1. Petroleum and Natural Gas Engineering, Department of Energy and Mineral Engineering and EMS Energy Institute, The Pennsylvania State University, 3S Laboratory for Petroleum Research, 202 Hosler Building, University Park, PA 16802 e-mail:
2. U.S. Department of Energy, National Energy Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA 15236-0940 e-mail: