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

Abstract

ABSTRACT In 1785, James Hutton proclaimed present is key to past! Now our understanding of microbasin tectonics indicate that we should be saying, the past is key to present! Basement tectonics have a significant effect on later sedimentation patterns, even when intervening sediment thickness is on order of 16,000 meters (50,000 ft). In south Louisiana, relationship can be seen from Tuscaloosa (mid-Cretaceous) to Upper Miocene. Northwest-southeast basement transforms offset paleobathymetry trends, sediment isopachs, structural trends, and production. Gravity and magnetic mapping allow preparation of a basement pseudo-structure map which is used to put South Louisiana Basin into a microbasin context for predictive exploration. Basement horsts, grabens, and counter-rotated half-grabens influence location of major growth fault regimes and production trends. Growth faults are preferentially found over leading edge of high basement blocks, and major fields are often associated with these growth faults. Of major fields in study area, 78 per cent are found over basement grabens or immediate edge of grabens. Salt domes, stocks, pillows, sills, and tongues all have their origin in Jurassic Louann salt at depth. The location of these salt features, as well as original salt thickness, are directly linked to pre-salt structure. These basement grabens also form kitchens for hydrocarbon maturation. Migration takes place by pulsed expulsion up major growth faults to charge reservoirs near or above 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.