Installation of the Mardi Gras Pipeline Transportation System

Abstract

Abstract This paper describes the planning and installation of approximately 320 miles of the intermediate and deepwater sections of the Mardi Gras Transportation System pipelines. This paper provides an overview of the Mardi Gras Transportation System and addresses the challenges to the installation of large diameter pipelines, heavy in-line sleds, multiple pipeline segments, and shared use of the primary installation vessel with production facilities. Also presented are the development of the execution strategy, results of the installation to date, and lessons learned. Introduction BP and its partners are developing several deepwater prospects in the Southern Green Canyon and Mississippi Canyon areas of the Gulf of Mexico. The prospects include the Holstein, Mad Dog, Atlantis, and Thunder Horse field developments, in water depths ranging from 4,500 to 7,300 feet. Each field development will involve a floating production facility from which oil and gas will be exported by means of the Mardi Gras Transportation System. Booster platforms located on the continental shelf separate the export system into intermediate/deepwater and shallow-water segments. The deepwater segment will consist of segregated oil and gas steel catenary risers at each production facility, pipelines to the booster platforms or tie-in to an existing pipeline, and subsea wyes for current and future tie-ins. The total length of the intermediate (~400 to 3400 foot water depth) and deepwater (greater than 3400 foot water depth) export pipeline system including risers is approximately 320 miles. The pipeline diameters range from 16-inch to 28-inch and the riser diameters range 16-inch to 24-inch. Both oil and gas pipelines have excess capacity for future oil and gas production. The shallow-water segment will include oil pipelines from a booster platform in Mississippi Canyon to onshore storage facilities. The Southern Green Canyon production will be transported to a booster platform where it will connect into non-Mardi Gras systems for transportation to shore. The installation of these shallow water segments is not addressed in this paper. Mardi Gras Transportation System Pipelines Overview The intermediate and deepwater segments of the Mardi Gras Transportation System transports both oil and gas production from two development regions, Southern Green Canyon (SGC) and Mississippi Canyon (MC) back to shelf platforms. The Mardi Gras Transportation System is sub-divided into four general elements defined by product type and Gulf of Mexico area location, i.e., SGC or MC. Each element is operated by a separate limited liability company (LLC) which is named after a New Orleans Mardi Gras Krewe. In the SGC region, the Caesar Oil Pipeline System and the Cleopatra Gas Gathering System transport production from Holstein, Mad Dog and Atlantis fields to a shallow water platform. In the MC region, the Proteus Oil Pipeline System and the Okeanos Gas Gathering System transport production from the Thunder Horse field to shallow water platforms. These segments are shown in Figures 1 and 2. Figure 3 shows the complete Mardi Gras Transportation System and its connections to existing infrastructure. Unique Features of the Mardi Gras Pipeline Design The overall pipeline work scope for the Mardi Gras Transportation System involved route selection, engineering analysis, preparation of specifications, budget refinement, execution planning, and procurement, design and fabrication of various pipeline components.