1. Key Laboratory of Unconventional Oil & Gas Development (China University of Petroleum (East China)), Ministry of Education, Qingdao, Shandong 266580, P. R. China
2. School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, P. R. China
3. Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.