Controllable shock wave coal seam permeability improvement multi-parameter detection method and system

Abstract

The application belongs to the technical field of coal seam permeability detection, and discloses a controllable shock wave coal seam permeability multi-parameter detection method and system; the method comprises the following steps: obtaining coal body condition parameters, geological condition parameters and engineering condition parameters of a coal sample to be detected, and establishing multiple detection conditions; applying controllable shock waves according to different pulse action parameters, and obtaining energy conversion data, shock wave propagation data and coal body response data; determining energy conversion characteristics, shock wave propagation characteristics, coal body cracking response, porosity and permeability response and flow field response; comparing the characteristics and responses of different detection conditions and pulse action parameters, establishing the matching relationship between the condition parameters, pulse action parameters and coal seam permeability effect, and determining the applicable range of the pulse action parameters and the coal seam permeability boundary conditions; the application can form a continuous detection chain of controllable shock wave generation, propagation and coal body response, and provide a basis for pulse action parameter selection.

Description

Technical Field

[0001] This application relates to the field of coal seam permeability detection technology, and more specifically, to a controllable shock wave coal seam permeability multi-parameter detection method and system. Background Technology

[0002] Coal seam permeability enhancement treatment promotes the initiation, expansion, and connection of fractures by applying impact to the coal body, thereby improving the pore structure and fluid transport conditions of the coal body. The propagation process of the shock wave in the coal body and the effect of permeability enhancement are affected by a variety of factors, including coal rank, coal structure, gas and water state, geostress, temperature, the relationship between the coal seam and the surrounding rock, borehole structure, and impact parameters.

[0003] Existing detection methods typically measure parameters such as shock wave pressure, coal body fractures, permeability, or flow rate separately. The energy conversion data, shock wave propagation data, and coal body fracturing, porosity seepage, and flow field response data during the shock wave generation process are scattered and it is difficult to form a continuous correspondence along the generation, propagation, and coal body response process of the controllable shock wave. As a result, the detection results cannot fully reflect the chain of interaction between input energy, shock wave propagation characteristics, and coal seam permeability enhancement effect.

[0004] Existing detection methods typically lack a unified comparison of the detection results corresponding to pulse power, pulse frequency, and number of impacts under different coal body conditions, geological conditions, and engineering conditions. It is difficult to determine the matching relationship between various condition parameters and pulse action parameters and the coal seam permeability enhancement effect, and thus it is difficult to obtain the pulse action parameter range and coal seam permeability enhancement boundary conditions applicable to the corresponding coal seam conditions.

[0005] Therefore, how to correlate and detect the energy conversion process, propagation process, coal fracturing, porosity seepage, and flow field response of controllable shock waves under different coal body conditions, geological conditions, and engineering conditions, and determine the matching relationship between pulse action parameters and coal seam permeability enhancement effect based on this, is a problem that existing technologies need to solve.

[0006] In view of this, this application proposes a multi-parameter detection method and system for controllable shock wave coal seam permeability enhancement to solve the above problems. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this application is to provide a multi-parameter detection method and system for controllable shock wave coal seam permeability enhancement. By acquiring energy conversion data, shock wave propagation data, and coal body response data under different detection conditions and pulse action parameters, the method determines energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response, and flow field response. Furthermore, it establishes the matching relationship between coal body condition parameters, geological condition parameters, engineering condition parameters, and pulse action parameters and the coal seam permeability enhancement effect, thereby achieving the goal of determining the applicable range of pulse action parameters and the boundary conditions for coal seam permeability enhancement.

[0008] To achieve the above objectives, this application adopts the following technical solution:

[0009] In a first aspect, this application provides a multi-parameter detection method for controllable shock wave coal seam permeability enhancement, including:

[0010] Obtain the coal body condition parameters, geological condition parameters, and engineering condition parameters corresponding to the coal sample to be tested, and establish multiple testing conditions based on the coal body condition parameters, geological condition parameters, and engineering condition parameters;

[0011] Under various testing conditions, controllable shock waves were applied to the coal sample to be tested according to different pulse action parameters, and energy conversion data, shock wave propagation data, and coal body response data were obtained during the generation and propagation of the controllable shock waves.

[0012] The energy conversion characteristics of the controllable shock wave are determined based on the energy conversion data, the shock wave propagation characteristics of the controllable shock wave are determined based on the shock wave propagation data, and the coal body fracturing response, porosity and permeability response, and flow field response are determined based on the coal body response data.

[0013] By comparing the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response and flow field response under different detection conditions and different pulse action parameters, the matching relationship between coal body condition parameters, geological condition parameters, engineering condition parameters and pulse action parameters and coal seam permeability enhancement effect is established.

[0014] The applicable range of pulse action parameters and the boundary conditions for coal seam permeability enhancement under the corresponding detection conditions are determined based on the matching relationship.

[0015] Furthermore, the coal body condition parameters include coal rank, coal body structure, and gas-water state; the geological condition parameters include in-situ stress, effective stress, formation temperature, and coal seam-surrounding rock combination; and the engineering condition parameters include ring material, shape and size of the coal sample to be tested, simulated borehole direction, and simulated borehole size.

[0016] Furthermore, the shock wave propagation data includes pressure time history data acquired at different detection directions and different detection distances of the coal sample to be tested;

[0017] The arrival time, peak pressure, pulse duration, and pressure change curve of the shock wave are determined based on the pressure time history data. The attenuation characteristics, distortion characteristics, and propagation range of the shock wave are determined based on the arrival time, peak pressure, pulse duration, and pressure change curve of the shock wave corresponding to different detection locations.

[0018] Furthermore, the coal sample to be tested is combined with the simulated surrounding rock. Pressure time history data on both sides of the coal seam-surrounding rock interface are acquired in the direction of the interface between the coal sample to be tested and the simulated surrounding rock. The incident pressure wave, reflected pressure wave and transmitted pressure wave are identified according to the distance of the detection position relative to the coal seam-surrounding rock interface and the arrival order of the pressure peak. The wave superposition result between the coal seam and the surrounding rock is determined according to the arrival time, peak pressure and pulse duration of the incident pressure wave, reflected pressure wave and transmitted pressure wave.

