Stratigraphic Compartmentalization of Deep-Water Channel Systems, West Africa

Abstract

Deep-water channel compartmentalization and heterogeneity pose significant technical and business challenges to reservoir characterization and development. Some channel systems are better connected than expected, whereas others are more compartmentalized. A detailed understanding of stratigraphic architecture is fundamentally important to reduce connectivity uncertainty. We integrate an exceptional high-resolution seismic-reflection dataset (dominant frequency 40 Hz) from offshore West Africa with well-log, core, dynamic, and analog data to investigate stratigraphic controls on reservoir heterogeneity and compartmentalization of the Miocene ‘L’ deepwater channel system. Detailed analysis of the ‘L’ channel system indicates that it comprises terraces of remnant, isolated channel elements and possible down-dip heterogeneity of channel fill. The stratigraphic evolution was dominated by the development of at least three large-scale (>50 ms TWTT relief) composite erosional surfaces. Each erosional surface cut deeper than the last, thereby isolating terraces of high-quality sand at multiple stratigraphic levels. These terraces are remnants of channel elements that were deposited during an earlier phase of the channel system. Therefore, the development of large-scale erosional surfaces is fundamentally important to reservoir compartmentalization. We interpret these surfaces to be a diachronous expression of predominantly incision, but also multi-phase channel element cutting, filling, and stacking. This evolution has been interpreted to represent a combination of changing sea level, evolving sediment source characteristics, and the dynamic geomorphology of tectonically active continental margins. We place our interpretations in an architectural hierarchy, and consider the impact of reservoir compartmentalization and heterogeneity on fluid flow behavior during hydrocarbon production. These interpretations inform the modeling and prediction of 3D heterogeneity of deep-water reservoirs and illustrate the importance of detailed characterization at a very-fine scale in order to understand reservoir connectivity.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015