--> ABSTRACT: Sparta Sandstones: Future Exploration Potential in South-Central Louisiana, by Rowdy C. Lemoine, Thomas F. Moslow, Roger Sassen, and Ray E. Ferrell; #91022 (1989)

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Sparta Sandstones: Future Exploration Potential in South-Central Louisiana

Rowdy C. Lemoine, Thomas F. Moslow, Roger Sassen, Ray E. Ferrell

The middle Eocene Sparta Formation is an important exploration objective within the prolific Eocene-Oligocene trend of south-central Louisiana. Cumulative production from 20 multiple-reservoir fields in the trend exceeds 269 million bbl of crude, 50 million bbl of condensate, and 1.5 billion ft3 of gas. Additional reservoirs include the lower Eocene Wilcox, upper Eocene Cockfield, and Oligocene Frio Formations. This trend, coincident with the location of the Lower Cretaceous carbonate shelf edge, represents a series of unstable progradational clastic shelf margins. Principal structural traps are rollover anticlines, associated with down-to-the-basin growth faults, and salt domes.

Recent Sparta production is associated with progradational barrier island complexes. Storm washover fan sandstones (22% porosity, 324 md permeability), tidal-inlet channel sandstones (20% porosity, 140 md permeability), and upper shoreface sandstones (19% porosity, 113 md permeability) represent the optimum-quality reservoir facies. Organic-rich basinal shales are source rocks for crude oil downdip from production where they are thermally mature. Lateral migration best explains emplacement of hydrocarbons in reservoirs.

Regional dip-oriented cross sections and structure maps define the Sparta shelf-margin trend. In addition, regional net sand, sand percent, isopach, and characteristic log-signature maps illustrate principal depositional axes and sediment dispersal trends, thus emphasizing areas with future hydrocarbon potential. Exploration models for Sparta sandstones in south-central Louisiana must account for shelf-margin depositional styles, abrupt facies changes, and reservoir heterogeneities.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.