Method and device for measuring gas pressure and extraction parameters of underground coal mine

Abstract

The invention discloses a coal mine underground gas pressure and extraction parameter measuring method and device, and belongs to the technical field of coal mine gas parameter determination.The method comprises the steps that drilling pressure data are collected in real time, water pressure interference formed by coal seam crack water invasion is intelligently recognized and eliminated based on dynamic pressure curve slope threshold analysis, and a gas extraction parameter is obtained; a real gas pressure value is obtained after pressure stability judgment; after pressure measurement is completed, the pressure is relieved, and a flow detection stage is switched to; and based on the gas pressure value, the flow data and the drilling parameters, the coal seam permeability coefficient and the hectometer drilling gas flow attenuation coefficient are calculated. The influence of water pressure interference misjudgment and insufficient flow measurement range on the accuracy of the gas pressure data and the accuracy of the gas flow data in a traditional method is avoided, and therefore the accuracy and reliability of the coal seam gas permeability coefficient and the hectometer drill hole gas flow attenuation coefficient measured according to the gas pressure value and the gas flow data are improved.

Description

Technical Field

[0001] This invention relates to the field of coal mine gas parameter measurement technology, specifically a method and apparatus for measuring underground gas pressure and extraction parameters in coal mines. Background Technology

[0002] Coal seam gas pressure, permeability coefficient, and gas flow attenuation coefficient per 100-meter borehole are crucial parameters for coal mine gas control. Accurate measurement of these parameters is not only a scientific basis for gas extraction design but also a prerequisite for hazard classification and early warning. When groundwater intrudes into the detection chamber, the water pressure masks the true gas pressure. While direct measurement methods for underground coal seam gas pressure use correction formulas, they cannot distinguish between pressure increases originating from gas accumulation and hydraulic connectivity, easily leading to misjudgments and affecting the measurement results.

[0003] Coal seam gas pressure, permeability coefficient, and gas flow attenuation coefficient per 100-meter borehole are important parameters for coal mine gas control and outburst risk assessment. Their accurate measurement is the basis for gas drainage design and disaster early warning.

[0004] Traditional measurement methods rely on a single sensor structure and fixed threshold judgments, making it difficult to dynamically distinguish between the natural rise in gas seepage pressure and water pressure interference caused by coal seam fissure water intrusion. Once hydraulic connection occurs, the water pressure effect continuously masks the true gas pressure, causing the measurement system to mistakenly identify pressure changes caused by water pressure as a stable gas pressure state, resulting in a systematic deviation in the final pressure value. Meanwhile, gas flow measurement is limited by a single acquisition method, especially during the flow rate change from high to low after gas depressurization. It is difficult to simultaneously consider the measurement range during the high flow rate stage and the measurement accuracy during the low flow rate stage. This measurement error is further amplified, particularly in the low flow rate stage where coal seam permeability is poor, leading to incomplete or distorted flow data used to calculate the permeability coefficient and the gas attenuation coefficient per 100-meter borehole, affecting the overall reliability of the pumping parameters. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for measuring underground gas pressure and extraction parameters in coal mines, so as to solve the above-mentioned problems.

[0006] The technical solution of this invention is: A method for determining underground gas pressure and extraction parameters in coal mines, comprising the following steps: Connect the measuring device to the borehole and connect the pressure and flow measurement circuits. First, measure the initial gas flow rate of the borehole. After the measurement is completed, close the straight-through ball valve and connect only the pressure measurement circuit to collect borehole pressure data in real time and generate a pressure curve.

[0007] Based on dynamic pressure curve slope threshold analysis, when a sudden pressure increase within a preset time period is detected and the slope change exceeds a set multiple of the natural gas pressure rise slope, it is determined to be water pressure interference caused by coal seam fissure water intrusion. If the pressure increase within one day exceeds the preset threshold and the pressure curve slope change exceeds more than 5 times the natural gas seepage pressure rise slope before the change, water pressure interference is considered to exist. If there is gas pressure data with a gas pressure change not exceeding 0.015 MPa for three consecutive days before the pressure increase exceeds the preset threshold, the last value of that data segment is taken as the final gas pressure. If there is no gas pressure data with a gas pressure change not exceeding 0.015 MPa for three consecutive days, the pressure measurement is considered a failure, and drilling and pressure measurement need to be carried out again to eliminate water pressure interference. If there is no water pressure interference, when the pressure change within a set number of consecutive days is less than the set threshold, the pressure is determined to be stable, and this stable pressure value is recorded as the final gas pressure value.

