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Jair R. de S. Soares Filho1, Aloísio P. Miranda2, Antonio C. A. Rocha3, Márcio Pereira3
(1) Petrobras Internacional S.A. - BRASPETRO, Rio de Janeiro, Brazil
(2) Petrobras Internacional S.A. - BRASPETRO
(3) Petrobras Bolivia S.A

Abstract: Gas Exploration in Southern Bolivia - The Discovery of San Alberto and San Antonio Fields

The integration of Satellite Images, Surface Geology, Geochemistry and Seismic data led Petrobras Bolivia and partners to discover two giant gas fields in the Southern Bolivian Sub-Andean Zone.

The dominant structural style is referred to N-S trending folds and related thrust faults created by thin skin tectonics. Highly fractured devonian Huamampampa sandstones are the main target for hydrocarbon exploration, sourced by the devonian Los Monos shales. Devonian to Recent sediments outcrop in the area. Geological fieldwork helped in the definition of the structural styles and in the balancing of seismic data.

Since shallow and deep structural axis are not coincident, due to the occurrence of distinct detachment levels, a proper subsurface imaging of the deep exploratory targets becomes critical for a successful exploration campaign.

2D seismic data, traditionally with poor quality in these mountain front areas, were largely improved with the use of non-conventional acquisition geometry and pre-stack depth migration (PSDM). Conventional and PSDM seismic data were used as input for modern computer based structural balancing analysis, together with surface geology and well data. The combination of these exploration tools led to the definition of structurally more reliable prospects for the deep devonian targets.

As a result of this exploratory effort, the San Alberto Gas Field - a deeper pool of the former YPFB oil field - with reserves in excess of 5.3 TCF and the San Antonio Gas Field - with reserves in excess of 3.4 TCF were discovered.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana