Mapping the hydrostratigraphy and groundwater salinity of the Ord Bonaparte plains from AEM and NMR data

Abstract

This study is part of the groundwater investigations of the Ord Bonaparte plains in the East Kimberley region of Western Australia. A key project aim is to establish a spatial hydrostratigraphic framework to better understand the hydrogeology. To achieve this, AEM data, inverted using 1D SELMA model, were produced as conductivity sections and elevation grids. Interpretation of the AEM data, in conjunction with lithostratigraphic information from three petroleum wells and seven project bores, aided the mapping of hydrostratigraphic units of the Devonian to Permian sequence of the Bonaparte Basin. Mapping results show that the Carboniferous Weaber and Kushill Groups are dipping to the east-northeast and contain laterally continuous stacked aquifers. Within the strata, resistive signatures are associated with sandstone aquifers, slight to moderate conductors are mapped as fine textured aquitard, or as interbedded fine to coarse textured sediment forming semi-confining layers. A water table elevation map was constructed using surface NMR water content profile and machine learning approach to extrapolate across the study area. Using Archie’s Law, groundwater conductivity was predicted from AEM conductivity and porosity derived from borehole NMR measurements.