VERGES, JAUME¹, MAURA SANS³, ERNESTO CRISTALLINI², VERONICA PEREZ⁴, GUILLERMO JALFIN⁵, and MARIANO MARZO^3
1Institut Jaume Almera, CSIC, Barcelona, Spain
²Univ. Buenos Aires, Argentina
³Univ. Barcelona, Spain
⁴YPF, Buenos Aires, Argentina
⁵Maxus, Dallas, Texas

Abstract: Horseshoe Geometry of the San Jorge Basin Oil Fields: A Tectonic Framework

The San Jorge basin is an E-W trending intracontinental Mesozoic basin at the southern end of Argentina where the San Jorge Gulf mimics the geometry of the basin depocenter. The western domain of the basin has been inverted after rifting during Andean shortening. Several important oil fields follow both the northern and southern margins of the basin as well as the gently inverted anticlines displaying a horseshoe arrangement.

Reservoirs are middle Cretaceous fluvial deposits linked to post-rift normal faults with moderate displacements. Balanced cross-sections based on 3D seismic surveys permitted to calculate extension of ~6% in lower Cretaceous and 2% in middle Cretaceous levels in the southern domain. These amounts decrease to 3% in lower Cretaceous levels in the western domain. Shortening related to anticlines in La Faja Plegada is <10%.

Several of the major oil fields coincide with a regional slope-break at basement level observed in the western and southern domains of the basin. A Tertiary age for this break is inferred because of its post-rift development and abruptness.

The comprehension of this basin can give important clues for oil exploration towards the East within the offshore of Argentina.

Our study forms part of the PATH (Patagonian Architectural Transects for Hydrocarbon) project, funded by YPF S.A.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas