GLOBAL CYCLOSTRATIGRAPHIC ANALYSIS OF THE SEYCHELLES SOUTHERN SHELF FOR POTENTIAL RESERVOIR, SEAL AND SOURCE ROCKS

As part of the assessment of the exploration potential of the Seychell es area, Global Cyclostratigraphy, a model that hindcasts stratigraphy . was used to evaluate the likely spatial and temporal occurrence of p otential reservoir, seal and source rocks for the time interval betwee n the Triassic (230 MYA) and Middle Jurassic (160 MYA). Gravity and se ismic analyses indicated the presence of thick sediments on the Southe rn Shelf. A major trend of a gravity minimum was interpreted as a pale o-rift basin. The initial working hypothesis for the sedimentary infil ling of the rift was based on the analysis of paleogeographic reconstr uctions, seismic lines, and well data. The synrift section was interpr eted to be composed of a Triassic to Jurassic interval of lacustrine d eposition followed by a Jurassic marine transgression. The Global Cycl ostratigraphic evaluation focused on hindcasting the depositional char acteristics of the basin as it evolved and deducing the intervals that were most likely to produce and preserve hydrocarbons. Analyses of th e Seychelles area indicated that the stratigraphic potential varied si gnificantly from the Late Triassic through the Middle Jurassic, with t he most reservoir-prone units being deposited at highstand or lowstand , transgression or regression depending on the time interval in questi on. In Middle Jurassic time, for example, marine lowstand deposits wer e assessed to have the most reservoir potential, while in Early Jurass ic time, transgressive systems were assessed to have the most potentia l. Seal and source potential were similarly ranked.