Hydraulic conductivity derived from geophysical logging in the Guarani Aquifer System

Abstract

Hydraulic conductivity (K) is a crucial parameter for different applications in groundwater studies, such as vulnerability and aquifer assessment, groundwater management, contamination velocity estimation, and numerical simulations of groundwater flow and transport. Although there are diverse approaches in order to obtain K values, only a small number of these methods allow determination of high-resolution K changes in great aquifer depths. In an attempt to solve this difficulty, the present work developed and tested a new approach, in which porosity values, estimated from sonic and gamma ray logs, were used to calculate K values with high spatial availability by using the Kozeny-Carman model. These tests were conducted in a deep well (1242 m), which exploits the Guarani Aquifer System water. The mean K values found by the proposed approach were similar to K value derived from pumping test. From the use of this approach, it was noted that Pirambóia formation presents strong K variability, while Botucatu formation is relatively homogeneous, in accordance with the depositional context of these two geological units. Finally, we confirm that K values obtained from the pumping tests represent the geometric mean of the K values along the filtered section of tested wells.