The Jurassic Petroleum System of the Sub-Andean Basins - Paleogeography and Geochemistry of the Organic Rich Sequences

Craig Schiefelbein¹ and Carlos Urien^2
1GSI, Shenandoah, TX
²Urien & Associates, Buenos Aires, Argentina

The SubAndean basins of South America are among the most prolific oil-producing areas of the world with production from formations ranging in age from Devonian to Tertiary. Depositional centers containing organic-rich source intervals concentrated in sedimentary facies ranging in age from Devonian to Neogene were developed along the Andes piedmont and represent a conspicuous paleogeography governed by tectonic episodes.

In order to accurately predict volumes of hydrocarbons expected in this region the petroleum system concept must be applied, necessitating a thorough understanding of all key ingredients including source, reservoir, and seal rock, as well as timing and efficiency of generation, migration and accumulation. A fundamental element to this approach is the integration of oil geochemistry within a meaningful geologic framework. This is as important as understanding the regional stratigraphic relationships, regional structural fabric and evolution of structural elements. Since crude oils are compositional derivatives of their source, identification of genetically related crude oil families and mapping their aerial and stratigraphic distribution provides important information related to source depositional environment, lithofacies and age. In this manner oils derived from Jurassic source rocks can be confidently distinguished from oils that originated from Paleozoic and/or Cretaceous source rocks.

This paper demonstrates how a multivariate statistical comparison of oil data representing all major Sub-Andean basins can be used to identify important Jurassic source rocks such as those occurring in the Neuquen Basin (Los Molles, Vaca Muerta) of Argentina and the Marañon and Ucayali Basins (Pucara) of Peru.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas