This report details the evaluation of formation damage to each well from either drilling or production.
Achieving economic fluid flow rates from deep geothermal reservoirs is one of the most significant technical challenges confronting the Australian geothermal industry. Geothermal resources hosted within sedimentary basins, also known as Hot Sedimentary Aquifers (HSA) were targeted by developers because unlike fractured granite systems, they were thought to have high natural permeability, so these systems may not require significant reservoir enhancement to achieve economic fluid flows. However, the natural permeability of sedimentary reservoirs can be reduced by diagenesis, where the nature of sediments changes as they are buried. Diagenesis is controlled by parameters including temperature, pressure, mineralogy, and fluid-rock interactions. Drilling activities can also cause damage to the sedimentary rocks in the vicinity of the drill hole, masking the true permeability of the reservoir.
Finally, the act of producing hot water from sedimentary reservoirs can also cause formation damage as fine particles migrate under production towards the well.
Two geothermal wells have been drilled into HSA plays in Australia: Panax Geothermal Ltd tested their Penola prospect with the 4025 m Salamander-1 well, targeting the Pretty Hill Formation in the Otway Basin, and the Origin Energy Ltd -Geodynamics Ltd JV tested their “Innamincka Shallows” prospect with the 2416 m deep Celsius-1 well, targeting the Hutton Sandstone in the Cooper-Eromanga Basin (Figure 3A).
This project entitled Reservoir Quality in Sedimentary Geothermal Resources is a collaborative research effort between research institutions the University of Adelaide, CSIRO, the South Australian Museum, geothermal development companies Geodynamics Ltd and Raya Group Ltd, and is co-funded to the tune of $1.25 million by the Australian Government’s Australian Renewable Energy Agency (ARENA).