A method and system for rapid determination of coal reservoir pore gas pressure

Abstract

The present application belongs to the technical field of coal reservoir gas pressure measurement, and discloses a coal reservoir pore gas pressure rapid measurement method and system. The system comprises a sampling site automatic desorption module, a dead volume calibration module, a gas loss amount reduction module, a coal sample volume reduction module and a control system. The coal sample tank is a piston container, which is divided into a coal sample cavity and a pressurizing cavity. The dead volume calibration module calibrates the system empty volume, and the gas loss amount reduction module realizes automatic compensation of multiple components. The coal sample volume reduction module injects oil to compact the shaft and restore the pore volume. The measurement method comprises the following steps: downhole coal sample sampling, automatic measurement and conversion of loss amount, system access and vacuum pumping, dead volume calibration, automatic compensation of gas loss amount, coal sample compaction and pore volume restoration, reading of pressure value after adsorption equilibrium, etc. The present application realizes rapid, efficient, accurate and safe measurement of coal seam gas pressure under the condition of free hole sealing, effectively improves the gas pressure measurement efficiency and data reliability.

Description

Technical Field

[0001] This invention belongs to the field of coal reservoir gas pressure measurement technology, specifically relating to a rapid method and system for measuring pore gas pressure in coal reservoirs. Background Technology

[0002] Coal reservoir gas pressure is one of the core indicators for assessing the risk of coal and gas outbursts and reflecting the storage and migration potential of free gas in each seam. At the same time, coal reservoir gas pressure is also fundamental for predicting gas outbursts during coal seam mining and evaluating gas flow characteristics. Accurate measurement of coal reservoir gas pressure is of great significance for establishing a comprehensive disaster early warning system.

[0003] Traditional methods for measuring gas pressure in coal reservoirs require pre-embedding a guide pipe after drilling into the target coal seam and connecting a pressure gauge outside the borehole to continuously monitor changes in gas pressure within the borehole. This process is time-consuming and involves a large amount of engineering work. Factors such as loosened surrounding rock and blasting disturbances can affect the borehole sealing starting position and sealing effect, leading to leakage in the pressure measuring borehole. Furthermore, the guide pipe is easily blocked by water and slag, water seepage from the bottom of the borehole, and cross-contamination between the pressure measuring borehole and the extraction borehole can all negatively impact measurement accuracy. Key parameters such as the borehole sealing starting position and the time for compensating gas injection rely heavily on experience, making it difficult to determine the reliability of the data.

[0004] Meanwhile, existing coal seam gas pressure measurements assume that the coal seam is a single CH4 adsorption system. In reality, coal reservoir gas is a multi-component mixture, with gases such as CO2 and N2 competing with CH4 for adsorption, affecting the actual distribution of gas pressure in the coal reservoir. Strongly adsorbing CO2 has a buffering effect on pressure decay, while weakly adsorbing N2 accelerates pressure drop; traditional techniques do not consider this effect. When the volume fraction of CH4 in the coal seam is below 90%, it leads to a larger systematic error in the mine gas pressure measurement results, distorting the conclusions of hazard assessments. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to solve the above problems and provide a method and system for rapid determination of pore gas pressure in coal reservoirs.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A rapid measurement system for pore gas pressure in coal reservoirs includes an automated desorption module at the sampling site, a dead volume calibration module, a gas loss reduction module, a coal sample volume reduction module, and a control system. The automated desorption module at the sampling site includes an electronic level gauge desorber, a mining data acquisition instrument, and a coal sample container. The electronic level gauge desorber is connected to the coal sample container and is used to automatically measure the amount of gas loss during the process of exposing the coal sample to the container and sealing it after underground sampling. It is also equipped with a CH4 / CO2 gas concentration sensor as a gas component determination device to measure the gas components extracted from the coal seam in real time. The mining data acquisition instrument is connected to the electronic level gauge desorber and is used to collect and upload the temperature T0, mass m, underground atmospheric pressure P0, and gas component ratio of the desorbed sample to the control system or local storage via a wireless transmission module. The coal sample container is a piston-equipped container, divided into a coal sample chamber and a pressurization chamber by the piston. The coal sample chamber is used to hold the pressure sample, and both the coal sample chamber and the pressurization chamber are connected to pneumatic solenoid valves. The pneumatic solenoid valves on the coal sample chamber are connected to gas compensation lines and volume reduction lines, and both gas compensation lines and volume reduction lines are equipped with solenoid valves. The pneumatic solenoid valves on the pressurization chamber are connected to oil injection lines, and the oil injection lines are also equipped with solenoid valves. The piston inside the coal sample container is equipped with a displacement sensor for detecting piston displacement. The dead volume calibration module includes a calibration container and a fixed container. The fixed container is located on the gas compensation pipeline. The module is connected to the fixed container and is used to calibrate the empty volume of each segment of the system by the helium expansion-segmental balance method. The gas loss restoration module includes a gas cylinder, a PID automatic pressure control valve, and a pressure sensor. The gas cylinder is connected to the fixed container via the PID automatic pressure control valve. The PID automatic pressure control valve is located between the gas cylinder and the fixed container and is connected to the control system. Based on the compensation pressure value set by the control system and the real-time feedback pressure sensor signal, it realizes automatic quantitative compensation of gas loss according to the downhole loss and gas composition. The compensation gas enters the fixed container from the gas cylinder via the PID automatic pressure control valve, and then enters the coal sample chamber of the coal sample tank, realizing the in-situ restoration of the gas loss of the pressure-tested coal sample. After the oil injection pipeline and the volume reduction pipeline merge, they are connected to the coal sample volume reduction module. The coal sample volume reduction module includes a constant speed and constant pressure pump, which is used to control the axial pressure of the coal sample by injecting oil into the pressurization chamber at constant pressure through the oil injection pipeline to restore the coal seam pressure environment. The module also restores the pore volume of the pressure-measuring coal sample through the volume reduction pipeline by feedback from the displacement sensor and quantitative oil injection. The control system is connected to the on-site automated desorption module, dead volume calibration module, gas loss reduction module, and coal sample volume reduction module, and is used to collect data and control the actions of each module.

