--> Abstract: Avulsion Clusters in Alluvial Basins: Statistical Tools for Quantifying Sand-Body Distributions and Implications for Reservoir; #90063 (2007)

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Avulsion Clusters in Alluvial Basins: Statistical Tools for Quantifying Sand-Body Distributions and Implications for Reservoir Modeling and Interpretation

 

Hajek, Elizabeth1, Paul Heller1, Snehalata Huzurbazar2, Benjamin Sheets3, Chris Paola4 (1) University of Wyoming, Laramie, WY (2) University of Wyoming, Laramie, (3) ExxonMobil Upstream Research Company, Houston, TX (4) University of Minnesota, Minneapolis, MN

 

Current models for predicting basin-scale fluvial stratigraphy stem largely from theory and typically focus on the spatial and temporal distribution of coarse-grained channel-belt deposits in fine-grained overbank material. Such stratigraphy is dominantly controlled by long-term channel avulsion behavior within a basin. Avulsion models used to predict channel-belt distributions typically assume channels move, either randomly or deterministically, to low spots throughout the model space. Recent observations of ancient deposits and physical experiments indicate that there is a previously-unrecognized pattern of channel-belt organization, where clusters of closely-spaced channel-belt deposits are separated from each other by extensive intervals of overbank deposits. Using a combination of field, remote sensing, 3D seismic, well-log, and experimental data, we quantitatively characterize the distribution of channel deposits in the Ferris Formation (Upper Cretaceous/Lower Paleogene; Hanna Basin, Wyoming) and experimental stratigraphy generated at the St. Anthony Falls Research Lab (University of Minnesota). We use Ripley's K-Function to show that both basins exhibit statistically-significant channel-belt clustering over certain spatial scales. This parameter describes degree of channel-body clustering at a range of distances and might ultimately be used as a model input to characterize spatial lithologic heterogeneity in alluvial reservoirs and basins. Furthermore, our observations suggest that avulsion clusters form reservoir-scale features that may not appear channel-like in shape but rather may form irregular sand-dominated zones. Hence, seismic cubes processed to enhance lithologic differences may offer advantages over volumes processed to maximize vertical resolution in clustered alluvial intervals.

 

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