1. Key Laboratory of Coalbed Methane Resource and Reservoir Formation ProcessMinistry of EducationXuzhou 221008 Jiangsu China
2. School of Resources and GeosciencesChina University of Mining & TechnologyXuzhou 221116 Jiangsu China
3. Research Institute of Petroleum Exploration & Development of Changqing Oilfield CompanyPetroChina Xi'an 710021 Shaanxi China