Decreasing Gas Pressure Research Articles

Investigation on Key Parameters of N2 Injection to Enhance Coal Seam Gas Drainage (N2-ECGD)

Practice shows that CO2/N2-ECBM is an effective technology to enhance coalbed methane. However, there are few field tests in which the technology is applied to enhance the gas drainage in underground coal mines, and the effect is uncertain. In this study, firstly, the reasons for the decrease of gas drainage efficiency in the exhaustion period were analyzed based on the theory of fluid mechanics. Secondly, the mechanism of N2 injection to enhance coal seam gas drainage (N2-ECGD) was discussed: with the gradual decrease of gas pressure in the drainage process, coal seam gas enters a low-pressure state, the driving force of flow is insufficient, and the drainage enters the exhaustion period. The nitrogen injection technology has triple effects of “promoting flow”, “increasing permeability” and “replacing”. Thirdly, the numerical simulations of the nitrogen pressure on drainage effect were carried out based on the fully coupled model. The results show that the higher the nitrogen pressure, the greater the displacement effect between injection and drainage boreholes, the larger the effective range. Finally, a field test of N2-ECGD was carried out in the Liu Zhuang coal mine in Huainan Coalfield, China. The results show that N2 injection can significantly enhance the gas flow rate and CH4 flow rate in the drainage boreholes, and the coal seam gas content decreased 39.73% during N2 injection, which is about 2.6–3.3 times that of the conventional drainage. The research results provide an important guidance for promoting the application of N2-ECGD in underground coal mines.

Generation of beam plasma near a dielectric target irradiated by a pulsed large-radius electron beam in the forevacuum pressure range

We have investigated generation of beam plasma near a dielectric (ceramic) target irradiated by a pulsed large-radius electron beam in the forevacuum pressure range 3–15 Pa. The electron beam was accelerated with voltage up to 8 kV. Under a certain threshold accelerating voltage increase in the plasma density was observed near the dielectric target as compared with beam plasma density without the target. A decrease in gas pressure leads to smaller value of this threshold voltage. The observed dependencies are apparently caused by two factors: secondary electrons being emitted from the ceramic target and charging of surface of the ceramic target by the e-beam. The secondary electrons, emitted from the ceramic target, provide “additional” ionization of the gas. The charge on the dielectric target surface creates a field that accelerates the slow secondary electrons, which provides an increase in plasma density near the ceramic target. The negative charge on the target slows down the beam electrons, and thus increases total ionization cross section of gas by electron impact. The value of negative charge on the dielectric surface increases with decreasing gas pressure.

A computational study of the double hysteresis phenomenon during reactive sputtering

When process parameters such as the reactive gas partial pressure or the discharge voltage are studied as a function of the reactive gas flow during reactive magnetron sputtering, the obtained curve has an S-shape. A direct consequence of this behaviour is that process control based on the reactive gas flow exhibits hysteresis. Under specific conditions, it is possible to observe two S-shaped curves: one when the reactive gas pressure is increased, the other during the return to the initial state by decreasing the reactive gas pressure. This behaviour has been described as double hysteresis behaviour. The origin of the double hysteresis behaviour is computationally studied by high-throughput calculations using a previously developed model. The influence of different process and material parameters were evaluated based on newly developed measures to characterize the calculated process curves. This high-throughput analysis reveals that the double hysteresis behaviour is linked to the difference in the removal rate of non-reacted implanted ions during the increase and decrease of the reactive gas pressure. Within the parameter space a region can be defined for which the double hysteresis behaviour is strong. The latter can not only assist further experiments to study this behaviour but also defines conditions to limit its impact. For Al, a discharge current density of approximately 0.025 A cm−2 was found to maximize double hysteresis.

Investigation on the mechanical behavior, permeability and failure modes of limestone rock under stress-seepage coupling

Limestone rock widely exists in various rock engineering, its mechanical behavior and permeability evolution have a great influence on the safety and stability of related engineering projects. To study the mechanical behavior, permeability and failure modes of limestone rock under stress-seepage coupling, triaxial compression coupled with permeability tests were carried out. Experimental results reveal that the failure of limestone still conforms to the Mohr-Coulomb criterion under stress-seepage coupling, and effective confining pressure σ3eff can indicate the effect of gas pressure PG and confining pressure σ3 on the deformation parameters of limestone samples. Peak stress σP and residual stress σR increase with the enhancement of confining pressure and decrease with the ascent of gas pressure. Permeability evolution of limestone under different gas pressures and confining pressures is generally similar, and the trend of initial permeability kI, peak permeability kP and residual permeability kR decreasing with effective confining pressure σ3eff can be expressed by the exponential function. The increase of confining pressure and decrease of gas pressure will retard the acoustic emission (AE) response and inhibit the propagation of microcracks. More importantly, limestone samples always show composite failure modes dominated by tensile cracks under low confining pressure, while under high confining pressure, the limestone samples show shear failure modes. The difference is limestone samples are composed of tensile microcracks on the microscale under stress-seepage coupling, and the proportion of shear microcracks grows as gas pressure PG and confining pressure σ3 increases. This research can provide a basic reference for relevant engineering applications.

Effect of water on methane diffusion in coal under temperature and pressure: A LF-NMR experimental study on successive depressurization desorption

Coalbed methane production is a process of desorption, diffusion, and seepage with the successive decrease of reservoir pressure. However, desorption at atmospheric pressure has been mainly used to investigate the gas diffusion of water-bearing coal. The influence of confining pressure and gas pressure on methane diffusion is not considered in this case. So, the question is, how does the variation of the methane diffusion coefficient of water-bearing coal during desorption? How is it different from dry coal? What is the difference between the methane diffusion behavior of anthracite and bituminous coal? To address these problems, we select low-volatile anthracite in the south of Qinshui Basin and high-volatile bituminous coal in the south of Junggar Basin. The methane diffusion of water-bearing and dry coal during the successive depressurization desorption is compared by low field nuclear magnetic resonance. The influence mechanism of water on methane diffusion is explored from the pore structure, wettability, and external stress. The results show that the methane diffusion coefficient of water-bearing anthracite and bituminous coal increases with the decrease of gas pressure. The methane diffusion of water-bearing coal is affected by the combination of the increase of methane desorption volume (positive effect) and the increase of effective stress (negative effect). When the gas pressure decreases from 6 MPa to 2 MPa, the negative effect is dominant, and the effective diffusion coefficient of methane in coal is poor; When the gas pressure is less than 2 MPa, the positive effect is dominant and the effective diffusion coefficient increases significantly. The homogeneity of methane effective diffusion path of water-bearing anthracite is enhanced, resulting in higher methane desorption rate and effective diffusion coefficient than dry coal. The methane effective diffusion pore size of water-bearing bituminous coal decreases, resulting in the effective diffusion coefficient of methane less than that of dry coal. These results are of great significance to reveal the methane diffusion behavior of coalbed methane in the actual production.

Impact of Fractal Features on Gas Adsorption and Desorption Capacities and Ad-/Desorption Hysteresis in Coals Based on Synchrotron Radiation SAXS

Gas adsorption and desorption capacities and ad-/desorption hysteresis in coal are important for carbon capture and storage (CCS) and coalbed methane (CBM) development. To investigate the impact of fractal features on gas adsorption and desorption capacities and ad-/desorption hysteresis in coals, five coal samples were collected and carried out methane (CH4) and CO2 isothermal ad-/desorption experiments. Small angle X-ray scattering (SAXS) was applied to characterize the fractal features of the coal pore structure. The results show that five coal samples show surface fractal features, represented by surface fractal dimension (Ds). The adsorption and desorption capacities of CO2 are stronger than those of CH4. In the adsorption stage, Ds and Langmuir adsorption volume (VL-ad) show a positive relationship for CH4 and CO2, due to the van der Waals force and available adsorption sites. In the desorption stage, Ds and Langmuir desorption volume (VL-de) show a positive relationship for CH4 and CO2, because most adsorbed gas molecules can desorb and diffuse out of the pores when gas pressure decreases. No obvious correlation was found between Ds and Langmuir adsorption pressure (PL-ad) as well as between Ds and Langmuir desorption pressure (PL-de) for CO2 and CH4. An improved hysteresis index (IHI) was adopted to characterize the degree of gas ad-/desorption hysteresis. The IHI values of CO2 vary from 12.2 to 35.2%, and those of CH4 vary from 8.9 to 50.3%. The curves of Ds vs. IHI for CO2 and CH4 are like an irreversible “V” shape, which yields to be further studied. This work further extends SAXS application in exploring the impact of coal pore structure on gas adsorption related phenomena, which is beneficial for CCS technology and CBM development.

Experimental study on intensity and energy evolution of deep coal and gas outburst

Coal and gas outburst is the most serious dynamic disasters in coal mining. The essence of mechanics is the instability and destruction process of coal and rock caused by energy accumulation and release. With mining depth increase, complex geological and stress conditions make coal and gas outburst present new characteristics, which severely restricts the reliability and effectiveness of disaster warning. For this study, the coal and gas outburst tests at different simulation depths were carried out to explore more effective prediction and prevention measures. The results show that a two-phase flow of coal and gas is ejected from the outburst mouth at high speed for 0.6–1.5 s. As the simulation depth increases, both the critical gas pressure and relative outburst intensity decrease, but the unit outburst intensity increases. The deep coal and gas outburst was characteristic of low threshold of gas pressure, easy to trigger and high intensity. The evolution of acoustic emission (AE) energy has experienced “steady-rise-peak” process. The cumulative AE energy in the early incubation is relatively small which is gradually increases at the later incubation. The cumulative AE increases sharply exposed strong outburst risk at the excitation. The propagation of impact force in the roadway has experienced “rise-peak-decrease” process, showing a “crest effect”. The cumulative AE energy increases exponentially with the peak impact force. According to the range of changes in the outburst indicators N1 and N2, the outburst risk is divided into five levels: no risk, low risk, medium risk, high risk and strong risk. A new prediction method for coal and gas outburst based on acoustic emission parameters is proposed, and its applications are discussed.

Ion beam composition in ion source based on magnetron sputtering discharge at extremely low working pressure.

In an ion source based on a pulsed planar magnetron sputtering discharge with gas (argon) feed, the fraction of metal ions in the ion beam decreases with decreasing gas pressure, down to the minimum possible working pressure of the magnetron sputtering discharge. The use of a supplementary vacuum arc plasma injector provides stable operation of the pulsed magnetron sputtering discharge at extremely low pressure and without gas feed. Under these conditions, the pressure dependence of the gaseous ion fraction displays a maximum (is nonmonotonic).

The synergistic mechanism between transfer layer and surface passivation of diamond-like carbon film under different gas pressure environments

The low friction behavior and mechanism of diamond-like carbon (DLC) film are studied under different gas pressure environments. The results present that DLC film against Al2O3 and steel balls shows a relatively stable friction coefficient in the air environment, but it shows an unstable and relatively low friction coefficient under gas pressure of 5 Pa. Under gas pressure of 10−3 Pa, the DLC film fails rapidly although it achieves a short superlubricity state. With the decrease of gas pressure, the gas passivation effect on the surface of DLC film will be weaker and weaker while the formation degree of transfer layer will be more and more continuous and dense. The first-principles calculations imply that interfacial adhesion has a significant influence on the formation of tribofilms and surface wear. Further analysis shows that the low friction behavior and mechanism of DLC films in air, low vacuum (5 Pa) and high vacuum (10−3 Pa) environment are not controlled by graphitization mechanism, but are caused by the synergistic action of transfer layer mechanism and surface passivation mechanism.

Mathematical Modeling of the Operation of an Expander-Generator Pressure Regulator in Non-Stationary Conditions of Small Gas Pressure Reduction Stations

Long-distance gas transfer requires high pressure, which has to be reduced before the gas is conveyed to the customers. This pressure reduction takes place at natural gas pressure reduction stations, where gas pressure is decreased by using gas flow energy for overcoming local resistance, represented by a throttling valve. This pressure energy can be reused, but it is difficult to implement it at small pressure reduction stations, as the values of unsteadiness significantly increase when the gas approaches consumers, whereas gas flow rate and pressure decrease. This work suggests replacing throttling valves at small pressure reduction stations for expander-generator units, based on volumetric expanders. Two implementations are proposed. A mathematical model of gas-dynamic processes, which take place in expander-generator units, was developed using math equations. With its help, a comparison was made of the stability of the operation of two possible control schemes in non-stationary conditions, and the feasibility of using an expander-generator regulator as a primary one for a small natural gas pressure reduction station was confirmed.

