Influence of fluvial crevasse-splay deposits on sandbody connectivity: Lessons from geological analogues and stochastic modelling

To investigate the importance of crevasse-splay elements for the connectivity of fluvial sandbodies, an integrated study has been undertaken that combines data from outcropping and subsurface fluvial successions, and modern rivers, with outputs from forward stratigraphic models and object-based modelling. Literature-derived analogue data on over 2100 crevasse-splay elements from many fluvial systems have been synthesized to obtain quantifications of the proportion and geometry of crevasse-splay units, and of their topological relationships with channel deposits. Some of the analogue data are used to inform inputs to stochastic modelling that is applied to determine how the presence of crevasse-splay deposits affects the connectivity of successions in which channel sandstones are preserved as channelized bodies or compartmentalized point-bar units.& nbsp; Architectural configurations are documented that are variably characterized by (i) crevasse-splay sandbody compartmentalization, (ii) channel-sandbody connections that increase sandbody size and the likelihood of borehole connectivity, and (iii) intercommunication between different channel sandbodies. Analyses of analogue data demonstrate scaling relationships between the morphometry of crevasse-splay elements and associated channel elements and river catchments. Results also demonstrate how the proportions of channel and crevassesplay deposits tend to covary in stratigraphic volumes. This information, when ported to stochastic models, yields results showing how the influence of crevasse-splay elements on static connectivity varies ? in relative terms ? as a function of architectural style, net-to-gross ratio and channel-sandbody geometry. Channel-body connections may be more important for smaller and relatively sand-poor fluvial systems, whereas mud-plug compartmentalization of splay elements may be more important for successions with larger channel-body width-to-thickness aspect ratios and lower net-to-gross ratios.& nbsp; The results of this work can be applied to facilitate and improve the characterization and modelling of the static connectivity of subsurface successions that include crevasse-splay deposits. The results also reveal the possible influence of certain geological controls (channel avulsion, river-system scale, overbank cannibalization) on static connectivity.