[0008] Furthermore, the coal sample volume reduction module also includes a vacuum pump and a buffer tank; the vacuum pump is connected to the buffer tank, which is connected to the pipeline where the oil injection pipeline and the volume reduction pipeline converge, and is equipped with an electromagnetic valve, which controls the pipeline to connect to the vacuum pump or a constant speed and constant pressure pump.

[0009] Furthermore, the calibration container of the dead volume calibration module is connected to the fixed container via an electromagnetic valve. The calibration container is equipped with a replaceable set of calibration blocks for multiple segmented calibration processes of "vacuuming-helium injection-balanced pressure measurement".

[0010] Furthermore, the system also includes a constant temperature water bath for placing coal sample containers and maintaining a constant temperature environment to ensure consistent temperature parameters.

[0011] Furthermore, the control system includes a computer and a data acquisition and processing module for real-time acquisition, control, and analysis of test data.

[0012] Furthermore, the gas cylinders include methane cylinders, helium cylinders, carbon dioxide cylinders, and nitrogen cylinders.

[0013] Furthermore, all of the pneumatic solenoid valves are equipped with valve position feedback sensors to monitor whether the valve position is abnormal.

[0014] A rapid method for determining pore gas pressure in coal reservoirs, employing the system described above, includes the following steps: S1. Coal samples are taken underground and divided into two parts. The pressure sample is placed in a coal sample container, and the desorption sample is automatically measured for gas loss using an electronic level gauge-type desorber. It also uploads temperature T0, mass m, atmospheric pressure P0, and gas composition in real time. S2. Calculate the desorption sample loss based on the gas law. Convert the lost gas amount into the pressure sample and set it as the gas compensation amount; S3. Connect the coal sample container to the rapid coal reservoir pore gas pressure measurement system to obtain the coal sample container pressure; S4. Automatically compensate for gas loss based on gas composition; S5. Use a constant speed and constant pressure pump to inject oil into the pressurized chamber of the coal sample container and compact it to an axial pressure of 30MPa. S6. Inject oil to restore the pore volume of the coal sample, ensuring that the coal sample volume is restored to its original downhole pressure state; S7. After the coal sample has reached adsorption equilibrium for at least 8 hours, the pressure value of the coal sample container is the measured value of the pore gas pressure in the coal reservoir.

[0015] Furthermore, the underground gas loss amount Q will be automatically measured and determined during the coal sample desorption process. loss And transmit Q via wireless transmission module lossThe coal core temperature T0 and coal core mass m are uploaded to the control system in real time; then the relevant desorption parameters are entered, and the gas loss curve of the desorbed coal sample during the sampling process is automatically generated. At the same time, the gas loss of the unsealed coal sample during the sampling process is output, that is, the gas compensation amount of the pressure test sample is output. Among them, after the desorption parameters are automatically entered, the control system follows the standard GB / T-23250 for direct underground determination of coal seam gas content. The method involves fitting a linear curve of gas leakage from the desorbed sample and outputting its functional expression. After obtaining the intercept of the fitted line, it is converted into the gas loss per unit mass of the pressure sample during sampling using the ideal gas law. The gas compensation amount corresponding to the pressure sample is then calculated based on the sample weight. The desorption parameter processing procedure is as follows: After the gas content of the underground coal sample is automatically measured, the underground desorption data of the desorbed sample is imported into the control system, and a gas loss function expression is generated by linear fitting:

[0016] Where K and Let be an undetermined constant; y is the cumulative amount of gas desorption within time t. The x-axis is based on The value is determined by the coordinates of multiple desorption points, which determine the function expression of the linearly fitted line. When the value is 0, we get:

[0017] What is sought That is, the desorption sample at the sampling exposure time The gas loss within the sample is converted into the gas loss of the pressure sample using the gas state equation:

[0018] in, This refers to the underground atmospheric pressure. The temperature is the downhole temperature in Kelvin (K). Laboratory atmospheric pressure; For pressure sample at sampling time Gas loss within; Laboratory temperature, Kelvin (K). , The samples are the mass of the desorption sample and the pressure sample, respectively. Gas compensation amount of pressure sample In the subsequent gas quantity compensation operation, automatic gas quantity compensation is performed.

[0019] Furthermore, in steps S3 and S4, after connecting the coal sample container to the rapid coal reservoir pore gas pressure measurement system, the initial adsorption equilibrium pressure P1 of the pressure sample is read, and the required gas compensation amount is determined based on the pressure sample obtained from the desorption sample. The pressure P of the container after equilibrium is calculated based on the theoretical formula. 补偿 Through a dual closed-loop control system consisting of a PID automatic pressure control valve and a pneumatic solenoid valve, gas is injected into a fixed container with a resolution of 0.01 MPa, achieving precise automatic compensation of gas quantity.

[0020] Furthermore, the automatic compensation for gas loss includes the following steps: S1: Close the pneumatic solenoid valve on the coal sample chamber to isolate the gas loss reduction module and the coal sample, and set the compensation pressure setting value of the PID automatic pressure control valve to P. 补偿 ; S2: Open the gas inlet valve of the gas loss reduction module and inject a fixed amount of gas into the fixed container; S3: After the pressure stabilizes, close the air inlet valve, and then open the pneumatic solenoid valve on the coal sample chamber to achieve automatic gas compensation; Among them, the compensation pressure setpoint P 补偿 The calculation method is as follows: Based on the methane make-up amount Q under standard conditions b The pressure P of the container after equilibrium is calculated based on the theoretical formula. 补偿 :

[0021] Where T is 273.15 + coal sample temperature, K; R is 8.314; To determine the empty volume of the container and related piping; For the gas at the initial gas pressure The gas compressibility factor corresponding to temperature T; Z is the gas compressibility factor at compensated pressure. Gas compressibility factor corresponding to temperature T; Among them, for the empty volume of fixed containers and pipes The determination was performed using the helium expansion-segmented equilibrium method. The empty volume of each segment of the system was calculated based on the ideal gas law, and the volume was calibrated with a calibration error ≤0.05mL.