[0019] Furthermore, pressure time history data and strain time history data corresponding to continuous impacts are obtained at different pulse frequencies. The shock wave response segment, peak pressure and pulse duration are determined based on the pressure time history data, and the strain response segment, maximum strain value and residual strain value are determined based on the strain time history data.

[0020] The timing of adjacent impact responses is determined by the start and end times of the corresponding shock wave response segments and strain response segments. The cumulative impact of repeated impacts is determined by the changes in peak pressure, pulse duration, maximum strain value, and residual strain value corresponding to adjacent impacts, thus forming the coal seam shock wave superposition rule.

[0021] Furthermore, the coal body response data includes strain data and fracture data;

[0022] Based on strain data, the instantaneous and cumulative deformation of the coal sample under controllable shock wave action are determined. Based on the crack data before and after the impact, the changes in new cracks, primary crack extension and crack connectivity are determined. Based on the number of new cracks, crack extension length, crack width and crack connectivity, the cracking response and cracking influence range of the coal body are determined.

[0023] Furthermore, the coal body response data also includes pore distribution, porosity, permeability, fluid pressure distribution, and steady-state flow rate obtained under different impact cycles;

[0024] The pore-permeability response is determined based on the changes in pore distribution, porosity, and permeability before and after the impact, and the flow field response is determined based on the changes in fluid pressure distribution and steady flow rate before and after the impact.

[0025] Furthermore, based on the geometric conditions of the coal sample to be tested, the simulated surrounding rock, the simulated borehole, and the ring material, combined with the material parameters of the coal sample to be tested, the simulated surrounding rock, and the ring material, the interface conditions between the coal sample to be tested and the simulated surrounding rock, and the loading conditions corresponding to the current testing conditions, a numerical model for coal seam impact permeability enhancement is established.

[0026] The numerical model for enhancing the permeability of coal seams based on the shock wave propagation data and coal body response data obtained from the experiment was verified. The verified numerical model was then used to obtain the distribution of impact stress, coal body damage, pore pressure, and fluid flow inside the coal sample to be tested.

[0027] Furthermore, the method for establishing the matching relationship includes:

[0028] By comparing the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response, and flow field response corresponding to different detection conditions and different pulse action parameters, the pulse action parameters corresponding to the start of coal seam permeability enhancement, continuous enhancement, stable state, and excessive effect are determined based on the comparison results. The coal body condition parameters, geological condition parameters, engineering condition parameters, and pulse action parameters corresponding to each state of coal seam permeability enhancement are correlated with the coal seam permeability enhancement effect to form the matching relationship. The range of pulse action parameter values ​​from the start of coal seam permeability enhancement to the continuous enhancement or stable state is determined as the applicable range.

[0029] Secondly, this application provides a controllable shock wave coal seam permeability enhancement multi-parameter detection system, and implements the aforementioned controllable shock wave coal seam permeability enhancement multi-parameter detection method, including:

[0030] The working condition construction module is used to obtain the coal body condition parameters, geological condition parameters, and engineering condition parameters corresponding to the coal sample to be tested, and to establish multiple testing working conditions based on the coal body condition parameters, geological condition parameters, and engineering condition parameters;

[0031] The impact detection module is used to apply controllable shock waves to the coal sample under different pulse action parameters under various detection conditions, and to obtain energy conversion data, shock wave propagation data and coal body response data during the generation and propagation of the controllable shock waves.

[0032] The feature extraction module is used to determine the energy conversion characteristics of the controllable shock wave based on the energy conversion data, the shock wave propagation characteristics of the controllable shock wave based on the shock wave propagation data, and the coal body fracturing response, porosity and permeability response, and flow field response based on the coal body response data.

[0033] The matching analysis module is used to compare the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response and flow field response corresponding to different detection conditions and different pulse action parameters, and to establish the matching relationship between coal body condition parameters, geological condition parameters, engineering condition parameters and pulse action parameters and coal seam permeability enhancement effect;

[0034] The parameter determination module is used to determine the applicable range of pulse action parameters and the boundary conditions for coal seam permeability enhancement under the corresponding detection conditions based on the matching relationship.

[0035] The technical effects and advantages of the controllable shock wave coal seam permeability enhancement multi-parameter detection method and system proposed in this application are as follows:

[0036] This application obtains energy conversion data, shock wave propagation data, and coal body response data during the generation and propagation of controllable shock waves, and determines the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response, and flow field response respectively. This enables the dispersed detection data to form a continuous correspondence according to the generation, propagation, and coal body response processes of shock waves, thereby improving the completeness of the characterization of the coal seam permeability enhancement process.

[0037] This application establishes multiple detection conditions based on coal body condition parameters, geological condition parameters, and engineering condition parameters, and compares the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response, and flow field response corresponding to different detection conditions and different pulse action parameters. This enables the analysis of the influence of different coal body conditions, geological conditions, and engineering conditions on the controllable shock wave propagation and coal seam permeability enhancement effect, thereby improving the permeability enhancement effect analysis of coal seams.

