Abstract
The scale of current marine stakeholder activity in the North Sea is such that considerable effort is required to minimise the impact of operations conducted adjacent to one another. Impacts are typically spatial – vessels wanting to work in the same physical space at the same time, or acoustic – geophysical sources from separate seismic operations interfering with one another.
Site surveys are one example where significant planning is required to minimise such simultaneous operations (SIMOPS). BP had two different approaches to reduce the impact of SIMOPS at two site survey locations during 2012.
A large site survey in the Clair field (West of Shetland) required the acquisition of High Resolution (HR) seismic data within 8km of an Ocean Bottom Cable (OBC) seismic survey. At this range, acoustic interference between the two geophysical systems is significant. Avoiding acoustic SIMOPS altogether was impossible as weather constraints dictated both surveys were shot during summer months. A redesigned data processing flow was devised to reduce or eliminate seismic interference, enabling acceptable data in both surveys during significant periods of simultaneous acquisition.
A site survey at a southern North Sea platform highlighted a different SIMOPS issue – potential physical interaction with fishing equipment, during the height of the lobster and shellfish season. The survey required acquisition of bathymetry and side scan sonar data to identify seabed features. By using a tetherless, low logistics Gavia AUV solution, the overall survey footprint and fouling risk was minimised as no towed equipment was required. The survey area required for the vessel was approximately a quarter of the size of a conventional towed sensor survey, greatly reducing the impact to the fishing community.
In addition, excellent data quality was achieved.