AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Scale Invariance in Fluvial Bars: Implications for Reservoir Modelling of Fluvial Systems
(1) Geology & Petroleum Geology, University of Aberdeen, Aberdeen, United Kingdom.
Bars form an important architectural element within the deposits of fluvial systems. An understanding of the controls on bar dimensions will help in reconstructing fluvial deposits in the rock record and aid in the accurate construction of reservoir models for fluvial systems. Previous work has suggested that bar dimensions vary with bar type (e.g. point bars and braid bars) and that there are significant variations in lithofacies between preserved bar types. Here we present length and width values of mid-channel bars, point bars, lateral (attached) bars, transverse bars and braid bars measured from remotely sensed imagery. The length (referred to as A-axis) is the maximum visible extent of the bar parallel to the flow direction, and the width (referred to as B-axis) is the maximum visible extent perpendicular to the flow direction. A data set consisting of 1007 data points from 38 rivers in different tectonic and climatic settings from around the world was collected. The mean width:length ratio is 0.27±0.0044, with a standard deviation of 0.0709. There is no significant difference in width length ratio between any of the studied bar types. The minimum value is 0.092 and the maximum value is 0.497. A correlation coefficient of r2=0.9489, indicates that the length and width values can be correlated. The frequency distribution shows that the majority (83.52%) of width:length ratio values range between 0.15 and 0.35. Therefore, plan view dimensions of bars in fluvial systems have to be considered as scale invariant. The width:length ratio is not influenced by bar type, termination type, gradient, planform geometry, tectonic setting or climate.