EVALUATION OF PETROPHYSICAL HETEROGENEITY WITHIN FLUVIAL ARCHITECTURAL ELEMENTS OF THE CRETACEOUS BURRO CANYON FORMATION, COLORADO

High heterogeneity of fluvial reservoir deposits influences the distribution of petrophysical properties, static connectivity, and fluid flow. To explore the impact of fluvial architecture, sedimentary structures, and facies variations on reservoir properties, we studied well-exposed outcrops of the Cretaceous Burro Canyon Formation in Deer Creek and Escalante Canyon, Colorado. The single depositional sequence of the Burro Canyon Formation contains a series of stacked amalgamated and semi-amalgamated channel complexes, composed of architectural elements in a hierarchical array that ranges from bed sets to channel fills to amalgamated channel complexes. A combination of detailed stratigraphic measured sections, outcrop gamma-ray measurements, and Unmanned Aerial Systems (UAS)-based photogrammetry are used to constrain three and two dimensional (2-D and 3-D) maps and static reservoir models of the fluvial deposits. We created maps and models that highlight the contrast in heterogeneity, orientation, and local trends of distribution for grain size and petrophysical properties such as porosity and permeability within the architectural elements. Results suggest that flow efficiency in the subsurface is most effective perpendicular to paleoflow direction in amalgamated channel complexes due to greater sandstone connectivity. However, the lateral and thickness variabilities of preserved sandstone channels play an important role in flow efficiency. Reservoir heterogeneity accounts for the larger variations in flow efficiency through low petrophysical zone values that might trap fluids and create baffles that affect the flow direction and paths. Conglomeratic facies that form channel lags above basal scour surfaces create barriers that decrease the efficiency of the fluid-flow though the reservoirs. Our work shows the importance of an adequate characterization of sedimentary structures and facies architecture to evaluate petrophysical properties in evaluation of flow pathways within subsurface reservoirs.