1 State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum Beijing 102249 China jiawf@cup.edu.cn xianchenggang@cup.edu.cn.
2 Unconventional Oil and Gas Institute, China University of Petroleum Beijing 102249 PR China.
3 Sinopec Research Institute of Petroleum Exploration and Development Beijing 102206 PR China wujunwen@iccas.ac.cn.