Tectonic Controls from Reservoir Architecture: The Cretaceous Pinda FM; Block 0, Angola

Peter Sixsmith¹, Bryan Bracken¹, Sunday Shepherd², Jessica M. Ali-Adeeb¹, Robert Scamman³, and Art Bradley^3
1ETC, Chevron, San Ramon, CA
²ETC, Chevron, Houston, TX
³Southern Africa Strategic Business Unit (SASBU), Chevron, Houston, TX

The Cretaceous Pinda Formation, Block 0, offshore Angola was deposited as a mixed carbonate-clastic coastal system. We present a regional tectono-stratigraphic framework that has been constructed from detailed analysis of over 30,000 ft of core combined with well-log data from some 200+ wells, and block-wide 3D seismic data. The Albian Pinda Fm reaches thicknesses of over 3000’ and contains a series of regressive-to-transgressive mixed lithology wedges that record long-term coastal retreat. Each wedge comprises marine, marginal-marine and fluvial depositional environments, the youngest of which is capped regionally by shelf limestone. The entire Albian section was deposited contemporaneously with active salt movement in the underlying Aptian Loeme evaporite deposits. Large growth faults developed that sole in the Loeme salt producing syn-depositional accommodation centers and this is reflected in massively expanded (4-5 times) Pinda-aged growth sections. Post-Pinda displacement along these growth faults created “rafted” blocks of Pinda separated by growth sections of younger sediments. Structural controls such as these make it challenging to characterize reservoir architectures within individual fields.

Recognizing the tectono-stratigraphic control and the distribution of sedimentary facies is proving crucial for further exploration and development of Block 0 and neighboring blocks. Despite the structural and diagenetic overprints, multiple oil columns within some fields, and stratigraphic complexity, the best reservoir rocks are consistently found in shoreface and fluvial depositional environments. Establishing a consistent regional sequence stratigraphic framework has improved predictions of where these high-quality reservoir facies occur in this complex multi-reservoir petroleum system and is helping to secure the Pinda as a commercial producer for decades to come.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery