ABSTRACT: Impact of high frequency sediment cycles on reservoir prediction

Although the concepts of sequence stratigraphy include sediment flux as an important variable, in practice sediment supply is commonly assumed to be mostly a function of base-level change. Sediment supply cycles forced by paleoclimatic cycles, and the phase relationship of the sedimentation cycles with sea-level-caused base-level changes, are not considered. However, variations in both the volume and type of sediment delivered to a basin over a climate cycle can be significant, with the greatest changes producing a maximum volume up to two orders of magnitude greater than the minimum and a yield that may shift from conglomerate to clay. Further, because the climatic succession of a climate cycle is dependent on paleogeography, the timing of maximum and minimum values of the sediment supply cycle relative to glacioeustatic sea level is dependent on location. Therefore, sediment supply cycles can affect how the distributions of potential reservoirs, seals, and source rocks are interpreted from seismic records and, therefore, affect the projection of geologic risk associated with exploration.

In this presentation, we demonstrate the influence of high-frequency climate change on sediment flux and the deposition of potential reservoir rock within a stratigraphic sequence by comparing the Miocene section of the Surma basin, Bangladesh, and the Plio-Pleistocene section of the Gulf of Mexico. In the Surma basin, reservoirs are most likely to occur in transgressive and highstand systems tracts, while reservoirs in the Gulf of Mexico are more likely in lowstand prograding complexes and fans.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia