Abstract: Impact of Reservoir Heterogeneity on Waterflood Performance: Examples from Albian/Cenomanian Reservoirs, Cabinda, Angola

FLAHERTY, G. M.; R. J. MINCK; F. DOMINGOS

The Albian Pinda and Cenomanian Vermelha Formations of Cabinda, Angola have produced 900 MMB of approximately 5000 MMBOOIP. Fifty percent of the total OOIP is under waterflood. Future expansion projects will target the remaining 2500 MMBOOIP with probable and possible waterflood reserves of 250 MMBO.

The Pinda and Vermelha Formations consist of mixed carbonate and siliciclastic rocks deposited by barrier island and associated shallow marine systems. The reservoirs are capable of prolific production, but facies dependent permeability variations cause bypassed oil in mature floods and below target injection in new floods. Timely implementation of reservoir management plans has prevented reservoir variability from decreasing ultimate recovery.

High resolution geological models are the foundation for the reservoir management plans. Multidisciplinary teams construct the models via a six step process that includes; core analysis, mineral based formation evaluation, lithofacies identification, facies controlled geostatistical modeling, scale up, and calibration with production data.

Low injectivity and conformance inhibiting permeability stratification within Pinda reservoirs were addressed by drilling additional injection wells in favorable facies and an aggressive profile modification program. In the Vermelha, recognition of facies controlled permeability variations resulted in conversion from peripheral injection to a pilot pattern waterflood. Models incorporating reservoir heterogeneity provide a basis for understanding the performance of existing floods and will guide the design of new projects.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria