Deepwater Response Options - a Modelling Study Comparing Subsea Dispersant Injection and Mechanical Recovery using residual surface oil as a simplified effectiveness indicator.

Abstract The low oil recovery rates reported during Macondo (3–5% of the released oil) have caused discussions regarding efficiency mechanical compared to other spill response options. These unfortunately been used as reference in several later modelling studies and analysis. Multiple factors could explain these rates, such operational priorities, where dispersants and/or situ burning are given priority before recovery; extended safety zones; availability adequate equipment storage capacity collected oil; number units available; level training available remote sensing support guide operations. This study uses OSCAR model simulate a deep-water release evaluate effect different options both separately combination. evaluated subsea dispersant injection, recovery, combination these. As expected, Subsea Dispersant Injection (SSDI) was highly effective resulted significant reduction residual surface (8% volume, versus 28% for non-response option, NR). However, using large offshore systems also reduced with similar amount (9% volume). results deviate significantly from numbers after incident scaled rates. increased this is mainly due inclusion updated descriptions capabilities, exclusion zone, more realistic representation distribution units' interactions oil, (efficient only on thick parts slick). capabilities based specifications multiple providers authorities (Norwegian Clean Seas organisation (NOFO), Oil Spill Response (OSRL), Norwegian Coastal Administration (NCA), US Bureau Safety Environmental Enforcement (BSEE) others). justified by well-established contingency plans, exercises annual performance testing oil.