A primary objective of the Statfjord 4D-seismic program is to improve recovery by identifying unswept oil pockets in the Brent reservoirs for infill drilling. To assist the mapping of bypassed pay from time-lapse seismic data, a detailed 4D Earth model was constructed over the central portion of the Statfjord field. The Earth model integrates seismic data from a preproduction survey acquired in 1979 and repeat surveys from 1991 and 1997.