Concrete Gravity Platform In Shallow Offshore Louisiana Water

Abstract

Abstract In June 1978, the first concrete gravity platform was installed in United States federal offshore platform was installed in United States federal offshore waters. Located off the Louisiana coast in Breton Sound Block 53, the structure rests in an approximate water depth of 12 ft on a totally submerged hull section used for oil storage. The platform contains a full range of oil and gas production facilities, auxiliary equipment, living quarters, and heliport. The remainder of the production complex consists of a well support structure and a vent structure, both of steel and connected to the platform by means of steel bridges. The concrete platform was built in Port Bienville, MS, then towed to Venice, LA, where it was outfitted with all of the production and support equipment. Once equipped, the structure was towed to the site, installed on a shell mat, and secured with pin piles and riprap. Once the platform was in place, pin piles and riprap. Once the platform was in place, the support structures and bridges were installed. This paper will detail the design of the platform, tow of platform with and without equipment, platform, tow of platform with and without equipment, site preparation, and installation of the entire production complex. The unique nature of the production complex. The unique nature of the platform caused several problems in both design and platform caused several problems in both design and construction. This paper will discuss several problems of design, construction, and operation of the concrete gravity structure. Introduction Atlantic Richfield purchased Lease No. OCS-G 3340 in the Jan. 1976 Dept. of Interior lease sale This tract is located in Breton Sound area and is known as Block 53. The lease consists of 815 acres and the west boundary is the final decree line between federal OCS lands and the State of Louisiana. This area is on the east side of the Mississippi River Delta and is approximately 75 miles south of New Orleans. The water depth varies from 10 to 20 ft. The water depth at platform site is 12 ft. Fig. 1 shows the location of the platform. Atlantic Richfield drilled its first well using a posted style drilling barge in Aug. 1976. A total of eight wells were drilled with the last being drilled in Feb. 1978. Six wells were completed out of the eight drilled. The wells were tested and shut in until production facilities could be constructed and installed. A number of production schemes were reviewed and evaluated. It was decided that a single-deck concrete structure with crude oil storage in the underwater base would be used. A contract was signed with Marine Concrete Structures in Jan. 1977 to design and construct a concrete gravity platform to meet Atlantic Richfield's specifications. After the platform construction was completed in Marine Concrete's yard in Port Bienville, MS, it then was towed to a contractor's yard in Venice, LA, where the production and support equipment were installed. The platform was then towed to the Breton Sound Block 53 installation site. This paper trill describe the production facilities and paper trill describe the production facilities and discuss the design, construction, and installation of the concrete platform. PRODUCING FACILITIES DESCRIPTION PRODUCING FACILITIES DESCRIPTION The Breton Sound block 53 platform is a complete production platform designed to produce 5000 B/D of oil, 2000 B/D of water and 10,000 Mcf/D of natural gas. The layout of the equipment is shown in Fig. 2. To meet the design criteria, the platform is equipped with production and test separators to separate the oil and gas. Both separators are designed to operate from 100 psig to 1440 psig. The gas from the separators is compressed as necessary to approximately 1000 psig, then dehydrated and metered to a gas pipeline. Water and oil from the separators are dumped to a free water knockout where oil and free water are separated.