Simulation On Adsorbed Gas And Free Gas Content Of Coal Reservoir In Fukang Mining Area, Xinjiang

Given that low rank coal reservoir embraces high permeability and free gas content with possibility of economic and efficient exploitation, similar to low rank basin conditions abroad, appropriate researches were conducted to low rank bituminous coal reservoir of typical wells in Fukang mining area centered on predicting adsorbed gas and free gas content in coal reservoir. The results of CH4 adsorption isothermal experiment reflect that CH4 adsorption amount increases linearly with pressure increasing under relatively low pressure interval(0-5MPa), CH4 adsorption amount tends to increase gently with pressure increasing under relatively middle pressure interval(5-17MPa), and adsorption almost stays stable under high pressure interval(17-28MPa). The results of coal porosity and permeability mechanics experiment under overburden pressure indicate that pore volume and porosity both decrease with increase of overburden pressure, presenting a negative exponential function. Pore volumes of transition pores and micropores account for approximate 70% of the total pore volumes, and specific surface area is above 98%, and the proportion of macropores volumes is 20%. Pores maintain relatively good connectivity with a measured porosity ranging from 4.27% to 6.82%. Static modulus of coal increases with axial stress increasing, on the contrary, poisson ratio and confining pressure represent a negative relationship. By means of hydrochemistry and well testing results of coal reservoir, calculation method of gas saturation in different coal seams is come up with and prediction models of adsorbed gas and free gas content are obtained through numerical simulation. In the end, adsorbed gas and free gas content buried above 2000 m are estimated and analyzed for gas coal well #1 and Dahuangshan mine in Fukang mining area, the result show that adsorbed gas content varies from 7.04-14.27m3/t, free gas content from 0.04-0.66m3/t, and the total gas content is between 7.18-14.49 m3/t under air dried basis; compared to desorption gas content in site, there is a high degree of accuracy.