Coal rock resistivity dynamic real-time testing device and method in water injection process

Abstract

The invention provides a coal rock resistivity dynamic real-time testing device and method in a water injection process, the device comprises a measuring electrode, a resistivity measuring system, a data acquisition system and a data processing system, the measuring electrode is used for forming an electrode network and is in contact with coal rock, and the resistivity measuring system is used for measuring the resistivity of the coal rock. The resistivity measurement system is used for measuring the resistivity of the coal rock; the data acquisition system is used for acquiring resistivity data in real time; and the data processing system is used for carrying out inversion processing on the collected resistivity data to obtain a resistivity distribution image in the coal rock. According to the invention, continuous or quasi-continuous resistivity measurement is carried out on a water injection area by arranging a specific electrode array according to the change rule of the resistivity of the coal rock along with factors such as moisture content, pore structure and ion migration in the water injection process, and the resistivity of the water injection area is measured through a data acquisition and processing system. The water injection state, the permeation path and the wetting effect in the coal rock are dynamically reflected in real time, and a scientific basis is provided for real-time adjustment and optimization of water injection parameters.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety production technology, and in particular to a device and method for dynamic real-time testing of coal and rock resistivity during water injection. Background Technology

[0002] Water injection is a common technique in coal mine production, primarily used for dust control, gas outburst prevention, fire prevention, and permeability enhancement in coalbed methane extraction. Traditional evaluation of water injection effectiveness relies on observing water output and measuring changes in coal sample moisture content, flow rate, and pressure before and after injection. These methods suffer from limitations such as lag, localization, or indirectness, making it difficult to reflect the real-time, dynamic, and comprehensive penetration path, wetting range, and effects of water injection within the coal seam. Currently, there is a lack of a method to directly, dynamically, and in real-time test changes in the resistivity of the coal seam during water injection. This makes it difficult to accurately grasp the wetting process and effects of water injection within the coal seam, thus limiting the optimization of water injection strategies. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a dynamic real-time testing device and method for coal and rock resistivity during water injection, so as to solve the shortcomings of existing coal mine water injection monitoring methods in terms of real-time performance, dynamism, and accuracy.

[0004] To achieve the above objectives, this invention proposes a dynamic real-time testing device for coal and rock resistivity during water injection. The device includes measuring electrodes arranged in the coal seam, a resistivity measurement system connected to the measuring electrodes, a data acquisition system connected to the resistivity measurement system, and a data processing system connected to the data acquisition system. The measuring electrodes form an electrode network and are in contact with the coal and rock. The resistivity measurement system measures the resistivity of the coal and rock based on the measuring electrodes. The data acquisition system collects resistivity data in real time. The data processing system performs inversion processing on the collected resistivity data to obtain a true resistivity distribution image inside the coal and rock.

[0005] In the above scheme: the resistivity measurement system is a multi-channel resistivity tomography system. This system utilizes the characteristic that different materials have different resistivities, applies current excitation to the object under test, measures the boundary voltage, and then inverts the resistance distribution inside the object.

[0006] This invention also proposes a method for dynamic real-time testing of coal and rock resistivity during water injection, including the aforementioned device for dynamic real-time testing of coal and rock resistivity during water injection, and further including the following steps:

[0007] S1. Arrange at least one water injection borehole and at least one set of measuring electrodes in the coal seam. All measuring electrodes together form an electrode network and are in contact with the coal and rock.

[0008] S2. Before injecting water into the water injection borehole, the initial resistivity of the coal and rock is measured by the resistivity measurement system to obtain the initial resistivity distribution of the coal seam before water injection as a reference.

[0009] S3. During the water injection process in the water injection borehole, the resistivity inside the coal and rock is dynamically scanned and measured at preset time intervals using a resistivity measurement system.

[0010] S4. Resistivity data obtained by dynamic scanning measurement is acquired in real time through a data acquisition system;

[0011] S5. The collected resistivity data is inverted through the data processing system to obtain the true resistivity distribution image inside the coal and rock.

[0012] S6. Based on the variation pattern of the real resistivity distribution image, dynamically evaluate the water injection range, wetting uniformity and infiltration rate, and provide a basis for real-time adjustment and optimization of water injection parameters.

