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Abstract: Cusiana Trend Exploration, Llanos Foothills, Colombia--The Opening of a New Hydrocarbon Province

A. B. Hayward, F. T. Addison, J. O'Leary, C. Espinosa

The discovery of the Cusiana field in 1992 followed 30 years of exploration in the Llanos fold and thrust belt of Colombia. Early exploration activity focused on large surface anticlines that were all fresh water flushed--a consequence of along strike exposure of the reservoir rocks.

The potential for deeper, subthrust, trapping geometries was recognized in the early 1970s however, exploration at the time was hindered by very poor quality seismic data and significant drilling difficulties. The 1980s exploration effort was characterized by continued poor quality seismic data and drilling difficulties combined with a geological perception that there was no effective reservoir and the majority of the structures post dated the major period of hydrocarbon generation and migration.

The Cusiana discovery with a gross hydrocarbon column in excess of 1500^prime reservoired within the Mirador (Eocene), Barco (Palaeocene) and Guadalupe (Upper Cretaceous) Formations in a large thrust anticline demonstrated the presence of a working hydrocarbon system. Subsequent exploration of the trend to the north has resulted in the discovery of four further giant oil and gas fields, Cupiagua (500 MMBBLS, 1-2 tcf) and the Florena/Pauto/Volcanera complex with estimated reserves of 1 billion barrels and 10 tcf.

Key to this success has been the seismic imaging of the trapping geometries resulting from a significant improvement in the quality of the seismic data--a consequence of improvements in both acquisition and processing technology, combined with a recognition that pure quartz arenites retain reservoir quality at significant depths of burial--and that despite original depths of burial of greater than 18,000 ft, reservoir quality was not a major risk for further exploration success.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela