ABSTRACT: Global Cyclostratigraphic Analysis of the Indo-African Rift Basin Fill

PERLMUTTER, M. A., P. BRENNAN, and S. HOOK, Texaco EPTD, Houston, TX, and D. PASTA and K. DEMPSTER, Texaco FED, Bellaire, TX

Global Cyclostratigraphy, a model that forecasts stratigraphy by integrating long-term, tectonic basin evolution and short-term changes in sediment yield caused by Milankovitch-induced climate changes, was used to evaluate the likely distribution and potential of reservoir, seal, and source rocks in the rift basins associated with the breakup of East and West Gondwana. A regional evaluation was made for the time interval between the Late Triassic (230 Ma) to the mid-Cretaceous (100 Ma). Regional gravity and seismic analyses suggest the presence of thick sediments, with a major gravity minimum interpreted as a paleo-rift basin. Working hypotheses included a Triassic and Early Jurassic interval of lacustrine deposition followed by Early to Middle Jurassic marine flooding. Evaluations fo used on forecasting the depositional characteristics of the basin as it evolved and deducing the intervals that were most likely to produce and preserve hydrocarbons. In lacustrine settings, highest reservoir potential is predicted to occur in delta and beach deposits delivered by axial river systems and in submarine fans that ran parallel to the major border fault through the deepest part of the lake basin. Transgressive strata are forecast to contain the coarsest sediments. Certain (not all) intervals will also have high potential in fault-side outwash plains and beaches. Overall, seal and source potential are considered high for lake environments in this region. In marine settings, highest reservoir potential is forecast for lower shelf shoreline deposits and submarine fans. These env ronments also have the highest seal potential.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)