[0022] Furthermore, volume calibration involves injecting gas at a certain pressure into the reference system and the calibration container to determine the pressure of the reference system before and after equilibrium is reached, and then automatically calculating the volume of the reference system and the volume of the calibration container. The calibration method is as follows: 1) The system automatically imports volume V A ~V D After connecting the target reference system to the calibration container, place the target reference block into the calibration container according to the predetermined combination, open the solenoid valve and evacuate the vacuum. 2) Close the solenoid valve, inject gas at a pressure of 0.6~0.8MPa into the reference frame, and record the pressure P1 before equilibrium; 3) Open the solenoid valve. After the gas expands to the point where the calibration container is stable, record the pressure P2 after equilibrium is reached. 4) Replace the standard block combination in the calibration container, evacuate the vacuum, and repeat steps 2-3 until the calibration is completed. Based on the pressure and volume obtained during the calibration process, the ideal gas law system is obtained: ① ② ③ ④ The resulting system of equations is combined pairwise, resulting in a total of six combined solutions: ①②, ①③, ①④, ②④, ②③, and ③④. The average value of the solutions is taken, and the volume of the reference frame is output. With reference to the calibrated container volume ; in, The corresponding system has fixed container and pipeline empty volumes. .

[0023] Furthermore, obtaining the gas compressibility factor includes the following steps: S1: Introduce the gas-phase equilibrium state for nonpolar / weakly polar gases in the RKS / PR equations, and solve for the corresponding initial gas pressure based on the equations. The gas compressibility factor at temperature T; S2: Based on formula get Value, combined with actual value Solving the PR equation yields the following results: The trial value is used, and the least squares method is applied to approximate the actual value, with the accuracy controlled to one ten-thousandth.

[0024] Furthermore, in step S4, when the gas loss is automatically compensated, the selection of the components of the compensation gas is determined according to the volume fraction of CH4 in the gas components measured in step S1: when the volume fraction of CH4 is higher than 90%, only methane is introduced; when CH4 is lower than 90%, CH4, CO2 and N2 are introduced according to the proportion of gas components.

[0025] Furthermore, in steps S5 and S6, a constant speed and constant pressure pump is used to first inject oil into the pressurized cavity of the coal sample container to apply axial pressure. After the preset axial pressure is reached, the electromagnetic valve is used to switch to quantitatively inject oil into the coal sample cavity to fill the pore volume. In conjunction with the displacement sensor, closed-loop control is achieved to ensure that the volume restoration error is ≤0.1mL.

[0026] Furthermore, the process of restoring the pore volume of the coal sample by oil injection includes the following steps: S1: Open the oil injection line on the pressurization chamber and use the constant pressure injection mode of the constant speed and constant pressure pump to achieve the set value of the axial pressure of the pressure test sample; S2: After the test sample is compacted, oil is injected to fill the pore volume of the coal sample; the solenoid valve on the oil injection line is closed, and then the solenoid valve on the volume reduction line is opened. The pressure of the lower volume reduction line is set to match the gas pressure in the coal sample cavity, and the sample is injected using the quantitative injection mode of a constant speed and constant pressure pump. Low viscosity silicone oil by volume; oil filling amount The calculation method is as follows:

[0027] Where D is the inner diameter of the coal sample container; H is the remaining distance between the piston and the bottom, which is measured by a displacement sensor; The mass of the pressure sample in the coal sample container; The density of distilled water at 20°C is 1. This is the true relative density of the coal sample, the same as that of the desorption sample.

[0028] Furthermore, the helium expansion-segmented balance method is controlled by PLC timing, with each valve operating at intervals of 1 to 3 seconds, and the pressure stability criterion is that the pressure change within 30 seconds is ≤0.005MPa.

[0029] Furthermore, in step S7, after the pressure measurement is completed, the control system automatically generates a complete measurement report including the pt curve, compensation amount, dead volume spectrum, and error analysis, so as to realize full traceability of the measurement process.

[0030] The beneficial effects of this invention are as follows: This invention provides a method and system for rapid determination of pore gas pressure in coal reservoirs. Through automated downhole desorption metering and high-precision surface compensation and restoration, it achieves rapid determination of the actual gas pressure in coal seams under non-sealing conditions. Compared with existing technologies, this invention has the following advantages: (1) It realizes the measurement without sealing, avoids the problems of sealing failure, air leakage, blockage, water inrush and gas leakage caused by traditional sealing, simplifies downhole engineering operations, and significantly reduces engineering workload and construction risks.

[0031] (2) The downhole electronic desorption instrument is used to automatically measure the gas loss during the sampling process and upload temperature, mass, pressure and gas composition data in real time. Combined with the surface PID pressure control automatic compensation module, the multi-component gas is accurately restored with high compensation accuracy and the error is controlled within 0.05mL, effectively eliminating human experience dependence and loss estimation deviation.

[0032] (3) Introduce an automatic dead volume calibration module (helium expansion - segmented balance method + multi-combination equation solution), with a calibration error ≤0.05mL, to ensure accurate system volume calculation and provide a reliable basis for gas quantity compensation.

[0033] (4) Through the piston structure of the special coal sample tank, the constant speed and constant pressure pump for oil injection and compaction (30MPa axial pressure) and displacement feedback, the pore volume of the coal sample is restored in situ. Combined with the "gas quantity-volume-temperature" state restoration compensation model, the stress-temperature-gas state of the coal seam is truly restored.

[0034] (5) The entire process adopts an intelligent control system with one-click automated operation (PID closed loop, solenoid valve timing control), reducing human intervention and reducing operation error; the gas component sensor intelligently judges the CH4 threshold (90%) and compensates CH4, CO2 and N2 in a targeted manner, solving the system error caused by multi-component competitive adsorption.

[0035] (6) Verification tests show that the system is applicable to various coal seam conditions, the measurement cycle is greatly shortened, the data reliability is significantly improved, and the gas outburst prevention work in coal mine areas is effectively guaranteed to advance rapidly and improve the accuracy of gas disaster prediction and early warning.

[0036] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the rapid measurement system for pore gas pressure in coal reservoirs according to the present invention.

[0038] Figure 2 This is a schematic diagram of the gas quantity compensation operation of the PID automatic pressure control valve in this invention.

[0039] Figure 3 This is a schematic diagram of the volume calibration operation performed by the dead volume calibration module in this invention.

[0040] Figure 4 A schematic flowchart of the method for rapid determination of pore gas pressure in coal reservoirs in this invention.

[0041] Reference numerals in the attached diagram: 1-Helium cylinder; 2-Methane cylinder; 3-Pressure regulating valve; 4-PID automatic pressure control valve; 5-PID external pressure sensor; 6-Calibration container; 7-Fixed container; 8-Coal sample container pressure sensor; 9-Pressure chamber; 10-Piston; 11-Coal sample chamber; 12-Buffer container; 13-Vacuum pump; 14-Constant speed and constant pressure pump; 15-Oil filling bottle. Detailed Implementation

[0042] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0043] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0044] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0045] Example 1 like Figures 1-3 As shown, this is a rapid measurement system for pore gas pressure in coal reservoirs, including an automated desorption module at the sampling site, a dead volume calibration module, a gas loss reduction module, a coal sample volume reduction module, and a control system.

[0046] The automated desorption module at the sampling site includes an electronic level gauge desorber, a mine data acquisition instrument, and a coal sample container. The electronic level gauge desorber, connected to the coal sample container, automatically measures the amount of gas lost during the process of exposing the coal sample to the container and sealing it after underground sampling. It is also equipped with a CH4 / CO2 gas concentration sensor to measure the gas composition of the coal seam being tested in real time. The mine data acquisition instrument, connected to the electronic level gauge desorber, collects and wirelessly transmits the temperature T0, mass m, underground atmospheric pressure P0, and gas component percentage of the desorbed sample to the control system or local storage.

[0047] The coal sample container is a piston-equipped vessel, divided into a coal sample chamber 11 and a pressurization chamber 9 by a piston 10. The coal sample chamber 11 is used to hold the pressure sample. Both the coal sample chamber 11 and the pressurization chamber 9 are connected to pneumatic solenoid valves. The pneumatic solenoid valves in the coal sample chamber 11 are connected to gas compensation lines and volume reduction lines, and these lines are equipped with solenoid valves V6 and V9, respectively. The pneumatic solenoid valves in the pressurization chamber 9 are connected to an oil injection line, which is equipped with a solenoid valve V8. A displacement sensor is installed on the piston 10 inside the coal sample container to detect piston displacement. A coal sample pressure sensor 8 is also installed on the gas compensation line connected to the coal sample container to monitor the pressure inside the coal sample chamber 11 in real time.

[0048] The dead volume calibration module includes a calibration container 6 and a fixed container 7. The fixed container 7 is located on the gas compensation pipeline and is connected to the calibration container 6 via solenoid valves V4 and V5. The calibration container 6 contains replaceable calibration block combinations for multiple segmented calibration processes involving "vacuuming-helium injection-balanced pressure measurement." The calibration process is time-controlled by a PLC, with valve actions occurring at intervals of 1–3 seconds. The pressure stability criterion is a pressure change ≤0.005 MPa within 30 seconds. The reference frame volume and calibration container volume are calculated based on multiple solutions to the ideal gas law, with a calibration error ≤0.05 mL.

[0049] The gas loss restoration module includes a helium cylinder 1, a methane cylinder 2, a pressure regulating valve 3, and a PID automatic pressure control valve 4. Both helium cylinder 1 and methane cylinder 2 are connected via the pressure regulating valve 3, solenoid valve V1, and the PID automatic pressure control valve 4. An external PID pressure sensor 5 is connected to the PID automatic pressure control valve 4. The PID automatic pressure control valve 4 is connected to solenoid valves V2 and V5, and then to the fixed container 7. The PID automatic pressure control valve 4 is connected to the control system and automatically performs quantitative compensation based on the set compensation pressure value and the real-time feedback signal from the external PID pressure sensor 5. The compensation gas enters the fixed container 7 from the cylinder via the PID automatic pressure control valve 4, and then enters the coal sample chamber 11 of the coal sample container, achieving in-situ restoration of the gas loss from the pressure-measuring coal sample. The PID automatic pressure control valve 4 reads the pressure sensor feedback value every 25 milliseconds and performs closed-loop regulation until the pressure stabilizes within ±0.01 MPa of the set value.

[0050] The oil injection line and the volume reduction line merge and connect to the coal sample volume reduction module. The coal sample volume reduction module includes a constant-speed and constant-pressure pump 14, a vacuum pump 13, a buffer container 12, and an oil injection bottle 15. The vacuum pump 13 is connected to the buffer container 12, which is connected to the pipeline where the oil injection line and the volume reduction line merge via a solenoid valve V10. The solenoid valve switches the connection between the control line and the vacuum pump 13 or the constant-speed and constant-pressure pump 14. By opening the solenoid valve V8 and closing the solenoid valves V9 and V10, the constant-speed and constant-pressure pump 14 injects oil into the pressurized chamber 9 at constant pressure through the oil injection line to control the axial pressure of the coal sample and restore the coal seam pressure environment. By opening the solenoid valve V9 and closing the solenoid valves V8 and V10, the constant-speed and constant-pressure pump 14 injects oil quantitatively through the volume reduction line to restore the pore volume of the pressure-measuring coal sample, achieving closed-loop control in conjunction with a displacement sensor. The system also includes a constant-temperature water bath for placing the coal sample container and maintaining a constant temperature environment to ensure consistent temperature parameters.

