Co-accumulating mechanisms of unconventional gas in the coal measure of the Qinshui Basin

Qinshui basin has a good resource potential of unconventional gases in the coal measure. Study on the co-ac- cumulation mechanisms of coal measure gas will be conducive to the comprehensive utilization of natural gas. Based on the test results of geo-chemistry and reservoir properties,the authors characterized the gas generation potential and gas reservoirs. Based on the depositional sequences,lithological associations and gas logging data of typical wells in this basin,the authors established three types of gas co-accumulations and discussed its distribution in the sequence frame- work. The co-mining prospect of natural gas in the coal measure was evaluated after investigating the forming process and dynamics of gas reservoirs. It was found that the coal measure in Qinshui basin has a solid basis for natural gas generation and the dynamics of gas generation,migration,accumulation and reservoir conditions were well coupled in the geological history,which provides good conditions for the co-accumulations of natural gas in different reservoirs. The Carboniferous-Permian Shanxi and Taiyuan formations developed three types of natural gas co-accumulation,with respect to the coalbed methane,shale gas and tight sandstone gas,indicating that the coal measure in this area is favor- able for co-exploration and development. Development of the shale gas and tight sandstone gas separately,however,is at high risks.