--> Reconstructing the Three-Dimensional Fluvial Architecture of the Salt Wash Member of the Morrison Formation, Utah, Using Structure-From-Motion Photogrammetry and Terrestrial Laser Scanning

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Reconstructing the Three-Dimensional Fluvial Architecture of the Salt Wash Member of the Morrison Formation, Utah, Using Structure-From-Motion Photogrammetry and Terrestrial Laser Scanning

Abstract

Fluvial sandstones serve as important reservoirs in petroleum geology, but these deposits can be difficult to characterize due to the complex three-dimensional arrangement of lithologies and sedimentary facies. We use Structure-from-Motion (SfM) photogrammetry and terrestrial laser scanning to capture three-dimensional exposures of fluvial sandstones from the Salt Wash Member of the Morrison Formation in central Utah. Structure-from-Motion uses multiple overlapping images of the same object combined with image-based terrain extraction algorithms to reconstruct the location of individual points in a three-dimensional reference frame. We collected over 3000 photos of the strata from approximately 100 meters above the outcrop surface using a Helikite-mounted camera. The resulting digital terrain model produced by SfM photogrammetry has a resolution of approximately 10–20 cm and is perfect for providing a regional framework. Terrestrial laser scanning was used to capture specific features at a 1–2 cm resolution. These georeferenced data sets were augmented with measured sections, facies mapping and outcrop observations. We examined a specific sandstone body in the Salt Wash Member that is exposed in vertical, lateral, and plan-view orientations. This sandstone is composed of at least two smaller-order sandstone bodies, the upper of which scours into the lower unit. Paleocurrents from trough cross-strata are typically parallel to the trend of the sandstone bodies. Both sandstone bodies contain lateral accretion sets, trough cross-stratification, and fining upward packages. Pebble- and granule-sized sediments are common throughout the deposit. Many of the uppermost sandstone beds in the area are bioturbated. The terrestrial laser scanning and SfM data allow the distance between accretion sets, the spacing between cross-stratification sets, and other features to be measured accurately. These data can be used to constrain input parameters for stochastic reservoir models.