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Quantitative Seismic Geomorphology of Pliocene and Miocene-age Fluviodeltaic Reservoirs in the Northern Gulf Of Mexico Shelf Province

Carla M. Sanchez

The University of Texas at Austin. Bureau of Economic Geology.

Austin, TX. USA.

[email protected]

Predictive relationships between reservoir quality and fluviodeltaic systems morphology offer the opportunity to reduce uncertainty in reservoir characterization for these complex systems. The study area encompasses 900 square kilometers of three-dimensional seismic and 170 well log suites in the Northern Gulf of Mexico Shelf Province.

Pliocene-age channel widths range from 80 to 140 meters. On the other hand, Miocene-age channel widths vary between 700 and 1,000 meters. These data show aspect ratios ranging from 15 to 130 for Miocene-age channels and from 1.5 to 8 for Pliocene-age channels. A cyclic pattern of low to high aspect ratios can be recognized in variability of this parameter through the Pliocene. Such cyclicity may be due to a variety of influences including base-level and climatic changes in the drainage basin. High frequency and large magnitude climatic changes could have hampered the ability of Pliocene-age channels to adjust their shape and pattern to sediment load type, resulting in an absence of relationships between channel sediment load type, sinuosity, and width to depth ratios.

It has been suggested that during Miocene times the United States Gulf Coast regional climate was warm and humid. Assuming these climatic conditions, for these Miocene-age fluvial systems, equations developed for rivers located in sub-humid settings have the strongest application to understanding Miocene discharge in the northern Gulf of Mexico. Paleodischarge estimates in the order of 105 cubic meters per second have been obtained for Miocene-age fluvio-deltaic systems in the study area using an empirical relationship for tropical and sub-humid climates.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid