Platform Removal Method for Larger Offshore Structures: Case Histories-South Pass 62 "B" and High Island A 343 "A" and "B" Platform Abandonments

Abstract

ABSTRACT The Gulf of Mexico platforms in 236', 237', and 375' water depths were salvaged and transported to artificial reef sites. The jackets were salvaged from High Island 343 and South Pass 62 using the same salvage method and equipment. The unique projects included the following achievements:First jackets salvaged and relocated to a Louisiana Artificial Reef Program site and second jacket donated to an Alabama artificial reef site.Largest jacket salvaged to date in the Gulf of Mexico. This paper documents the major accomplishments in the salvage and relocation of the three platforms and addresses the viability of the salvage procedure for even larger jackets. INTRODUCTION The removal of offshore platforms in water depths of 200' and greater has received attention in the past five years as the first of these larger structures have been abandoned. Many more such removals are planned in the near and distant future. Because the removal of larger structures is more costly than typical shallow water salvages, operators and contractors are exploring methods to effect cost savings. These larger, heavier jackets cannot be lifted from the water vertically, set onto a cargo barge, and transported to shore for scrap or reuse, as is typically done with smaller structures. Many methods have been proposed for removal of larger jackets. Some are extensions of conventional salvage procedures, while others propose unproven methods. All three platforms discussed in this paper were successfully salvaged by lifting the jacket with a derrick ship and towing it to a reef site. At the reef site, the jackets were toppled onto their side using the derrick ship mooring system. BACKGROUND Platform abandonment is a term often, if not quite accurately, used interchangeably with platform removal, platform disposal, or platform Decommissioning to describe what happens when the producing life of a structure ceases. Abandoning the structure by ceasing production and physically vacating the premises is only the beginning of the abandonment and removal process. The Minerals Management Service (MMS) currently mandates the removal of offshore platforms on the Outer Continental Shelf (OCS) within one year of lease termination. All piling and conductors must be severed and removed to 5 meters below the mudline. Over 400 structures have been removed from the Gulf of Mexico according to MMS records. All but approximately 12 of these structures were located in water depths of 200' or less. In 1985, the National Research Council (NRC) estimated that by the year 2020 there would be over 5,480 platforms removed from the Gulf of Mexico. Although most of these will be shallow water platforms, the NRC predicts 357 will be in water depths greater than 200'. In recent years, a number of the Gulf coast states have recognized that offshore platforms are a valuable source of reef material for fisheries enhancement and have established several sites for placement of the structures as artificial reefs. Platforms are now actively solicited for these artificial reef programs.