U.S., Gulf of Mexico Blocks GB 70 and 71
Landmark: Gulf of Mexico’s first 10,000 psi 4"x2" subsea clustered well arrangement
The Sea Star field is located on the shelf in the Gulf of Mexico at 750 ft (230 m). The Sea Star field incorporates Garden Banks blocks 70 and 71. The project was a farmout prospect picked up by Phillips when the original leaseholder gave up on the idea of producing the field using a conventional platform structure. There were three predrilled wells on-site when the lease was obtained. Because the intent was to install a jacket structure, the wells were drilled with the wellheads roughly 30 ft (10 m) above the sea floor and in turn act as guides to align the structure with the wells. When the completion scheme switched to subsea, the 30 ft (10 m) wellhead height proved a concern with respect to bending moments while installing subsea hardware. The decision was made to utilize FMC’s flexible pipe lay-away technology to install the tree and flexible pipe jumper to a clustered manifold (installed adjacent to the existing wells) in an effort to minimize installation loads on the well casing. The trees and manifold were designed to accommodate a gas/condensate production rate of 60 mmcf/d per well. The initial development tied back two wells to the manifold, with the expansion capacity for 1-2 more new-drilled subsea completions.
The Sea Star was the first 10,000 psi extension of FMC's 3"x2" and 4"x2" 5,000 psi flexible pipe lay-away technology and guideline trees used in the Americas. Sea Star was also the first use of the "clustered" manifold subsea architecture and the ROV "flying lead" umbilical connection in the Gulf of Mexico, in 1995. Sea Star also established the dual tubing string completion/workover riser as the economic standard for completing and working over subsea wells in less than 3,000 ft (900 m) water depths.