--> Abstract: 3D Seismic Definition of Pleistocene Sediment Gravity-flow Depositional System, Niger Delta Slope Area, Gulf of Guinea, by K. A. Kanschat, J. M. Armentrout, J. J. Tsakma, L. Antrim, and D. R. McConnell; #90942 (1997).

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Abstract: 3D Seismic Definition of Pleistocene Sediment Gravity-flow Depositional System, Niger Delta Slope Area, Gulf of Guinea

KANSCHAT, KATHERINE A., JOHN M. ARMENTROUT, JEROME J. TSAKMA, LISA ANTRIM and DENNIS R. McCONNELL

3D seismic surveys facilitate construction of observationally constrained, depositional models. Analysis of a proprietary 3D survey over the Niger delta slope (OPL 221) provides examples of deep-water, gravity-flow depositional systems. These systems consist of confined-flow channel-form elements grading downslope into less confined-flow, lobe-form to sheet-form elements. The gravity-flow systems are imaged on amplitude extraction and coherency maps for discrete stratigraphic intervals immediately above regionally significant sequence boundaries. Study of these systems at shallow stratigraphic depths provides high resolution depositional models for interpreting deeper, lower resolution exploration objectives. Prediction of reservoir quality sands in this exploration frontier requires analogs.

The sediment gravity-flow systems appear to be confined to slope-valley topography. They consist of three architectural elements: 1) upper slope, small-scale channel-form elements converging downslope into, 2) single channel-form and nested channel-form elements with linear to sinuous map patterns, grading further downslope into, 3) slope-basin lens- to sheet-form components mapped as lobe-form or fan-form elements. Three types of channel-form elements are observed: 1) erosional, 2) erosional-depositional, and 3) depositional. The depositional channel-form elements have geometries strongly suggestive of channel-levee-overbank complexes formed by deposition from turbid-flow events. Within the fan-form sheets, lateral accretion of depositional elements suggests compensation sedimentation of amalgamated depositional events. In one case, the gradation from mapped channel-form to lobe-form to fan-form elements occurs over less than 5 km.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria