Combining Sparse Nodes with Dense Streamers to Address Salt-Basin Imaging Challenges in the Barents Sea

Abstract

Summary The Nordkapp Basin in the Barents Sea is considered an underexplored basin with limited amount of good quality seismic for exploration. The salt diapirism is prolific with diapirs penetrating all the way up to the seafloor. In order to image the complex salt flanks, accurate 3D velocity models for imaging is required. Experience from TopSeis acquisition both in the Barents Sea and the North Sea has provided sufficient evidence to continue a similar acquisition setup for recording of the seismic wavefield. In addition to a high quality seismic wavefield, a high-resolution 3D velocity model is required to image around and up against the irregular salt bodies. This can be achieved by deploying Ocean Bottom Seismic nodes on the seafloor. Recent Full Waveform Inversion (FWI) technology can obtain very accurate models to high frequencies even from very sparse node geometries. A split-spread source-over-streamer acquisition geometry using six wide-tow sources in addition to a long offset FWI front source has been used to acquire 3700 km2 of high-quality data. Seafloor nodes in a sparse grid of 1200 x 1200 m was deployed to record the necessary low frequencies and long offset full azimuth data required to build an accurate velocity model.