Carlos Daniel Arregui¹

(1) Perez Companc S.A, Neuquén, Argentina

ABSTRACT: Basement Inherited Hydrocarbon Traps In The Neuquén Basin, Argentina

The Neuquen Basin is located in the west of Argentina. It is filled with more than 7000 m of Jurassic and Cretaceous sediments. Two cratonic margins are the northeast and southeast boundaries meanwhile a Volcanic Arc is considered it's western margin. The purpose of this paper is to demonstrate the influence of basement structural patterns in the generation of hydrocarbon traps using examples from five hydrocarbon accumulations. The subsidence began in Upper Triassic - Lower Jurassic times with a rift stage that created isolated depocenters arranged in a basement inherited fabric. During the thermal subsidence period three sedimentary cycles limited by tectonic reactivations are recognized. The Lower - Upper Jurassic cycle ends with a tectonic reactivation that generated oblique movements of the ancient faults producing different inversion degrees according to the orientation of the main stress. The Upper Jurassic-Lower Cretaceus and Upper Cretaceous-Lower Tertiary cycles are limited by structural reactivations that kept the regional pattern generated during Upper Jurassic tectonic event. The author proposes a classification as Type I and Type II structural traps according to the relationships between structural inversion and area of hydrocarbon concentration. Type I are the accumulations located in the footwall areas of basement inherited faults (Puesto Hernandez, Catriel Oeste, Entre Lomas) affected by a mild inversion that didn't change the polarity of the faults. Type II are the accumulations located in the hangingwall of strongly inverted basement inherited faults (Medanito, Rio Neuquen). Consequentely, the reconstruction of basement patterns is essencial for understanding the hydrocarbons accumulations genesis.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado