--> Abstract: Three-Dimensional Connectivity of Channel Point Bar Architectural Elements; #90063 (2007)

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Three-Dimensional Connectivity of Channel Point Bar Architectural Elements

 

Willis, Brian1 (1) Chevron Energy Technology Company, Houston, TX

 

A point bar deposit composed of a upward-fining set of lateral accretion beds was one of first architectural elements defined in outcrop and interpreted in terms of depositional processes. Despite this early success there has been remarkably few fundamental advancements since the 1960's in our understanding of the distribution of heterogeneities within these deposits. Poorly understood issues include: 1) the stacking and lateral connectivity of adjacent bar deposits across channel fills and the channel belt axis; 2) lateral bedding truncation geometries within point bar deposits due to downstream migration and channel cutoff; and 3) the influence of vertical superposition of successive migrating channel bars within “multi-storey” bodies. Visualizations are presented to illustrate relationships of channel geometry, bed grain size, and migration pattern to specific bedding geometries and facies variations within resulting point bar deposits. Additional movie clips show effects of different configurations of channel switching and channel aggradation on 3D point bar deposit connectivity. Conclusions include: 1) significant volumes of outer bank accretion deposits can strongly influence downstream bar connectivity; 2) low flow drapes can block downstream connectivity of adjacent bars; and 3) vertical aggradation increases connectivity not only by allowing a super positioning of downstream migrating bars but also by increasing connections of bars across a channel belt axis. Simulated deposits indicate that there may be too much emphasis on examining exposures with well-defined lateral accretion beds, which are predicted to comprise less than half the volume of “meandering” channel belts and may be less important to an understanding of larger-scale fluvial reservoir productivity than the character of deposits within bar crossover areas and channel fills.

 

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