Rapid risk assessment for temporarily moored MODUs

The significant number of Moored Mobile Offshore Drilling Units (MODUs) that lost station in hurricanes Ivan, Katrina, and Rita have resulted in a change in the way offshore deepwater drilling is executed. Risk assessments are now a requirement for temporary moorings operating on the Gulf Outer Continental Shelf (OCS). The nature of such operations does not allow for long lead-time assessment and thus requires a rapid method to allow for timely well planning and permit approval. This paper will outline a commonly used process of assessing site-specific risks of operating a moored MODU on a wide variety of current offshore locations in the Gulf of Mexico. A description will be provided of the 108-year Gulf of Mexico hurricane database used to calculate seasonal and directional event probabilities. A description of the Gulf of Mexico production matrix that includes throughput will be provided with statistics on the top producing assets. Comparisons of location complexity, mooring system characteristics, and historical influence will all be described to help gain understanding of the processes at work in performing a rapid risk assessment. Comparisons will also be made with the checklist consequence assessment which is contained in API RP 95F 2nd Edition. This paper will provide insight to operators and drilling contractors on how rapid risk assessment can be consistently performed and what factors in the planning stages have the biggest impact on risk. Statistics will be displayed and explained that show nearly two thirds of all applied for drilling locations are achievable with acceptable risk and that the other third can be achievable with proper scheduling, equipment choice, or MODU. Discussion on applicability and adjustments to the risk assessment methodology to jack-ups and DP MODUs will also be outlined.