Characterization of Fluvial-Eolian Aquifer Reservoirs: Integrating Digital Outcrop Models and GPR Data

Abstract

The Rio do Rasto and Botucatu Formations represent the main aquifer reservoirs in the state of Santa Catarina Brazil. The vertical facies succession of these formations comprises reservoirs formed by a complex fluvial-eolian interaction. The analysis of the depositional architecture, the use of geophysical data and of high-resolution virtual outcrop models from these reservoirs improved the understanding and of high-resolution heterogeneities at different scales and allowed the development of lithological and aquifer models that demonstrate this interaction. At megascopic scale, the reservoirs are composed of fine-grained sediments interbedded with with sandy bodies deposited in a fluvio-eolian context of the Rio do Rasto Formation, and large-scale eolian dunes deposited in a dry eolian system of the Botucatu Formation. At macroscopic scale, the fluvial-interpreted reservoir presented more vertical and lateral heterogeneities relative to the eolian reservoir. Unconformity surfaces and clay layers act as its main flow barriers. At mesoscopic heterogeneity reflects lithofacies and sedimentary structures within eolian and fluvial facies associations. In this scale the major parameters that impact the flow migration are textural and structural differences associated with eolian and fluvial depositional processes.