Operational mapping of the DWH deep subsurface dispersed oil

摘要

Mapping of the deep dispersed oil feature from the blowout of the MC252 wellhead was organized by the subsurface mapping unit within the Unified Area Command starting in early August, 2010. The operational process employed and the challenge presented by the response situation are reviewed. Colored dissolved organic matter fluorescence, used to establish existence of the subsurface oil prior to this time, had largely fallen below background levels for the sensors by this time. Dissolved oxygen (DO), deficits in which were assumed to be related to consumption of oil by microbes, was the only routinely observed variable in vertical profiles that displayed a persistent and obvious anomaly. The DO anomaly was therefore used to identify the presence and magnitude of the dispersed oil impact. An adaptive sampling plan employing daily review of DO profiles to provide vessel guidance was established and permitted a coarse mapping of the feature within 4 weeks. The DO anomaly extended from the wellhead to the WSW for more than 350 km, bounded to the north by the upper slope (approximately 1000 m isobath), with a cross-slope extent of 60-100 km, and was also present to the ENE of the wellhead out to 60 km.