Deepwater, Subsalt Prospects Open New Era For Gulf of Mexico Action

Morpeth Seastar [58663 bytes]

SEASTAR, A MULTI-USE TENSION leg platform (TLP) designed by Atlantia Corp., will be used by British-Borneo Petroleum Syndicate plc unit British-Borneo Petroleum Inc., Houston, to develop the Morpeth deepwater discovery in the Gulf of Mexico.

The system is designed for relatively small fields with few well completions.

In the Morpeth application, "no more than a handful" of wells will be required to develop the field, said Alan J. Gaynor, chief executive officer of British-Borneo Petroleum Syndicate.

Morpeth, a planned subsea development with wells tied back to a SeaStar-design TLP, will cover Ewing Bank Blocks 921, 964, and 965 in 1,500-1,700 ft of water about 75 miles off Louisiana. Production is to begin during summer 1998. British-Borneo is currently in the development drilling phase of the project (OGJ, Nov. 25, 1996, p. 24).

Morpeth will be the first SeaStar installation.

As currently configured, SeaStar is designed for subsea oil and gas well completions, but further development work is being done for surface completions and through-tubing well service applications. SeaStar can also be used as a full production platform with quarters, capable of handling oil and gas with compression. Because it can be scaled down in size, it can be used for moderate to small payloads in deep water.

Additionally, it can function as a pumping/compression platform, a workover structure, a riser platform, or a utility platform to extend the capabilities of an existing deepwater production platform.

The U.S. Department of Energy helped fund early development of the system. But since 1995 advances in its development have been accomplished through the direct financial support and cooperative efforts of British-Borneo Petroleum.

System specifics

SeaStar can accommodate as many as 10 wells and be installed in 1,000-6,000 ft of water. It enables operators to fast-track development, with a design-installation time of 18-24 months.

The design accommodates average payloads of 500-2,000 tons, but that can be increased to up to 4,000 tons, depending on availability of offshore heavy lift equipment.

Current thinking is that SeaStar's maximum production capability is 100 MMcfd of gas or 50,000 b/d of oil.

The system can use flexible pipe, steel catenary, or vertical-tensioned risers.

SeaStar has sufficient buoyancy to support deck, topsides facilities, and its flexible risers. Also, the system has sufficient excess buoyancy to develop the design tendon pre-tension.

Mooring can be accomplished with either one or two tendons per corner, but the latter provides safety and operating redundancy. Tendons can be installed in segments or as single pieces. Each consists of a hull top connector; a tendon body, making up most of the length; a bottom connector, which attaches to the foundation, or anchor point; and tendon installation fittings at the top and bottom for tendon transport, installation, and removal.

Bottom piles can either be driven or drilled and grouted, according to Atlantia. In the Morpeth design, tendons will be connected directly to piles.