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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 12 (1962), Pages 63-87

The Potential Down-Dip Limits of Production from the Oligogene and Miocene of Southeastern Louisiana

The New Orleans Geological Society Study Group (*), Donald I. Andrews, H. J. Ackerman, Jr., Ray Bane, Leo R. Bader, A. T. Green, Jr., Gabriel Dengo, Karl H. Pilati, James P. Raymond, Jr., John W. Skelly, Louis O. Vidrine, Raymond G. Voelker

ABSTRACT

Hydrocarbon accumulations in any petroleum province are largely associated with a particular lithic facies. The "favorable" facies in both sandstone and carbonate strata of Oligocene and Miocene age in southeastern Louisiana is generally the mid-dip, marine shelf facies. The location of potential productive areas down-dip from those now known may be inferred by analyzing this facies in areas of control and extrapolating it into undrilled areas.

The Oligocene is divided into the Frio and Anahuac groups, and the Miocene into lower, middle, and upper groups.

The Frio group consists of alternating sands and shales in the western portion of the area and limestone and shales in the east. Additional objective sands may be expected in a narrow belt immediately south of fields presently productive from the Frio, while much deeper sands may occur farther south.

The Anahuac, consisting of a calcareous basal portion and a sandy upper portion, is generally sandy in the west and calcareous in the east. Sands are expected to be present south of the existing productive area in the west, but favorable limestone facies can be expected in the east only on strike with the presently known occurrences of porous sections.

Thick shales and limestones make up the lower three-quarters of the Anahuac group; the upper quarter consists largely of sand. Sands are significant in quantity only in the western portion, and decrease south and east from Baton Rouge. Potentially productive areas are believed to exist immediately south of fields now producing from Anahuac sands. Only limestone and shale are present cast of Lake Pontchartrain; however, porous zones in reef and bank limestones are considered to be bona fide exploration objectives.

Transgressive shales at the top and base of the lower Miocene group bound a richly-productive section of alternating marine sands and shales. Two narrow belts of possible favorable sand development are postulated to the south of existing lower Miocene fields and downdip from two indicated depocenters.

The middle Miocene consists of transgressive shales overlain by a generally regressive marine sand and shale section of great productivity. Four depocenters are shown on the sand-percentage map; sand content generally decreases only in a southerly direction. An extensive, highly prospective area of well-developed sands is postulated south of current production in Terrebonne and Lafourche Parishes.

A single regressive sequence of marine sands and shales comprises the very productive upper Miocene group. Neither sand-percentage nor thickness vary significantly along strike but there is a rapid increase in thickness and a decrease in sand-percentage basinward. Limited deep well control precludes the prediction of a downdip limit of the productive sand facies at this time, but it does appear to extend south of existing production.


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