ABSTRACT: Microbasin Analysis of South Louisiana: An Exploration Model, or: Hutton and Lyell Were Wrong!

ADAMS, RICHARD L.

In 1875, James Hutton proclaimed "the present is the key to the past!" Now our understanding of microbasin tectonics indicate that we should be saying, "the past is the key to the present!" Basement tectonics have a significant effect on later sedimentation patterns, even when the intervening sediment thickness is on the order of 50,000 feet. In South Louisiana, NW-SE basement transforms offset paleobathymetry trends, sediment isopachs, structural trends, and production.

Gravity and magnetic mapping allow the preparation of a basement pseudo-structure map which is used to put the South Louisiana Basin into a microbasin context for predictive exploration.

Basement horsts, grabens and counter-rotated half-grabens influence the location of major growth fault regimes and production trends. Growth faults are found over the leading edge of basement high blocks; and major fields are often associated with these growth faults. Of the major fields in the study area, 78% are found over or near the immediate edge of the grabens.

Salt domes, stocks, pillows, sills, and tongues all have their origin in the Jurassic Louann salt at depth. The location of these salt features, as well as the original salt thickness are directly linked to the presalt structure.

These basement grabens also form the "kitchens" for hydrocarbon maturation. Migration takes place by pulsed expulsion up major growth faults to charge reservoirs near or above the top of abnormal pressure.

By combining these data into a three dimensional framework a comprehensive exploration plan can be implemented, even for a mature province such as South Louisiana.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana