Thematic Set: Full-azimuth modelling and field trial at Heidrun

Over recent decades, the Heidrun Field in the Norwegian Sea has been imaged several times with conventional narrow-azimuth seismic surveys. The extensively faulted structure and the presence of a dome-shaped feature cause imaging challenges in some areas. A modelling study shows that a survey design with increased crossline offset and fold, such as a four-vessel wide-azimuth or coil shooting design, can produce improved subsurface images with fewer artefacts, sharper fault edges, and more consistent amplitudes along horizons compared to images from conventional acquisition. Based on the modelling results, a field trial with coil shooting acquisition was carried out at Heidrun. The survey design with 18 intersecting coils provided full-azimuth, high fold data over a 2.5 × 2.5 km2 target area with sufficient surrounding aperture for comparing the migrated data with previously acquired conventional seismic data. Preliminary processing of the coil shooting data show fewer dip conflicts and an improved fault definition at the reservoir level compared to conventional survey data. However, due to a smaller migration aperture, the images from the field trial have lower spatial frequency content, so some details of the structure are lost.