1. Geospatial Research Ltd., Dept. of Earth Sciences, University of Durham, DH1 3LE, UK (e-mail: richard@geospatial-research.co.uk)
2. e-Science Research Institute, University of Durham, DH1 3LE, UK
3. Reactivation Research Group, Dept. of Earth Sciences, University of Durham, DH1 3LE, UK
4. Current address: GeoPressure Technology Ltd., Mountjoy Research Centre, Stockton Road, Durham, DH1 3UZ, UK
5. Current address: Institute of Geoscience Research, Curtin University of Technology, GPO Box U1987, Perth WA6845, Australia
6. Current address: BP, Chertsey Road, Sunbury-on-Thames, Middlesex, TW16 7BP, UK