[0013] In the above scheme, step S1 specifically involves: pre-drilling water injection boreholes and several monitoring boreholes in the coal seam. The water injection boreholes are drilled horizontally from the working face of the coal seam into the coal seam, and the monitoring boreholes are drilled downwards from the top face of the coal seam. The monitoring boreholes are arranged around the water injection boreholes and along their extension direction. Multiple measuring electrodes are arranged at certain intervals in the monitoring boreholes. Multiple measuring electrodes in the same monitoring borehole form a group, creating a vertical electrode string. Multiple vertical electrode strings constitute a three-dimensional electrode network. A surface reference electrode is arranged above or around the water injection area. The spacing and number of measuring electrodes can be adjusted according to the required detection accuracy and actual field conditions. The surface reference electrode provides a stable potential reference point and assists in forming a larger detection depth and range.

[0014] In the above scheme, step S4 specifically involves: transmitting the measured raw voltage and current data to the data processing system via the data acquisition system, where the data is displayed, stored, and preliminarily processed in real time. The core data acquired in real time by the resistivity measurement system are voltage and current. Resistance and resistivity can be derived using Ohm's law and the resistivity calculation formula based on voltage and current.

[0015] In the above scheme, step S5 specifically involves: the data processing system calculating the apparent resistivity of each measuring point based on the original voltage and current data and the electrode device coefficients; using the finite element method or high-density resistivity inversion algorithm to perform three-dimensional inversion on the real-time acquired apparent resistivity data to reconstruct the true resistivity distribution inside the coal seam; and employing time-shifted resistivity tomography to compare and analyze the resistivity inversion results at different time points, dynamically tracking the diffusion of the water injection front, changes in water cut, and hydraulic connectivity, and promptly detecting abnormal water injection situations.

[0016] In the above scheme, step S6 specifically involves: using the inverted three-dimensional resistivity distribution data to draw a resistivity distribution cloud map using Orgin drawing software, and then using Fluent fluid simulation software to simulate and display the water flow infiltration path, wetting range, and low resistivity anomaly zone; analyzing the water infiltration rate, infiltration resistance, and infiltration anisotropy based on the resistivity change trend; and dynamically adjusting and optimizing the water injection pressure, flow rate, water injection time, water injection borehole parameters, and subsequent water injection borehole deployment based on real-time monitoring results, which helps to comprehensively understand the water injection effect and avoid localization and lag.

[0017] In the above scheme, the monitoring boreholes are arranged in a plum blossom shape, parallel line shape, or cross shape, which facilitates the construction of a three-dimensional electrode network, realizes multi-dimensional and three-dimensional monitoring of the resistivity distribution inside coal and rock, and effectively expands the detection range.

[0018] In the above scheme: the measuring electrode adopts a ring-shaped multi-point electrode to ensure good contact with the hole wall.

[0019] The beneficial effects of this invention are:

[0020] 1. Utilizing the variation of resistivity in coal and rock during water injection with factors such as water content, pore structure, and ion migration, a specific electrode array is arranged to continuously or quasi-continuously measure the resistivity of the injection area. A data acquisition and processing system dynamically reflects the water injection status, infiltration path, and wetting effect within the coal and rock in real time, enabling timely detection of water injection anomalies and avoiding delays. 2. The data processing system employs an inversion algorithm to obtain more refined resistivity distribution images, accurately reflecting the infiltration pattern of water within the coal body. This helps to comprehensively understand the water injection effect and avoid localized biases. 3. Applicable to coal seams with different geological conditions and water injection purposes, it has good prospects for widespread application. It can be widely used in scenarios such as coal seam water injection before gas drainage, dust control water injection at working faces, water injection for fire prevention in goaf areas, and monitoring the effects of reservoir modification after hydraulic fracturing. It is of great significance for improving the level of safe production and efficient utilization of resources in coal mines. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0022] Figure 2 This is a schematic diagram of the resistivity measurement system and data processing flow.

[0023] Figure 3 This is a comparison diagram of the resistivity distribution of coal and rock before and after water injection.

[0024] Figure 4 This is a cross-sectional view of the coal and rock strata after water injection. Detailed Implementation

[0025] like Figure 1 As shown in Figure 4, a dynamic real-time testing device for coal and rock resistivity during water injection mainly consists of a measuring electrode 1 arranged in the coal seam, a resistivity measuring system 2 connected to the measuring electrode 1, a data acquisition system 3 connected to the resistivity measuring system 2, and a data processing system 4 connected to the data acquisition system 3.

[0026] Measuring electrode 1 is used to form an electrode network and contact the coal and rock. Resistivity measurement system 2 is used to measure the resistivity of the coal and rock based on measuring electrode 1. Data acquisition system 3 is used to acquire resistivity data in real time. Data processing system 4 is used to perform inversion processing on the acquired resistivity data to obtain a true resistivity distribution image inside the coal and rock.

