The Wilcox has long been recognized as an important petroleum resource, producing from deltaic, fluvial and shallow marine sandstone reservoirs since the 1930s. Recent drilling in the Perdido Fold Belt (PFB), Alaminos Canyon, Offshore Continental Shelf (OCS) area, Keathley Canyon and Walker Ridge has confirmed a new exploration play in the deep basin component of the Wilcox petroleum system, with significant discoveries in distal turbidite systems.

The Wilcox Group in the Gulf of Mexico Basin spans much of the Upper Paleocene and Lower Eocene. In outcrop the Wilcox is characterized by a variety of paralic and very shallow marine depositional settings, and is represented by interbedded sandstone and shale plus locally abundant lignite. Updip of the Lower Cretaceous shelf edge, relatively dense shallow subsurface well control allows documentation of fluvial and deltaic depositional systems. Downdip from the Lower Cretaceous shelf edge, the Wilcox consists of delta front, open shelf, estuarine and widespread prodelta depositional facies. Relatively sparse well control shows mostly sand-poor sections for the prodelta and shelf depositional systems. Downdip from the shelf and prodelta, the next Wilcox well penetrations are 250 miles farther in the basin, in the southern Alaminos Canyon OCS area referred to as the PFB in the deepwater Gulf of Mexico.

Recently released drilling and test data shed new light on play concepts and the hydrocarbon potential of the trend. To date the distribution and quality of the reservoir is considered the most significant risk element for the trend. Key results of the BAHA wells (AC 600 #1 and AC 557 #1) document a thick (>4000 ft) progression of Lower Tertiary deepwater facies and establish the presence of extensive Wilcox equivalent turbidite sands located more than 250 miles downdip from their fluvial and deltaic equivalents. Similar thick turbidites have also been discovered 200 miles to the east, in new exploration wells in this emerging trend. Sand character and distribution interpreted from wireline logs, core, paleo and seismic data indicate a systematic progression from lower slope to regionally extensive basin-floor fan systems to sediment-starved distal basin plain.

Since the deep test at BAHA in 2001, 20 additional deep wildcats have been drilled in the Lower Tertiary Trend, all encountering thick, low-permeability turbidite sands. Recognizing the uncertainty in deliverability from this new trend, Chevron, Statoil and Devon embarked on an extended well test at their Jack discovery. Leveraging technical work for the much shorter duration Tahiti well l test (2004), Chevron planned a more complex and extensive well test at Jack. This test exceeded expectations and delivered more than 6000 barrels a day from a portion of the overall Jack reservoir. Currently, Chevron and other operators are examining various development scenarios, including utilizing a floating production, storage and offloading (FPSO) system to develop 3–4 wells in a field to mitigate the risk of the reservoir deliverability. With continued exploration and appraisal success, the entire Wilcox trend has become an increasingly important exploration and development play in the deepwater Gulf of Mexico. This emerging trend has the potential of delivering 3–15 billion barrels of oil equivalent from many structures located throughout the deepwater turbidite Wilcox depositional basin, and individual prospects have a resource potential of 50–500 million barrels of oil equivalent.

This presentation is an update to one given at a Northsiders Luncheon on May 17, 2005, titled “The Wilcox—Outcrop to Deep Water,” by Larry Zarra, David Meyer and Scott Neal.

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