1. School of Energy Resources, China University of Geosciences, Beijing 100083, P.R. China
2. Coal Reservoir Laboratory of National Engineering Research Center of CBM Development & Utilization, China University of Geosciences, Beijing 100083, China
3. School of Engineering, Fraser Noble Building, King’s College, University of Aberdeen, Aberdeen AB24 3UE, U.K.
4. School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China