Adding the Temporal Coherence Dimension to 4D Seismic Data - Assessing Connectivity in the Schiehallion Field

摘要

The Schiehallion Field is located in the West of Shetlands area of the North Sea. In Schiehallion, connectivity has been recognized as a key factor for reservoir management; flow barriers are often subtle and connectivity cannot be guaranteed from a static 3D seismic image. Here, a new methodology is proposed and applied to the Schiehallion Field to assess reservoir connectivity using multiple 4D seismic surveys. Coherence analysis is used to assess the spatial variability of the time-lapse seismic. Flow barriers between compartments with different 4D signal result in sharp discontinuities in trace-to-trace coherence of the time-lapse difference seismic cube, producing delineation of low coherence values along the flow barriers. By comparing five seismic monitor surveys shot in the Schiehallion Field, flow barriers that are constant through production time can be identified. Comparisons with the actual barriers in the reservoir model suggest that many of the model barriers are too discontinuous hence cause better connectivity than the real data suggests, and the reservoir needs to be broken into several more compartments. The update of the reservoir model with the new set of barriers allows a better match between the reservoir simulation and the observed 4D seismic effects.