The Government-Industry-Academia research collaboration entitled Reservoir Quality in Sedimentary Geothermal Resources is comprised of three programs relating to the “failure analysis” of Hot Sedimentary Aquifer (HSA) geothermal exploration wells Salamander 1, drilled in the Otway Basin, and Celsius 1, drilled in the Cooper-Eromanga Basin. The project aims were to conduct a scientific research-driven analysis of the two geothermal wells – the only ones drilled in HSA reservoirs in Australia, and to evaluate why the achieved fluid flow rates were significantly lower than expected. Two failure analysis Programs were undertaken. The first Program involved evaluating the primary reservoir quality of the two target formations – the Pretty Hill Formation in the Otway Basin, and the Hutton Sandstone in the Cooper-Eromanga Basin. The second Program involved evaluating formation damage that may have been caused during the drilling of the two wells and subsequent production tests. Researchers from the University of Adelaide, CSIRO and the South Australian Museum collaborated to conduct petrology, SEM, TEM, QEMSCAN, cathodoluminescence and seismic attribute analysis. Laboratory experiments simulating secondary mineral growth and fines production under different conditions were conducted. Analysis of results to allow reservoir behaviour to be modelled also occurred. The conclusions reached from Program 1 were that diagenetic factors have made the deep, hot water reservoirs less permeable than hoped, but that the effects are not uniform basin-wide, and that it may be possible to identify more permeable zones using seismic and petrology. Program 2 concluded that formation damage is more likely in hot water settings than hydrocarbon reservoirs under production, but there are ways that this can be mitigated.

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