The Perdido Fold Belt, Northwestern Deep Gulf of Mexico, Part 2: Seismic Stratigraphy and Petroleum Systems

Abstract

Analysis of 12,000 km of two-dimensional multifold seismic data shows a thick succession of Mesozoic and Cenozoic deep-water strata in the Perdido fold belt, northwestern deep Gulf of Mexico. These strata differ in seismic facies, areal distribution, and reservoir/petroleum potential. Mesozoic strata are interpreted as dominantly fine-grained carbonates and show minor thickness changes. Cenozoic strata are largely mud-dominated siliciclastic turbidite deposits and vary considerably in thickness across the fold belt. These changes reflect the shifting position of Cenozoic marginal-marine depocenters. Mesozoic reservoir potential consists of fractured Upper Jurassic and Cretaceous deep-water carbonates. Cenozoic reservoir potential consists of siliciclastic deep-water turbidites. Portions of the Paleocene to lower Eocene strata are sand-prone and are the downdip equivalents of the lower and upper Wilcox shallow-marine depocenters. These strata are all incorporated within the folds. Lower to middle Oligocene strata coincide with the main growth phase of the fold belt. Potentially sand-prone middle Oligocene to lower Miocene strata are the downdip equivalents of the Vicksburg (early Oligocene), Frio (Oligocene), and Oakville (early Miocene) shallow-water depocenters. These strata form potential stratigraphic traps against the folds. Mesozoic source potential was modeled assuming Oxfordian, Tithonian, Barremian, and Turonian source beds. One-dimensional thermal maturation modeling showed these sources reached peak oil generation between 51 and 39 Ma, 39 and 8 Ma, 32 and 2 Ma, and 26 and 8 Ma, respectively. Cenozoic source potential was modeled using an Eocene source. Modeling showed this source reached only early oil generation in the basinward half of the fold belt. Thermal maturation was reached by source beds at different times in different locations due to changes in burial depth, amount of structural uplift, and underlying thickness of autochthonous salt. All of these factors indicate that seal and reservoir carry significant risk, but that the potential exists for large petroleum accumulations.