The Captain field, UK North Sea Block 13/22A, includes one of the largest subsea templates installed in the North Sea, according to the joint venture that engineered and supplied the system.
The template manifold serves as a drilling template for 18 wells and as a pipe manifold for production, water injection, and future polymer injection.
Texaco North Sea UK Co., 85%, operates the field, and Korea Captain Co. Ltd., 15%, holds the remaining working interest in the field, which is in about 150 m of water (Fig. 1).
A joint venture between Cameron, a division of Cooper Cameron Corp., and Halliburton Subsea, a division of Halliburton Co., provided systems engineering and project management along with equipment and installation services for the expansion.
They received a contract for the project in March 1999, with template manifold installation in August 2000 and first oil in December 2000.
Two-phase development
Texaco developed the Captain field in two phases. The first phase came on stream in March 1997 and has a wellhead protector platform and a floating production, storage, and offloading vessel (FPSO), moored 1.5 km from the platform.
The FPSO has crude processing and water-injection facilities and offloads crude to shuttle tankers.
The Captain expansion includes a subsea production system and a new bridge-linked platform connected to the existing platform. The subsea system has the 18 slot, 740-tonne template manifold installed about 3.5 km from the platforms. Manifold dimensions are length, 213 ft; width, 59 ft; and height, 29 ft.
Pipelines between the bridge-linked platform and the template manifold include a 16-in. high GOR production line, 16-in. low GOR production line, 12-in. test line, 12-in. power water line, 12-in. water-injection line, and two 3-in. lines-one for service and the other for future polymer injection.
The template manifold incorporates 33 sets of flowline hubs,18 sets of guide posts, and 40 block gate valve assemblies, each with up to 4 gate valves. Three ball valves and one choke also are permanently mounted on the template.
Subsea wellheads, trees
The subsea wellheads on the template are Cameron single trip, 183/4-in. wellheads, rated for a 10,000-psi working pressure. Each wellhead assembly includes a 30-in. conductor housing, 183/4-in. wellhead housing, 113/4-in. casing hangers, and weight-set seal assemblies.
The horizontal trees (Cameron SpoolTrees), installed on the wellheads, have a 6,170-psi working pressure and can be simply converted from production to water injection, according to Cameron.
The company also says features on the trees not required for a specific application are blanked off, and injection trees are configured for future inclusion of a diver-installed polymer injection package.
A Cameron CAMTROL, electro-hydraulic system controls the subsea installation. The system is stand-alone and linked to the Captain A platform distributed control system (DCS). The transmitted multiplexed signals control the subsea installation through tree-mounted subsea control modules (SCMs) and a template manifold-mounted subsea monitoring module (SMM).
Graphic well-screen displays at the master control unit, in an air-conditioned, purged control room on the platform, show data gathered and monitored by the SCMs and SMM.
The subsea system receives chemical injection fluids continually with the flow to each individual supply line in the umbilical metered and adjusted from the topside chemical injection package, according to Cameron.
