Biggus, of course, I plead anno dominii. We actually did both under Tapestry with hours split 70:30 with MAFF/DAFS picking up the bulk.
Our flt cdr produced a comprehensive guide to recognizing oil rigs and on one wonderful sortie, a GSU ride, we were given an air borne retask from a canned GSU sortie west of UK to an oil rig surv in the North Sea assisting a mine hunter that was escorting a rig being towed through the area.