Use of ordinary kriging to estimate the distribution of the permeable lithofacies: example of Rio Claro Aquifer in Paulínia/SP

Abstract

The distribution of hydraulic conductivity values represents crucial information for the elaboration of mathematical models of flow and transport of contaminants, as well as the planning of the remediation systems to contaminant removal in the subsurface. It is common practice to construct the hydraulic conductivity fields from discrete information obtained from the construction of geological models. However, such an approach presents as a limitation the subjectivity in the elaboration of such models, since this stage involves subjectivity in the adoption of criteria used in the definition of facies distribution and lithological contacts. In the present work a different approach is proposed, in which geological information of sub-surfaces are converted to values of hydraulic conductivity, which are used as input data for the construction of three-dimensional hydraulic conductivity fields from ordinary geostatistical methods. The distribution of hydraulic conductivity values above a cutoff value indicates the geometry and connectivity of permeable facies. The proposed approach was tested in the Rio Claro Aquifer in Paulínia/SP from the use of sub-surface geological data from 255 borehole data. The results indicate that the high values of hydraulic conductivity are distributed along a continuous belt of east-west direction and reflect the depositional context of the Rio Claro Aquifer, in which the sandy facies are the result of the amalgamation of channel fills and marginal bar, with marked vertical accretion along a narrow belt. The sandy bodies geometry has important implications for the determination of the facies architecture of the Rio Claro Formation in the municipality of Paulínia as well as the behavior of the groundwater flow and contaminants transport in the local shallow aquifer.