1. Department of Earth and Environmental Engineering, Columbia University918 S. W. Mudd, 500 West 120th Street, New York, NY 10027, USA
2. Department of Chemical and Petroleum Engineering, University of Calgary2500 University Drive NW, Calgary, Alta. T2N 1N4, Canada
3. Department of Economics, University of Calgary2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada