Percolation Mechanism For Exploiting Coal Bed Methane In Low Permeability Reservoir Based Mechanism Of Coupled Thermal-hydrologic-mechanical And Its Applications

In coal seam gas production,the flow process of coal seam gas and water is affected by many factors.Here,the features of reservoir and the percolation mechanism of fluid are analyzed.Focusing on the influence of the adsorption / desorption of coal seam gas,the change of reservoir pressure and temperature.And considering the water in reservoir,based on the research,the equations including coal deformation equation,fluid seepage equation(including gas seepage equation and water seepage equation),and temperature field governing equation are established.At the same time,permeability model including the temperature effects is developed for the structural feature of fracture and matrix system.Simultaneous above equations win the gas-water two phases THMmultiphysics coupled mathematical model.The coupled THM control equations are solved by COMSOL Multiphysics,having CBM exploitation as the background.Crustal stress,initial temperature in Reservoir,the degree of development of cracks as well as initial water saturation are studied in the process of numerical simulation.The result shows that the lateral pressure coefficient is smaller,the CBM reservoir pressure transmission is faster,the speed of output rate will be higher.For the same reason,fracture development degree and initial reservoir the higher the temperature has the similar influence in output rate.On the contrary,if initial water saturation is lower,the CBM reservoir pressure transmission is faster,the speed of output rate will be lower.