1. Unconventional Oil & Gas and Renewable Energy Research Institute, China University of Petroleum, Qingdao, Shandong 266580, PR China
2. Coal
Reservoir Laboratory of National Engineering Research Center of Coalbed
Methane (CBM) Development and Utilization, School of Energy Resources, China University of Geosciences, No. 29 Xueyuan Road, Haidian District, Beijing 100083, PR China