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Three-Dimensional Eolian Bounding Surface Architecture of the Entrada Sandstone, Utah: Expanding Our Understanding of Reservoir Heterogeneity in Wet Eolian Systems

Abstract

Eolian depositional systems host significant but heterogenous petroleum reservoirs around the world (e.g., Norphlet Formation, Rotliegend Group, and Navajo Sandstone). Wet eolian systems are typically more heterogenous than dry systems due to the presence of interbedded cross-strata, damp interdune, and sabkha deposits. Although several studies have relied on measured sections and correlations to describe the facies and nature of the bounding surfaces preserved within wet eolian systems, few have taken advantage of more advanced methods to accurately constrain the architecture of 1st and 2nd order flow-inhibiting bounding surfaces over prospect-scale areas. We pair traditional field methods (e.g., measured stratigraphic sections, paleocurrent analysis, and handheld gamma-ray spectrometry) with advanced technologies (e.g, high precision GPS data and drone-derived outcrop models) to help resolve the detailed surface morphologies and the three-dimensional (3D) stratigraphic architecture of wet eolian systems. Generating precise, large-scale surface reconstructions also allows us to contemplate autogenic (e.g., dune-dune interactions) and allogenic (e.g., climate and sea level) forcing mechanisms on erg development.

This study focuses on 3D exposures of the Middle Jurassic Entrada Sandstone that crop out on Rone Bailey Mesa, 60 km south of Moab, Utah. These outcrops offer the unique opportunity to characterize the 3D facies distribution and bounding surface architecture that impact reservoir heterogeneity. The creation of a digital outcrop model allows us to (1) explore the lateral and vertical facies architecture and heterogeneity present in the Entrada Sandstone at Rone Bailey Mesa, and (2) consider analogous architectures in subsurface hydrocarbon reservoirs found in wet eolian systems. These data provide quantitative inputs for parameterizing reservoir models of wet eolian systems and provide a fundamental basis from which predictive relationships among eolian facies can potentially be identified.