Study on geological condition of coalbed methane in Urumqi-Dahuangshan Area

According to a big difference between the gas productions of the coalbed methane developed wells in Urumqi-Dahuangshan Area, under the premise of the construction technique and gas drainage system as well as external factors affected as the same, the geological factor became the major factor affected to the high differences to the gas production of the coalbed methane wells. Therefore an analysis study was conducted on the coalbed methane geological conditions, gas content features, reservoir features and others in these area. The study results showed that the seams in the study area had the characteristics of the high thickness, multi seams, low metamorphic grade, the nappe structure developed within the study area, strata deformation serious and the high inclined seam. The air dried basis gas content of the main target seam was 0.76～14.2 m3/t and the average gas content was 8.19 m3/t. The methane concentration was 64.68%～89.65% and the average concentration was lower than 80%. In coal reservoir, the large and medium pores were taken a high percentage, the pore filled was low, the connection was good, different seam would have a different methane adsorption capacity and the permeability distribution was uneven. The pressure gradient of coal reservoir mostly lower than 0.95 MPa/hm and reservoir was the under pressure reservoir.