[0008] After the pressure stabilization determination is completed, the gas path is manually switched to the pressure relief circuit for pressure relief. After pressure relief is completed, the gas path is switched to the flow detection path. Gas flow data is collected through the dual flow sensor collaborative measurement system. The branch paths of the second flow sensor and the first flow sensor are automatically switched according to the real-time flow value to cover the full flow range. The gas flow data can be processed to obtain the effective flow value.

[0009] Based on the final gas pressure value, initial borehole gas flow rate, gas flow rate data, and borehole parameters, the coal seam permeability coefficient and the 100-meter borehole gas flow rate attenuation coefficient are calculated according to the permeability coefficient calculation formula and the 100-meter borehole gas flow rate attenuation coefficient formula, respectively. The final gas pressure and the corresponding pressure rise curve, the 100-meter borehole gas flow rate attenuation coefficient, the effective flow rate, the coal seam permeability coefficient value, and the gas pressure rise curve over time are output.

[0010] Furthermore, in the step of intelligently identifying water pressure interference based on dynamic pressure curve slope threshold analysis, the preset judgment conditions are: the pressure rise exceeds the preset threshold within 1 day, and the sudden change value of the pressure curve slope exceeds 5 times the natural gas seepage pressure rise slope before the sudden change occurs. The condition for determining pressure stability is: the pressure change is less than 0.015 MPa within 3 consecutive days.

[0011] Furthermore, when it is determined that water intrusion in the coal seam fissures is causing water pressure interference, the water pressure identification algorithm module triggers an alarm signal and automatically marks abnormal data segments. The system then traces back the pressure data before the water pressure intervention to determine if there is a data segment that meets the pressure stability conditions. If a data segment that meets the pressure stability conditions exists, the system fits and outputs the true gas pressure value based on that data segment. If no data segment that meets the pressure stability conditions exists, the borehole is deemed invalid and needs to be re-drilled for re-measurement.

[0012] Furthermore, the method for acquiring gas flow data through a dual flow sensor collaborative measurement system includes the following steps: After the pressure is measured, the gas is released and depressurized. After depressurization, the gas flow rate in the borehole decreases from high to low. Two sensors with different ranges are used. The main reason is that the flow rate decreases over a large range, and it is difficult to meet the requirements of range and accuracy at the same time using the same sensor.

[0013] During the initial high flow rate phase after depressurization, the branch path of the first flow sensor is activated; the range of the first flow sensor is 0LM~1SLM.

[0014] When the reading of the first flow sensor is lower than 20% of its range, the solenoid valve automatically switches to the second flow sensor branch path. The range of the second flow sensor is 0 CCM to 200 SCCM, in order to capture complete flow attenuation data.

[0015] Furthermore, the drilling parameters include: borehole diameter, borehole-coal seam angle, and coal seam section length.

[0016] Furthermore, the formula for calculating the coal seam permeability coefficient is as follows: ; ;in, F λ is the time standard, λ is the coal seam permeability coefficient, and k1, k2 and k3 are variable parameters.

[0017] when F In 10 -2 When k = ~1, k1 = 1, k2 = 1.61, k3 = 1 / 1.64.

[0018] when F When the range is 1 to 10, k1=1, k2=1.39, and k3=1 / 2.56.

[0019] when F In 10~10 2 At that time, k1=1.1, k2=1.25, k3=1 / 4.

[0020] when F In 10 2 ~10 3 At that time, k1=1.83, k2=1.14, k3=1 / 7.3.

[0021] when F In 10 3 ~10 5 At that time, k1=2.1, k2=1.11, k3=1 / 9.

[0022] when F In 10 5 ~107 At that time, k1=3.14, k2=1.07, k3=1 / 14.4.

[0023] parameter A and B The calculation formulas are as follows: .

[0024] .

[0025] in, q r1 is the gas emission velocity at the borehole surface and r1 is the borehole radius. P 0 represents the square of the original absolute gas pressure of the coal seam. P 1 represents the square of the absolute pressure inside the borehole when measuring flow rate, typically taken as 0.1 MPa. t For time; α is the coal seam gas content coefficient; q is the gas flow rate per unit area of ​​the borehole coal wall when the gas emission time is t.

