Study On The Gas Migration Mechanism In The Coal Reservoir Fracture Process Under The Synergistic Effect Of Force And Hea

As an important basic energy and industrial raw material in China,coal will play an irreplaceable role in economic and social development for a long time in the future.However,in the process of mining coal resources,the occurrence of coal mine accidents,especially coal and gas outburst accidents,cannot be completely avoided,which seriously threatens the safety production of coal mines.The implementation of simultaneous exploitation of coal and gas technology can not only improve the safety production level of coal mines,but also help improve the energy structure and alleviate the problem of energy shortage.However,with the deepening of mining depth,the effects of stress and temperature of coal reservoirs become more prominent,and the damage and deformation process of the coal reservoir is not easy to grasp under the influence of mining disturbance,and the permeability evolution law of the coal reservoir is complex,resulting in unclear understanding of the gas migration mechanism.In order to solve this problem,taking the K2 coal seam of Chongqing Songzao Coal Mine as the research object.The same coal sample is used to carry out permeability test of pore pressure reduction and triaxial-compression permeability test in order to simulate the scene of reducing reservoir pressure first and then mining coal,so the permeability evolution scenario in different stress areas is simulated.At the same time,the theoretical derivation method is used to analyze the deformation characteristics and permeability evolution law of coal reservoir affected by temperature,establish a coal reservoir permeability model with stress-temperature synergy,consider the stress-damage-permeability model of mining disturbance on coal reservoir,and the gas flow process of the extraction process is explored.The main research progress is as follows:(1)According to the stress characteristics of the original rock stress zone,the permeability test with the reduction of pore pressure under different temperature conditions is carried out,and the deformation and permeability characteristics of coal reservoir are analyzed.By considering the effects of effective stress,adsorption/desorption,thermal expansion and thermal cracking,the fracture deformation and permeability model of coal reservoir are derived,based on which the permeability evolution law of coal reservoir considering the influence of temperature in the original rock stress area is analyzed.(2)Considering the irreversible deformation of coal reservoir caused by mining disturbance,a triaxial-compressive permeability test is carried out on the basis of the permeability test with reduced pore pressure under different temperature conditions,and the deformation characteristics and permeability evolution law of coal reservoir damage under the influence of mining disturbance are analyzed.At the same time,from the theoretical point of view,the fracture deformation is analyzed,and conduct the study of fracture deformation and damage mechanics in the stress zone of the original rock,the stress-damage-permeability model is derived,which can be used to characterize the gas migration mechanism of coal reservoir in front of work considering the influence of temperature.(3)The evolution law of pore pressure over time and space during the extraction process is analyzed,and a coal reservoir permeability model considering extraction damage is established based on the derived stress distribution characteristics of the surrounding rock of the borehole and combine with the spatiotemporal evolution function of pore pressure.The evolution mechanism of gas in the extraction process with the extraction time and space is analyzed,the influence of extraction temperature on the evolution of permeability is explored,and the response mechanism of gas migration in the extraction process is further revealed.