Compaction and 4‐D time strain at the Genesis Field

Abstract

Reservoir compaction causes time shifts between different vintages of time‐lapse seismic data. We estimate these time shifts by picking the maxima of local cross‐correlations between patches of data. These local cross‐correlations can be calculated efficiently at all points in the volume at a cost that does not depend on the size of the patches. Once the time‐shift field has been computed throughout the volume, we take its temporal derivative to produce a “time‐strain” (δt/t) volume. In contrast to the time‐shift field itself, which accumulates through the section, the time strain is an instantaneous (or interval) property that is related to physical changes at that point in the subsurface. The Genesis field has undergone considerable production‐related compaction. By careful analysis of the Genesis 4‐D dataset, we estimate time strains at a scale that has the potential to impact reservoir management decisions.