[0026] First, calculate the parameters. A and B Then, the calculation results are substituted into the formula for calculating the coal seam permeability coefficient to calculate multiple permeability coefficients. λ and time standard F If selected λ The calculation formula corresponds to the time standard. F and by that λ Calculated time standard F Within the same range, then... λ The result is used as the measurement result of the coal seam permeability coefficient.

[0027] Furthermore, due to the long duration of the gas flow attenuation coefficient measurement process in a 100-meter borehole, it is susceptible to interference from various factors. Under conditions of poor coal seam permeability, the natural emission time is t. 10 The initial gas flow rate is very small, and due to the resistance and range limitations of the mechanical flow meter, flow measurement is difficult and the results are inaccurate. Therefore, the initial borehole gas flow rate and natural discharge time are selected as t. 10 The attenuation coefficient of the gas flow rate per 100 meters of borehole is calculated using the borehole gas flow rate data at that time. The formula for the attenuation coefficient of the gas flow rate per 100 meters of borehole is:

[0028] .

[0029] in, q 0 represents the initial gas flow rate during borehole drilling. q t For emissions t 10 Time-based borehole natural gas flow rate, t 10 The natural gas release time from the borehole is 10 days.β The gas attenuation coefficient per 100 meters of flow rate. e It is a natural constant.

[0030] A device for measuring underground gas pressure and extraction parameters in coal mines is disclosed. The device utilizes the aforementioned measurement method to measure underground gas pressure and extraction parameters. The device includes: a pressure detection path comprising a pressure sensor, a three-way connector, and a straight-through ball valve. The first interface of the three-way connector is connected to a borehole, the second interface is connected to one port of the straight-through ball valve, the other port of the straight-through ball valve is connected to a pressure relief port, and the third interface of the three-way connector is connected to the pressure sensor. After pressure measurement, the pressure relief port also serves as a port connected to a flow detection path. The flow detection path is detachably connected to the pressure relief port via a quick-connect fitting. The downstream of the flow detection path is configured with two branch sections, forming a dual-flow sensor collaborative measurement system. Each branch section is equipped with a flow sensor, designated as a first flow sensor and a second flow sensor. During pressure measurement, the straight-through ball valve is closed, and the pressure relief port is open to the atmosphere. After pressure measurement, when releasing pressure, the straight-through ball valve is opened, allowing high-pressure gas to be released through the pressure relief port. After depressurization, the depressurization port and quick-connect fitting are connected to open the flow detection path. A solenoid valve, located at the intersection of the two branches, controls the on / off state of the two branches. The main control circuit module is electrically connected to the pressure sensor, the two flow sensors, and the solenoid valve. The main control circuit module integrates a water pressure recognition algorithm module and a permeability coefficient calculation module. The permeability coefficient calculation module is input with the permeability coefficient calculation formula and the gas flow attenuation coefficient formula for a 100-meter borehole. The water pressure recognition algorithm module receives real-time pressure data collected by the pressure sensor and generates a pressure curve. Based on the generated pressure curve sample threshold, it analyzes the pressure curve, determining whether a sudden pressure rise exceeds a set multiple to identify water pressure interference. If water pressure interference exists, it tracks the data in reverse and outputs the true gas pressure value. If no water pressure interference exists, it directly takes the stable pressure value as the final gas pressure value. A display panel, connected to the main control circuit module, displays the data and results.

[0031] Furthermore, it also includes a filter, which is configured in the flow detection path, located upstream of the solenoid valve. This effectively prevents impurities such as coal dust from entering the flow sensor, avoiding damage to the flow sensor and ensuring the accuracy of the flow sensor readings.

[0032] Compared with the prior art, the beneficial effects of the present invention are: The measurement method of this invention is based on dynamic pressure curve feature analysis to achieve automatic identification and filtering of hydraulic interference. It uses a dynamic rate threshold analysis algorithm to overcome the misjudgment of gas pressure caused by coal seam fissure water intrusion in traditional equipment. Combined with standardized stability judgment criteria, it reduces the error of the final gas pressure data, significantly reduces the risk of misjudgment, and ensures the authenticity and reliability of pressure detection results.

[0033] The measurement method of this invention addresses the characteristic that the flow velocity of gas in the borehole decreases from high to low and the decrease span is relatively large after depressurization. It uses sensors with corresponding ranges to collect flow data at different stages after depressurization, realizing seamless capture of flow throughout the entire cycle, eliminating the problem of data loss in the low flow range of the later stage of decay by a single sensor, and improving the calculation accuracy of extraction parameters. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the internal structure of the measuring device of the present invention.

