Neogene Evolution of a Confined Upper Slope Canyon System with Emphasis on Canyon Fill Architecture, Offshore Equatorial Guinea

Jobe, Zane¹, Jim Hewlett² (1) Stanford University, Stanford, CA (2) Hess Corporation, Houston, TX

The slope canyon systems of the Rio Muni Basin, offshore Equatorial Guinea have persisted for more than 80 million years and contain world class hydrocarbon reservoirs. An excellent 3D seismic reflection survey along with borehole, palynologic, and wireline log data beautifully illustrate the aggrading upper slope canyon system ~ 25 km offshore. The slope canyons maintain themselves through syn-depositional faulting and display low sinuosities. During the Neogene, the slope canyons aggraded more than 600 m, while migrating laterally less than 500 m.

Slope canyon fill is characterized by three main depositional elements: 1) thalweg elements that stack upon each other as the canyon aggrades vertically; 2) lateral accretion packages/elements that occur on the inner bends of the low sinuosity canyons; and 3) shingled reflection packages that stack in a down-canyon fashion, usually found just down slope of a knick point.

These three elements are modified by syn-depositional faulting, both small down canyon slumps and large, canyon margin bounding faults that exaggerate the canyon topography and cause the canyons to aggrade rather than migrate. This faulting gives rise to very complex geometries in a dip sense that seem quite simple in a strike sense. The faulting could complicate reservoir connectivity and continuity in similar upper slope canyon systems globally.