--> ABSTRACT: Petroleum Systems in the Golfo San Jorge Basin, Argentina, by Eduardo G. Figari, Esteban Strelkov, Guillermo A. Laffitte, Maria S. Cid de la Paz, Sergio F. Courtade, Jorge Celaya, Andres Vottero, Pedro Lafourcade, Ramon Martinez, and Hector J. Villar; #90906(2001)

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Eduardo G. Figari1, Esteban Strelkov1, Guillermo A. Laffitte2, Maria S. Cid de la Paz1, Sergio F. Courtade1, Jorge Celaya1, Andres Vottero1, Pedro Lafourcade1, Ramon Martinez1, Hector J. Villar3

(1) REPSOL YPF, Madrid, Spain
(2) Consultant, N/A, Argentina
(3) CIRGEO, N/A, Argentina

ABSTRACT: Petroleum Systems in the Golfo San Jorge Basin, Argentina

The East-West trending Golfo San Jorge basin is the oldest and most prolific oil basin of Argentina. Located in the central part of Patagonia Terrane, it is an intracratonic extensional basin. During late Jurassic-early Cretaceous times, the extension related to the Gondwana break-up generated many isolated small half-graben basins, with a NW-SE structural trend. Later, a new extensional-transtensional stress field originated a WNW-ESE trending, and reduced extensional deformation continued until the Oligocene. The sedimentary record that reaches more than 8 km thick, overlays an igneous metamorphic prejurassic basement. Two petroleum systems are recognized: 1) The D-129 (Barremian-Aptian)-Bajo Barreal (!) accounts for the major oil generation. The lacustrine source rock shows TOC contents up to 3%, S2 pyrolysis peaks between 2-10 mg HC/g rock and HI values varying from 200 to 500 mg/g TOC; visual kerogen analysis indicates abundant amorphous material occasionally accompanied by Botryococcus-related algae. The oils are characteristic of predominant lacustrine algal contribution and show signatures of an anoxic fresh-water to brackish environment with carbonate influence. 2) The A.A. Bandera (Neocomian) -Bajo Barreal (!) is restricted to the west domain and includes only a small portion of the discovered reserves. Organic contents of the source rock are around 2% TOC or higher, with S2 yields of 10 mg HC/g rock and hydrogen indices ranging 400 mg/g TOC. Predominantly amorphous kerogen is associated with abundant Celyphus rallus algal remains (distal lacustrine setting, stratified water column). Some oil occurrences in the southwest show contribution from both source rocks.

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