Effect of Environmental Parameters on Streamer Discharge in Short Air Gap between Rod and Plate

Environmental meteorological parameters (temperature, humidity, air pressure, etc.) have an important impact on short gap streamer discharge. Based on the streamer theory and particle continuity equation of gas discharge, a short gap streamer discharge simulation model is established, and the influence of environmental parameters on the dynamic development process of streamer discharge is simulated and analyzed. The short gap air gap discharge characteristics were tested in a self-made gas discharge chamber. The results show that at low humidity (relative humidity <80%), with the increase of humidity, the electron density of the streamer channel increases, the field strength of the streamer head increases, the streamer development speed speeds up, and the gap breakdown voltage decrease; At higher humidity (relative humidity >80%), with the increase of humidity, the electron density of the streamer channel decreases, the field strength of the streamer head decreases, the development speed of the streamer slows down, and the gap breakdown voltage increase. With a decrease of gas pressure, the electron density of the streamer channel decreases, the field strength of the streamer head decreases, the development speed of the streamer increases, and the gap breakdown voltage decreases; The temperature change has little effect on the streamer development process.

Characteristics of gas pressure change during the freezing process of gas-containing coal

To investigate the characteristics of gas pressure changes during the freezing of gas-containing composite coal, an experimental device for determining the freezing response characteristics of gas-containing coal was independently designed. Coal samples with different firmness coefficients from the No. 3 coal seam in Yuxi Coal Mine in Jincheng, Shanxi Province, were selected to determine the different freezing response characteristics. The gas pressure evolved under different temperatures (-10 °C-15 °C-20 °C-25 °C-30 °C) and different adsorption equilibrium pressures (1.0 MPa, 1.5 MPa, 2.0 MPa). The research results reveal that, during the freezing process of the gas-containing coal sample, the gas pressure in the coal sample tank changed as a monotonously decreasing function and underwent three stages: rapid decline, decline, and slow decline. The relationship between the gas pressure of the coal sample tank and the freezing time is described by a power function. Low temperatures promoted gas adsorption. As the freezing temperature decreased, the decrease of gas pressure in the coal sample tank became faster. During the freezing process, the adsorption capacity of soft coal was larger, and the gas pressure of soft coal was lower.

CBM exploration: Permeability of coal owing to cleat and connected fracture

Coalbed methane (CBM) resources cannot be efficiently explored and exploited without a robust understanding of the permeability of fracture-size heterogeneities in coal. In this study, two sister coal samples were imparted with pre-developed cleat and connected fractures, and the permeability of the coal samples was measured under different conditions of controlled confining and gas pressures. Furthermore, the implications of the results for CBM exploration and exploitation were discussed. The permeability of coal with cleat development ranged from 0.001–0.01 mD, indicating ultra-low permeability coal. The gas migration in this coal changed from a linear flow to a non-linear flow, with the increase in gas pressure (>1 MPa). Thus, the permeability of the coal initially increased and then decreased. However, the Klinkenberg effect does not exist in this ultralow-permeability coal. For the coal sample with connected fracture, permeability ranged from 0.1–10 mD, which is larger by hundred orders of magnitude than that of the sample with cleat. For this coal, with a decrease in gas pressure (<1 MPa), the Klinkenberg effect significantly increased the permeability of the coal. With an increase in the applied confining pressure, both the Klinkenberg coefficient and permeability of the coal presented a decreasing trend. It is suggested that field fracture investigation is a prerequisite and indispensable step for successful CBM production. The coal beds that cleat network is well conductive to the connected fracture can be an improved target area for CBM production. During CBM production, a variety of flow regimes are available owing to the decrease in CBM reservoir pressure. In particular, under the low CBM reservoir pressure and low in situ geo-stress conditions, the gas migration in the CBM reservoir with connected facture development exhibits remarkable free-molecular flow. Thus, the reservoir permeability and predicted CBM production will be enhanced.

Coal strain and permeability evolution in a 2D fractured model based on computerized tomography image reconstruction

