KOLLA, V.¹, P. BOURGES¹, M. MORICE², and J. DURAND^3
1Elf Exploration Angola, Luanda, Angola
²Elf Exploration Production, Pau, France
³ELF Exploration Production, Paris, France

Abstract: Deep-water Meandri-channel and Related Depositional Forms in Recent and Subsurface Exploration Fans

Side-scan imagery and high-resolution seismic profiles of recent fans and 3D seismic data of subsurface exploration fans aided by coring are shedding much light on the reservoir architecture of meandri channel and related depositional forms. The most important features of recent and subsurface deep-water meandering channels are: sinuosities up to 2.5- 3.0, vertical aggradation and lateral channel migration on various scales, channel avulsion and branching, cutoff meanders, washover fans at meander loops, overbanks and several types of lobeform deposits. Almost all the features associated with the meandering channels have reservoir-prone lithologies. The overbanks of low-relief channels are more sand-prone than those of high-relief channels. In addition to the kind of lobeforms that occur at the termini of straight channels, a variety of crevasse-splay type lobeforms exist in association with the meandering channels. The type of crevasse-splay lobeform depends on the depth of the thalweg of the main channel, the depth of levee-breaching the gradients leading to the adjacent basinal areas and the energy of sediment-gravity flows. Both the channel-terminus and crevasse-splay lobeforms, unlike the classical 'lobes' are complex, have commonly straight channels of varying dimensions, and consist of channel fills, overbank deposits and several, channel-attached, relatively small lobes and splays in varying proportions. The reservoir geometry and continuity in these lobeforms could thus be very complex.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas