Analogía entre cuerpos de areniscas fluviales cretácicas de superficie y subsuelo. Cuenca del Golfo de San Jorge, Argentina.

SERGIO M. GEORGIEFF Y LUCIANO DI BENEDETTO

San Miguel de Tucumán

Jornada; Jornadas Geológica de la Fundación Miguel Lillo; 2006

Fundación Miguel Lillo

Sedimentological descriptions and fluvial architecture studies were performed in extensive and continuous Cretaceous fluvial outcrops from Ballena Hill (Golfo de San Jorge Basin, Santa Cruz, Argentina). These works have allowed to reconstruct the architecture and tectonic evolution of an hydrocarbon-bearing fluvial sandstones in a closed oil field. Ballena Hill is an almost symmetrical anticline with 5 km long, 1-2 km wide and an altitude of 550 m.a.s.l. The west side of anticline is faulted by a reverse high angle fault. Cretaceous fluvial rocks (Aptian-Albian, an ignimbrite was dated in 94±0,7 Ma) belonging to Bajo Barreal Formation (Chubut Group) crop out in both side of anticline. The architecture of channel belt (thickness, width, geometry, paleocurrent directions and spatial distribution) was compared with well data of Cañadón Vasco oil field, in order to reconstruct the channel belts in subsurface. The correlation between outcrops and subsurface deposits were also supported with 2D seismic lines. The interpretation from well and seismic data indicates that the main west fault is an ancient normal fault, which generated the sedimentary space and also controlled the drainage, and the distribution of channel belts. Well images (microresistive-type) were analysed to determine the thickness of trough cross stratification and calculate the width of channel belts throughout the equation of Bridge and Tye (2000).Finally, following these criteria the well to well channel belts correlation, were realized for Castillo and Bajo Barreal Formations.