4D seismic pressure-saturation inversion at Gullfaks field, Norway

David Lumley, Don Adams, Mark Meadows, Steve Cole and Ray Ergas* of 4th Wave Imaging, a Californian company specializing in advanced 4D seismic software development, describe its application of proprietary pressure-saturation inversion to the Statoil operated Gullfaks field, offshore Norway. Time-lapse 4D seismic reservoir monitoring is experiencing rapid acceptance as a practical reservoir management tool, as evidenced by three full days of technical presentations on the topic at the recent June 2003 EAGE Conference in Stavanger, Norway. The 4D seismic technique is useful to help map bypassed oil, monitor costly injection programs, and improve our understanding of reservoir compartmentalization and the fluidflow properties of faults. Most of the applications to date have tended to be qualitative rather than quantitative. For example, 4D seismic practitioners often examine time-lapse seismic amplitude maps and develop a qualitative interpretation of where they think fluids are flowing in the reservoir, constrained by supporting data such as geologic control, well logs and engineering production information. However, there is a growing desire to obtain more quantitative results from 4D seismic data, for example, the ability to create pressure and saturation maps or volumes with calibrated physical units of saturation and pressure to assist engineering workflows and reservoir management decisions. This paper presents a case study in which we apply quantitative Pressure-Saturation Inversion (PSI) technology developed by 4th Wave Imaging to the 4D seismic project at the Gullfaks field, offshore Norway.