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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


AAPG Bulletin, V. 91, No. 2 (February 2007), P. 135-149.

Copyright copy2007. The American Association of Petroleum Geologists. All rights reserved.


Untested carbonate buildups in the Bermejo field, Ecuador: A potential new play type in the western Oriente Basin

Gwang H. Lee,1 John P. Castagna2

1Department of Environmental Exploration Engineering, Pukyong National University, Busan 608-737, South Korea; [email protected]
2Department of Geosciences, University of Houston, Houston, Texas 77204; [email protected]


We identified a previously unknown carbonate buildup in the Cretaceous M1 limestone in the Bermejo field, northwestern Oriente Basin of Ecuador. Thinner carbonate builduplike features are also seen in the deeper A limestone, which has produced small volumes of oil in the northern Bermejo field. The carbonate buildups can represent a significant new play type in the western Oriente Basin, where limestones have been known principally as a source rock. The M1 carbonate buildup, imaged as a lenslike event in three-dimensional seismic data, forms a circular feature in the isopach, amplitude, and dip maps. It is characterized by generally high but variable seismic amplitude, and its thicknesses (20 to gt 40 m; 66 to gt131 ft) exhibit a complicated pattern, suggesting weathering and/or localized carbonate growth. The dark and rough top surface and irregular edges of the M1 carbonate buildup, revealed by the dip map, probably suggest the formation of fracture-cavity-karst–type reservoirs. The Late Cretaceous convergence along the western Oriente Basin may have further fractured the carbonates in the area. The M1 carbonate buildup, assuming a porosity of 10%, can contain more than 4.0 times 107 bbl of liquid, which is particularly significant in the Bermejo field where production has been marginal.

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