Analysis of fluvial sand-body characteristics and connectivity, Williams Fork Formation, Plateau Creek Canyon, Piceance Basin, Colorado

Quentin A. German, Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309-0399, [email protected]

Variability in fluvial sand body type, dimension, geometry, and distribution of the Late Cretaceous Williams Fork Formation influences well placement and density within reservoirs of the Piceance Basin and other comparable fluvial reservoirs.  The upper, high net-to-gross (>50%) Williams Fork outcrops exposed in Plateau Creek Canyon on the western Piceance Basin margin offer important analog information to describe sand-body characteristics and analyze sand-body connectivity.  Given the various types of fluvial sandstone bodies (e.g., crevasse splays versus point bars) and their petrophysical and stratigraphic differences, it is important to understand their degree of amalgamation and how stacking patterns and stratigraphic heterogeneities affect static connectivity. 

Although the fluvial sand bodies of the upper Williams Fork Formation are laterally extensive, the variations of sand/shale distribution are below the resolution of conventional seismic. Therefore, these crevasse splays, point bars, and other fluvial deposits are identified and characterized based on outcrop studies using aerial lidar, orthophotography, digital photomosaics, measured sections, and behind outcrop cores.  Lidar data and high-resolution photomosaics are used to estimate sand-body dimensions and evaluate stacking patterns.  Measured sections and core data are used to address the sedimentology and petrophysical properties.  These data are combined to assemble high-resolution 3-D geologic models to evaluate multiple scenarios of static sand body connectivity.