Abstract: Petroleum Systems Characterization and Ages in the Neuquen Basin (Triassic-to-Tertiary), West-Central Andes, Argentina

Leonardo Legarreta, Carlos A. Gulisano, Ismael Orchuela, Salvador A. Minnti

The Neuquen Basin, implanted on the western margin of the South American Plate evolved from Late Triassic-Early Jurassic as a set of isolated troughs, some of them connected to the "Pacific Ocean," to an intra-arc to back-arc marine setting in Early-Late Jurassic. At the present day, a 7-km-thick succession of clastics, carbonates, evaporites, and volcanic rocks is preserved in between the eastern side of the Andean folded belt and the South American hinterland, affected by gentle deformation. On the southeastern margin of the basin occurs a relatively complex structural trend, as a result of the inversion tectonics related to an E-W regional strike-slip fault.

Five source-rock intervals are documented, the oldest consists of dark shales accumulated in a lacustrine environment (L. Triassic-E. Jurassic) and the others contain Type I and II organic matter as a consequence of anoxic conditions associated with marine flooding events that took place during the Jurassic and Early Cretaceous.

The presence of numerous reservoir levels (clastics, carbonates, and also sills) and many regional and local seal intervals (shales and evaporites) within the sedimentary pile, combined with a diverse structural style, allowed the oil and gas trapping. Hydrocarbons were generated in various kitchens working at different times, as result of the subsidence regime and geothermal gradient that diversely affected different regions of the Neuquen Basin.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela