--> Abstract: Petroleum Systems of the Sub-Andean Basins, by Carlos M. Urien and Craig F. Schiefelbein; #90039 (2005)

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Petroleum Systems of the Sub-Andean Basins

Carlos M. Urien1 and Craig F. Schiefelbein2
1 Urien & Associates, Buenos Aires, Argentina
2 Geochemical Solutions International, The Woodlands, TX

The foreland basins along the foothills of Sub-Andean Belt form a complex system of depositional troughs separated by transverse arches that share a similar geologic evolution but have a varied stratigraphic depositional history. The bulk of sedimentary fill is mainly Cretaceous and Cenozoic; however, Paleozoic sediments particularly south of the FitzCarrald Arch are important source and reservoir rocks.

This paper analyses the factors that exert the main geologic controls on the Sub-Andean Basins petroleum systems with respect to source rock deposition, petroleum migration, trapping and preservation.

Most sediments were deposited in a shelf or epicontinental environment, midway between the continental conditions on the shields and shield fringe and the marine platform, to deep water slope deposits in the foredeep area of the present Mobile Belt. Hence, sequences were deposited as clastic wedges that often have a dual sediment source: one, in the adjacent cratonic area and the other in the adjacent subduction related folded belt. Sub-Andean structures are controlled by an essentially undeformed, gently dipping platform or ramp that adjoins the shield areas to the east and a western faulted/folded deformed belt resulting from the tectonic events related to the origin of the Andes.

The habitat of oil in the Western South America Foreland Basins can be divided on the basis of crude oil chemistry into two petroleum mega-systems: Paleozoic and Cretaceous. The origin and distribution of these two families, which account for 99% of the oil found in the Sub-Andean basins, will be discussed in detail.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005