The closely watched Sardinia wildcat, designed to test the western reach of the vast lower tertiary trend in “ultra-deepwater” Gulf of Mexico, turned out to be a disappointment and blessing for operator Unocal and its partners.
Unocal formally declared the $37 million Sardinia exploration well a “dry hole” Aug. 31, after reaching a total depth of 27,575 feet, which included 6,345 feet of water column in remote Keathley Canyon. The effort simply did not yield commercial quantities of hydrocarbons, the company said.
However, the Sardinia well, which took just 60 days to reach its objective, encountered more than 1,100 feet of porous sandstones, an encouraging sign because of its thickness and the fact it contained some hydrocarbons.
“While the results of Sardinia are disappointing, we are encouraged by the thickness of the potential reservoir encountered in the lower tertiary in this rank wildcat,” said Mike Bell, who heads up Unocal’s exploration ventures in the U.S. Gulf.
Moreover, the fact a potential reservoir exists more than 100 miles from major lower tertiary discoveries to the east in Walker Ridge “is a positive development for Unocal’s deepwater program in the Gulf of Mexico,” Bell said.
Owners bidders at recent sale
And it was no coincidence that all four players in Sardinia — Unocal, Devon Energy, Spinnaker Exploration and Total — either together or individually scooped up available acreage relatively near the prospect in last month’s Western Gulf of Mexico Lease Sale 192.
It also was obvious that preliminary well results from Sardinia were held from the public until after the Aug. 18 sale, allowing the owners exclusive access to the information to help develop their bidding strategies going into the sale.
Sale 192 results compiled by the U.S. Minerals Management Service clearly show that that the lion’s share of the bidding activity in Keathley Canyon was confined to the southeast portion of the region, home of Sardinia and the promising lower tertiary trend.
In addition to the Sardinia owners, deepwater players ChevronTexaco, Shell, BP, ConocoPhillips, Petrobras, Anadarko Petroleum, Eni Petroleum, Kerr-McGee, Pioneer Natural Resources and EnCana also were active bidders in southeastern Keathley Canyon. Nearly all were involved in lower tertiary exploration prior to the lease sale.
The Sardinia well was plugged and abandoned while Unocal (40 percent) and partners Devon (35 percent), Spinnaker (12.5 percent) and Total (12.5 percent) continue to evaluate data collected from the Sardinia prospect, Unocal said.
Sardinia follows drilling of the Jack exploration well in Walker Ridge, another lower tertiary test. Although no wells results have been released, Jack also was abandoned pending review of the data.
At least some big reservoirs
So, while the jury remains out on the true extent of the lower tertiary trend in ultra-deepwater U.S. Gulf, there’s no question the play holds at least some big oil reservoirs. They include Cascade and more recently St. Malo, which turned up an impressive 450 feet of net oil pay in the discovery well and 400 feet of net in an appraisal well.
Unocal said it now plans to move the Discoverer Spirit drillship from Sardinia on Keathley Canyon block 681 to the Sequoia prospect on Mississippi Canyon block 941. Unocal operates Sequoia with a 20 percent interest.
Unocal said it expects to take a charge to expense in the 2004 third quarter of less than $1 million for the costs of the Sardinia well.