[0038] This application establishes a matching relationship between coal body condition parameters, geological condition parameters, engineering condition parameters, and pulse action parameters and the coal seam permeability enhancement effect. Based on the matching relationship, it determines the applicable range of pulse action parameters and the boundary conditions for coal seam permeability enhancement. This provides a basis for selecting pulse power, pulse frequency, and number of impacts, and improves the controllability of setting controllable shock wave coal seam permeability enhancement parameters. Attached Figure Description

[0039] Figure 1 This is a flowchart of a multi-parameter detection method for controllable shock wave coal seam permeability enhancement according to Embodiment 1 of this application;

[0040] Figure 2 This is a flowchart of the controllable shock wave coal seam permeability enhancement parameter detection process in Embodiment 1 of this application;

[0041] Figure 3 This is a block diagram of a controllable shock wave coal seam permeability enhancement multi-parameter detection system according to Embodiment 2 of this application. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] Example 1

[0044] See Figure 1-2As shown in the figure, this embodiment provides a multi-parameter detection method for controllable shock wave coal seam permeability enhancement, including:

[0045] The coal body condition parameters, geological condition parameters, and engineering condition parameters of the coal sample to be tested are obtained. Testing conditions are established based on these parameters, and different pulse loading conditions are set under each testing condition. Energy conversion parameters, shock wave propagation parameters, coal body fracturing parameters, porosity and permeability parameters, and flow field parameters during the controllable shock wave generation and propagation process are obtained through a large-scale triaxial test platform. The matching relationship between pulse loading conditions, coal body conditions, geological conditions, engineering conditions, and coal seam permeability enhancement effect is established by combining experimental test results and numerical simulation results. Based on this matching relationship, the engineering parameters and coal seam permeability enhancement boundary conditions under the corresponding testing conditions are determined.

[0046] The coal body condition parameters include coal rank, coal body structure, and gas-water state. The coal rank is determined based on the sampling coal seam and coal quality test results of the coal sample to be tested. The coal body structure is determined based on the integrity, primary fracture development, and fragmentation of the coal sample to be tested. The gas-water state is determined based on the gas pressure, gas content, and water content of the coal sample to be tested.

[0047] According to the gas and water state corresponding to the test conditions to be established, the coal sample to be tested is subjected to gas adsorption and water content adjustment so that the coal sample to be tested reaches the corresponding gas pressure, gas content and water content, and the gas and water state is maintained under sealed conditions.

[0048] The geological condition parameters include in-situ stress, effective stress, formation temperature, and coal seam-surrounding rock combination. In-situ stress is determined based on the axial stress and lateral confining pressure applied to the coal sample to be tested. Effective stress is determined based on the axial stress, lateral confining pressure, and fluid pressure in the coal sample to be tested. Formation temperature is determined based on the test temperature applied by the large-scale triaxial test platform. Coal seam-surrounding rock combination is determined based on the combination relationship between the coal sample to be tested and the simulated surrounding rock sample. The simulated surrounding rock sample includes a simulated roof rock sample placed on the top side of the coal sample to be tested and a simulated floor rock sample placed on the bottom side of the coal sample to be tested.

[0049] The engineering condition parameters include the ring material, the shape and size of the coal sample to be tested, the simulated drilling direction, and the simulated drilling size. The ring material is placed between the simulated drilling casing and the coal sample to be tested. The simulated drilling direction includes the direction along the coal seam bedding and the direction perpendicular to the coal seam bedding. The simulated drilling size includes the diameter and depth of the simulated drilling.

[0050] A set of values ​​for coal body condition parameters, geological condition parameters, and engineering condition parameters is defined as a testing condition. When analyzing the influence of a single coal body factor, geological factor, or engineering factor, the values ​​of the remaining parameters are kept unchanged while the values ​​of the parameters to be analyzed are changed to form a corresponding testing condition comparison group.

[0051] The pulse loading conditions include pulse power, pulse frequency, and number of impacts. When the pulse power, pulse frequency, or number of impacts is changed under the same detection conditions, the other two pulse loading parameters are kept unchanged to form a corresponding pulse loading condition comparison group.

[0052] The coal sample to be tested and the simulated surrounding rock sample are installed in the sample chamber of the large-scale triaxial test platform. The accommodating space of the sample chamber, the installation position of the energy converter, and the sensor detection position are adjusted according to the shape and size of the coal sample to be tested, the coal seam-surrounding rock combination, and the simulated borehole direction.

[0053] A simulated borehole is drilled in the coal sample to be tested. A simulated borehole casing and an energy converter are installed in the simulated borehole. A corresponding ring material is set between the simulated borehole casing and the coal sample to be tested. Water is injected into the simulated borehole so that the shock wave generated by the energy converter is transmitted to the coal sample to be tested through the water medium, the simulated borehole casing and the ring material.

[0054] Axial stress, lateral confining pressure, fluid pressure, and test temperature corresponding to the current testing conditions are applied to the coal sample to be tested using a large-scale triaxial test platform. When the changes in each loading parameter are within the detection error range of the corresponding testing device during the continuous testing period, a controllable shock wave is applied to simulate the coal seam environment under the corresponding ground stress, effective stress, and formation temperature conditions.

[0055] An electrical parameter detection device is set between the pulse power supply and the energy converter. A source-end fluctuation detection device is set near the energy converter. A water medium fluctuation detection device is set in the water medium propagation path in the simulated borehole. The voltage time history data, current time history data and discharge time corresponding to each impact are collected by the electrical parameter detection device. The source-end pressure time history data are collected by the source-end fluctuation detection device. The water medium pressure time history data when the shock wave propagates in the water medium is collected by the water medium fluctuation detection device.

[0056] The peak voltage and peak current input from the pulse power supply to the energy converter are obtained based on the voltage time history data and current time history data. The voltage and current values ​​corresponding to the same sampling moment within the discharge time range are multiplied, and the resulting products are accumulated according to the sampling interval between adjacent sampling moments to obtain the input energy. The peak voltage, peak current, input energy and discharge time are used as energy parameters.

[0057] The peak pressure at the source end, the duration of the pulse at the source end, and the curve of the change in pressure at the source end are obtained from the time history data of the pressure at the source end. The peak pressure at the source end, the duration of the pulse at the source end, and the curve of the change in pressure at the source end are used as the source end pressure parameters.

[0058] The peak pressure, pulse duration, and pressure change curves of the shock wave propagating in the water medium are obtained based on the water medium pressure time history data, and the peak pressure, pulse duration, and pressure change curves in the water medium are used as water medium pressure parameters.

[0059] Electrical energy parameters, source pressure parameters, and water medium pressure parameters are used as energy conversion parameters corresponding to the controllable generation and propagation process of shock waves in water.

