oa High-fidelity Velocity Model Building and Imaging Using Reflections, Refractions and Multiples Arrivals from Dual-sensor Streamer Data

We demonstrate the success of combining wavelet shift tomography, full waveform inversion (FWI) and separated wavefield imaging (SWIM) for Pre-Stack Depth Migration (PSDM) velocity model building and imaging. FWI utilizes the low frequency refraction arrivals, and SWIM exploits the greater illumination in the shallow section inherent in the multiple raypaths. The data under investigation were acquired in 2009 using dual-sensor cables over the Utsira High area offshore Norway. The 1600km2 surface seismic survey covers the largest exploration discovery offshore Norway in the last 30 years. Relatively thin target sands are situated below a complex chalk layer and span hundreds of square kilometers. The complex geology in the area leads to a large uncertainty in estimating the associated oil reserves. Currently the reserve estimates vary between 1.7 and 3.3 billion barrels; the aim of this study, a research collaboration between PGS and Lundin Norway, was to achieve more accurate depth predictions and better imaging of the target sands.