The intrepid miners who invaded the Rocky Mountains southwest of Denver in the 1800s would have loved the hills and valleys of the Sigsbee Escarpment.

Deepwater heavyweight Kerr-McGee has appropriately named their latest "black gold" production facility after legendary gold town Gunnison, Colo. At more that 7,600 ft (2,318 m), the town of Gunnison sits about twice as high as the waters of Garden Banks 667/668/669 are deep, but today's modern miners have hit a bonanza nonetheless. With a capacity of 40,000 b/d of crude oil and 200 MMcf/d of natural gas, the Gunnison truss spar initially will support seven platform wells and three subsea tiebacks when it comes on stream. Target date for completion of installation and commissioning of the huge spar is Q-1, 2004. And just to show everyone they're serious about their deepwater ventures, they've got another named Red Hawk slated for Q-2, 2004.

Kerr-McGee's Gulf of Mexico deepwater leaseholdings number 478, making it number one among deepwater independents and number five overall. Presently, the company produces from 13 deepwater facilities with an additional three under development - Gunnison, Durango and Red Hawk.
Spars take lead

All this activity has spurred an impressive construction boom, particularly in deepwater spars. Starting in 1997 with Neptune, a classic spar design, the development cycle has been shortened considerably with experience. Whereas Neptune took more than 5 years to evaluate and almost 3 years to construct, the Boomvang and Nansen prospects were evaluated in about 12 months and 8 months respectively, with construction taking only 2 years. If Gunnison hits its mark, a short 30 months will have elapsed since project sanction, speaking to the value of an aggressive learning curve.

Gunnison, like its predecessors Boomvang and Nansen, is a truss spar. It is 98 ft (29 m) in diameter and 549 ft (167 m) long. It will support a 10,770-ton topsides consisting of four decks and will be moored in place with a chain-wire-chain arrangement anchored to nine piles driven in three clusters of three spaced 120° apart. Wells have been drilled and completed and are waiting final connection of top tension production risers. Finishing touches are being applied to the topsides module in Houma, La. with onsite installation planned for October/November 2003.

Third generation spar to follow

Designed for efficient, low cost construction, Red Hawk is a cell spar. It consists of a cluster of seven tubes - three of 560 ft (170 m) in length and four of 280 ft (84 m). Tubes are comprised of cells constructed by welding cylindrical "cans" together, each can 20 ft (6 m) in diameter and 10 ft (3 m) long. Red Hawk is slated for deployment in Garden Banks 877 in about 5,300 ft (1,616 m) of water, and is a joint development with Devon. When brought on line, Red Hawk will process up to 120 MMcf/d of natural gas with ultimate capacity 300 MMcf/d.

With eight discoveries in up to 8,000 ft (2440 m) of water waiting in the wings, Kerr-McGee has their work cut out for them. But they expect to get maximum mileage out of their technically evolving innovative spar designs as they continue their gold rush, offshore style.