Clair Ridge: Learnings From Processing the Densest OBN Survey in the UKCS

Summary In 2017 BP acquired its densest ever full field marine ocean bottom node (OBN) survey over the Clair field. With a source sampling of 25m × 25m and receivers spaced at 50m × 100m the ultra-high density OBN (UHDOBN) sampling was an order of magnitude higher than the previous 2010 Clair Ridge HDOBC. The primary goal for the survey was a 4D baseline for the Clair Ridge area of the field however there were several 3D static imaging aspirations that the data also hoped to address. These included understanding the resolution limit of the data through interpolation, improved 3D imaging of key reservoir intervals on PP and PS data and to utilise the data density and rich azimuth distribution for robust fracture characterisation via azimuthal velocity analysis. The velocity model was rebuilt from scratch and then updated successfully using FWI using the legacy HDOBC data ahead of the survey starting. The final processed UHDOBN PP and PS images were completed within 12 months of the field data being delivered to the processing contractor and provided a step change improvement in imaging and attribute quality.