1. Curtin University, Kent Street, Bentley, WA 6151, Australia and Saudi Arabian Oil Company, P.O. Box 10925, Dhahran 31311, Saudi Arabia..
2. Curtin University, Kent Street, Bentley, WA 6151, Australia..
3. Formerly at Curtin University, Kent Street, Bentley, WA 6151, Australia; presently at Lawrence Berkeley National Laboratory, Energy Geosciences Division, Berkeley, California, USA.(corresponding author).