1. Statoil Research Centre, Trondheim, Norway and The Norwegian University of Science and Technology, Department of Petroleum Engineering and Applied Geophysics, Trondheim, Norway. .
2. Statoil Research Centre, Trondheim, Norway. .
3. Professor Emeritus, Arendal, Norway. .
4. The Norwegian University of Science and Technology, Department of Petroleum Engineering and Applied Geophysics, Trondheim, Norway. .