Design, Fabrication, and Integration Testing of the Garden Banks 388 Subsea Production Template
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INTRODUCTIONProject ProfileEnserch Exploration's Garden Banks 388 development has a production scheme based around a floating drilling and production facility and subsea drilling! production template. The Floating Production Facility (FPF) is a converted semisubmersible drilling rig that will drill and produce through a 24-well slot subsea template. This development is located in Block 388 of the Garden Banks area in the Gulf of Mexico approximately 200 miles southwest of New Orleans, Louisiana. The production system is beinginstalled in an area of known oil and gas reserves and will produce to a shallow water platform 54 miles away at Eugene Island 315.The FPF will be permanently moored above the template. The subsea template has been installed in 2190 feet of water and will produce through a 2,000 foot free-standing production riser system to the FPF. The produced fluids are partially separated on the FPF before oil and gas are pumped through the template to export gathering lines that are connected to the shallow water facility. The system designed through-put is 40,000 BOPD of oil and 120 MMSCFD of gas.Template SnapshotThe template's function is to provide a controlled drilling pattern for subsea wells and serve as a conduit to produce oil and gas to the FPF. The template has "slots" to accommodate 24 wells and provision to receive oil and/or gas production through two 12-inch pipelines from an adjacent field. The well slots on the template exterior rows can be either drilled and completed through the template structure or can tie in two 4-inch flowlines from satellite completions. The interior well slots can only be completed as template wells.The primary structure of the GB-388 template is an all steel welded space frame fabricated from wide flange, rolled tubular sections, and flat plate. The structure is 167 feet long, 86 feet wide, and 20 feet high over the area covered by the 24 well slots. The elevation rises to 30 feet at the riser base end of the template. The structure is secured to the sea floor by eight 42 inch diameter piles.A stiffened steel plate mudmat covers the base of the template, except the 24 well guides and the eight pile sleeves. The mudmat supported the 1,260 ton weight (lift weight) until the piles were driven. The template was leveled and locked into the piles by plastically deforming a section of each pile into premachined grooves in each of the 8 pile sleeves. The four piles in the wellbay area are 395 feet long and penetrate into the soil 350 feet. The four piles positioned around the base of the free-standing production riser are 305 feet long, with a penetration of 250 feet.The template structure is protected from corrosion by a high quality, two coat epoxy paint system backed up with Galvalum III type (aluminum alloy) cathodic protection anodes.The functional requirements for the GB-388 template include providing adequate space and structural support for drilling and completing up to 19 template wells.
