Wilcox Depositional Systems: Shelf to Deep Basin
Larry Zarra, David Meyer, Scott Neal, 2013. "Wilcox Depositional Systems: Shelf to Deep Basin", Shelf Margin Deltas and Linked Down Slope Petroleum Systems–Global Significance and Future Exploration Potential, Harry H. Roberts, Norman C. Rosen, Richard H. Fillon, John B. Anderson
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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 Late Paleocene and Early 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 is comprised of delta front, open shelf, estuarine, and widespread prodelta depositional facies. Relatively sparse well control shows the prodelta and shelf depositional systems are mostly sand poor. Downdip from this shelf and prodelta, the next Wilcox well penetrations are 250 miles farther in the basin, in southern Alaminos Canyon OCS area, deep-water Gulf of Mexico.
Recently released drilling data sheds new light on play concepts and hydrocarbon potential of the Perdido Fold Belt (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 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. Among the key results of the BAHA wells (AC 600 #1 and AC 557 #1), a thick (>4000 ft) progression of lower Tertiary (Oligocene to Paleocene) sands were encountered establishing the presence of extensive Wilcox 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 basin-floor fans to distal turbidite channel/levee systems. Since the initial test at BAHA in 1996, five additional deep wildcats have been drilled, including three at the Trident prospect (AC 903 #1 and #2, and AC 947 #1) which was announced as a discovery in 2001, and two at the Great White Prospect, (AC 857 #1 and AC 813 #1), which was announced as a discovery in 2002. 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 deep-water Gulf of Mexico.