[0060] By comparing the electrical energy parameters, source pressure parameters, and water medium pressure parameters under different pulse loading conditions, the correspondence between pulse power input, energy converter output, and shock wave propagation in water medium is analyzed to characterize the energy conversion characteristics during the generation and propagation of controllable shock waves.

[0061] Multiple detection positions are set along the bedding direction, perpendicular to the bedding direction, and at the coal seam-surrounding rock interface of the coal sample to be tested. A wave detection device and a strain detection device are set at each detection position, and the detection direction and detection distance of each detection position relative to the impact position of the energy converter are recorded.

[0062] The energy converter is controlled to perform impact loading according to the current pulse loading conditions. A corresponding impact sequence number is configured for each impact, and the detection conditions, pulse power, pulse frequency, number of impacts, impact sequence number, energy conversion parameters, detection direction and detection distance are associated.

[0063] The pressure time history data corresponding to each impact is collected synchronously by the fluctuation detection device at each detection location. The arrival time of the shock wave, peak pressure, pulse duration and pressure change curve are extracted from the pressure time history data. The arrival time of the shock wave, peak pressure, pulse duration and pressure change curve are used as the shock wave propagation parameters.

[0064] When extracting shock wave propagation parameters, the baseline range of pressure before the shock is determined based on the stable variation range of the pressure time history data before the shock and the detection error of the fluctuation detection device. The data segment that continuously exceeds the baseline range of pressure before the shock after the shock is determined as the shock wave response segment.

[0065] The start time of the shock wave response segment is taken as the arrival time of the shock wave, the maximum pressure value within the shock wave response segment is taken as the peak pressure, the duration of the shock wave response segment is taken as the pulse duration, and the pressure sample values ​​within the shock wave response segment are arranged according to the sampling time to form a pressure change curve.

[0066] Arrange the shock wave propagation parameters corresponding to each detection position in the same detection direction in ascending order of detection distance, and compare the arrival time, peak pressure, pulse duration and pressure change curves of shock waves corresponding to adjacent detection positions to obtain the arrival time change, pressure change and waveform change of shock waves when propagating along the corresponding detection direction.

[0067] When the peak pressure at the detection position far from the impact point is lower than the peak pressure at the adjacent detection position, and the difference between the two is greater than the detection error of the fluctuation detection device, the peak pressure attenuation in the corresponding detection interval is recorded, and the shock wave attenuation result is formed based on the change of peak pressure with detection distance.

[0068] The source pressure change curve, water medium pressure change curve, and pressure change curve corresponding to each detection location were time-aligned according to the arrival time of the shock wave. The peak pressure, pulse duration, and number of pressure peaks of each pressure change curve were compared to obtain the shock wave distortion characteristics generated after the shock wave enters the water medium through the energy converter and enters the coal body through the simulated borehole casing and ring material.

[0069] The shock wave distortion features are used to characterize the peak pressure changes, pulse duration changes, and pressure peak number changes generated during shock wave propagation. Among them, the pressure value that forms a local maximum value relative to the adjacent sample value in the pressure change curve and exceeds the stable change range of the pressure change curve before the impact occurs is regarded as a candidate pressure peak. When the pressure difference between the candidate pressure peak and the adjacent local minimum pressure values ​​on both sides is greater than the detection error of the corresponding wave detection device, the candidate pressure peak is identified as a pressure peak, and the spatial distribution of the shock wave distortion features is recorded according to the detection direction and detection distance.

[0070] Along the coal seam-surrounding rock interface, detection positions are sequentially set on the side of the coal sample to be tested and the side of the simulated surrounding rock sample, along the propagation path of the shock wave pointing towards the coal seam-surrounding rock interface. Pressure time history data on both sides of the coal seam-surrounding rock interface are obtained. Based on the distance of each detection position relative to the coal seam-surrounding rock interface and the arrival order of the pressure peak, the propagation direction of the pressure wave is determined, and the reflection propagation and transmission propagation formed after the shock wave reaches the coal seam-surrounding rock interface are identified.

[0071] The pressure wave propagating towards the coal seam-surrounding rock interface is taken as the incident pressure wave, the pressure wave returning from the coal seam-surrounding rock interface to the side of the coal sample to be tested is taken as the reflected pressure wave, and the pressure wave entering the simulated surrounding rock sample from the coal seam-surrounding rock interface is taken as the transmitted pressure wave. The arrival time, peak pressure and pulse duration of the incident pressure wave, reflected pressure wave and transmitted pressure wave are compared to form the wave superposition result between the coal seam and the surrounding rock.

[0072] Based on the differences in shock wave superposition results of different coal seam-surrounding rock combinations, the influence of coal seam and surrounding rock combinations on shock wave reflection, transmission, and pressure changes near the interface is analyzed.

[0073] The strain time history data corresponding to each impact is collected synchronously by the strain detection device at each detection location. The strain baseline range before impact is determined based on the stable change range of the strain time history data before impact and the detection error of the strain detection device. The data segment that continuously exceeds the strain baseline range before impact after the arrival of the shock wave is determined as the strain response segment.

[0074] The maximum strain value is obtained from the strain response segment. After the strain response segment ends, a stable sampling period in which the strain change is within the detection error range of the strain detection device is selected. The difference between the average strain value in the stable sampling period and the average strain value in the stable sampling period before the impact is taken as the residual strain value. The maximum strain value is used to characterize the instantaneous deformation of the coal body under the action of the shock wave, and the residual strain value is used to characterize the cumulative deformation of the coal body after repeated impacts.

[0075] The shock wave response segments corresponding to each detection position are checked in order of increasing detection distance along the same detection direction. The distance between the farthest detection position where the shock wave response can be detected and the impact position where the energy converter is located is taken as the effective propagation distance in the corresponding detection direction.

[0076] Based on the strain response segment, coal fracturing parameters, and porosity-permeability parameters corresponding to each detection direction, when a strain response segment exists at the detection location, or when new fractures, extension of primary fractures, or changes from unconnected to connected fractures are identified, or when the change in porosity or permeability relative to the pre-impact state is greater than the detection error of the corresponding detection device or method, the detection location is determined as an effective action location.