[0051] The control system includes a computer and a data acquisition and processing module, which are connected to all modules. It is used for real-time data acquisition, valve control, algorithm calculation, and report generation. All pneumatic solenoid valves are equipped with valve position feedback sensors to monitor for abnormal valve positions.

[0052] Example 2 This embodiment describes a measurement method based on the rapid coal reservoir pore gas pressure measurement system described in Embodiment 1. The method specifically includes the following steps: A rapid method for determining pore gas pressure in coal reservoirs, employing the system described above, includes the following steps: S1. Coal samples are taken underground and divided into two parts. The pressure sample is placed in a coal sample container, and the desorption sample is automatically measured for gas loss using an electronic level gauge-type desorber. It also uploads temperature T0, mass m, atmospheric pressure P0, and gas composition in real time. S2. Calculate the desorption sample loss based on the gas law. Convert the lost gas amount into the pressure sample and set it as the gas compensation amount; S3. Connect the coal sample container to the rapid measurement system for pore gas pressure in the coal reservoir to obtain the initial adsorption equilibrium pressure P1 in the coal sample container. S4. Automatically compensate for gas loss based on gas composition; S5. The coal sample container is compacted. Open the solenoid valve V8, connect the oil injection line, and use the constant speed and constant pressure pump to inject oil into the pressurized chamber of the coal sample container in constant pressure injection mode to compact it to an axial pressure of 30MPa. S6. Inject oil to restore the pore volume of the coal sample, ensuring that the coal sample volume is restored to its original downhole pressure state; S7. After the coal sample has reached adsorption equilibrium in the constant temperature water bath for at least 8 hours, read the pressure value displayed by pressure sensor 8 in the coal sample chamber 11. This value is the measured pore gas pressure of the coal reservoir. The control system automatically generates a curve including the pt curve and the compensation amount Q. b A complete measurement report, including dead volume calibration charts and error analysis, enables full traceability of the measurement process.

[0053] In step S1, the underground gas loss Q is automatically measured and determined during the desorption process of the coal sample. loss And transmit Q via wireless transmission module loss The coal core temperature T0 and coal core mass m are uploaded to the control system in real time; then the relevant desorption parameters are entered, and the gas loss curve of the desorbed coal sample during the sampling process is automatically generated. At the same time, the gas loss of the unsealed coal sample during the sampling process is output, that is, the gas compensation amount of the pressure test sample is output. In step S2, after the desorption parameters are automatically entered, the control system determines the content of coal seam gas directly underground according to the standard GB / T-23250. The method involves fitting a linear curve of gas leakage from the desorbed sample and outputting its functional expression. After obtaining the intercept of the fitted line, it is converted into the gas loss per unit mass of the pressure sample during sampling using the ideal gas law. The gas compensation amount corresponding to the pressure sample is then calculated based on the sample weight. The desorption parameter processing procedure is as follows: After the gas content of the underground coal sample is automatically measured, the underground desorption data of the desorbed sample is imported into the control system, and a gas loss function expression is generated by linear fitting:

[0054] Where K and Let be an undetermined constant; y is the cumulative amount of gas desorption within time t. The x-axis is based on The value is determined by the coordinates of multiple desorption points, which determine the function expression of the linearly fitted line. When the value is 0, we get:

[0055] What is sought That is, the desorption sample at the sampling exposure time The gas loss within the sample is converted into the gas loss of the pressure sample using the gas state equation:

[0056] in, This refers to the underground atmospheric pressure. The temperature is the downhole temperature in Kelvin (K). Laboratory atmospheric pressure; For pressure sample at sampling time Gas loss within; Laboratory temperature, Kelvin (K). , The samples are the mass of the desorption sample and the pressure sample, respectively. Gas compensation amount of pressure sample In the subsequent gas quantity compensation operation, automatic gas quantity compensation is performed.

[0057] In steps S3 and S4, after connecting the coal sample container to the rapid coal reservoir pore gas pressure measurement system, the initial adsorption equilibrium pressure P1 of the pressure sample is read, and the required gas compensation amount is determined based on the pressure sample obtained from the desorption sample. The pressure P of the container after equilibrium is calculated based on the theoretical formula. 补偿 Through a dual closed-loop control system consisting of a PID automatic pressure control valve and a pneumatic solenoid valve, gas is injected into a fixed container with a resolution of 0.01 MPa, achieving precise automatic compensation of gas quantity.

[0058] The automatic compensation for gas loss includes the following steps: S1: Close the pneumatic solenoid valve on the coal sample chamber to isolate the gas loss reduction module and the coal sample, and set the compensation pressure setting value of the PID automatic pressure control valve to P. 补偿 ; S2: Open the gas inlet valve of the gas loss reduction module and inject a fixed amount of gas into the fixed container; S3: After the pressure stabilizes, close the air inlet valve, and then open the pneumatic solenoid valve on the coal sample chamber to achieve automatic gas compensation; Among them, the compensation pressure setpoint P 补偿 The calculation method is as follows: Based on the methane make-up amount Q under standard conditions b The pressure P of the container after equilibrium is calculated based on the theoretical formula. 补偿 :

