1. Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, Xuzhou, 221008 Jiangsu Province, China
2. School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, 221008 Jiangsu Province, China
3. Research Institute of Petroleum Exploration & Development, Langfang, 065007 Hebei Province, China