During the past decade, extremely positive results have been obtained by an Elf operated Group in Block 3, Offshore Angola. This block, located within the southern part of the Lower Congo basin, was awarded in 1980 and previous to that date, only one well had been drilled to test the Tertiary objectives. Since then, 41 exploration wells have been drilled resulting into 22 discoveries. Proven reserves exceed 1 billion bbl of recoverable oil; all reserves discovered to date are associated with the Pinda Carbonate Reservoir of Albian Age.
This successful exploration has occurred because of a step by step multi-disciplinary approach that incorporated Elf long experience in West Africa' particularly in relation to turtle-back structures associated with salt tectonics, detailed sedimentology, sequence stratigraphy, geochemistry and 3D seismic interpretations; these seismic interpretations are completed using an Elf powerful work station: SISMAGE. The results of the technical evaluation are: more accurate prospect delineation and a better reservoir character prediction.
Gravity sliding concept and modelisation clearly explain the paleogeography of the prolific albian reservoirs and the tectonic history of the Pinda structures resulting from "rafting" and halokynesis. 3D seismic has significantly improved the definition of trap geometry. Present efforts are focused on resolving imaging problems caused by tectonic complexity (dips, faults, collapses) and seismic velocity anomalies related with lithologic facies variations and/or diagenetic events.
AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France