--> Abstract: Stratigraphic and Spatial Changes in Channel Morphology Related to Deepwater Processes in Confined and Ponded Slope Mini-Basin; #90063 (2007)

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Stratigraphic and Spatial Changes in Channel Morphology Related to Deepwater Processes in Confined and Ponded Slope Mini-Basins, Angola

 

Clark, Julian D.1, Tim R. McHargue1 (1) Chevron Energy Technology Company, San Ramon, CA

 

Near surface seismic data from offshore Angola show a high-resolution stratigraphy in the deep-water clastic fill of a series of highly confined salt withdrawal basins. High-resolution imaging of the stratigraphic architecture and deposit geometry provides insights into the depositional processes involved in the successive filling and spilling of a series of slope mini-basins, and the distributary systems of the terminal basin.

Detailed stratigraphic interpretation and quantification of channel parameters show the interpreted interplay between auto- and allo-cyclic processes involved in filling such confined basins.

Sediment, supplied through deeply incisional conduits, infills the local accommodation space of each mini-basin through distributary processes. As flows reach the spill point, high sinuosity migrating channels develop due to sediment bypass across the low gradients of the ponded fill deposits. When flows breach the spill point, the depocenter shifts to the downdip basin, lowering the depositional equilibrium profile, resulting in channel incision though the spill point and updip erosion of previously deposited sands.

 

In the terminal basin a dendritic channel distributary system develops, with an intricate channel branching network and spatial changes in channel parameters. The channelized portions of this distributary network are interpreted to represent largely auto-cyclic processes by which sediment is distributed within this confined basin. Stratigraphic changes in channel density are interpreted to represent largely allo-cyclic controls on sedimentation.

 

Quantitative relationships between channel pattern and sediment processes resolved in this high-resolution dataset can be used to infer depositional processes, and in particular predict reservoir quality, in lower-resolution seismic data.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California