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Mosquera, Alfonso1, Héctor J. Villar2, Guillermo A . Laffitte3 
(1) Tecpetrol S.A, Buenos Aires, Argentina 
(2) FCEN-UBA, Buenos Aires, Argentina 
(3) M&P system, Buenos Aires, Argentina

ABSTRACT: Oil Play in the Pre-Cuyo “Basement” of the Huincul High, Los Bastos Block, Southern Neuquen Basin, Argentina

The Huincul High strike-slip fault system is an outstanding geological feature in the southern portion of the Neuquen basin, the most prolific hydrocarbon basin of Argentina (EUR: 9700 MMBOE). To date, a EUR of 1500 MMBOE of hydrocarbon has been discovered in the Huincul High, mostly in clastic reservoirs of Middle to Upper Jurassic age (Tordillo, Lotena, and Lajas Fms.). Traps are anticlines associated with inverted hemigraben faults, having a strong stratigraphic overprint given by growth strata architecture (Centenario field: 200 MMBOE. and Sierra Barrosa - Aguada Toledo Fields: 210 MMBOE.). Most of the oils accumulations are genetically related to the marine marly shales of Vaca Muerta Fm (Upper Jurassic) while most of the gas pools would have been sourced from the marls and shales of Los Molles Fm. 
In Los Bastos Block, Los Molles lower section is as an organic rich (TOC: 1.4% - 3.5%) type II to II/III source rock with moderate to high oil generation potential and is currently in the peak oil to the late oil/wet gas generation phases (remnant IH: 100-150mg/g). Despite its good source quality and thermal maturity, no large oil fields have been discovered to date in the basin. 
However, recent deep exploration drilling, led to the assessment of minor Los Molles sourced oil accumulations in altered and naturally fractured volcaniclastic rocks of the Pre-Cuyo Gr. (Late Triassic-Early Jurassic). Yet-to-find larger oil fields may become a frontier exploration target in basement anticlines, provided good quality reservoirs are encountered.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.