A small detrital basin located in the Pilbara; WA was identified as a potential site for Managed Aquifer Recharge (MAR) of surplus water generated from nearby BHP mining operations. To initially assess the potential of a site for MAR, a hydrogeological conceptual model is required, along with a subsequent exploration program to test key targets. Traditionally these objectives are primarily met by exploratory hydrogeological drilling to identify the depth to target injection stratigraphy, the location of major structure and dykes, and the thickness and potential clay-rich inclusions of detrital cover. There was limited historical drilling available at the target location. However, several existing geophysical datasets were identified as covering most or all the target detrital basin. These consisted of an open-file airborne TDEM dataset and various mostly open-file airborne magnetic datasets. BHP also had a 2D seismic test line dataset. The XTEM data was inverted, and a conductivity volume generated. This dataset identified the basal clays, a clay-rich layer typically found at the base of iron-rich detrital cover. A surface to the top of this anomaly was generated to assist with hydrogeological conceptualisation/modelling of different MAR scenarios. The magnetic datasets were re-gridded, merged, filtered, and imaged. Key structures and dykes were then mapped from both the magnetic imagery and AEM derived depth-slices and iso-surfaces. The 2D seismic section revealed a syncline-like feature in the cover-metasediment contact, the location of which coincided with an important structure identified from the EM and magnetic datasets, implying that the contact has been preferentially eroded along the structure. These results ultimately translated to a reduction in required exploratory hydrogeological drilling to the effect of ~$500k, ~430 person-hours high-risk hazard exposure, reduced land clearing, and brought forward the timing of the knowledge acquired as the existing datasets did not require lengthy land access approvals.

Open-Access Online Publication: May 29, 2023