre-extraction outburst-prevention effect of the coal are comprehensively determined, and the standard residual gas content W of the coal seam in the section is inspectedC'YThe determination specifically comprises the following steps:
W′CY＝min(Wj'+WCC，WCR)
in the formula, WCRM is the gas content at the initial outburst depth of the outburst coal seam3T; when the gas pressure at the initial outburst depth of the outburst coal seam is unknown, the value is 8m3T; w when the gas pressure at the initial outburst depth of the outburst coal seam is knownCRIs calculated as follows:
wherein a and b are adsorption constants; a. thedAsh content of coal,%; madWater content of coal,%; pi is the porosity of the coal, m3/m3(ii) a Gamma is the volume weight of coal, t/m3；PCRThe relative gas pressure at the initial outburst depth of the outburst coal seam is MPa; paAt standard atmospheric pressure, take0.101325Mpa。
Step three: dividing the measurement area into n investigation sections, and presetting the coal seam gas extraction radius as R1、R2……RnIn each investigation section, measuring boreholes are arranged with a borehole spacing of 2R1、2R2……2RnAnd measuring the original reserves of the coal bed gas in the sections in the drilling construction process.
Determining the sizes of a plurality of expected coal seam gas extraction radiuses according to previous extraction experiences of a mine or an adjacent mine, wherein the preset coal seam gas extraction radiuses are R respectively1、R2……RnThe selected measuring area is divided into n investigation sections, the measuring boreholes in each investigation section are respectively arranged according to the distance 2R1、2R2……2RnDesigning and constructing, wherein the drilling construction process is the same as the construction process of the daily extraction drill hole of the mine, and the hole diameter and the length of the drill hole are consistent with the parameters of the daily extraction drill hole of the mine, but the drill hole and the length of the drill hole meet the relevant requirements of the standard of the gas drainage standard of the coal mine. The number of the measuring drill holes in each investigation section in the measuring area is not less than 9, at least 2 boundary condition drill holes are respectively constructed on two sides of each investigation section, the spacing of the boundary condition drill holes is consistent with the spacing of the drill holes in each investigation section, as shown in fig. 4 to 5, the bedding arrangement is that the drill holes are arranged along the coal seam in the coal seam roadway, and the bedding arrangement is an arrangement mode that the drill holes are constructed towards the adjacent coal seam in the rock roadway or the coal seam roadway.
Further, calculating the average original gas content of the coal bed in each investigation section
The method specifically comprises the following steps:
wherein, WOriginal iM original gas content measured for the ith measurement borehole in the investigation section3T; n is the number of the measured drill holes in the investigation section;
calculating the original reserves Q of the coal bed gas in each investigation sectionOriginal sourceThe method specifically comprises the following steps:
wherein S is the planar area of the investigation section, m2(ii) a h is the thickness of the coal seam in the investigation section, m; gamma is the volume weight of coal in the investigation section, t/m3。
Step four: and (3) hole sealing and grid connection of the test drill holes, connecting the test drill holes in the same investigation section with the same flow guide pipe through a grid connection rubber pipe, and connecting the flow guide pipe to a collecting pipe of the gas extraction system.
After the test drilling construction is finished, hole sealing work of the drilled hole is finished within 24 hours, the hole sealing process is the same as the daily extraction drilling hole sealing process of the mine, and materials and hole sealing parameters used for hole sealing are consistent with the daily extraction drilling hole of the mine, but the standard requirement of the coal mine gas drainage standard is met. After the test drilling hole sealing work is finished, the grid connection work is finished within 24h, the extraction drilling holes in the same investigation section are connected into the same collecting pipe, the outlet of the collecting pipe is connected with a guide pipe of the coal bed gas extraction radius measuring system, and then the coal bed gas extraction radius measuring system is connected to a pipeline of the coal bed gas extraction system through a grid connection rubber pipe.
Step five: continuously acquiring data of flow and methane concentration in the flow guide pipe, fitting the function relation of the attenuation change of the gas flow of the drill hole along with time, calculating the total pure quantity of the gas extracted by the drill hole in the extraction time t and the actual gas pre-extraction rate of each investigation section, and obtaining the pre-extraction time t when each investigation section reaches the standard gas pre-extraction rate1、t2……tnAnd a pre-pumping time t1、t2……tnThe extraction radius is R1、R2……Rn。
After the measuring drill hole is connected with a coal seam gas extraction radius measuring system, the system continuously acquires extraction mixed flow and methane concentration of the collecting pipe of each investigation section, displays the extraction mixed flow and the methane concentration on a display screen of the host in real time and is used for determining the coal seam gas extraction radius. The measured time can be set by a keyboard on the host computer, butAccording to the coal bed gas content and the air permeability coefficient, the coal bed gas content is more than or equal to 8m in principle3At the time of/t, the observation time is not less than 60 days, and when the gas content of the coal bed is less than 8m3At/t, the observation time is not less than 30 d.