Coal heterogeneity, especially fracture distribution, affects the mechanical response and fluid seepage in the coal reservoir under complex stress conditions, which is important for exploiting coalbed methane and preventing gas outburst. The internal pores and fractures of coal samples were scanned using an X-ray industrial CT detection system in the State Key Laboratory of Coal Resources and Safe Mining of China University of Mining and Technology (Beijing). Based on CT images, 3D models of coal samples were reconstructed using MIMICS reconstruction and digital terrain model threshold segmentation. The number, size, and fractal dimension of pores and fractures were calculated basing from the vertical section of the 3D models to evaluate the heterogeneity of coal samples, and 2D numerical models of fractured coal samples were established using the Image Import module of COMSOL Multiphysics. Coal strain and permeability evolution during the reduction of gas pressure under constant confining stress were calculated in the numerical models. Results show that the distribution of pores and fractures is dominant to coal permeability. With gas pressure decreasing, the distribution of strain and gas flow rate in the coal samples is inhomogeneous, the maximum of which is observed at the fractures. Furthermore, the shrinkage and gas flow rate of the samples reduce with decreasing gas pressure, thereby alleviating the inhomogeneous distribution of coal strain and gas flow rate. As the gas pressure is decreased, the porosity of the coal samples decreases, the initial width of the fractures increases, and the ratio of current flow to initial flow decreases. When the gas pressure is changed from 2.0 MPa to 1.5 MPa, the ratio of current permeability to initial permeability of the coal samples initially decreases and then increases. Therefore, a dominant switch of effective stress and gas desorption on the permeability and mechanical response occurs. When the gas pressure is decreased, the effect of coal matrix shrinkage due to gas desorption on the permeability of the coal samples exceeds the effect of effective stress.

Numerical Simulation of Borehole Parameters for Coal Seam Gas Pre-Drainage

Borehole parameters are quite important for gas drainage. This paper studies the impact of borehole diameter and time on gas drainage and performs numerical simulation on the distribution of gas pressure under the conditions of different borehole diameters and drainage times. The simulation results reveal that, as the borehole diameter increases, the gas drainage volume increases along with it and the gas pressure decreases, but such effect on gas drainage is limited. In terms of drainage time, the longer the drainage time, the greater the drainage impact scope. Taking a gas pressure drop of 51% as the indicator of the effective pre-drainage radius, the distance from the point with a gas pressure drop of 51% to the position of the borehole is the effective pre-drainage radius. When the pre-drainage reached the 30th, 45th, 60th, 75th, and 90th day, the effective pre-drainage radius was 1.04m, 1.29m, 1.51m, 1.68m, and 1.82m respectively. According to the numerical simulation results, the effective pre-drainage radius varies with the pre-drainage time, and the fitting analysis of the two indicates that the relationship between the two can be described by a power function.

Numerical Simulation of Coupled Thermal-Hydrological-Mechanical-Chemical Processes in the Spontaneous Combustion of Underground Coal Seams

In this study, we develop a fully coupled thermal-hydrological-mechanical-chemical (THMC) model to analyze the spontaneous combustion process of underground coal seams, focusing on investigating the influences of the pressure difference between oxygen and coal, the rate of coal-oxygen reaction heat, and the activation energy. The simulation results show that as oxygen propagates into the coal seams, the coal-oxygen reaction causes the spontaneous combustion of coal to heat. The consumption of oxygen leads to an increase in oxygen consumption along the way and a decrease in gas pressure. The permeability near the right boundary increases while significantly reducing the area far away from the right boundary as the predominant effect of spontaneous combustion. Additionally, a sensitivity study shows that a more considerable pressure difference and coal-oxygen reaction heat contribute to promoting the coal temperature, while the activation energy has a slight effect. Moreover, an increase in coal-oxygen reaction heat and activation energy accelerates the oxygen consumption rate and thus causes a lower oxygen concentration. Overall, the results provide a basis for the prediction and prevention of coal seam spontaneous combustion.

Dissociation‐Induced Deformation of Hydrate‐Bearing Silty Sand During Depressurization Under Constant Effective Stress

AbstractHydrate dissociation‐induced deformation plays a crucial role in reservoir stability during the exploitation of natural gas hydrates. During the depressurization‐induced dissociation of pore hydrate, both hydrate saturation loss and effective stress rise tend to enhance the deformation. Previous studies have not been able to distinguish between deformations caused by these two factors. In this study, triaxial tests were conducted on carbon dioxide hydrate‐bearing sediments with constant effective stress but continuously decreasing gas pressure. Another stepwise depressurization test was conducted as a supplement to monitor the variation of hydrate saturation. The results show that the partial dissociation of hydrate along with the change of pressure‐temperature state cause deformation within the hydrate‐stability field. Effective confining pressure compresses the dissociating sediment under isotropic stress but restrains compression under constant deviatoric stress. Deviatoric stress enhances the deformation during axial loading, creep and depressurization‐induced dissociation.

