High-frequent 4D-surveys for Identification of Subtle Reservoir Property Changes

The potential of ultra-frequent 4D acquisition is tested by simple 1-D modeling for a reservoir thickness of 5 meter. By linear changing the reservoir parameters from oil-filled to water-filled situation over 680 days, and assuming that a new seismic dataset is acquired every day, we find that a stacking procedure using data from 80 proceeding days yield a stable result that is close to the noise free result. The random noise level used in the synthetic test is 10 %. Systematic noise sources, such as velocity variations in the water layer, tidal variations and changes in weather conditions over calendar time, are expected to be major challenges for this method. We find that it is possible to correct for velocity changes in the water layer, by a simple estimation of timeshifts of the water layer reverberations.