Eastern Section Meeting

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Interpretation of the Paleogene Strata in Southeastern Louisiana: Investigating the Potential for Deep Reservoirs

Abstract

As part of a structural and stratigraphic framework for Gulf Coast petroleum assessments, the U.S. Geological Survey has recently done detailed interpretation of Paleogene strata in southeastern Louisiana from the state border with Mississippi in north-central East Feliciana Parish to Louisiana state waters south of Terrebonne Parish. The resulting structural and stratigraphic framework is based on regional 2D seismic surveys correlated with deep geophysical logs and associated biostratigraphic data. These interpretations attempt to bridge the data gap between the well-understood stratigraphic and structural settings of the stable shelf and the poorly understood settings of the continental-slope south of the Paleocene shelf edge where well penetrations deeper than Miocene are sparse.

Formation top interpretations were focused on the top of Oligocene, Vicksburg Group, Jackson Group, Sparta Sand (Claiborne Group), Upper and Lower Wilcox Group, Midway Group, and top of Upper Cretaceous. The seismic interpretation shows that Oligocene strata thicken down-dip of the stable shelf. There is also significant thickening of Wilcox Group deposits observed down-dip of the expanded fault zone. Based on the variable amplitudes and discontinuous, mounded character of the seismic reflectors, a portion of these Oligocene and Wilcox Group deposits may be sandstones of reservoir quality. Potential reservoirs are likely to be found within anticlinal fold structures and within fault terminated strata where up-dip closures might impede hydrocarbon migration. Preliminary interpretations have been made to identify reservoirs with similar characteristics to those of recent offshore discoveries such as Blackbeard east and west located 20 miles south in South Timbalier.