Impact of a pressurised membrane: Contact time

Pressurised membranes are used in various situations involving humans (protections, sports, etc). In this context, impacts mechanics of membranes is critical since under or over inflated membranes may create injuries. The effect of inflation pressure on contact time is investigated on a model experiment using a spherical membrane. Both gas pressure and impact speed decrease contact time. Direct measurements of gas pressure and temperature variations indicate an adiabatic compression in strong interaction with the membrane. The contact time of an inflated membrane is described by three dimensionless numbers, (i) the relative inflation P˜, (ii) the presso-elactic number PE that considers the gas-membrane interaction and (iii) the presso-inertial number IP that scales membrane inertia to pressure forces. A model of pressurised membrane impact is provided and compared with experiments. It shows that contact time depends mainly on IP with corrections on PE and P˜.

Mechanical criterion for coal and gas outburst: a perspective from multiphysics coupling

Although a series of hypotheses have been proposed, the mechanism underlying coal and gas outburst remains unclear. Given the low-index outbursts encountered in mining practice, we attempt to explore this mechanism using a multiphysics coupling model considering the effects of coal strength and gas mass transfer on failure. Based on force analysis of coal ahead of the heading face, a risk identification index Cm and a critical criterion (Cm ≥ 1) of coal instability are proposed. According to this criterion, the driving force of an outburst consists of stress and gas pressure gradients along the heading direction of the roadway, whereas resistance depends on the shear and tensile strengths of the coal. The results show that outburst risk decreases slightly, followed by a rapid increase, with increasing vertical stress, whereas it decreases with increasing coal strength and increases with gas pressure monotonically. Using the response surface method, a coupled multi-factor model for the risk identification index is developed. The results indicate strong interactions among the controlling factors. Moreover, the critical values of the factors corresponding to outburst change depending on the environment of the coal seams, rather than being constants. As the buried depth of a coal seam increases, the critical values of gas pressure and coal strength decrease slightly, followed by a rapid increase. According to its controlling factors, outburst can be divided into stress-dominated, coal-strength-dominated, gas-pressure-dominated, and multi-factor compound types. Based on this classification, a classified control method is proposed to enable more targeted outburst prevention.

Study on Dynamic Behavior Law and Microseismic Monitoring in Stoping Process of Roadway with High Gas and Wide Coal Pillar

In order to study the dynamic characteristics and microseismic distribution in the mining process of roadway with high gas and wide coal pillar, combined with the two dynamic events of N2105 working face in Yuwu Coal Industry, theoretical analysis and field measurement research were carried out. According to the theory of structural mechanics and geomechanics, the causes of dynamic appearance are analyzed. Combined with the specific situation, the influence of mining depth, coal pillar width, gas pressure, and content on the dynamic performance is analyzed. Stress monitoring and microseismic monitoring are carried out on one side of coal seam. The results show that, with the increase of the mining distance, the backside roof of the goaf is prone to unbalanced fracture due to the lack of lateral stress, and the impact pressure generated is used for the reserved protective coal pillar behind the goaf, causing the floor heave of coal seam. The combined stress generated by the anticlinal structure below the working face interacts with the abutment pressure of the working face to produce superposition effect, which promotes the occurrence of dynamic appearance. The critical depth of rock burst in Yuwu Coal Industry is about 600m. The increase of coal elastic energy caused by roof subsidence is more uniform with the increase of coal pillar width. The decrease of gas pressure in coal seam promotes the rock burst disaster. The vertical stress of coal seam at one side of the working face shows different evolution characteristics along the trend and strike. The vertical stress of coal seam in the lateral range of 53 m is adjusted to different degrees and tends to be stable until 300 m behind the working face. The active microseismic area in the middle of the working face was located 50 m in front of the working face, and the microseismic activity continued to 30–50 m behind the working face. The active microseismic area at the side of the roadway was located 30 m in front of the working face, and the microseismic activity continued to 100–180 m behind the working face. The inflection point, where the stress in the elastic area of coal pillar increases sharply, corresponds to the active microseismic area, which indicates that the dynamic characteristics in the mining process of roadway with high gas and wide coal pillar are related to the distribution law of microseismic. This study has a certain guiding significance for optimizing the width of reserved coal pillar, monitoring the coal seam stress/microseismic, and understanding the dynamic disaster of coal and rock under complex conditions.