Double-Difference Waveform Inversion of 4D Ocean Bottom Cable Data: Application to Valhall, North Sea

Abstract

Changes in reservoir properties resulting from extracting hydrocarbons and injecting fluid are critical to optimize production. These properties can be characterized using waveform inversions of time-lapse seismic data. The conventional approach for analysis using waveform tomography is to take the difference of seismic inversion obtained using baseline and subsequent time-lapse datasets that are imaged independently. By contrast, double-difference waveform inversion (DDWI) jointly inverts time-lapse seismic datasets for reservoir changes. We use a 2D synthetic example to demonstrate the advantage of DDWI in mitigating spurious estimates of property changes. We then apply both conventional full waveform inversion(FWI) and DDWI to time-lapse datasets collected by ocean bottom cables (OBC) in the Valhall field in the North Sea. The data sets are acquired one year apart. DDWI gives a cleaner and more easily interpreted image of the model changes, as compared to that obtained with the conventional FWI scheme.