Quantifying spatial and architectural relationships from fluvial outcrops

Abstract

Outcrop analogue studies allow detailed investigation of sandstone body geometry and architecture within fluvial systems. Characterization of these elements is fundamental to understanding and quantifying sandstone body connectivity within hydrocarbon reservoir models, and hence improving recovery from those reservoirs being modeled. This study utilized a laterally and vertically continuous terrestrial light detection and ranging (lidar) data set from the La Serrata section of the Oligocene–Miocene Huesca fluvial fan, in the Ebro Basin in Spain. This data set was used to create a high-resolution three-dimensional digital outcrop model of a 2 km2 cliff section representing the heterogeneity in the medial (midfan) portion of a large fluvial fan. Geostatistical information (i.e., sandstone body width and thickness) extracted from the models using quantitative analytical techniques, integrated with traditional sedimentary log data, allowed the calculation of probability density functions of 42 sandstone bodies from corrected (true) width measurements. These data show that sandstone bodies are up to 6 m thicker and 209 m wider than previous studies have estimated. Furthermore, an observed temporal trend of thickening and widening of sandstone bodies up section before a reduction in the uppermost portion provides evidence for possible avulsion events. These data, compared with previous studies of this and other fluvial systems, illustrate the efficacy of digital outcrop models as quantitative tools for accurate characterization of critical reservoir elements from outcrop analogues.