Estimating Sinuosity of an Outcropping Submarine Leveed-Channel Complex

Slatt, Roger M.¹, Staffan K. Van Dyke², Janice M. Dodson¹ (1) University of Oklahoma, Norman, OK (2) Aera Energy Co, Bakersfield, CA

Detailed lithologic variability of submarine leveed-channel deposits and reservoirs normally cannot be determined from 3D seismic, seafloor or shallow sub-sea imagery because of the lack of closely-spaced wells. Outcrops provide a means to at least partially overcome this deficiency since lateral bed characteristics can be documented. But, with very few exceptions, sinuosity is difficult-to- impossible to document owing to the size and orientation of most outcrop belts relative to channel trends. To partially overcome this problem we have used a combination of techniques---including measured stratigraphic sections, behind-outcrop drilling/logging/coring, ground-penetrating radar and electromagnetic induction surveys, and 2D shallow seismic reflection acquisition--- to build a partial, scaled 3D geologic model of a sinuous leveed-channel complex (Cretaceous Dad Sandstone, Wyoming). This leveed-channel complex consists of ten channel-fill sandstones, each separated by thin-bedded facies, and all confined within a master channel. The complex is 67m (200ft.) thick and 500m (1500ft.) wide, with 57% net sand. Individual channel-fills typically consist of debrites and slumps on one side and massive to cross-bedded sandstones on the other, which we interpret as ‘cutbank-like' and ‘pointbar-like' facies, respectively. This distribution provides a means of estimating the orientation of sinuous channel bends. The width of the channel complex provides a constraint from which the degree of sinuosity can be estimated; the range for these 10 channel-fills is 1.33-2.00.

This 3D model not only estimates sinuosity, but relates it to the distribution of lithologies, thus providing information on lithologic variability which can be used for reservoir modeling and simulation.