[0027] Specifically, resistivity measurement system 2 is a multi-channel resistivity tomography system. This system utilizes the characteristic that different materials have different resistivities. By applying current excitation to the object under test, measuring the boundary voltage, and then reversing the resistance distribution inside the object.

[0028] A method for dynamic real-time testing of coal and rock resistivity during water injection, based on the aforementioned dynamic real-time testing device for coal and rock resistivity during water injection, further includes the following steps:

[0029] S1. Arrange at least one water injection borehole 5 and at least one set of measuring electrodes 1 in the coal seam. All measuring electrodes 1 together form an electrode network and are in contact with the coal and rock.

[0030] S2. Before injecting water into the water injection borehole 5, the initial resistivity of the coal and rock is measured by the resistivity measurement system 2 to obtain the initial resistivity distribution of the coal seam before water injection as a reference for comparison.

[0031] S3. During the water injection process in the water injection borehole, the resistivity measurement system 2 is used to dynamically scan and measure the resistivity inside the coal and rock at preset time intervals.

[0032] S4. Resistivity data obtained by dynamic scanning measurement is acquired in real time through data acquisition system 3.

[0033] S5. The collected resistivity data is inverted through the data processing system 4 to obtain the true resistivity distribution image inside the coal and rock.

[0034] S6. Based on the variation pattern of the real resistivity distribution image, dynamically evaluate the water injection range, wetting uniformity and infiltration rate, and provide a basis for real-time adjustment and optimization of water injection parameters.

[0035] Step S1 specifically involves pre-drilling water injection boreholes 5 and several monitoring boreholes 6 in the coal seam. The water injection boreholes 5 are drilled horizontally from the working face of the coal seam into the interior of the coal seam, while the monitoring boreholes 6 are drilled downwards from the top face of the coal seam. Each monitoring borehole 6 is arranged around the perimeter of the water injection boreholes 5 and along their extension direction. Multiple measuring electrodes 1 are arranged at certain intervals in the monitoring boreholes 6. Multiple measuring electrodes 1 in the same monitoring borehole 6 form a group, creating a vertical electrode string. Multiple vertical electrode strings constitute a three-dimensional electrode network. A surface reference electrode is arranged above or around the water injection area. The spacing and number of measuring electrodes 1 can be adjusted according to the required detection accuracy and actual field conditions. The surface reference electrode provides a stable potential reference point and assists in achieving a greater detection depth and range.

[0036] The monitoring borehole 6 is arranged in a plum blossom shape, parallel line shape, or cross shape, which facilitates the construction of a three-dimensional electrode network and enables multi-dimensional and three-dimensional monitoring of the resistivity distribution inside coal and rock, effectively expanding the detection range.

[0037] Measuring electrode 1 is a ring-shaped multi-point electrode to ensure good contact with the hole wall.

[0038] Step S4 specifically involves: transmitting the measured raw voltage and current data from the data acquisition system 3 to the data processing system 4 for real-time display, storage, and preliminary processing. The core data acquired in real-time by the resistivity measurement system 3 are voltage and current. Using voltage and current, resistance and resistivity can be derived through Ohm's law and the resistivity calculation formula.

[0039] Step S5 specifically involves: the data processing system 4 calculating the apparent resistivity of each measuring point based on the original voltage and current data and the electrode device coefficients; using the finite element method or high-density resistivity inversion algorithm to perform three-dimensional inversion on the real-time acquired apparent resistivity data to reconstruct the true resistivity distribution inside the coal seam; and employing time-shifted resistivity tomography to compare and analyze the resistivity inversion results at different time points, dynamically tracking the diffusion of the water injection front, changes in water content, and hydraulic connectivity, and promptly detecting abnormal water injection situations.

[0040] Step S6 specifically involves: using the inverted three-dimensional resistivity distribution data to create a resistivity distribution cloud map using Orgin plotting software; then using Fluent fluid simulation software to simulate and display the water flow infiltration path, wetting range, and low resistivity anomaly zone; analyzing the water infiltration rate, infiltration resistance, and infiltration anisotropy based on the resistivity change trend; and dynamically adjusting and optimizing the water injection pressure, flow rate, water injection time, water injection borehole parameters, and subsequent water injection borehole deployment based on real-time monitoring results. This helps to comprehensively understand the water injection effect and avoid localization and lag.

