Full-azimuth Ocean Bottom Seismic for Imaging Beneath Complex Overburden at Johan Sverdrup

Structural interpretation of reservoir events at the Johan Sverdrup field in the North Sea can be challenging in areas with complex overburden. Re-mobilised sands (injectites) with very high velocity relative to surrounding sediments cause strongly localized pull-up of deeper reflections. In addition, shallow channels less than 200m below sea bed filled with low velocity sediments cause pull-down effects. Both pull-up and pull-down effects can leave imprints in the interpretation of reservoir events. We will show how Ocean Bottom Seismic (OBS) data with long offset and rich azimuth can help resolve such problems, by either under-shooting the injectities completely, or by providing high quality data to enable better processing and velocity model building, including FWI. The survey was acquired at a reduced cost by using a system with multi-component nodes connected by passive cables. We will show that good data quality was achieved using this system, and we will discuss the additional processing steps required.