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Márcio Rocha Mello1
(1) Cidade Universitaria, Rio de Janeiro (RJ), Brazil

Abstract: The oil and gas frontiers for exploration in South America

As a result of the giant oil discoveries in the Brazilian and Subandean sedimentary basins over the past few years, major oil companies have started to explore new petroleum systems in South America. The end of national oil monopolies has intensified interest in exploration, as oil companies recognize that these basins represent some of the best frontiers for the appropriation of large oil reserves. A detailed geochemical and biological marker investigation of he most important oil provinces in South American highlights the similarities and differences between the petroleum habitats of major Paleozoic and Mezosoic/Cenozoic sedimentary basins. The study included 200 oil samples from reservoirs ranging in age from Devonian to Miocene, and 100 selected source rocks of the same ages. This approach allowed correlation between the oils and source rocks, in order to determine the factors that control their composition and provenance (e.g. paleoenvironments of deposition and age the source rocks, thermal evolution, biodegradation stage and geographic distribution).

The results indicate that most of the hydrocarbons discovered to date were generated from source rocks deposited in seven main types of hypoxic-anoxic lacustrine to marine paleoenvironments, ranging in age from Frasnian to Miocene. These are: lacustrine freshwater, lacustrine brackish-saline water, marine siliciclastic, marine carbonate, marine anoxic with predominance of calcareous mudstone lithology, and marine deltaic with predominance of either siliciclastic or carbonate rocks.

Based on the oil types detected, the most promising frontiers for exploration are offshore Venezuela, targeting marine carbonate Upper Cretaceous oils, and offshore deep water Brazil, onshore Venezuela, and Colombia targeting marine deltaic oils.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana