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D. Claude1, J.C. Navarre2, J. Gerard1, F. Temple2, C. Cazzola2, N. Langridge3
(1) Elf Exploration Production, Pau, France
(2) Elf Exploration Production
(3) Elf Exploration Angola, Paris, France

Abstract: Variations of architecture, facies and depositional models of stratigraphically-controlled turbiditic deposits : examples from the Lower Congo Teriary Basin (Angola)

Understanding stratigraphic changes in the reservoir architecture of channelised turbidites is a key step in the construction of a reservoir model that properly incorporates multiple orders of heterogeneities. Cored wells in the deep offshore of Congo and Angola yielded valuable insights on both sedimentologic processes (including soft-sediment deformation) and biogenic processes. Integrating these data with very detailed 3D seismic analyses involving new technologies (« peeling », attribute maps, etc.... ) yielded a stratigraphic hierarchy for these complex turbiditic deposits. The methodology to identify and quantify the resulting hierarchical position of these deposits ( channel « complexes » for 4th-order, channel « stories » for 5th-order, and channel « phases » for 6th-order) is based on iterative seismic picking that respects the successive orders of time-lines. These time-lines are defined from cored facies and hinges particularly upon interpretation of shaly facies (muddy debris-flows, contourites, hemipelagites). In this presentation we illustrate stratigraphic units at different scales by defining their geometry (3D seismic), their sedimentary infilling (facies and processes involved), and their temporal evolution (observations on the stacking pattern). 4th- and 5th-order units are described by their erosional vs. erosional/depositional contexts. 6th-order units show varying combinations of the following phases : cut, fill, spill, and/or construction, and finally abandonment. Reservoir heterogeneity in the detailed reservoir model incorporates multiple orders of stratigraphic units.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana