Abstract: Using AVO to Reduce Risk in a Frontier Basin, Case Study: San Julian Basin, Offshore Argentina

Donna Venable, Derek Skolyes, John DeWildt, Joe Erickson

The analysis of reconnaissance AVO data was integrated with other geophysical and geochemical studies in an effort to reduce the risks associated with exploring in a frontier basin. The currently undrilled, San Julian basin is located adjacent to two other basins which are known to contain hydrocarbons. Geochemical modeling of the wells in the nearby San Jorge and Austral basins have shown that the source rocks have passed into the gas window. It has also been demonstrated that certain hydrocarbon bearing rocks in the Austral basin exhibit AVO effects.

A 3,200 km grid of seismic data from the San Julian basin was processed to preserve relative amplitude information and to remove multiple energy. The AVO analysis were performed using robust statistical methods (Walden) to provide more reliable estimates of gradient and intercept than would be calculated by a traditional least-squares approach. These AVO attributes were combined in various manners to better highlight anomalies.

Gravity and magnetic data were used in an attempt to isolate AVO anomalies associated with shallow volcanic rocks. The remaining AVO anomalies appear to be in structurally high positions and are confined to a single depocenter within the basin. The existence and extent of this depocenter or sub-basin has been confirmed by gravity and magnetic modeling and the analysis of seismic data.

The AVO study helps to support the premise of the existence of hydrocarbon bearing source and reservoir rocks in this frontier basin.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994