[0059] Where T is 273.15 + coal sample temperature, K; R is 8.314; To determine the empty volume of the container and related piping; For the gas at the initial gas pressure The gas compressibility factor corresponding to temperature T; Z is the gas compressibility factor at compensated pressure. Gas compressibility factor corresponding to temperature T; Among them, for the empty volume of fixed containers and pipes The determination was performed using the helium expansion-segmented equilibrium method. The empty volume of each segment of the system was calculated based on the ideal gas law, and volume calibration was performed with a calibration error ≤0.05mL. Volume calibration was achieved by injecting gas at a certain pressure into the reference system and calibration container, obtaining the pressure of the reference system before and after equilibrium, and automatically calculating the volumes of the reference system and calibration container. The calibration method is as follows: 1) The system automatically imports volume V A ~V D After connecting the target reference system to the calibration container, place the target reference block into the calibration container according to the predetermined combination, open the solenoid valve and evacuate the vacuum. 2) Open solenoid valves V1, V2, V5, and V6, and close solenoid valves V9 and V3. Inject helium gas at a pressure lower than 1 MPa through the pressure regulating valve and the PID automatic pressure control valve. After stabilization, close solenoid valve V2 and record the stable pressure P1. Record the pressure P1 before equilibrium. 3) Open the solenoid valve V4. After the gas expands to the point where the calibration container is stable, record the pressure P2 after equilibrium is reached. 4) Replace the standard block combination in the calibration container, and change the reference system volume one by one. Make sure that solenoid valves V3, V7, and V1 are closed and all other valves are open. Evacuate the inner container and pipeline of the system for more than 2 hours. Then close all valves and vacuum pumps and repeat steps 2 to 3 until the calibration is completed. Based on the pressure and volume obtained during the calibration process, the ideal gas law system is obtained: ① ② ③ ④ The resulting system of equations is combined pairwise, resulting in a total of six combined solutions: ①②, ①③, ①④, ②④, ②③, and ③④. The average value of the solutions is taken, and the volume of the reference frame is output. With reference to the calibrated container volume ; in, The corresponding system has fixed container and pipeline empty volumes. .

[0060] The steps for obtaining the gas compressibility factor are as follows: S1: Introduce the gas-phase equilibrium state for nonpolar / weakly polar gases in the RKS / PR equations, and solve for the corresponding initial gas pressure based on the equations. The gas compressibility factor at temperature T; S2: Based on formula get Value, combined with actual value Solving the PR equation yields the following results: The trial value is used, and the least squares method is applied to approximate the actual value, with the accuracy controlled to one ten-thousandth.

[0061] In step S4, during automatic compensation of gas loss, the composition of the compensation gas is selected based on the volume fraction of CH4 in the gas composition measured in step S1: when the volume fraction of CH4 is higher than 90%, only methane is introduced; when the volume fraction of CH4 is lower than 90%, CH4, CO2 and N2 are introduced according to the proportion of gas components.

[0062] In steps S5 and S6, a constant speed and constant pressure pump is used to inject oil into the pressurized cavity of the coal sample container to apply axial pressure. After the preset axial pressure is reached, the electromagnetic valve is used to switch to quantitatively inject oil into the coal sample cavity to fill the pore volume. A displacement sensor is used to achieve closed-loop control to ensure that the volume restoration error is ≤0.1mL.

[0063] The process of restoring the pore volume of the coal sample by injecting oil includes the following steps: S1: Open solenoid valve V8, close solenoid valves V9 and V10, and realize the set value of the axial pressure of the pressure sample through the constant pressure injection mode of the constant speed and constant pressure pump; S2: After the test sample is compacted, oil is injected to fill the pore volume of the coal sample; solenoid valves V8 and V10 are closed, and the pressure of the lower volume reduction pipeline is set to match the gas pressure in the coal sample cavity. Solenoid valve V9 and the pneumatic solenoid valve on the coal sample cavity are opened, and the quantitative injection mode of the constant speed and constant pressure pump is used to inject the oil. Low viscosity silicone oil by volume; oil filling amount The calculation method is as follows:

[0064] Where D is the inner diameter of the coal sample container; H is the remaining distance between the piston and the bottom, which is measured by a displacement sensor; The mass of the pressure sample in the coal sample container; The density of distilled water at 20°C is 1. This is the true relative density of the coal sample, the same as that of the desorption sample.

[0065] Among them, the helium expansion-segmented balance method is controlled by PLC timing, with each valve operating at intervals of 1 to 3 seconds, and the pressure stability criterion is that the pressure change within 30 seconds is ≤0.005MPa.

[0066] Before the test begins, a gas tightness test is performed on the system: gas with a pressure of 1 MPa or higher is introduced, and solenoid valves V1, V2, V3, V4, and V10 are closed; after the gas pressure stabilizes (approximately 0.5 hours to adapt to the temperature), solenoid valves V8 and V9 are closed, and the pressure data is observed. If the pressure remains stable within 1 hour, it is considered that the gas tightness is good. If there is a leak, leak detection and repair are performed, and the gas tightness test is repeated.

[0067] The entire method combines hole-sealing-free operation, automated downhole loss measurement, high-precision dead volume calibration (error ≤0.05mL), multi-component gas PID automatic compensation, and coal sample pore volume restoration to achieve rapid determination of pore gas pressure in coal reservoirs. This significantly reduces the workload, cycle time, and leakage errors associated with traditional hole-sealing pressure measurement. A pneumatic solenoid valve position feedback sensor monitors valve position anomalies throughout the process, ensuring safe and stable system operation.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A rapid measurement system for pore gas pressure in coal reservoirs, characterized in that, It includes an automated desorption module for the sampling site, a dead volume calibration module, a gas loss reduction module, a coal sample volume reduction module, and a control system; The automated desorption module at the sampling site includes an electronic level gauge desorber, a mining data acquisition instrument, and a coal sample container. The electronic level gauge desorber is connected to the coal sample container and is used to automatically measure the amount of gas loss during the process of exposing the coal sample to the container and sealing it after underground sampling. It is also equipped with a CH4 / CO2 gas concentration sensor as a gas component determination device to measure the gas components extracted from the coal seam in real time. The mining data acquisition instrument is connected to the electronic level gauge desorber and is used to collect and upload the temperature T0, mass m, underground atmospheric pressure P0, and gas component ratio of the desorbed sample to the control system or local storage via a wireless transmission module. The coal sample container is a piston-equipped container, divided into a coal sample chamber and a pressurization chamber by the piston. The coal sample chamber is used to hold the pressure sample, and both the coal sample chamber and the pressurization chamber are connected to pneumatic solenoid valves. The pneumatic solenoid valves on the coal sample chamber are connected to gas compensation lines and volume reduction lines, and both gas compensation lines and volume reduction lines are equipped with solenoid valves. The pneumatic solenoid valves on the pressurization chamber are connected to oil injection lines, and the oil injection lines are also equipped with solenoid valves. The piston inside the coal sample container is equipped with a displacement sensor for detecting piston displacement. The dead volume calibration module includes a calibration container and a fixed container. The fixed container is located on the gas compensation pipeline. The module is connected to the fixed container and is used to calibrate the empty volume of each segment of the system by the helium expansion-segmental balance method. The gas loss restoration module includes a gas cylinder, a PID automatic pressure control valve, and a pressure sensor. The gas cylinder is connected to the fixed container via the PID automatic pressure control valve. The PID automatic pressure control valve is located between the gas cylinder and the fixed container and is connected to the control system. Based on the compensation pressure value set by the control system and the real-time feedback pressure sensor signal, it realizes automatic quantitative compensation of gas loss according to the downhole loss and gas composition. The compensation gas enters the fixed container from the gas cylinder via the PID automatic pressure control valve, and then enters the coal sample chamber of the coal sample tank, realizing the in-situ restoration of the gas loss of the pressure-tested coal sample. After the oil injection pipeline and the volume reduction pipeline merge, they are connected to the coal sample volume reduction module. The coal sample volume reduction module includes a constant speed and constant pressure pump, which is used to control the axial pressure of the coal sample by injecting oil into the pressurization chamber at constant pressure through the oil injection pipeline to restore the coal seam pressure environment. The module also restores the pore volume of the pressure-measuring coal sample through the volume reduction pipeline by feedback from the displacement sensor and quantitative oil injection. The control system is connected to the on-site automated desorption module, dead volume calibration module, gas loss reduction module, and coal sample volume reduction module, and is used to collect data and control the actions of each module.

