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Jack well comes up aces ‘Ultra-deepwater’ well yields 350’ oil pay, confirming hot lower tertiary play Ray Tyson Petroleum News Houston Correspondent
ChevronTexaco and partners Devon Energy and EnCana have uncovered more than 350 feet of net oil pay on their Jack prospect, the third significant discovery in the Gulf of Mexico’s emerging lower tertiary trend.
The Sept. 7 announcement came just weeks after Devon said the Jack exploration well on Walker Ridge Block 759 had been temporarily abandoned. But no information was provided on the well’s success or failure.
It also came on the heels of an announced dry hole at the closely watched Sardinia wildcat on Keathley Canyon block 681, more than 100 miles from lower tertiary discoveries St. Malo, Cascade and now Jack. However, the Sardinia well, designed to test the western limits of the massive play, did penetrate an encouraging 1,100 feet of porous sandstone, raising the possibility of a reservoir in the area.
Jack operator ChevronTexaco said an appraisal well would be drilled to determine the size of the discovery. The well was drilled to a total depth of about 29,000 feet in nearly 7,000 feet of water.
“Jack … is confirmation of further potential of our exploration acreage,” said Kathleen Arthur, vice president of ChevronTexaco’s Gulf of Mexico deepwater business unit.
Stephen Hadden, Devon’s senior vice president of exploration and production, said the Jack discovery “further demonstrates the potential for significant reserve additions and production in the years ahead.”
ChevronTexaco operates Jack with a 50 percent working interest. Devon and EnCana each hold a 25 percent working interest in the discovery. Lower tertiary trend of great interest Interest in the Gulf of Mexico’s lower tertiary trend reached a feverish pitch last October with disclosure of the St. Malo discovery on Walker Ridge block 678. The exploration well turned up more than 450 feet of net pay, followed by an appraisal well that encountered more than 400 feet of pay.
The St. Malo appraisal was actually a re-entry and deepening of a dry hole drilled in 2001, which was drilled to a shallower objective. The appraisal was deepened about 2,000 feet to a total depth of 28,903 feet. The prospect is in roughly 7,000 feet of water.
Devon holds a 22.5 percent working interest in St. Malo. Unocal is the operator with a 28.75 percent working interest. Petrobras holds a 25 percent stake in the prospect, followed by ChevronTexaco with 12.5 percent, EnCana with 6.25 percent, ExxonMobil with 3.75 percent and Eni with 1.25 percent.
Jack is just over 20 miles southwest of St. Malo and, like Sardinia, was designed to help establish boundaries of the “ultra-deepwater” lower tertiary oil play.
But it was the 2002 Cascade discovery on Walker Ridge block 206, more than 30 miles northeast of St. Malo and over 50 miles northeast of Jack, which got the exploration ball rolling on the potential of the lower tertiary play. Cascade uncovered an “encouraging hydrocarbon bearing column,” according to operator BHP Billiton. The owners hope to drill an appraisal well at Cascade late this year or early next year, which could shed yet more light on the extent of the trend.
BHP’s 2003 Chinook discovery on Walker Ridge 468, also a geologically deep find, is about 19 miles south of Cascade The well exceeded a total depth of 27,650 feet and was said to have encountered a gross hydrocarbon column of 620 feet with 260 feet of net oil pay.
With mounting discoveries in the lower tertiary trend, owners of the various fields believe development in the area could begin as early as 2008. They continue to weigh their options, including the possible use of a floating production system and tankers to transport the oil to shore.
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