The display screen on the host machine of the coal seam gas extraction radius measurement system can display the daily extraction pure quantity (m) by taking the time (d) as the abscissa in real time3And/d) is a graph of a vertical coordinate, after the set observation time is reached, the coal bed gas extraction radius measurement and analysis system automatically fits the observation result to obtain a function relation of the attenuation change of the gas flow of the drill hole along with the time, and when the fitting correlation coefficient is less than 0.8, the system automatically prompts that the fitting degree is low and the data of the group is recommended to be discarded.
Further, the function relation of the attenuation change of the gas flow of the drill hole along with the time is specifically as follows:
qt＝q0e-αt
wherein q istFor the investigation of the total purity of the drilled gas extraction in the section at the time t, m3/d；q0For investigating the total purity m of initial gas extraction drilled in a section3α is the pure quantity attenuation coefficient of the drilling gas extraction in the investigation section, d-1(ii) a t is the time for extracting gas in the drill hole, d; fitting a functional relation of the drill hole gas flow along with the time attenuation change, and discarding the data of the group of flow and methane concentration if the fitting correlation coefficient is less than 0.8;
the method is characterized in that the total pure quantity Q of the gas extraction of the drill hole in the investigation section is calculated while the fitting of the function relation of the gas flow of the drill hole along with the time attenuation change is carried outcThe method specifically comprises the following steps:
measuring total purity Q of drilled gas extraction according to investigation sectioncAnd original reserves Q of coal bed gas in each investigation sectionOriginal sourceCalculating the actual gas pre-extraction rate η of each section under investigation at time ttThe method specifically comprises the following steps:
comparing the actual gas pre-extraction rates η of the respective investigation sectionstAnd the pre-extraction rate η of gas reaching the standard0And determining the gas extraction radius of the coal seam.
Coal seam gas extraction radius measurement system automatically compares actual gas pre-extraction rate η of each investigation sectiontAnd the pre-extraction rate η of gas reaching the standard0The measured borehole spacing is found to be 2R respectively1、2R2……2RnThe pre-extraction time t of each investigation section for realizing gas extraction standard reaching1、t2……tnAnd the pre-pumping time t (a certain pumping hole aperture, a hole sealing process and the like) under the current pumping condition of the mine is also obtained1、t2……tnTemporal extraction radius R1、R2……Rn。
The method for measuring the gas extraction radius by using the coal seam gas extraction radius measuring system simplifies the step of measuring the extraction radius, is more convenient to operate, shortens the measuring period, and enables the measuring result to better accord with the actual engineering. The system for measuring the coal bed gas extraction radius is convenient to operate and high in practicability, and the measuring period of the coal bed gas extraction radius is greatly shortened. The method can truly reflect the mine gas extraction condition, has simple requirements on field test conditions, strong applicability and practicability and reliable measurement results, improves the traditional measurement principle and measurement method of the pressure and content of the coal seam gas, and improves the scientificity of design and construction of the gas extraction drill hole of the coal seam underground.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.
Claims (10)
1. A coal seam gas extraction radius measuring system is characterized by comprising a guide pipe, a handheld measuring instrument and a host, wherein the guide pipe is connected between a collecting pipe and a grid-connected rubber pipe of a gas extraction system, and a flow sensor and a methane concentration sensor are arranged in the guide pipe; the host comprises a display, a keyboard, an integrated circuit and a power supply, wherein the display and the keyboard are respectively connected with the integrated circuit board, the flow sensor and the methane concentration sensor are also respectively connected with the integrated circuit board, and the power supply comprises a storage battery and an electricity utilization interface; and data are wirelessly transmitted between the handheld measuring instrument and the host.
2. The system for measuring the coal seam gas extraction radius according to claim 1, wherein the section of the draft tube is circular, the diameter of the draft tube is 80 mm-200 mm, and the length of the draft tube is greater than 200 mm; the guide pipe is arranged between a collecting pipe and a grid-connected rubber pipe of the gas extraction system in a straight and straight mode.
3. The coal seam gas extraction radius measurement system according to claim 1, wherein the host is further provided with a data transmission serial port, and the data transmission serial port is connected with a downhole looped network; the electricity utilization interface is connected with an underground intrinsic safety power line.
4. The system for measuring the coal seam gas extraction radius according to claim 1, wherein the handheld measuring instrument collects data records of flow rate and methane concentration from a host.
