When Hurricane Ivan passed through the Viosca Knoll and Main Pass areas of the Gulf of Mexico, it generated waves equivalent to or in excess of 100-year return period conditions for many sites along its track. Despite the severe conditions, however, the number of platforms destroyed or damaged by Ivan was less than the number destroyed or damaged by Hurricane Andrew in 1992. The center of Ivan passed within 50 nm of 29 ChevronTexaco platforms. Within that population are 18 multi-leg jacket platforms designed to 50- year or 100-year hurricane wave criteria, ten minimum structures and the deepwater Petronius compliant tower (VK 786A). Several of the shelf platforms were subject to wave conditions approaching or exceeding the local 100-year level, while Petronius was subject to waves approaching the local 1,000-year level. In spite of the severe environments experienced, the performance of these structures was very much in line with what would be expected from designs developed in accordance with the principles of the more recent RP-2A design guidelines. Five of the 29 platforms suffered structural damage during the storm. Of those five, the jacket structures MP 144A, MP 298A, and VK 900A and the Petronius deepwater platform sustained repairable damage. One of the ten non-redundant minimum shelf platforms (VK 294A) was toppled. The performance of the shelf platforms indicates that RP-2A criteria generally ensure robust structural behavior when design wave conditions are encountered. Initial findings from the shelf platforms indicate that the structural damage that did occur is related to corrosion problems and instances of legs not being fully-grouted, which can in turn be linked to fabrication and installation methods and to maintenance. The performance of the Petronius compliant tower confirms that adequate margin was included through a design process that took great care to ensure structural redundancy and robustness in the more complex compliant tower design.
Hurricane Ivan entered the Gulf of Mexico on September 14, 2004, and made landfall at Gulf Shores, Alabama on September 16. Its course took it over some of the most developed areas of the Viosca Knoll and Main Pass regions. During its passage through these regions, Ivan decreased in strength from a marginal Category 4 hurricane to a Category 3. Somewhat surprisingly, however, Ivan generated the largest waves ever measured in the Gulf of Mexico, exceeding local 100-year levels at many locations along its track.
Despite the fact that some 150 platforms were in Ivan's path, damage to offshore platforms was less than that incurred by Hurricane Andrew in 1992, which was of similar wind intensity to Ivan during its passage through the developed areas but generated smaller waves. Damage assessments performed by the MMS indicate seven platforms were destroyed during Ivan, with significant damage occurring to at least 24 others. For the most part, fixed facilities in Ivan's path performed well, despite that fact that design criteria were exceeded in many locations.