| Summary: | 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.
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