Seven Types of Offshore Oil Production Platforms

Source: U.S. Minerals Management Service, Gulf of Mexico Region, Offshore Information, October 1999

A fixed platform (FP) is supported by piles driven into the seabed and is economically feasible for water depths up to 1,650 feet. The compliant tower (CT) is a narrow, flexible tower that can operate in water depths of up to 3,000 feet. The Sea Star or floating “mini tension leg” structure is suitable for smaller reservoirs and operates in water depths up to 3,500 feet. The floating production system (FPS) is anchored in place and can be dynamically positioned using rotating trusters. Connected to wellheads on the ocean floor this system can be used in water depths up to 6,000 feet. Subsea systems (SS), connected to nearby platforms, can operate at great depths. However, the drilling and completion cost penalties of subsea systems make these arrangements less preferable than floating structures.

Composite production risers (CPR) technology (replaced steel) is expected to be most appropriate for TLPs (tension leg platforms) and for SPAR platforms, which are vertical floating cylinders (Johnson 2003). TLPs and SPAR platforms consist of floating structures held in place by vertical tendons connected to the sea floor. TLPs and SPAR platforms account for 39 percent of announced Gulf of Mexico deepwater projects. It is expected that the availability of the CPR technology will significantly expand the operating reach of TLPs and SPAR platforms beyond 6,000 feet of water depth.

Worldwide, it is estimated that “there will be up to 22 deepwater projects each year during the next decade” (Hillegeist 2001). Of these, 10 are expected to be located in the Gulf of Mexico with 39 percent, or four projects, likely to use TLP or SPAR platforms. Of these four projects each year, one is expected to be located in excess of 6,000 feet water depth. Each year, this one project will be a strong candidate for the CPR technology (Johnson 2003).