1. School of Energy Science & Engineering, Henan Polytechnic University, Jiaozuo, China
2. Institute of Efficient Development and Utilization of Coal-measure Gas, Henan Polytechnic University, Jiaozuo, China
3. China United Coalbed Methane Corporation, Ltd, Beijing, China
4. CNOOC Energy Tech-Drilling & Production Co, Tianjin, China