5. A coal seam gas extraction radius measuring method, which utilizes the gas extraction radius measuring system of any one of claims 1 to 4, and is characterized by comprising the following steps:
the method comprises the following steps: selecting a measuring area, wherein at least one measuring area is selected from each horizontal area, each mining area and each geological unit to determine the gas extraction radius;
step two: calculating the gas pre-extraction rate up to the standard, including calculating the gas pre-extraction rate up to the standard of a non-outburst coal seam and an outburst coal seam;
step three: dividing the measurement area into n investigation sections, and presetting the coal seam gas extraction radius as R1、R2……RnIn each investigation section, measuring boreholes are arranged with a borehole spacing of 2R1、2R2……2RnMeasuring the original reserves of the coal bed gas in the sections in the drilling construction process;
step four: the hole sealing and the grid connection of the test drill holes are carried out, the measurement drill holes in the same investigation section are connected with the same flow guide pipe through a grid connection rubber pipe, and the flow guide pipe is connected to a collecting pipe of a gas extraction system;
step five: continuously acquiring data of flow and methane concentration in the flow guide pipe, fitting the function relation of the attenuation change of the gas flow of the drill hole along with time, calculating the total pure quantity of the gas extracted by the drill hole in the extraction time t and the actual gas pre-extraction rate of each investigation section, and obtaining the pre-extraction time t when each investigation section reaches the standard gas pre-extraction rate1、t2……tnAnd a pre-pumping time t1、t2……tnThe extraction radius is R1、R2……Rn。
6. The method for measuring the coal seam gas extraction radius according to claim 5, wherein the standard gas pre-extraction rate η is0The calculation of (2) is specifically:
wherein, W'CYM for investigating the standard residual gas content of the coal seam in the section3/t；
To investigate the average original gas content, m, of the coal seam in a section3/t；
Calculating the original reserves Q of the coal bed gas in each investigation sectionOriginal sourceThe method specifically comprises the following steps:
wherein S is the planar area of the investigation section, m2(ii) a h is the thickness of the coal seam in the investigation section, m; gamma is the volume weight of coal in the investigation section, t/m3；
And will η0、QOriginal sourceThe calculated result is input into the gas extraction radius measuring system through a keyboard.
7. The method for measuring coal seam gas extraction radius according to claim 5 or 6, characterized in that in the calculation of the standard gas pre-extraction rate of the non-outburst coal seam, the standard residual gas content W 'of the coal seam in the section is considered'CYIs calculated as:
W′CY＝W′j+WCC
wherein, W'jM is the amount of the gas which can be desorbed after reaching the standard3/t；WCCThe residual gas content m of the coal under the standard atmospheric pressure3/t；
Residual gas content W of coal under standard atmospheric pressureCCIs calculated as:
wherein a and b are adsorption constants; a. thedAsh content of coal,%; madWater content of coal,%; pi is the porosity of the coal, m3/m3(ii) a Gamma is the volume weight of coal, t/m3。
8. The method for measuring coal seam gas extraction radius according to claim 5 or 6, characterized in 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 section is considered'CYThe determination specifically comprises the following steps:
W′CY＝min(W′j+WCC，WCR)
in the formula, WCRM is the gas content at the initial outburst depth of the outburst coal seam3T; when the gas pressure at the initial outburst depth of the outburst coal seam is unknown, the value is 8m3T; w when the gas pressure at the initial outburst depth of the outburst coal seam is knownCRIs calculated as follows:
wherein a and b are adsorption constants; a. thedAsh content of coal,%; madWater content of coal,%; pi is the porosity of the coal, m3/m3(ii) a Gamma is the volume weight of coal, t/m3；PCRThe relative gas pressure at the initial outburst depth of the outburst coal seam is MPa; paThe standard atmospheric pressure is 0.101325 MPa.
9. The method for measuring the coal seam gas extraction radius according to claim 5, wherein in the third step, the average original gas content of the coal seam of each investigation section is calculated
The method specifically comprises the following steps:
wherein, WOriginal iM original gas content measured for the ith measurement borehole in the investigation section3T; n is the number of the measured drill holes in the investigation section;
calculating the original reserves Q of the coal bed gas in each investigation sectionOriginal sourceThe method specifically comprises the following steps:
wherein S is the planar area of the investigation section, m2(ii) a h is the thickness of the coal seam in the investigation section, m; gamma is the volume weight of coal in the investigation section, t/m3。
10. The method for measuring the coal seam gas extraction radius according to claim 5, wherein in the fifth step, the function relation of the attenuation change of the borehole gas flow along with time is specifically as follows:
qt＝q0e-αt
wherein q istFor the investigation of the total purity of the drilled gas extraction in the section at the time t, m3/d；q0For investigating the total purity m of initial gas extraction drilled in a section3α is the pure quantity attenuation coefficient of the drilling gas extraction in the investigation section, d-1(ii) a t is the time for extracting gas in the drill hole, d; fitting a functional relation of the drill hole gas flow along with the time attenuation change, and discarding the data of the group of flow and methane concentration if the fitting correlation coefficient is less than 0.8;
the method is characterized in that the total pure quantity Q of the gas extraction of the drill hole in the investigation section is calculated while the fitting of the function relation of the gas flow of the drill hole along with the time attenuation change is carried outcThe method specifically comprises the following steps:
measuring total purity Q of drilled gas extraction according to investigation sectioncAnd original reserves Q of coal bed gas in each investigation sectionOriginal sourceCalculating the actual gas pre-extraction rate η of each section under investigation at time ttThe method specifically comprises the following steps:
comparing the actual gas pre-extraction rates η of the respective investigation sectionstAnd the pre-extraction rate η of gas reaching the standard0And determining the gas extraction radius of the coal seam.
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