1. Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, China University of Mining and Technology, Xuzhou, Jiangsu 221008, China
2. Energy and Mineral Engineering, G3 Center and EMS Energy Institute, Pennsylvania State University, University Park, Pennsylvania 16801, United States
3. School of Mines, Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China, China University of Mining and Technology, Xuzhou 221116, China