Claims

1. A device for dynamic real-time testing of coal and rock resistivity during water injection, characterized in that: The system includes a measuring electrode (1) for placement in the coal seam, a resistivity measuring system (2) connected to the measuring electrode (1), a data acquisition system (3) connected to the resistivity measuring system (2), and a data processing system (4) connected to the data acquisition system (3). The measuring electrode (1) is used to form an electrode network and contact the coal and rock. The resistivity measuring system (2) is used to measure the resistivity of the coal and rock based on the measuring electrode (1). The data acquisition system (3) is used to acquire resistivity data in real time. The data processing system (4) is used to perform inversion processing on the acquired resistivity data to obtain a true resistivity distribution image inside the coal and rock.

2. The dynamic real-time testing device for coal and rock resistivity during water injection as described in claim 1, characterized in that: The resistivity measurement system (2) is a multi-channel resistivity tomography system.

3. A method for dynamic real-time testing of coal and rock resistivity during water injection, characterized in that: The device for dynamic real-time testing of coal and rock resistivity during water injection, as described in any one of claims 1-2, further includes the following steps: S1. Arrange at least one water injection borehole (5) and at least one set of measuring electrodes (1) in the coal seam. All measuring electrodes (1) together form an electrode network and are in contact with the coal and rock. S2. Before injecting water into the water injection borehole (5), the initial resistivity of the coal and rock is measured by the resistivity measurement system (2) to obtain the initial resistivity distribution of the coal seam before water injection as a reference for comparison. S3. During the water injection process in the water injection borehole, the resistivity of the coal and rock interior is dynamically scanned and measured using a resistivity measurement system (2) at preset time intervals. S4. The resistivity data obtained by dynamic scanning measurement is collected in real time through the data acquisition system (3); S5. The collected resistivity data is inverted through the data processing system (4) to obtain the real resistivity distribution image inside the coal and rock. S6. Based on the variation pattern of the real resistivity distribution image, dynamically evaluate the water injection range, wetting uniformity and infiltration rate, and provide a basis for real-time adjustment and optimization of water injection parameters.

4. The method for dynamic real-time testing of coal and rock resistivity during water injection according to claim 3, characterized in that, Step S1 specifically involves: pre-drilling water injection boreholes (5) and several monitoring boreholes (6) in the coal seam. Both the water injection boreholes (5) and the monitoring boreholes (6) are drilled from the top of the coal seam downwards, and each monitoring borehole (6) is arranged around the water injection borehole (5). Multiple measuring electrodes (1) are arranged in the monitoring boreholes (6) at a certain interval. Multiple measuring electrodes (1) in the same monitoring borehole (6) form a group, forming a vertical electrode string. Multiple vertical electrode strings constitute a three-dimensional electrode network. Surface reference electrodes are arranged above or around the water injection area.

5. The method for dynamic real-time testing of coal and rock resistivity during water injection according to claim 4, characterized in that, Step S4 specifically involves transmitting the measured voltage and current raw data to the data processing system (4) via the data acquisition system (3), and then displaying, storing, and performing preliminary processing in real time via the data processing system (4).

6. The method for dynamic real-time testing of coal and rock resistivity during water injection according to claim 5, characterized in that, Step S5 is as follows: The data processing system (4) calculates the apparent resistivity of each measuring point based on the original voltage and current data and the electrode device coefficient; uses the finite element method or high density resistivity inversion algorithm to perform three-dimensional inversion on the real-time acquired apparent resistivity data to reconstruct the real resistivity distribution inside the coal seam; and uses time-shifted resistivity tomography technology to compare and analyze the resistivity inversion results at different time points, and dynamically track the diffusion of the water injection front, the change of water content, and the hydraulic connectivity.

7. The method for dynamic real-time testing of coal and rock resistivity during water injection according to claim 6, characterized in that, Step S6 specifically involves: using the inverted three-dimensional resistivity distribution data to draw a resistivity distribution cloud map using Orgin plotting software, and then using Fluent fluid simulation software to simulate and display the water flow infiltration path, wetting range, and low resistivity anomaly zone; based on the resistivity change trend, analyzing the water infiltration rate, infiltration resistance, and infiltration anisotropy. Based on real-time monitoring results, the water injection pressure, flow rate, water injection time, water injection borehole parameters, and subsequent water injection borehole deployment are dynamically adjusted and optimized.

8. The method for dynamic real-time testing of coal and rock resistivity during water injection according to claim 4, characterized in that: The monitoring boreholes (6) are arranged in a plum blossom shape, parallel line shape or cross shape.

9. The method for dynamic real-time testing of coal and rock resistivity during water injection according to claim 8, characterized in that: The measuring electrode (1) is a ring-shaped multi-point electrode.

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