External Controls on Miocene Deep-Water Slope Channel System Evolution, West Africa

Abstract

Predicting sandbody architecture and understanding the controls on stratigraphic variability are critical technical and business challenges facing many deep-water reservoirs. In order to address these challenges, we studied high-resolution 3D seismic data (dominant frequency ~40 Hz) of the Miocene Angolan continental slope to document variability of channelized stratigraphic architecture over large spatial (>2000 sq. km) and temporal (>17 Ma) scales. We interpret marked temporal changes in the scale of channel systems. Early during the development of the succession, the system was dominated by numerous, larger channel systems, which evolved to be smaller. This change in stratigraphic architecture can be directly linked to the development of an up-dip graben, which progressively captured and redirected more sediment. Once the graben was filled, sediment delivery to the slope was rejuvenated, resulting in a wide range of channel systems, including the largest observed during the Miocene. Sediment supply from the African continent was also likely greater as the graben was filled to spilling. These trends in deepwater channel stratigraphy are applicable in other settings subjected to syn-depositional deformation and dynamic onshore landscape evolution. Thus, an understanding of up-dip controls can inform predictions of down-dip stratigraphic architecture in data-limited settings. This also potentially works in reverse: the continental slope stratigraphic record can inform up-dip changes in boundary conditions of sediment-routing systems.

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