1. National Engineering Research Center of China United Coalbed Methane Co., Ltd., Beijing 100095, China
2. PetroChina Coalbed Methane Company Limited, Beijing 100028, China
3. Oil & Gas Survey, China Geological Survey, Beijing 100083, China
4. Key Laboratory of Unconventional Oil & Gas, China Geological Survey, Beijing 100029, China
5. Key Laboratory of Unconventional Oil & Gas Development, Ministry of Education, Qingdao 266580, China
6. School of Petroleum Engineering, China University of Petroleum, Qingdao 266580, China