Engineering Consistent Constraints for the Inversion of Changes in Pressure and Saturation on Ekofisk

A high resolution, time lapse seismic inversion into pressure and saturation changes is performed. This provides insights into well performance and pressure distribution within a geo-mechanically active chalk reservoir (Ekofisk). The inversion is constrained by reservoir engineering concepts and predictions to reduce the non-uniqueness involved, and to maintain consistency with the physics of flow. At the heart of this inversion scheme is the effective union of engineering data and different seismic products such as reservoir time strain, percentage changes in elastic properties to influence the inversion. Quantitative interpretation on this field using the inversion results shows good agreement with well production data and helps to explain strong localised anomalies in both the Ekofisk and Tor formations. Analysis shows that the hardening signals around producers are due to lack of pressure support and reservoir compaction; whereas softening signals are attributed to high pressure flooding around injectors.