Utilizing Channel-Belt Scaling Parameters to Constrain Lateral Extent and Drainage Basin Character

Milliken, K.T.; Willis, B.J.; Connell, S.D.; Bracken, B.; Payenberg, T.H.D.; and Sixsmith, P.
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Fluvial systems possess a range of scaling relationships that reflect drainage-basin controls on water and sediment flux. In hydrocarbon exploration and production, scaling relationships for fluvial deposits can be utilized to constrain environmental and sequence-stratigraphic interpretations, as well as predict the lateral extent of fundamental reservoir flow units.

This study documents the scales of channel fills, channel bars, channel belts, and coastal-plain incised valleys from well-constrained Quaternary fluvial systems. Data on channel-fill and point-bar to channel-belt scales were compiled from published thicknesses for sinuous to straight single-channel systems, with spatial dimensions measured from GoogleEarth and ArcGIS georeferenced geologic maps. Fluvial systems included in this database span 3 orders of magnitude in drainage area, from continental-scale systems to small tributaries, and span tropical to sub-polar climatic regimes.

One component of this study focused on trunk- stream reaches upstream from backwater effects, so as to minimize inclusion of distributive, highly avulsive systems. The other component investigates channel-belt and channel patterns within backwater zone.

All scaling relationships are represented by statistically significant power laws, with absolute dimensions that scale to drainage area. A key criterion for scaling fluvial dimensions to drainage basin includes sampling comparable upstream locations as width, thickness, and width to thickness ratios vary substantially upstream of backwater compared to within backwater zones. Additionally, dimensions of channel fills, point bars and channel belts, and incised valleys define distinct populations. Mean width-to-thickness ratios for channel fills are ~10:1, whereas channel-belts commonly range from 20-250:1 depending upon sinuosity. Scales of Quaternary examples compare well with previous compilations of channel-belt scales interpreted in the ancient record, and with theory.

Comparison of these quaternary scaling relationships with width to thickness trends observed in the subsurface datasets can be utilized to predict the relative updip to downdip location of preserved fluvial strata. Furthermore, the scaling relationships can be used to reconstruct regional evolution of pale-drainage or catchment areas.

AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013