Surface Systems & Vessels
HOUSTON -- In the aftermath of the 2005 hurricanes in the Gulf of Mexico (GoM), the America Petroleum Institute (API) is making recommendations for assessing the behavior of existing deepwater floaters.
John Murray with FloaTEC compared the results to the responses predicted based on pre-Katrina criteria at the 20th Deep Offshore Technology conference and exhibition in Houston today.
In accordance with the interim recommendation of the API committees, a set of metocean conditions has been defined for a region in the GoM where spars, TLPs, and semisubmersibles are in operation. The responses of typical floater designs, including motions, air gaps, and riser and mooring tensions, have been estimated for these new criteria.
"The largest increases in the environmental condition from pre- to post-Katrina are in waves and wind," Murray said. The increase in the associated current is comparatively marginal for the 100-year hurricane condition. In all cases, the structures are intact, and environments are collinear and incident at 45 degrees.
The effect that the new metocean criteria might have on an existing installation would have to be addressed specifically for an individual installation. There are, however, a number of options available, such as making adjustments to the moorings, ballast management, and local reinforcement of the structure if needed. Other considerations depend on the level of conservatism used in the original designs such as multi-directional versus long crested wave conditions, Murray concluded.