2. The system according to claim 1, characterized in that, The coal sample volume reduction module also includes a vacuum pump and a buffer tank; the vacuum pump is connected to the buffer tank, which is connected to the pipeline where the oil injection pipeline and the volume reduction pipeline merge, and is equipped with an electromagnetic valve, which controls the pipeline to connect to the vacuum pump or a constant speed and constant pressure pump.

3. The system according to claim 2, characterized in that, The calibration container of the dead volume calibration module is connected to the fixed container via an electromagnetic valve. The calibration container is equipped with a replaceable set of calibration blocks for multiple segmented calibration processes of "vacuuming-helium injection-balanced pressure measurement".

4. The system according to claim 1, characterized in that, The system also includes a constant temperature water bath for placing coal sample containers and maintaining a constant temperature environment to ensure consistent temperature parameters.

5. The system according to claim 1, characterized in that, The control system includes a computer and a data acquisition and processing module, which is used to acquire, control, and analyze test data in real time.

6. The system according to claim 1, characterized in that, The gas cylinders include methane cylinders, helium cylinders, carbon dioxide cylinders, and nitrogen cylinders.

7. The system according to claim 1, characterized in that, All pneumatic solenoid valves are equipped with valve position feedback sensors to monitor whether the valve position is abnormal.

8. A method for rapid determination of pore gas pressure in coal reservoirs, characterized in that, The system according to any one of claims 1 to 7 comprises the following steps: S1. Coal samples are taken underground and divided into two parts. The pressure sample is placed in a coal sample container, and the desorption sample is automatically measured for gas loss using an electronic level gauge-type desorber. It also uploads temperature T0, mass m, atmospheric pressure P0, and gas composition in real time. S2. Calculate the desorption sample loss based on the gas law. Convert the lost gas amount into the pressure sample and set it as the gas compensation amount; S3. Connect the coal sample container to the rapid coal reservoir pore gas pressure measurement system to obtain the coal sample container pressure; S4. Automatically compensate for gas loss based on gas composition; S5. Use a constant speed and constant pressure pump to inject oil into the pressurized chamber of the coal sample container and compact it to an axial pressure of 30MPa. S6. Inject oil to restore the pore volume of the coal sample, ensuring that the coal sample volume is restored to its original downhole pressure state; S7. After the coal sample has reached adsorption equilibrium for at least 8 hours, the pressure value of the coal sample container is the measured value of the pore gas pressure in the coal reservoir.

9. The method according to claim 8, characterized in that, Automatic measurement of gas loss in well to measure gas loss Q in desorption process of coal sample loss , and Q loss , coal core temperature T0, and coal core mass m are uploaded to the control system in real time; then, relevant desorption parameters are inputted, a coal sample gas loss curve in the sampling process is automatically generated, and the gas loss amount of the coal sample in the sampling process is outputted at the same time, that is, the gas compensation amount of the pressure measuring sample is outputted; Among them, after the desorption parameters are automatically entered, the control system follows the standard GB / T-23250 for direct underground determination of coal seam gas content. The method involves fitting a linear curve of gas leakage from the desorbed sample and outputting its functional expression. After obtaining the intercept of the fitted line, it is converted into the gas loss per unit mass of the pressure sample during sampling using the ideal gas law. The gas compensation amount corresponding to the pressure sample is then calculated based on the sample weight. The desorption parameter processing procedure is as follows: After the gas content of the underground coal sample is automatically measured, the underground desorption data of the desorbed sample is imported into the control system, and a gas loss function expression is generated by linear fitting: Where K and Let be an undetermined constant; y is the cumulative amount of gas desorption within time t. The x-axis is based on The value is determined by the coordinates of multiple desorption points, which determine the function expression of the linearly fitted line. When the value is 0, we get: What is sought That is, the desorption sample at the sampling exposure time The gas loss within the sample is converted into the gas loss of the pressure sample using the gas state equation: in, This refers to the underground atmospheric pressure. The temperature is the downhole temperature in Kelvin (K). Laboratory atmospheric pressure; For pressure sample at sampling time Gas loss within; Laboratory temperature, Kelvin (K). , The samples are the mass of the desorption sample and the pressure sample, respectively. Gas compensation amount of pressure sample In the subsequent gas quantity compensation operation, automatic gas quantity compensation is performed.

