The Value of Dual-Azimuth Acquisition: Imaging, Inversion and Development over the Dugong Area

The Dugong area in the Norwegian North Sea was surveyed by North-South (N–S) orientated, variable depth streamer data, and recently, East-West (E–W) orientated triple source multi-sensor data. By reprocessing the original N-S data in combination with the E–W, we found that a combined dual-azimuth (DAZ) volume can provide significant imaging improvements supporting the de-risking of nearfield exploration targets. The uplift came in the form of enhanced structural imaging, resolution, signal-to-noise ratio and amplitude reliability. These were due to the complimentary illumination, sampling, and cable-varying characteristics of the two surveys, combined with advanced DAZ velocity model building and reprocessing methods. The benefits were found to directly aid in development decisions. Firstly, an inversion study utilizing both azimuths in a joint manner yielded more reliable probabilistic estimates of reservoir-level oil sands when compared to a single azimuth inversion due to the richer illumination and hence amplitude fidelity. Secondly, DAZ full-waveform inversion (FWI) imaging facilitated a substantial improvement to near-surface resolution with the potential for shallow hazard identification.