--> Abstract: Autocyclic Processes and Resultant Stratigraphy of Deepwater Fan Experiments; #90063 (2007)

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Autocyclic Processes and Resultant Stratigraphy of Deepwater Fan Experiments

 

Bloch, Roger B.1, David C.J.D Hoyal1, Benjamin A. Sheets1, Christopher M. Edwards1, Vitor Abreu2 (1) ExxonMobil Upstream Research Company, Houston, TX (2) ExxonMobil Exploration Company, Houston, TX

Tank experiments emulating depositional processes on deep water fans demonstrate the relationship between autocyclic flow processes and their resultant surfaces and deposits. The experiments have constant discharge and sediment flux, and use crushed plastic in a saline solution to enhance turbidity current density. Fan growth evolves thus: 1) a distributary channel forms, 2) a lobate deposit develops at channel mouth, 3) the lobe grows in width and/or height 4) deposition propagates up the channel, and 5) the channel avulses, initiating a new cycle. The resultant stratigraphy reflects these cycles of erosion and deposition superimposed on longer-term fan progradation. In proximal positions, an individual cycle produces an erosional basal surface that is a composite feature created by multiple scouring events. In strike-oriented section, the depth of scour tends to decrease over time within a cycle. Backfilling processes yield an architecture dominated by scour-fill in the stratigraphically lower part of a cycle and a broader, lobate geometry in the upper part. In distal positions, lateral migration of lobes produces a shingled and mounded architecture on a surface of little or no erosion. Overall fan progradation affects the large-scale architecture such that in proximal regions, scour-fill, unfilled channels and small erosional remnants dominate. In the mid-fan region, lobate deposits of older cycles are incised by younger cycles dominated by scour-fill. At distal positions, laterally-offset and vertically-stacked lobes develop. This architecture is compared to seismic geometry of an East Breaks (Gulf of Mexico) Quaternary fan, and has implications for reservoir connectivity and performance.

 

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