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Characterizing Fluvial Architecture Using UAV-Based Photogrammetry and Outcrop-Based Modeling: Implications for Reservoir Performance, Southwestern Piceance Basin, Colorado

Abstract

The Lower Cretaceous Burro Canyon Formation in the southwestern Piceance Basin, Colorado, represents low-sinuosity to sinuous braided-fluvial deposits that consist of amalgamated channel complexes, amalgamated and isolated fluvial-bar channel fills, and floodplain deposits. Lithofacies primarily include granule-cobble conglomerates, conglomeratic sandstones, cross-stratified sandstones, upward-fining sandstones, and gray-green mudstones. The stratigraphic variability of the fluvial architectural elements and their lithological and petrophysical heterogeneity influence reservoir connectivity and fluid flow. To assess the effects of variable sandstone-body geometry and internal lithofacies and petrophysical heterogeneity on reservoir performance, conventional field methods are combined with unmanned-aerial-vehicle- (UAV-) based photogrammetry to create representative outcrop-based reservoir models. Two- and three-dimensional outcrop reservoir models and fluid-flow simulations compare various reservoir scenarios. Resulting breakthrough time and sweep efficiency suggest reservoir performance is most effective perpendicular to paleoflow direction in amalgamated channels. Perpendicular to paleoflow, breakthrough time is 9% shorter than parallel to the paleoflow and sweep efficiency is, on average, 16% greater due to greater sandstone connectivity in this orientation. Variability of preserved channels and lateral pitchouts results in lower recovery efficiency. Facies heterogeneity can account for 50% variation in breakthrough time and slightly lower recovery efficiency (5%). Cemented conglomerates that form channel lags above basal scour surfaces can also create fluid-flow barriers that increase breakthrough time and decrease sweep efficiency (25%) and recovery efficiency (22%). Results also show that coarsely resolved grids experience delayed breakthrough by as much as 40% and 10% greater volumetric sweep efficiency, on average. Results highlight the importance of properly incorporating stratigraphic details into 3-D reservoir models and preserving those details through proper upscaling methods.