Enhancing geological and hydrogeological understanding of the Precipice Sandstone aquifer of the Surat Basin, Great Artesian Basin, Australia, through model inversion of managed aquifer recharge datasets

• Published in: Hydrogeology journal 2020-02, Vol.28 (1), p.175-192
• Main Authors: Hayes, Phil, Nicol, Chris, La Croix, Andrew D., Pearce, Julie, Gonzalez, Sebastian, Wang, Jiahao, Harfoush, Ahmed, He, Jianhua, Moser, Andrew, Helm, Lauren, Morris, Ryan, Gornall, David
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Aquifer management; Aquifer models; Aquifer recharge; Aquifers; Artesian basins; Datasets; Earth and Environmental Science; Earth Sciences; Gas production; Geological faults; Geology; Geophysics/Geodesy; Groundwater; Groundwater recharge; Groundwater resources; Hydrogeology; Hydrology/Water Resources; Injection; Oil and gas production; Permeability; Porosity; Pressure; Sandstone; Sedimentary rocks; Spatial variability; Spatial variations; Treated water; Waste Water Technology; Water Management; Water Pollution Control; Water Quality/Water Pollution; Water resources; Water resources management; Water supply
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-019-02079-9

The Precipice Sandstone is a major Great Artesian Basin aquifer in the Surat Basin, Queensland, Australia, which is used for water supply and production of oil and gas. This report describes use of observed groundwater pressure responses to managed aquifer recharge (MAR) at a regional scale to test recent geological descriptions of Precipice Sandstone extent, and to inform its hydrogeological conceptualisation. Since 2015, two MAR schemes have injected over 20 GL of treated water from coal seam gas production into the Precipice Sandstone, with pressure responses rapidly propagating over 100 km, indicating high aquifer diffusivity. Groundwater modelling of injection and inversion of pressure signals using PEST software shows the spatial variability of aquifer properties, and indicates that basin in-situ stresses and faulting exert control on permeability. Extremely high permeability, up to 200 m/day, occurs in heavily fractured regions with a dual-porosity flow regime. The broader-scale estimates of permeability approach an order of magnitude higher than previous studies, which has implications for the management of water resources in the Precipice Sandstone. Results also show the Precipice Sandstone to have broadly isotropic permeability. The results also support a recent geological interpretation of the Precipice Sandstone as having more limited lateral extent than initially considered. The study shows the effective use of MAR injection data to improve geological and hydrogeological understanding through groundwater model inversion. It also demonstrates the utility of combining hydrogeological and reservoir-engineer datasets in areas explored and developed for both groundwater resources and oil and gas resources.