[0035] Figure 2 This is a flowchart of the measurement method of the present invention.

[0036] Figure 3 This is a schematic diagram of the overall panel layout.

[0037] Among them, 1. First flow outlet, 2. Straight-through ball valve, 3. Flow inlet, 4. Filter, 5. Display panel, 6. Second flow outlet, 7. Handle, 8. Quick connector, 9. Pressure relief port, 10. Solenoid valve, 11. Pressure sensor, 12. First flow sensor, 13. Second flow sensor, 14. T-connector. Detailed Implementation

[0038] The following is combined Figures 1 to 3 The specific embodiments of the present invention will be described in detail below. In the description of the present invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0039] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0040] It should be noted that the circuit connections involved in this invention all adopt conventional circuit connection methods and do not involve any innovation.

[0041] Example like Figure 2 As shown, a method for determining underground gas pressure and extraction parameters in coal mines includes the following steps: Connect the flow inlet 3 of the measuring device to the borehole, and connect the pressure measurement and flow measurement circuits. First, measure the initial gas flow rate of the borehole. After the measurement is completed, close the straight-through ball valve 10 and connect only the pressure measurement circuit to collect borehole pressure data in real time and generate a pressure curve.

[0042] Based on dynamic pressure curve slope threshold analysis, when a sudden pressure increase within a preset time period is detected and the slope change exceeds a set multiple of the natural gas pressure rise slope, it is determined to be water pressure interference caused by coal seam fracture water intrusion. Fitting calculations are performed based on the gradual change characteristic segment of the pressure curve. If the pressure increase within one day exceeds a preset threshold, and the slope change exceeds five times the natural gas permeability pressure rise slope before the change, water pressure interference is considered present. If there is gas pressure data with a change not exceeding 0.015 MPa for three consecutive days before the pressure increase exceeds the preset threshold, the last value of that data segment is taken as the final gas pressure. If there is no gas pressure data with a change not exceeding 0.015 MPa for three consecutive days, the pressure measurement is considered a failure, and drilling and pressure measurement must be repeated to eliminate water pressure interference. If there is no water pressure interference, when the pressure change within a set number of consecutive days is less than a set threshold, the pressure is considered stable, and this stable pressure value is recorded as the final gas pressure value.

[0043] After the pressure stabilization determination is completed, the gas path is manually switched to the pressure relief circuit for pressure relief. After pressure relief is completed, the gas path is switched to the flow detection path. Gas flow data is collected through the dual flow sensor collaborative measurement system. The second flow sensor branch path and the first flow sensor branch path are automatically switched according to the real-time flow value to cover the full flow range. The gas flow data can be processed to obtain the effective flow value.

[0044] Based on the final gas pressure, initial borehole gas flow rate, gas flow rate data, and borehole parameters, the coal seam permeability coefficient and the 100-meter borehole gas flow rate attenuation coefficient are calculated according to the permeability coefficient calculation formula and the 100-meter borehole gas flow rate attenuation coefficient formula, respectively. The final gas pressure, 100-meter borehole gas flow rate attenuation coefficient, effective flow rate, coal seam permeability coefficient, and gas pressure rise curve over time are output.

[0045] In the intelligent identification of water pressure interference based on dynamic pressure curve slope threshold analysis, the preset judgment conditions are: the pressure rise exceeds the preset threshold within 1 day, and the sudden change value of the pressure curve slope exceeds 5 times the natural gas seepage pressure rise slope before the sudden change occurs. The condition for pressure stability judgment is: the pressure change is less than 0.015MPa within 3 consecutive days.

[0046] When it is determined that water intrusion into coal seam fissures is causing water pressure interference, the water pressure identification algorithm module triggers an alarm signal and automatically marks abnormal data segments. The system then traces back the pressure data before the water pressure intervention to determine if there is a data segment that meets the pressure stability conditions. If a data segment that meets the pressure stability conditions exists, the system fits and outputs the true gas pressure value based on that data segment. If no data segment that meets the pressure stability conditions exists, the borehole is deemed invalid and needs to be re-drilled for re-measurement.

[0047] The method for acquiring gas flow data using a dual-flow sensor collaborative measurement system includes the following steps: After the pressure is measured, the gas is released and depressurized. After depressurization, the gas flow rate in the borehole decreases from high to low. Two sensors with different ranges are used. The main reason is that the flow rate decreases over a large range, and it is difficult to meet the requirements of range and accuracy at the same time using the same sensor.

