1. School of Resources and Geoscience, China University of Mining and Technology, Xuzhou 221116, China
2. Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process of the Ministry of Education, China University of Mining and Technology, Xuzhou 221116, China
3. School of Mines, Inner Mongolia University of Technology, Hohhot 010051, Inner Mongolia, China
4. College of Geoscience and Survey Engineering, China University of Mining and Technology, Beijing 100083, China