10. The method according to claim 9, characterized in that, In steps S3 and S4, after connecting the coal sample container to the rapid coal reservoir pore gas pressure measurement system, the initial adsorption equilibrium pressure P1 of the pressure sample is read, and the required gas compensation amount is determined based on the pressure sample obtained from the desorption sample. The pressure P of the container after equilibrium is calculated based on the theoretical formula. 补偿 Through a dual closed-loop control system consisting of an ID automatic pressure control valve and a pneumatic solenoid valve, gas is injected into a fixed container with a resolution of 0.01 MPa, achieving precise automatic compensation of gas quantity.

11. The method according to claim 10, characterized in that, Automatic compensation for gas loss includes the following steps: S1: Close the pneumatic solenoid valve on the coal sample chamber to isolate the gas loss reduction module and the coal sample, and set the compensation pressure setpoint of the PID automatic pressure control valve to P. 补偿 ; S2: Open the gas inlet valve of the gas loss reduction module and inject a fixed amount of gas into the fixed container; S3: After the pressure stabilizes, close the air inlet valve, and then open the pneumatic solenoid valve on the coal sample chamber to achieve automatic gas compensation; Among them, the compensation pressure setpoint P 补偿 The calculation method is as follows: Based on the methane make-up amount Q under standard conditions b The pressure P of the container after equilibrium is calculated based on the theoretical formula. 补偿 : Where T is 273.15 + coal sample temperature, K; R is 8.314; To determine the empty volume of the container and related piping; For the gas at the initial gas pressure The gas compressibility factor corresponding to temperature T; Z is the gas compressibility factor at compensated pressure. Gas compressibility factor corresponding to temperature T; Among them, for the empty volume of fixed containers and pipes The determination was performed using the helium expansion-segmented equilibrium method. The empty volume of each segment of the system was calculated based on the ideal gas law, and the volume was calibrated with a calibration error ≤0.05mL.

12. The method according to claim 11, characterized in that, Volume calibration is performed by injecting gas at a certain pressure into the reference system and the calibration container, obtaining the pressure of the reference system before and after equilibrium, and automatically calculating the volume of the reference system and the volume of the calibration container; the calibration method is as follows: 1) The system automatically imports volume V A ~V D After connecting the target reference system to the calibration container, place the target reference block into the calibration container according to the predetermined combination, open the solenoid valve and evacuate the vacuum. 2) Close the solenoid valve, inject gas at a pressure of 0.6~0.8MPa into the reference frame, and record the pressure P1 before equilibrium; 3) Open the solenoid valve. After the gas expands to the point where the calibration container is stable, record the pressure P2 after equilibrium is reached. 4) Replace the standard block combination in the calibration container, evacuate the vacuum, and repeat steps 2-3 until the calibration is completed. Based on the pressure and volume obtained during the calibration process, the ideal gas law system is obtained: ① ② ③ ④ The resulting system of equations is combined pairwise, resulting in a total of six combined solutions: ①②, ①③, ①④, ②④, ②③, and ③④. The average value of the solutions is taken, and the volume of the reference frame is output. With reference to the calibrated container volume ; in, The corresponding system has fixed container and pipeline empty volumes. .

13. The method according to claim 11, characterized in that, The steps for obtaining the gas compressibility factor are as follows: S1: Introduce the gas-phase equilibrium state for nonpolar / weakly polar gases in the RKS / PR equations, and solve for the corresponding initial gas pressure based on the equations. The gas compressibility factor at temperature T; S2: Based on formula get Value, combined with actual value Solving the PR equation yields the following results: The trial value is used, and the least squares method is applied to approximate the actual value, with the accuracy controlled to one ten-thousandth.

14. The method according to claim 8, characterized in that, In step S4, during automatic compensation of gas loss, the composition of the compensation gas is selected based on the volume fraction of CH4 in the gas composition measured in step S1: when the volume fraction of CH4 is higher than 90%, only methane is introduced; when the volume fraction of CH4 is lower than 90%, CH4, CO2 and N2 are introduced according to the proportion of gas components.

15. The method according to claim 8, characterized in that, In steps S5 and S6, a constant speed and constant pressure pump is used to inject oil into the pressurized chamber of the coal sample container to apply axial pressure. After the preset axial pressure is reached, the electromagnetic valve is used to switch to quantitatively inject oil into the coal sample chamber to fill the pore volume. A displacement sensor is used to achieve closed-loop control to ensure that the volume restoration error is ≤0.1mL.

16. The method according to claim 15, characterized in that, The process of restoring the pore volume of a coal sample by injecting oil includes the following steps: S1: Open the oil injection line on the pressurization chamber and use the constant pressure injection mode of the constant speed and constant pressure pump to achieve the set value of the axial pressure of the pressure test sample; S2: After the test sample is compacted, oil is injected to fill the pore volume of the coal sample; the solenoid valve on the oil injection line is closed, and then the solenoid valve on the volume reduction line is opened. The pressure of the lower volume reduction line is set to match the gas pressure in the coal sample cavity, and the sample is injected using the quantitative injection mode of a constant speed and constant pressure pump. Low viscosity silicone oil by volume; oil filling amount The calculation method is as follows: Where D is the inner diameter of the coal sample container; H is the remaining distance between the piston and the bottom, which is measured by a displacement sensor; The mass of the pressure sample in the coal sample container; The density of distilled water at 20°C is 1. This is the true relative density of the coal sample, the same as that of the desorption sample.

17. The method according to claim 11, characterized in that, The helium expansion-segmented balancing method is controlled by PLC timing, with each valve operating at intervals of 1 to 3 seconds. The pressure stability criterion is that the pressure change within 30 seconds is ≤0.005MPa.

18. The method according to claim 8, characterized in that, In step S7, after the pressure measurement is completed, the control system automatically generates a complete measurement report including the pt curve, compensation amount, dead volume spectrum, and error analysis, so as to realize full traceability of the measurement process.

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