[0048] During the initial high flow rate phase after depressurization, the branch path of the first flow sensor is activated; the range of the first flow sensor is 0LM~1SLM.

[0049] When the reading of the first flow sensor 12 is lower than 20% of its range, the solenoid valve 10 automatically switches to the branch path of the second flow sensor. The range of the second flow sensor 13 is 0 CCM to 200 SCCM, so as to capture complete flow attenuation data.

[0050] Drilling parameters include: borehole diameter, borehole-coal seam angle, and coal seam section length.

[0051] The formula for calculating the coal seam permeability coefficient is shown in Table 1: Table 1. Formulas for determining air permeability coefficient ,in, F λ is the time standard, and λ is the coal seam permeability coefficient.

[0052] parameter A and B They are respectively: ; .

[0053] in, q The velocity of gas escaping from the borehole surface. r1 represents the borehole radius. P 0 represents the square of the original absolute gas pressure of the coal seam. P 1 represents the square of the absolute pressure inside the borehole when measuring flow rate, typically taken as 0.1 MPa. t For time; α q is the coal seam gas content coefficient; q is the gas emission time. t Gas flow rate per unit area of ​​the coal face during drilling.

[0054] The calculation process is as follows: First calculate A and B Then, substitute the calculation results into Table 1 to calculate the air permeability coefficient. λ and time standard F Let's look at the calculated results. F Is the value present? λ The formula used corresponds to F Within the range, if it is within the range, then λ If the calculation result is correct, otherwise, try another one. λ The calculation formula is followed until the correct result is obtained. The row whose calculated time criterion falls exactly within the range of values ​​in the left column of the table is then selected. λ This refers to the measurement result of the coal seam permeability coefficient.

[0055] Because the process of determining the gas flow attenuation coefficient in a 100-meter borehole is lengthy and susceptible to interference from various factors, the natural emission time is approximately t when the coal seam permeability is poor. 10 The initial gas flow rate is very small, and due to the resistance and range limitations of the mechanical flow meter, flow measurement is difficult and the results are inaccurate. Therefore, the initial borehole gas flow rate and natural discharge time are selected as t. 10 The attenuation coefficient of the gas flow rate per 100 meters of borehole is calculated using the borehole gas flow rate data at that time. The formula for the attenuation coefficient of the gas flow rate per 100 meters of borehole is: ;in, q 0 represents the initial gas flow rate during borehole drilling. q t For emissions t 10 Time-based borehole natural gas flow rate, t 10 The natural gas release time from the borehole is 10 days. β The gas attenuation coefficient per 100 meters of flow rate. e It is a natural constant.

[0056] like Figure 1 and Figure 3As shown, a device for measuring underground gas pressure and extraction parameters in coal mines is disclosed. This device utilizes the aforementioned measurement method to measure underground gas pressure and extraction parameters. The device includes: a housing, a pressure detection passage, a flow detection passage, a solenoid valve 10, a main control circuit module, and a display panel 5. The flow detection passage, a straight-through ball valve 2, the solenoid valve 10, and a flow sensor are located inside the housing. A handle 7 is provided on the top of the housing. The pressure detection passage includes a pressure sensor 11, a three-way connector 14, and a straight-through ball valve 2. The first interface of the three-way connector 14 is used to connect to the borehole, and the second interface is connected to the straight-through ball valve 2. One port of ball valve 2 is connected, and the other port of ball valve 2 is connected to pressure relief port 9. The third interface of tee connector 14 is connected to pressure sensor 11. After pressure measurement, pressure relief port 9 also serves as a port connected to the flow detection path. The flow detection path is detachably connected to pressure relief port 9 via quick connector 8. The downstream of the flow detection path is configured with two branch sections, each equipped with a flow sensor. As a dual flow sensor collaborative measurement system, the two flow sensors are the first flow sensor 12 and the second flow sensor 13. During pressure measurement, ball valve 2 is closed, and pressure relief port 9 is connected to pressure relief port 9. Pressure port 9 is open to the atmosphere. After pressure measurement, when releasing pressure, the straight-through ball valve 2 opens, and the high-pressure gas is released through pressure port 9. After pressure release, pressure port 9 connects to quick connector 8, opening the flow detection path. Solenoid valve 10 is located at the intersection of the two branches to control the opening and closing of the two branches. The main control circuit module is electrically connected to pressure sensor 11, two flow sensors, and solenoid valve 10. The main control circuit module integrates a water pressure recognition algorithm module and an air permeability coefficient calculation module. The air permeability coefficient calculation module is input with the air permeability coefficient calculation formula and a 100-meter drill bit. The formula for the gas flow attenuation coefficient is used. The water pressure identification algorithm module is used to receive real-time pressure data collected by the pressure sensor 11 and generate a pressure curve. Based on the generated pressure curve sample threshold, the pressure curve is analyzed. It is determined whether the pressure rise exceeds a set multiple to determine whether there is water pressure interference. If water pressure interference exists, the data is tracked in reverse and the real gas pressure value is output. If there is no water pressure interference, the stable pressure value is directly taken as the final gas pressure value. The display panel 5 is connected to the main control circuit module and is used to display data and results. The display panel 5 is located outside the housing.

