Numerical simulation of surface gas extraction based on CBM-SIM in Lishu coal mine

To meet different requirements of time and space for gas extraction in preparation and planning area, based on the coalbed methane well test in Lishu coal mine, coalbed methane simulation software CBM-SIM was used to do history match and achieve precise reservoir parameters. For vertical wells in rectangular pattern, CBM-SIM was applied to predict gas rate for 5 years, 10 years and 15 years for 7 diffrent kinds of well spacing, and the dynamic change of gas content for 5 years, eventually determine the best well spacing in different area. Based on the above conclusion, considering all factors, wells were drilled in Lishu coal mine, and gas extraction was predicted by simulation. The results of the study show that the optimal well spacing for preparation areas is 200m×250m and 300 m×300 m for planning areas. 7 wells were placed in preparation areas and 64 wells in planning areas; the recovery ratio for 5 years in the preparation area will be 32.30%~38.20%, the gas content can be reduced to below 8 m³/t, meeting the requirements for safe production in the mine; the recovery ratio in the planning area will be 30.00%~39.05% for 5 years, 41.78%~52.06% for 10 years. Except the planning areas and Ⅲ Ⅴ, the gas content can be decreased to below 8 m³/t in other areas, for extraction for 15 years, the recovery ratio will be 48.20%~62.04%. The research results provide reference for the coal and gas co-extraction in Lishu coal mine and other mining areas of the deep thin coal seam in Northeast China.