Big Foot, one of the biggest tension-leg platforms (TLP) ever built in the deepwater Gulf of Mexico, is being moved to sheltered waters just weeks before it was to ramp up after subsea installation tendons were damaged, Chevron Corp. said Tuesday.
The Walker Ridge development, expected to hold more than 200 million boe, is considered one of the jewels in Chevron's deepwater program. Big Foot originally was to have started up last November, and Chevron then pushed the ramp up to the second quarter (see Daily GPI, April 13; Dec. 13, 2013).
The TLP, in 5,200 feet of water, is about 225 miles south of New Orleans with a design capacity of 25 MMcf/d of natural gas and 75,000 b/d of liquids.
The field was discovered nine years ago in Walker Ridge, which has become one of the hottest areas in the deepwater (see Daily GPI, Jan. 5, 2006). Chevron has been the operator since the start and holds a 60% stake with partners Statoil ASA (27.5%) and Marubeni (12.5%).
According to Chevron, the steel tendons, which hold the TLP in place, were pre-installed in preparation for connecting to the 450-foot-tall TLP. Once in place, the steel tubes, between 24 inches and 32 inches in diameter, would tether the production platform to the seabed.
Over the past weekend, however, six of the 16 tendons lost buoyancy and sank. Chevron was using remote-controlled robot submarines because the water is too deep for divers.
No one was injured in the incident and there was no environmental damage, Chevron said. The production platform, designed to house up to 200 people, also wasn't damaged because it wasn't connected to any subsea wells or tendons at the time of the incident.
Damage to the tendons is being assessed. The startup date now is uncertain.
Capital costs for Big Foot had risen steadily to more than $5 billion from $4 billion, and they now are likely to be a lot higher, according to Tudor, Pickering, Holt & Co.
"At peak production, we would expect the field to generate around $1.3 billion of gross post-tax cash flow per year at $75/bbl Brent." Oil prices now are hovering around $60/bbl.