The events surrounding the Deepwater Horizon (Macondo) disaster have changed the face of deepwater operations. Safety and environmental systems (SEMS) plans and capping or containment capabilities are required to meet current Bureau of Safety and Environmental Enforcement (BSEE) permitting requirements for the Gulf of Mexico (GOM). More generally, industry must identify the operational risks associated with future deepwater operations and specify their plans for responding to those risks, in order to maximize the effectiveness of methods to prevent and respond to potential future releases of hazardous, polluting hydrocarbons. This paper describes a study of public BSEE (previously MMS and BOEMRE) data on incidents involving releases of formation fluids to the environment. The purpose of this study was to provide a factual basis for identifying the operational risk of hydrocarbon releases in offshore operations as a starting point for additional work on identifying opportunities to reduce the frequency, severity, and consequences of such releases, especially for deepwater operations.

Incidents reported over the past 15 years were reviewed and organized in a spreadsheet. A total of 90 non-pipeline incidents were identified as including enough description to be useful. Most of these incidents were spills greater than 50 barrels (bbls), but blowouts, fires, and explosions are important and included. To the extent possible, the review determined: the flow path taken from the formation to the point in the well or production system where the fluids were released, the release point, the barriers that were used to reestablish control, and what can these events tell us about potential future deepwater events.

It is notable that most of these releases occurred in shelf operations rather than deepwater (water depth ≥ 1,000 ft), which was expected due to the much larger number of wells on the GOM shelf. Nearly two-thirds of the releases happened during active drilling, completion, workover, or well-servicing operations. The remaining events occurred during other operations, particularly production, and include two spills after the wells were plugged and abandoned (P&A’d). The number of blowouts per year was relatively small, varying from 2 to 9 for the 15 year period. The number of blowouts has remained roughly constant despite the recent decrease in the rig activity level. Similarly, the size of most spills was relatively small, if the Macondo event is excluded. Nevertheless, the data gives a factual basis for identifying the kinds of events that could lead to future catastrophes if not prevented or identified and controlled successfully.

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