[0077] The radial distance between the effective impact location, which is furthest from the impact location of the energy converter, and the impact location is taken as the effective influence radius in the corresponding detection direction.

[0078] The effective propagation distance and effective influence radius corresponding to the bedding direction, perpendicular bedding direction, and coal seam-surrounding rock interface direction are obtained respectively to characterize the influence of coal structure, coal seam-surrounding rock combination, and simulated borehole direction on the propagation range and actual effect range of shock waves.

[0079] Pressure time history data and strain time history data corresponding to continuous impacts were collected at different pulse frequencies. The shock wave response segment and strain response segment corresponding to the same detection position were compared according to the impact sequence number. When the shock wave response segment or strain response segment corresponding to the later impact begins, the response segment corresponding to the previous impact has not yet ended, and the overlap of the occurrence time of adjacent impact responses is recorded.

[0080] By correlating the detection locations and durations of time overlap under different pulse frequencies, the increase or decrease of peak pressure, the increase or decrease of pulse duration, the increase or decrease of maximum strain value, and the cumulative changes of residual strain value, the relationship between the shock wave response and coal deformation response during repeated impacts is obtained, and the relationship is used as the superposition rule of coal seam shock waves under repeated action of different pulse frequencies.

[0081] For adjacent impacts that do not overlap in time, the peak pressure, pulse duration, maximum strain value and residual strain value corresponding to the same detection location are compared according to the impact sequence number. When the absolute value of the difference between at least one parameter and the adjacent impact is greater than the detection error of the corresponding detection device, the cumulative effect of the coal body state change caused by repeated impacts on the propagation of the subsequent shock wave and the coal body deformation response is recorded, and the cumulative effect is incorporated into the coal seam shock wave superposition rule.

[0082] Before impact loading, the initial surface crack distribution and initial internal crack distribution of each coal sample to be tested are obtained, and the current surface crack distribution and current internal crack distribution of the corresponding coal sample to be tested are obtained after different impact times. The internal state of the coal body corresponding to different impact times is obtained through stage testing of the same coal sample to be tested, or by loading parallel coal samples with the same coal body condition parameters, geological condition parameters and engineering condition parameters to the corresponding impact times. The parallel coal samples are processed using the same sample preparation method and test loading method. When using parallel coal samples, the initial crack distribution of each parallel coal sample is obtained before impact loading.

[0083] The initial and current fracture distributions of the same coal sample before and after impact are correlated to identify newly formed fractures, extended portions of original fractures, and connected portions of fractures formed after the impact wave. The number of newly formed fractures, fracture extension length, fracture width, and fracture connectivity are obtained for different detection directions and distances.

[0084] The number of newly formed fractures, fracture extension length, fracture width, and fracture connectivity are used as parameters for coal body fracturing. By comparing the changes in these parameters according to the number of impacts, the process of fracture initiation, propagation, and connectivity in the coal body can be obtained.

[0085] The farthest location where new fractures, primary fracture extensions, or fracture connectivity changes are determined along each detection direction. The distance between the farthest location and the impact location of the energy converter is taken as the fracture-inducing influence distance under the corresponding detection direction. The fracture-inducing influence range of the coal seam is formed according to the fracture-inducing influence distance corresponding to each detection direction.

[0086] After different number of impacts, in-situ porosity and permeability testing or sampling testing is carried out in the corresponding coal body area according to the predetermined detection direction and detection distance to obtain the pore distribution, porosity and permeability of the corresponding coal body area, and the pore distribution, porosity and permeability are used as porosity and permeability parameters.

[0087] The porosity and permeability parameters are obtained through internal structure detection, pore structure detection, and permeability detection of the coal sample. Among these methods, tomography can be used to detect internal fractures and macroscopic pore distribution in the coal body, low-field nuclear magnetic resonance can be used to detect pore distribution in the coal body, and porosity and permeability can be obtained by using porosity detection devices and permeability detection devices, respectively. The detection method used can obtain the corresponding porosity and permeability parameters.

[0088] By comparing the porosity and permeability parameters corresponding to the non-impact state and different impact times, the changes in coal seam pore distribution, porosity increase / decrease, and permeability increase / decrease after the impact wave are obtained. Based on the changes in porosity and permeability parameters corresponding to different detection directions and detection distances, the response relationship between impact stress wave and coal porosity and permeability characteristics is analyzed.

[0089] A fluid inlet, a fluid outlet, and multiple fluid pressure detection points are set in the coal sample to be tested. Before impact loading and after different impact times, seepage detection is performed using the same fluid medium, inlet pressure, and outlet pressure. The fluid pressure corresponding to each fluid pressure detection point and the stable flow rate corresponding to the fluid outlet are collected.

[0090] The fluid pressure distribution inside the coal sample to be tested is formed based on the fluid pressure corresponding to each fluid pressure detection location, and the flow rate detection result is formed based on the stable flow rate corresponding to the fluid outlet. The fluid pressure distribution and flow rate detection result are used as flow field parameters.

[0091] By comparing the flow field parameters before and after different number of impacts, the dynamic changes in the seepage field distribution and fluid transport state under the action of the shock wave are obtained, and the porosity parameters and flow field parameters are correlated according to the detection direction and detection distance.

[0092] When the porosity or permeability corresponding to the detection location changes relative to the state before the impact, and the change is greater than the detection error of the corresponding detection device or method, the change is recorded as the shock wave-induced porosity-permeability response. The pore distribution is used to characterize the change in the pore structure of the coal body under different impact numbers, and is not used as the sole basis for numerical judgment of the porosity-permeability response.

[0093] When the fluid pressure at at least one fluid pressure detection location changes relative to the pre-impact state, and the corresponding change is greater than the detection error of the fluid pressure detection device, the change in fluid pressure distribution is recorded; when the steady flow rate changes relative to the pre-impact state, and the corresponding change is greater than the detection error of the flow rate detection device, the change in steady flow rate is recorded; the dynamic changes in the seepage field under the action of the shock wave are characterized by the changes in fluid pressure distribution and steady flow rate.

[0094] Based on the detection conditions, pulse loading conditions, detection direction, and detection distance, the energy conversion parameters, shock wave propagation parameters, maximum strain value, residual strain value, coal body fracturing parameters, porosity and seepage parameters, and flow field parameters are correlated to analyze the correspondence between the generation and propagation of controllable shock waves, coal body fracturing, porosity and seepage changes, and dynamic changes in the seepage field.

[0095] Numerical geometric models are established based on the actual shapes and dimensions of the coal sample to be tested, the simulated surrounding rock sample, the simulated borehole, the simulated borehole casing, and the ring material. The material parameters corresponding to the coal sample to be tested and the simulated surrounding rock sample are set according to the experimentally obtained coal mechanical parameters, surrounding rock mechanical parameters, and porosity and permeability parameters. The interface conditions between the coal sample to be tested and the simulated surrounding rock sample are set according to the actual contact relationship between them.

[0096] Axial stress, lateral confining pressure, fluid pressure, and test temperature are set as the geological boundary conditions for numerical simulation. Simulated borehole direction, simulated borehole size, and ring material parameters are set as engineering conditions. The source end pressure change curve corresponding to the current pulse power is used as a single impact load. The single impact load is repeatedly applied according to the pulse frequency and number of impacts to establish a numerical model of coal seam impact permeability enhancement under the corresponding detection conditions.

[0097] The arrival time of the shock wave, peak pressure, pulse duration, maximum strain value, residual strain value, porosity, permeability, fluid pressure and steady flow rate obtained from the experiment were compared with the corresponding values ​​in the numerical simulation results. The fracture distribution, fracture connectivity and fracture-inducing influence range obtained from the experiment were correlated with the coal body damage distribution obtained from the numerical simulation according to the detection direction and detection distance. The model parameters corresponding to the coal body, surrounding rock and their interface were checked based on the comparison results.

[0098] The model verification is completed when the difference between each numerical simulation result and the experimental detection result is less than or equal to the detection error of the corresponding detection device or detection method, and the coal damage distribution obtained by numerical simulation corresponds to the crack distribution, crack connection location and crack-causing influence range obtained by experimental detection in the same detection direction and detection distance.

[0099] The impact stress distribution, coal body damage distribution, pore pressure distribution, and fluid flow distribution inside the coal sample to be tested were obtained using a verified numerical model of coal seam impact permeability enhancement. The coupling relationship between shock wave propagation, coal body cracking, pore permeability change, and seepage field change was analyzed in combination with the experimental test results. The coupling relationship was used as the basis for establishing the matching relationship between pulse loading conditions, coal body conditions, geological conditions, engineering conditions and coal seam permeability enhancement effect.

[0100] For the comparison group of detection conditions corresponding to different coal grades, coal body structures and gas-water states, the shock wave attenuation results, shock wave distortion characteristics, effective propagation distance, effective influence radius, porosity and permeability parameters and flow field parameters corresponding to each detection condition are compared. The influence of different coal grades, coal body structures and gas-water states on the propagation process of coal seam shock waves and the relationship between shock stress waves and coal porosity and permeability characteristics is obtained.

[0101] A comparative group of detection conditions corresponding to different in-situ stress, effective stress, formation temperature, and coal seam-surrounding rock combinations was established. The shock wave propagation parameters, wave superposition results, coal body fracturing parameters, porosity and permeability parameters, and flow field parameters corresponding to each detection condition were compared to obtain the influence of geological conditions on shock wave propagation, coal seam fracturing, and coal seam permeability enhancement.

[0102] For different ring materials, coal sample shapes and sizes, simulated borehole directions and sizes, a comparative group of testing conditions was established. The shock wave attenuation results, shock wave distortion characteristics, effective propagation distance, effective radius of influence, fracturing influence range, pore permeability parameters and flow field parameters corresponding to each testing condition were compared to obtain the influence of engineering conditions on shock wave propagation and coal seam permeability enhancement effect.

[0103] For each pulse loading condition comparison group, the energy conversion parameters, shock wave propagation parameters, coal seam fracturing parameters, porosity and permeability parameters, and flow field parameters corresponding to changing the pulse power, pulse frequency, or number of impacts alone are compared to obtain the matching relationship between pulse loading conditions, coal seam shock wave propagation process, and coal seam fracturing effect.

[0104] By correlating coal body condition parameters, geological condition parameters, engineering condition parameters, and pulse loading conditions with effective propagation distance, effective influence radius, fracturing influence range, porosity and permeability parameter changes, and flow field parameter changes, the matching relationship between the permeability enhancement effect of controllable shock wave on coal seams under different coal body, geological, and engineering conditions is obtained.

[0105] The coal seam permeability enhancement effect is characterized by the effective propagation distance and effective influence radius, which represent the propagation and range of the shock wave; by the fracturing influence range and coal body fracturing parameters, which represent the degree of coal seam fracturing; and by the increase or decrease in porosity, the increase or decrease in permeability, and the dynamic changes in the flow field, which represent the changes in porosity and seepage after fracturing.

[0106] Under the same detection conditions, the pulse power, pulse frequency, and number of impacts are changed respectively. Based on the changes in the effective propagation distance, effective radius of influence, fracture-inducing influence range, porosity parameters, and flow field parameters corresponding to each pulse loading condition, when a new fracture, the extension of a primary fracture, or the change of a fracture from unconnected to connected occurs under a certain pulse loading condition, and the permeability and stable flow rate increase relative to the state before the impact, and the increase is greater than the corresponding detection error, the pulse loading condition is determined as the pulse loading condition under which the coal seam permeability enhancement effect begins to form.

[0107] When the pulse power, pulse frequency, or number of impacts is increased, the farthest effective position or the farthest position that forms the crack-causing influence distance moves away from the impact position where the energy converter is located to the next detection position. Alternatively, if the permeability or stable flow rate increases relative to the previous pulse loading condition and the increase is greater than the corresponding detection error, and neither of the two farthest positions moves closer to the impact position, and the decrease in permeability and stable flow rate is within the corresponding detection error range, the corresponding pulse loading condition is recorded as the enhanced permeability condition.

