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NELSON, K. J., and CHEVRON International Limited Exploration Staff, Chevron International Limited (Bolivia), Santa Cruz, Bolivia

ABSTRACT: Exploration within the Sub-Andean Thrust Belt of Southern Bolivia

The Sub-Andean thrust belt of Southern Bolivia is a proven hydrocarbon province. Chevron began a regional study of the area in 1988 and chose the Caipipendi block due to its high potential for significant new oil reserves. A regional work program designed to acquire and integrate seismic data, geologic field data, geochemistry, and gravity data was used to generated structural models, evaluate regional risk components and to detail leads.

The structural style within the Caipipendi block is interpreted as being an in sequence, thin skinned thrust belt with eastward verging folds and thrust faults. Tight surface anticlines associated with a Middle Devonian detachment have been later folded by deeper fault bend folds associated with the Silurian detachment. While the tight surface folds are presently producing oil, the deeper broader structures associated with the Silurian detachment have not been tested. Seismic data, utilized for the first time in this part of the Sub-Andean thrust belt, integrated with balanced structural cross sections, is the key to evaluating this new play.

Geochemical analysis, including oil biomarker work, indicate that the oils are sourced from the Silurian-Devonian sequence. A generative oil system model formulated by integrating the geochemical analysis with maturation modeling indicates that the Devonian Los Monos formation is the primary oil source.

Anticipated reservoirs for the new play are Carboniferous and Devonian sandstones which are also productive elsewhere in the basin.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.