ORGANIZING THE CONTRAST: INTEGRATING OUTCROP AND NUMERICAL MODELS TO DECIPHER THE STRATAL HIERARCHY OF DEEPWATER FANS (Invited Presentation)

Unconfined deep-water fans are the terminus for continentally derived sediments and are increasingly the focus of hydrocarbon exploration and development; they are commonly conceptualized as stratigraphically homogeneous based on qualitative analyses of outcrops, seismic data, and well data. Previous studies have aimed to address levels or “hierarchies” of the variation in stratigraphic architecture and rock properties across vertical scales. However, there remains a lack of consensus on the concept of “hierarchy” in deepwater fans; this has resulted in significant uncertainty as to how stratigraphy heterogeneities vary within and across scales. While two key depositional models of stratal organization have been proposed - scale-dependent and scale-independent - the former (hierarchical) model suggests variations in rock properties, stratal architecture, and stacking patterns change across orders (e.g., beds, elements, complexes). Yet, the latter scale-independent (fractal) model suggests consistency across each order.

Here, we investigate outcrop and numerical models to test the scale-dependence of stratigraphic heterogeneities by assessing the property variation across multiple levels of time-correlative stratal packages. We demonstrate that heterogeneities, such as facies and stacking patterns, show a scale-dependent variation in style and length-scales, and that a significant difference in the volumes and internal connectivity associated with each opposing model exists. Our results have significant implications for characterizing the sediment gravity flows that generated these deposits, evaluating the hydrocarbons these deposits may contain, and how they may perform. If stratigraphic predictions are made in a scale-independent framework, results will be limited and non-unique because the three-dimensional variation of stratigraphic features depends on their hierarchical order. We conclude that predictions of stratal organization, and understanding the flow processes responsible for those deposits, fundamentally relies on an understanding of process-based, scale-dependent hierarchy.