[0108] When the farthest effective position and the farthest position of the fracture-inducing effect remain unchanged, and the changes in permeability and stable flow rate relative to the previous pulse loading condition are both within the corresponding detection error range, the corresponding pulse loading condition is recorded as the stable condition for enhanced permeability.

[0109] When the number of newly formed fractures increases, or the increase in fracture extension length or fracture width relative to the previous pulse loading condition is greater than the measurement error of fracture image detection, while the permeability or stable flow rate decreases relative to the previous pulse loading condition and the decrease is greater than the corresponding detection error, the corresponding pulse loading condition is recorded as an over-acting condition.

[0110] Based on the pulse loading conditions corresponding to the initial formation, continuous enhancement, stabilization, and excessive effect of the permeability enhancement effect in the experimental tests, and using the calibrated coal seam impact permeability enhancement numerical model to conduct numerical simulation analysis on the pulse loading conditions between adjacent experimental parameters, the pulse loading condition interval from the initial formation of the coal seam permeability enhancement effect to the state of maintaining the enhanced permeability enhancement effect or the state of the permeability enhancement effect is determined as the applicable range of pulse power, pulse frequency, and number of impacts under the corresponding test conditions.

[0111] When the detected and simulated pulse loading conditions do not produce a coal seam permeability enhancement effect, the applicable range of the corresponding pulse loading parameters that have not yet been obtained under the current detection conditions is recorded; when the maximum detected or simulated pulse power, pulse frequency or number of impacts is reached, and the coal seam permeability enhancement effect is still in an enhanced state, the corresponding maximum parameter is recorded as the current detection upper limit, and the current detection upper limit is not used as the boundary condition for coal seam permeability enhancement.

[0112] For different coal body conditions, geological conditions and engineering conditions, the applicable range of corresponding pulse loading conditions and the differences in coal seam permeability enhancement effects are compared. The control effects of coal rank, coal body structure, gas-water state, geostress, effective stress, formation temperature, coal seam-surrounding rock combination, ring material, coal sample shape and size and simulated borehole direction on coal seam permeability enhancement effects are quantitatively analyzed.

[0113] Based on the impact stress distribution, coal damage distribution, pore pressure distribution, and fluid flow distribution under different pulse loading conditions, the excitation process of shock wave propagation on the coal seam seepage field is analyzed. The coal body conditions, geological conditions, engineering conditions, and pulse loading conditions corresponding to the initial formation of the coal seam permeability enhancement effect, the transition from the enhanced permeability enhancement state to the stable permeability enhancement state, and the first occurrence of excessive action are jointly determined as the coal seam permeability enhancement boundary conditions under the corresponding detection conditions. When no coal seam permeability enhancement effect has been formed within the current detection range, it is recorded as the corresponding coal seam permeability enhancement boundary conditions not yet obtained. When the current detection limit is reached but the permeability enhancement effect is still in the enhanced state, only the conditions corresponding to the initial formation of the coal seam permeability enhancement effect are taken as the obtained coal seam permeability enhancement boundary conditions.

[0114] The applicable ranges of pulse power, pulse frequency, and number of impacts determined under the corresponding detection conditions are used as engineering parameters. The output parameters for each detection condition are: energy conversion parameters, shock wave propagation parameters, shock wave attenuation results, shock wave distortion characteristics, wave superposition results, coal seam shock wave superposition rules, effective propagation distance, effective influence radius, coal body fracturing parameters, fracturing influence range, porosity and permeability parameters, flow field parameters, matching relationship, engineering parameters, and coal seam permeability enhancement boundary conditions. This forms a multi-parameter detection result for controllable shock wave coal seam permeability enhancement.

[0115] Example 2

[0116] See Figure 3 As shown, this embodiment provides a controllable shock wave coal seam permeability enhancement multi-parameter detection system, and implements the controllable shock wave coal seam permeability enhancement multi-parameter detection method, including:

[0117] The working condition construction module is used to obtain the coal body condition parameters, geological condition parameters, and engineering condition parameters corresponding to the coal sample to be tested, and to establish multiple testing working conditions based on the coal body condition parameters, geological condition parameters, and engineering condition parameters;

[0118] The impact detection module is used to apply controllable shock waves to the coal sample under different pulse action parameters under various detection conditions, and to obtain energy conversion data, shock wave propagation data and coal body response data during the generation and propagation of the controllable shock waves.

[0119] The feature extraction module is used to determine the energy conversion characteristics of the controllable shock wave based on the energy conversion data, the shock wave propagation characteristics of the controllable shock wave based on the shock wave propagation data, and the coal body fracturing response, porosity and permeability response, and flow field response based on the coal body response data.

[0120] The matching analysis module is used to compare the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response and flow field response corresponding to different detection conditions and different pulse action parameters, and to establish the matching relationship between coal body condition parameters, geological condition parameters, engineering condition parameters and pulse action parameters and coal seam permeability enhancement effect;

[0121] The parameter determination module is used to determine the applicable range of pulse action parameters and the boundary conditions for coal seam permeability enhancement under the corresponding detection conditions based on the matching relationship.

[0122] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A multi-parameter detection method for controllable shock wave-induced permeability enhancement in coal seams, characterized in that, include: Obtain the coal body condition parameters, geological condition parameters, and engineering condition parameters corresponding to the coal sample to be tested, and establish multiple testing conditions based on the coal body condition parameters, geological condition parameters, and engineering condition parameters; Under various testing conditions, controllable shock waves were applied to the coal sample to be tested according to different pulse action parameters, and energy conversion data, shock wave propagation data, and coal body response data were obtained during the generation and propagation of the controllable shock waves. The energy conversion characteristics of the controllable shock wave are determined based on the energy conversion data, the shock wave propagation characteristics of the controllable shock wave are determined based on the shock wave propagation data, and the coal body fracturing response, porosity and permeability response, and flow field response are determined based on the coal body response data. By comparing the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response and flow field response under different detection conditions and different pulse action parameters, the matching relationship between coal body condition parameters, geological condition parameters, engineering condition parameters and pulse action parameters and coal seam permeability enhancement effect is established. The applicable range of pulse action parameters and the boundary conditions for coal seam permeability enhancement under the corresponding detection conditions are determined based on the matching relationship.

2. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 1, characterized in that, The coal body condition parameters include coal rank, coal body structure, and gas-water state; the geological condition parameters include in-situ stress, effective stress, formation temperature, and coal seam-surrounding rock combination; and the engineering condition parameters include ring material, shape and size of the coal sample to be tested, simulated borehole direction, and simulated borehole size.

3. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 1, characterized in that, The shock wave propagation data includes pressure time history data acquired at different detection directions and different detection distances of the coal sample to be tested; The arrival time, peak pressure, pulse duration, and pressure change curve of the shock wave are determined based on the pressure time history data. The attenuation characteristics, distortion characteristics, and propagation range of the shock wave are determined based on the arrival time, peak pressure, pulse duration, and pressure change curve of the shock wave corresponding to different detection locations.

4. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 3, characterized in that, The coal sample to be tested is combined with the simulated surrounding rock. Pressure time history data on both sides of the coal seam-surrounding rock interface are acquired in the direction of the interface between the coal sample to be tested and the simulated surrounding rock. The incident pressure wave, reflected pressure wave and transmitted pressure wave are identified according to the distance of the detection position relative to the coal seam-surrounding rock interface and the arrival order of the pressure peak. The wave superposition result between the coal seam and the surrounding rock is determined according to the arrival time, peak pressure and pulse duration of the incident pressure wave, reflected pressure wave and transmitted pressure wave.

5. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 3, characterized in that, Under different pulse frequencies, pressure time history data and strain time history data corresponding to continuous impact are obtained. The shock wave response segment, peak pressure and pulse duration are determined based on the pressure time history data. The strain response segment, maximum strain value and residual strain value are determined based on the strain time history data. The timing of adjacent impact responses is determined by the start and end times of the corresponding shock wave response segments and strain response segments. The cumulative impact of repeated impacts is determined by the changes in peak pressure, pulse duration, maximum strain value, and residual strain value corresponding to adjacent impacts, thus forming the coal seam shock wave superposition rule.

6. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 1, characterized in that, The coal body response data includes strain data and fracture data; Based on strain data, the instantaneous and cumulative deformation of the coal sample under controllable shock wave action are determined. Based on the crack data before and after the impact, the changes in new cracks, primary crack extension and crack connectivity are determined. Based on the number of new cracks, crack extension length, crack width and crack connectivity, the cracking response and cracking influence range of the coal body are determined.

7. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 6, characterized in that, The coal body response data also includes pore distribution, porosity, permeability, fluid pressure distribution, and steady flow rate obtained under different impact numbers; The pore-permeability response is determined based on the changes in pore distribution, porosity, and permeability before and after the impact, and the flow field response is determined based on the changes in fluid pressure distribution and steady flow rate before and after the impact.

8. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 1, characterized in that, Based on the geometric conditions of the coal sample to be tested, the simulated surrounding rock, the simulated borehole, and the ring material, combined with the material parameters of the coal sample to be tested, the simulated surrounding rock, and the ring material, the interface conditions between the coal sample to be tested and the simulated surrounding rock, and the loading conditions corresponding to the current testing conditions, a numerical model for coal seam impact permeability enhancement is established. The numerical model for enhancing the permeability of coal seams based on the shock wave propagation data and coal body response data obtained from the experiment was verified. The verified numerical model was then used to obtain the distribution of impact stress, coal body damage, pore pressure, and fluid flow inside the coal sample to be tested.

9. The method for detecting multiple parameters of controllable shock wave coal seam permeability enhancement according to claim 1, characterized in that, The methods for establishing the matching relationship include: By comparing the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response, and flow field response corresponding to different detection conditions and different pulse action parameters, the pulse action parameters corresponding to the start of coal seam permeability enhancement, continuous enhancement, stable state, and excessive effect are determined based on the comparison results. The coal body condition parameters, geological condition parameters, engineering condition parameters, and pulse action parameters corresponding to each state of coal seam permeability enhancement are correlated with the coal seam permeability enhancement effect to form the matching relationship. The range of pulse action parameter values ​​from the start of coal seam permeability enhancement to the continuous enhancement or stable state is determined as the applicable range.

10. A controllable shock wave coal seam permeability enhancement multi-parameter detection system, implementing the controllable shock wave coal seam permeability enhancement multi-parameter detection method according to any one of claims 1-9, characterized in that, include: The working condition construction module is used to obtain the coal body condition parameters, geological condition parameters, and engineering condition parameters corresponding to the coal sample to be tested, and to establish multiple testing working conditions based on the coal body condition parameters, geological condition parameters, and engineering condition parameters; The impact detection module is used to apply controllable shock waves to the coal sample under different pulse action parameters under various detection conditions, and to obtain energy conversion data, shock wave propagation data and coal body response data during the generation and propagation of the controllable shock waves. The feature extraction module is used to determine the energy conversion characteristics of the controllable shock wave based on the energy conversion data, the shock wave propagation characteristics of the controllable shock wave based on the shock wave propagation data, and the coal body fracturing response, porosity and permeability response, and flow field response based on the coal body response data. The matching analysis module is used to compare the energy conversion characteristics, shock wave propagation characteristics, coal body fracturing response, porosity and permeability response and flow field response corresponding to different detection conditions and different pulse action parameters, and to establish the matching relationship between coal body condition parameters, geological condition parameters, engineering condition parameters and pulse action parameters and coal seam permeability enhancement effect; The parameter determination module is used to determine the applicable range of pulse action parameters and the boundary conditions for coal seam permeability enhancement under the corresponding detection conditions based on the matching relationship.

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