|The Perdido spar will bring production in from three fields—Great White, Silvertip and Tobago—with a production design of 130,000 boe/day. Click to enlarge.|
The Shell-operated Perdido Regional Development Spar has arrived in the ultra-deep waters of the Gulf of Mexico (GOM) and is currently being secured to the seafloor in 7,816 ft (2,382 m) of water, a process that will take about one month. Perdido will be the deepest oil development in the world, the deepest drilling and production platform in the world and have the deepest subsea well in the world to date. Other partners in the joint venture are BP and Chevron.
Designed to deliver 100,000 barrels of oil and 200 million scf of gas (a total 130,000 barrels of oil equivalent, boe) per day, the Perdido Spar will bring in production from three fields: Great White, Silvertip and Tobago.
When complete, the Perdido spar will be 882 feet (269 m) from the keel to the top of the drilling derrick, with a hull diameter of 118 feet (36 m). The spar will be moored by nine chain and polyester rope mooring lines to the sea bed; 22 wells will be linked to the Perdido Spar above. Oil and gas will be pumped to the surface against the extreme pressure of the deepwater by 1,500 hp electric pumps.
|The Paleogene reservoir. Click to enlarge.|
These fields are located in 10 Outer Continental Shelf blocks in Alaminos Canyon, approximately 200 miles south of Freeport, TX. This development will provide the first Gulf of Mexico commercial production from a Paleogene reservoir.
The concept for the regional development includes a common processing hub—the Perdido Spar platform—that incorporates drilling capability and functionality to gather, process and export production.
The Perdido development will represent the first application two new key technologies to enable production from ultra deepwater:
Full host-scale subsea separating and boosting, which enables improved recovery by removing about 2,000 psi of back pressure from the wells.
Wet tree direct vertical access (DVA) wells from a spar. Using a DVA configuration allows a larger number of subsea completions to be accessed by the facility’s rig drilling. The wet tree DVA system will use a single high pressure drilling and completion riser suspended from the host to access 22 subsea trees directly below the host. The configuration will allow the use of a surface blow-out preventer (BOP) for the drilling, completion and later sidetracking of wells. By utilizing a single well slot for accessing the wells beneath the host, the size and cost of the host can be reduced without limiting well count flexibility.
|The spar was towed in horizontal position out to its location, then raised upright to float. Click to enlarge.|
The spar platform. Spar platforms—named for logs used as buoys in shipping and moored in place vertically—are among the largest offshore platforms in use. The spar does not extend all the way to the seafloor, but instead is tethered to the bottom by a series of cables and lines.
The Perdido spar, built by French oilfield services company Technip, consists of a large-diameter, single vertical cylinder supporting a deck with an open truss with a hard tank bottom. This large cylinder helps stabilize the platform in the water, and allows for movement to absorb the force of a potential hurricane.
The first spar platform in the GOM was installed in September of 1996, with a cylinder measuring 705 feet long and 72 feet in diameter. The platform operated in 1,930 feet of water. The current water depth record for a spar host is 5,610 feet for Dominion’s Devil’s Tower spar, located on Mississippi Canyon Block 773.
Video of uprighting of Perdido Spar