Simulation Of The Dynamic Evolution Characteristics Of Coal And Rock Permeability Under The Interaction Of Water,Rock And Gas In Closed Gassy Mine

After the high gas mine is closed,a large amount of gas remains underground,which forms a complex gravity interaction system with the remaining mine water(or rebounded underground well)and coal reservoirs.The water and rock interaction in the hydrocarbons has changed the mine.Here we take the coal and rock samples from the Wangyun and Sihe high-gas mines as the research object,take the self-made waterrock-gas simulation reaction system as the experimental platform,combine on-site surveys and relevant statistical data,and comprehensively use scanning electron microscopes and X-rays.Various analysis methods such as diffractometer,X-ray fluorescence spectrometer,X-ray energy spectrometer,permeability meter,etc.,carried out simulation experiments,testing and numerical simulation under different mining area samples,different water quality conditions and different gas-phase conditions,and systematic research Under the conditions of a closed high gas mine,the interaction between acid mine water,gas and minerals in coal reservoirs and influencing factors.Under this condition,the impact of interaction on the permeability of coal reservoirs was explored and combined The simulation experiment parameters were numerically simulated.The main results are as follows:(1)Under the water-rock-gas system,the characteristics of mineral phase separation,element content,and microscopic morphology changes in coal are revealed.Before and after the reaction,the crystallinity and elemental content of the mineral phase in coal changed significantly.Among the aluminosilicate minerals,the crystallinity of kaolinite and plagioclase zeolite decreased significantly,the crystallinity of chlorite and turbidite increased slightly,and the crystallinity of carbonate minerals all showed a significant decreasing trend.The content of some elements such as Al,Si,Fe,and Ca in coal showed a decreasing trend,and the content of S element increased slightly.Reactive gas promotes the dissolution of minerals,and the fissures of the samples are obviously enlarged;adsorption gas promotes the mineral generation,and new minerals are generated on the surface of the samples,and the fissures of the coal body have a tendency to be plugged.The trend of the concentration of each ion in water is basically opposite to the trend of the elements in the mineral phase.(2)The changing trend of permeability and its influencing factors under the action of water-rock-gas are discussed.The permeability and the difference in permeability of the samples before and after the reaction showed an increasing trend.Different factors have different degrees of influence on permeability: among the water chemistry,p H is an important factor that can significantly affect the permeability change,while total Fe ions and sulfate ions are potential factors that may affect the permeability change.The higher the proportion of carbonate minerals in the mineral composition,the greater the amount of permeability change in the sample online the faster the rate of permeability change in the sample,and the opposite for clay minerals.In gas-phase conditions,reactive gases have a greater effect on the amount of permeability change than adsorbed gases.(3)Established a numerical model of reactive flow based on COMSOL Multiphysics.The simulation results show that the reaction process can be divided into three periods: in the early stage of the reaction,the solution concentration changes obviously,but the reaction rate grows slowly;in the middle stage of the reaction,the solution concentration and the reaction rate grow steadily;in the late stage of the reaction,the solution concentration and the reaction rate grow rapidly,and the minerals gradually finish the reaction.The concentration change curve shows that this process is a "penetration and then dissolution" process,after the fissure is penetrated,the internal minerals will start to dissolve from the entrance and exit at the same time,but the dissolution rate and dissolution process at the entrance and exit ends are somewhat different.This thesis contains 71 figures,14 tables and 93 references.