Published 1995 as part of Memoir 62
Copyright © 1995 The American Association of Petroleum Geologists.  All Rights Reserved.

Most of the hydrocarbon reserves in the Cuyo basin are contained in 15 oil fields that are mainly structurally controlled. They include several pools in the 40 million m³ range. Tectonic analysis based on seismic data tied to well control suggests that most closures relate to folds and reverse faults that are genetically associated with an earlier extensional fault system that developed during the early Mesozoic collapse of a late Paleozoic orogenic belt. Reconstruction of the source rock (Middle Triassic Cacheuta Formation) and reservoir paleogeography (Triassic-Tertiary Potrerillos, Río Blanco, Barrancas, and Papagayos formations) indicates that synsedimentary extension and differential subsidence were key factors that induced an irregular distribution of organic-rich strata and porosity development.

Cenozoic contraction linked to Andean orogenesis inverted the Triassic half-grabens and created structural closures. This resulted in local reservoir enhancement and access to effective charge after late Cenozoic regional migration. Prospective closures consist of elongate, irregularly spaced to en echelon anticlines and plunging noses. Axial surfaces display eastward or westward vergence, and shallow folds are replaced at depth by faulted structures (e.g., Tupungato, Barrancas, La Ventana, and Río Tunuyán fields).

The roots of the structural highs involve stratigraphic depocenters and high-angle faults that show normal separation at depth and reverse separation at intermediate levels (e.g., Vizcacheras field). The amount of inversion decreases from west to east, and in the most deformed areas, the cores of the folds were penetrated by faulting and popped up structures shaped as bivergent thrust wedges bounded by master faults and converging back-thrusts.