Elementary Channel Migration in Turbidite Systems: Random Or Process-Related Evolutions?

Richard Labourdette¹ and Martine Bez^2
1TOTAL S.A./Montpellier 2 University, Pau, France
²TOTAL S.A., Pau, France

The evolution and migration of elementary channels in turbidite complexes is still a big issue in subsurface turbidite reservoirs, leading to the preservation of internal shaly baffles in various places of the complex. This distribution is frequently represented using random object-based models in reservoir models, but a relationship between individual channels is observable in high resolution seismic datasets.

The morphology of well-imaged turbidite complexes from West Africa (from Upper Oligocene to Miocene deposits) was analysed to improve the understanding of their individual channel evolutions and assess depositional processes involved. The derived measurements are then treated statistically and compared with the regional, local and stratigraphic settings of the studied turbidite complexes.

One major control on channel migration evolution is clearly related to turbidite complexes erosive capacity. This character is directly conditioned by the slope gradient and the stratigraphic position of the observed turbidite complex. Channel sinuosity evolves dynamically, some meander loops undergo periods of accelerated meander growth whereas others show little lateral migration. Internal barriers in the channel belt, lead to sea-floor topography, gradient changes and thalweg jumps, all acting as turbidity flow deviations. Since deep-water flows are gravity driven, small topographic changes affect the momentum of individual flows as well as frequent changes in migration patterns. The prominent role seafloor gradient plays on depositional patterns is therefore evident.

This study presents a classification of the determinant factors inducing elementary channel migration variations. The thorough understanding of depositional processes involved in such evolutions is determinant in reservoir characteristic distribution.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas