Seismic Facies Architecture of Canyon-Channel Complexes – Deepwater, Offshore Mauritania

Caroline J. McKnoe¹, Simon C. Lang², and Tobias H.D. Payenberg^3
1 Woodside Energy Ltd, Perth, Australia
² University of Adelaide, South Australia, Australia
³ Australian School of Petroleum, University of Adelaide, Adelaide, Australia

High resolution depositional architecture within stacked submarine canyon-channel complexes can be recognized from shallow 3D seismic surveys, Offshore Mauritania. Detailed shallow seismic interpretations using high-resolution data can aid in the characterization of potential similar reservoirs in deeper sections, which are often accompanied by poorer data resolution. Depositional elements such as meandering channels, splays and frontal splay complexes are identified using root mean squared (RMS) amplitude extractions with seismic data. Reservoir prone elements include outer channel bends and proximal regions of frontal and channel splays.

RMS amplitude extractions using 40 ms slices indicate that the channels undergo minimal downward and lateral movement. This confines potential channel reservoirs to within the channel belt of approximately twice the channel width. Seismic data indicate vertical aggradation of the channels, generally accompanied by minimal lateral migration. Slope gradients of > 2º occur in the middle slope with gradients < 2º along the outer shelf, upper and lower slope regions. Varying seismic fill patterns are inferred to be linked to changes in slope profile and accommodation space.

The canyons studied show narrow width:depth (W:D) ratios ranging from 5:1 to 39:1, generally increasing down-slope with shape changes from V to U-shaped. Internal channels show similar narrow W:D ratios and range from 5:1 to 25:1. Downstream and lateral migration of channels with time is minimal and is confined to within the channel belts. Channel belt widths range from 815 m to 1650 m with channel widths ranging from 400 m to 700 m, both increasing down-slope.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005