Fixed-Offshore-Platform Performance in Hurricane Ivan

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 18325, "Assessment of Fixed-Offshore-Platform Performance in Hurricane Ivan," by F.J. Puskar, R.E. Spong, and A. Ku, Energo Engineering, and R.B. Gilbert and Y.J. Choi, U. of Texas at Austin, prepared for the 2006 Offshore Technology Conference, Houston, 1–4 May. Hurricane Ivan provided an opportunity to evaluate the American Petroleum Inst. (API) RP 2A design process for fixed platforms to ensure that it provides for well-designed structures. Specific findings and trends are reported related to global platform performance as well as component performance. A quantitative assessment to determine the adequacy of the API RP 2A design process uses a probability-based process that compares analytically predicted platform damage and survival to that actually observed after Ivan. Introduction Ivan was one of several hurricanes in the last 12 years that have damaged or destroyed fixed offshore platforms. Previous hurricanes were Andrew in 1992 and Lili in 2002. Katrina and Rita in 2005 also caused significant platform damage and destruction. These types of events provide an opportunity to determine how fixed platforms in the Gulf of Mexico (GOM) perform in hurricanes on both a qualitative and quantitative basis. The qualitative basis includes a review of the typical types of damage to topsides and jackets, as well as the general trends observed, such as the number and type of platforms with wave-in-deck damage. The quantitative basis involves the comparison of observed damage with what would have been predicted by API RP 2A, which is the basis for design of fixed platforms in the GOM. This provides a quantified assessment of the accuracy of API RP 2A and whether it is adequate for design. The full-length paper describes these assessments for Ivan on the basis of an in-depth study performed for the U.S. Minerals Management Service focusing on fixed platforms. Path By late afternoon on 15 September 2004, Ivan was in the east-central GOM, approaching the deepwater oil and gas facilities. During this time, the hurricane was a Category 4 storm on the Saffir-Simpson scale, with maximum sustained wind speeds of more than 135 miles/hr. Ivan tracked north over the deepwater facilities in the Mississippi Canyon blocks and into the Viosca Knoll (VK) and Main Pass (MP) block areas. The majority of the destroyed or damaged fixed platforms were in the VK and MP block areas. Ivan continued its northerly track through the eastern edge of the Mobile block area, making landfall as a major hurricane with maximum winds of 130 miles/hr on the early morning of 16 September just west of Gulf Shores, Alabama.