1. College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China
2. China United Coalbed Methane (Shanxi) LTD., Taiyuan 030032, China
3. Provincial Center of Technology Innovation for Coal Measure Gas Co-production, Taiyuan 030032, China
4. School of Energy, China University of Geosciences (Beijing), Beijing 100083, China