Validation of Empirical Source-To-Sink Scaling Relationships in a Large Hydrocarbon-Rich Basin: Gulf of Mexico Cenozoic Deepwater Fan Systems

Abstract

Empirical relationships between deep-water siliciclastic fan systems and their linked drainage basins have been established for modern and Quaternary depositional systems and in a few ancient, small-scale basins. Twenty years of mapping the Gulf of Mexico (GOM) Basin and the North American drainage network facilitates a much more rigorous test of these scaling relationships in a large continental size system with multiple mountain source terrains, rivers, deltas, slopes, and abyssal plain fan systems formed over 60 my of geologic time. The large number of drill wells and high quality industry seismic data in this prolific hydrocarbon basin provide the necessary, independent validation of deep-water fan occurrence and extent. Analysis of over 40 deep-water fan and apron systems ranging in age from Paleocene to Pleistocene in the GOM reveals that submarine fan systems scale predictably with interpreted drainage basin size. All deep-water fan system lengths, as measured from shelf edge to mapped termination, fall in a range of 10 to 50% of the drainage basin length. Most are comparable to large (Mississippi-scale) systems though some smaller systems are included in the database (e.g. Oligocene Rio Bravo system). Submarine fan lengths mostly fall in the range of 50% to 200% of estimated river backwater lengths though there is more scatter in the data due to difficulties in measuring backwater lengths in ancient, subsurface strata. Other empirical relationships examined reveal important characteristics of source to sink systems like the GOM. Poor correlations between fan length and delta width (along depositional strike) and fan area and delta area suggest that it is the larger drainage basin network that is paramount in determining fan dimensions, not a delta nearest the basin entry point. Shelf edge storage and transport process are variables intervening between the delta and fan scaling relationships. However, point bars in river systems do scale with drainage basin size and thus we would expect such subsurface measurements to provide additional ways of predicting deep-water fan dimensions prior to drilling.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015