ABSTRACT

In 1785, 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 16,000 meters (50,000 ft). In south Louisiana, the relationship can be seen from the Tuscaloosa (mid-Cretaceous) to the Upper Miocene. Northwest-southeast 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 preferentially found over the leading edge of high basement blocks, and major fields are often associated with these growth faults. Of the major fields in the study area, 78 per cent are found over basement grabens or 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 pre-salt 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.