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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Wilcox Depositional Systems: Shelf to Deep Basin
By
ChevronTexaco
New Orleans, Louisiana
Houston, Texas
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 (Alaminos Canyon OCS area) 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 from the Lower
Cretaceous shelf edge, relatively dense shallow
subsurface well control allows
documentation of fluvial, deltaic
and open
shelf depositional systems. Downdip from
the Lower Cretaceous shelf edge the Wilcox comprises delta front,
open shelf, estuarine and widespread prodelta depositional facies.
Relatively sparse well control shows a mostly sand poor section 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 Perdido Fold Belt (PFB) in the deepwater Gulf of Mexico.
Recently released drilling data sheds new light on play concepts and hydrocarbon potential of the PFB. Located in the southern Alaminos Canyon OCS area and extending into Mexican waters, the PFB consists of a series of large, northeast-southwest trending, salt-cored box folds containing Middle Jurassic to Holocene clastic and carbonate sequences. Based on regional
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correlations and seismic facies analysis, the initial exploratory targets
consisted of fractured Mesozoic carbonates and Lower
Tertiary turbidites. Given the absence of local stratigraphic control,
the presence, distribution and quality of the reservoir
objectives were considered to be among the most significant risk
elements for the trend. A key result of the BAHA wells (AC 600 #1
and AC 557 #1) was documenting a thick (>4000 ft) progression
of Lower Tertiary sands and establishing the presence of extensive
Wilcox equivalent turbidite sands located greater than 250 miles
down dip from their fluvial and deltaic
equivalents. Sand character
and distribution interpreted from wireline logs and seismic
data demonstrate a systematic progression from regional basinfloor
fans to distal turbidite channel/levee systems.
Since the deep test at BAHA in 2001, six additional deep wildcats have been drilled in the Perdido Fold Belt, including announced discoveries at Trident (AC 903 #1) in 2001, Great White (AC 857) in 2002 and Tobago (AC 859) in 2004. Additional wildcat wells in the PFB include Tiger (AC 818) and Toledo (AC 951) in 2004, both with status not released, and Diamondback (AC 739, drilling).
Success in the PFB also promoted extension of the Wilcox trend an additional 200 miles to the east, in Walker Ridge. Wildcat discoveries in Walker Ridge include Cascade (WR 206) in 2002, Chinook (WR 425) and St. Malo (WR 678) in 2003, and Jack (WR 759) in 2004. Additional wildcat wells in the eastern extension include Sardinia (KC 681), Hadrian (KC 919), Das Bump (WR 724) and Stones (WR 508, drilling).
With continued success and growing interest in the trend, the Perdido Fold Belt is likely to become an increasingly important exploration and development play in the deepwater Gulf of Mexico.
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