[0057] In some embodiments, a filter 4 is also included, which is configured in the flow detection path and located upstream of the solenoid valve 10. This effectively prevents impurities such as coal dust from entering the flow sensor, avoiding damage to the flow sensor and ensuring the accuracy of the flow sensor readings.

[0058] The operating procedure of the above device is as follows: After the drilling and sealing work of the gas pressure measurement borehole is completed downhole, the gas pipe is connected to the flow inlet 3, the straight ball valve 2 is opened, and the quick connector 8 on the left end of the filter 4 is inserted. The gas in the borehole flows through the solenoid valve 10, passes through the first flow sensor 12, and is discharged from the first flow outlet 1. When the gas flow rate is less than 160 SCCM, the passage of the first flow sensor 12 is closed, and the passage of the second flow sensor 13 is opened to continue measuring the borehole gas flow rate. The gas is discharged from the second flow outlet 6. The measurement is continuously measured for 10 minutes, and the average gas flow rate of 10 minutes is taken as the initial gas flow rate of the borehole.

[0059] Close the straight-through ball valve 2 and start measuring the gas pressure. The pressure sensor 11 automatically records the gas pressure rise curve inside the borehole. After the test is completed, the curve is analyzed and the pressure test results are given.

[0060] After completing the gas pressure test, disconnect the quick connector 8 and open the straight-through ball valve 2 to depressurize the borehole.

[0061] After the gas in the borehole is completely depressurized, insert quick connector 8 to start the borehole gas flow test. The borehole gas flow test is the same as the initial borehole gas flow test. All flow data is automatically saved during the entire test process.

[0062] The test ends after the scheduled test time is reached, and the pipeline connection of flow inlet 3 is disconnected.

[0063] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for determining underground gas pressure and extraction parameters in coal mines, characterized in that, Includes the following steps: Determine the initial gas flow rate in the borehole; Real-time acquisition of borehole pressure data and generation of pressure curves; based on pressure curve slope threshold analysis, determination of water pressure interference: if the pressure rises sharply within a preset time and the slope change exceeds a set multiple of the natural gas pressure rise slope, water pressure interference is determined to exist; otherwise, no water pressure interference is determined. When water pressure interference exists, the pressure data before the interference is traced back. If a data segment that meets the stability condition exists, the true gas pressure value is output based on that data segment; otherwise, the borehole is deemed invalid and needs to be re-drilled and measured again until a stable pressure value is obtained; when there is no water pressure interference, the stable pressure value is directly taken as the final gas pressure value. After the pressure stabilizes, the pressure inside the borehole is released, and then the gas flow rate data is measured and obtained. Based on the final gas pressure value, initial gas flow rate of the borehole, gas flow rate data, and borehole parameters, the coal seam permeability coefficient and the gas flow rate attenuation coefficient per 100 meters of borehole are calculated respectively, and the final gas pressure and the corresponding pressure rise curve, the gas flow rate attenuation coefficient per 100 meters of borehole, and the coal seam permeability coefficient are output.

2. The method for determining underground gas pressure and extraction parameters in a coal mine according to claim 1, characterized in that, Based on the pressure curve slope threshold analysis, the preset judgment condition for determining whether there is water pressure interference is: the pressure rise exceeds the preset threshold within 1 day, and the sudden change value of the pressure curve slope exceeds 5 times the natural gas seepage pressure rise slope before the sudden change. The condition for determining pressure stability is: the pressure change is less than 0.015 MPa within 3 consecutive days.

