1. Shandong University of Science and Technology Library, Qingdao 266590, China
2. College of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, China
3. Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process, Ministry of Education, Xuzhou 221008, China
4. School of Resources & Geosciences, China University of Mining and Technology, Xuzhou 221008, China