1. Engineering Technology Research Institute, PetroChina Southwest Oil and Gas Field, Chengdu 646002, China
2. Chengdu University of Technology, Chengdu, Sichuan 610065, China
3. Sinopec Research Institute of Petroleum Engineering, Beijing 100101, P.R. China
4. Shu Nan Gas Deposit, PetroChina Southwest Oil and Gas Field Company, LuZhou 646000, China