3. The method for determining underground gas pressure and extraction parameters in a coal mine according to claim 1, characterized in that, The method for measuring gas flow data includes the following steps: In the initial flow rate stage after depressurization, gas flow data is collected using a first flow sensor (12) with a range of 0LM~1SLM. When the reading of the first flow sensor (12) is lower than 20% of its range, the second flow sensor (13) with a range of 0CCM~200SCCM is switched to continue collecting gas flow data in order to capture complete flow decay data.

4. The method for determining underground gas pressure and extraction parameters in a coal mine according to claim 1, characterized in that, The drilling parameters include: borehole diameter, borehole-coal seam angle, and coal seam section length.

5. The method for determining underground gas pressure and extraction parameters in a coal mine according to claim 1, characterized in that, The formula for calculating the coal seam permeability coefficient is as follows: ; ; in, F Let λ be the time-dependent coefficient, and λ be the coal seam permeability coefficient. A and B For parameters; parameter A and B The calculation formulas are as follows: ； ； in, q r1 is the gas emission velocity at the borehole surface and r1 is the borehole radius. P 0 represents the square of the original absolute gas pressure of the coal seam. P 1 represents the square of the absolute pressure inside the borehole when measuring flow rate. t For time; α is the coal seam gas content coefficient; q is the gas flow rate per unit area of ​​the borehole coal wall when the gas emission time is t; k1, k2 and k3 are variable parameters. First, calculate the parameters. A and B Then substitute the calculation results into the coal seam permeability coefficient. λ The calculation formula yields multiple air permeability coefficients. λ and time standard F If the selected λ The calculation formula corresponds to the time standard. F and by that λ Calculated time standard F Within the same range, then... λ The value is used as the result of the measurement of the coal seam permeability coefficient.

6. The method for determining underground gas pressure and extraction parameters in a coal mine according to claim 1, characterized in that, The initial gas flow rate and natural drainage time of the borehole are selected as t. 10 The attenuation coefficient of the gas flow rate per 100 meters of borehole is calculated using the borehole gas flow rate data at that time. The formula for the attenuation coefficient of the gas flow rate per 100 meters of borehole is: ； in, q 0 represents the initial gas flow rate during borehole drilling. q t For emissions t 10 Time-based borehole natural gas flow rate, t 10 The natural gas release time from the borehole is 10 days. β The gas attenuation coefficient per 100 meters of flow rate. e It is a natural constant.

7. A device for measuring underground gas pressure and extraction parameters in coal mines, characterized in that, The method described in any one of claims 1-6 is used to determine the underground gas pressure and extraction parameters in a coal mine, wherein the measuring device comprises: The pressure detection path includes a pressure sensor (11), a three-way connector (14), and a straight-through ball valve (2). The first interface of the three-way connector (14) is used to connect to the borehole, the second interface is connected to one port of the straight-through ball valve (2), the other port of the straight-through ball valve (2) is connected to the pressure relief port (9), and the third interface of the three-way connector (14) is connected to the pressure sensor (11). The flow detection path is detachably connected to the pressure relief port (9) via a quick connector (8). The downstream of the flow detection path is configured as two branch sections, each of which is equipped with a flow sensor, forming a dual flow sensor collaborative measurement system. A solenoid valve (10) is located at the intersection of the two branches to control the on / off state of the two branches. The main control circuit module is electrically connected to the pressure sensor (11), two flow sensors and solenoid valve (10) respectively; the main control circuit module integrates a water pressure identification algorithm module and an air permeability coefficient calculation module. The air permeability coefficient calculation module is input with the air permeability coefficient calculation formula and the gas flow attenuation coefficient formula of 100-meter borehole. The water pressure identification algorithm module is used to receive the real-time pressure data collected by the pressure sensor (11) and generate a pressure curve. Based on the generated pressure curve sample threshold, the pressure curve is analyzed; it is determined whether the pressure rise exceeds the set multiple to determine whether there is water pressure interference. If there is water pressure interference, the data is tracked in reverse and the real gas pressure value is output. If there is no water pressure interference, the stable pressure value is directly taken as the final gas pressure value. The display panel (5) is connected to the main control circuit module and is used to display data and results.

8. The device for measuring underground gas pressure and extraction parameters in a coal mine according to claim 7, characterized in that, Also includes: The filter (4) is configured on the flow detection path, located upstream of the solenoid valve (10).

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