Seismic reservoir monitoring on Gullfaks

Abstract

Until recently, time-lapse seismic monitoring was considered unproven for tracking the movement of an oil-water contact (OWC). However, Statoil petrophysicists working on sonic logs from the Gullfaks Field in the Norwegian North Sea uncovered changes in log response that were favorable for seismic monitoring. Open hole logs from three wells drilled through the original OWC, compared to logs from wells drilled into water-flushed areas, showed consistently higher velocities in the water-filled zones than in those filled with oil.