PEEL, FRANK, BHP Petroleum Houston TX; and STEVE MATTHEWS, BP Exploration Houston TX

Abstract: Structural Styles Of Traps In Deepwater Fold/thrust Belts Of The Northern Gulf Of Mexico

The mid to lower slope of the Northern Gulf of Mexico contains several distinct fold/thrust belts which have recently become the focus of intense petroleum exploration activity. Well data and 3D seismic data are now becoming available to constrain the interpretation of the age, structural style and mechanisms of generation of these large and potentially prospective features.

Each of the fold belts is thin-skinned, created by gravity sliding/spreading of the continental margin sequence. Each belt has a distinct structural style which depends on several key factors: the nature of the basal decollement (thin or thick salt vs. overpressured shale); the thickness of the sedimentary section being folded, the amount of contraction, the duration of the folding episode, and the amount of salt diapirism/withdrawal.

Palinspastic restoration of individual structures reveals that in some cases the style of structure development progressively changed as the sedimentary section accumulated. Early structural styles consistent with a thin sedimentary section are overprinted by later styles consistent with the thicker section. In some cases this results in the amalgamation of several early short-wavelength folds in to one later structure. In other cases a relatively simple early fold is later cut by kink bands or thrust faults on one or both flanks.All these factors may result in complication of an apparently simple structure which must be considered when their potential is evaluated.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England