1. School of Resources and Environment, Henan Polytechnic University, Jiaozuo 454003, P. R. China
2. Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region, Henan Province, Henan Polytechnic University, Jiaozuo 454003, P. R. China
3. Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Wuhan 430074, P. R. China