The Permit covers an area of 9000 square kilometres, which covers the onshore component of the Gippsland Basin (Bairnsdale - Lakes Entrance area) and is prospective for Hot Sedimentary Aquifer (HSA) geothermal resources for power generation (Figure 1).
The exploration model targets potential permeable reservoir sequences which may contain brine fluid in excess of 150ºC at economically viable drill depths (3.5 - 4.0 kilometres) (Figure 2). Geothermal target areas within the tenement area are well located close to significant power station and transmission infrastructure.
Published analysis by the Victorian Department of Primary Industries into the State's geothermal energy resrouces demosntrated the potential for electricity generation, with evidence of low to mid enthalpy sedimentary aquifers in both the Otway and Gippsland Basins. Petratherm's internal geological, economic and permitting review of the license area indicates that a medium (30 MW) to large (200+ MW) geothermal power development could produce power at a cost of less than $100/MWh. The current and future Victorian pool price for electricity, combined with the current and forecast price of renewable energy certificates (RECs), or future carbon price under an emissions trading scheme (ETS) indicate that a commercially viable geothermal power development is achievable.
Approximately 50 wells have been drilled in the eastern onshore Gippsland Basin area where temperature and some continuous geothermal gradient data have been captured by the Victorian Department of Primary Industries. In the Lake Wellington/Lakes Entrance area a cluster of deep wells provide an accurate view of likely geothermal gradient at depths >3000 metres. High geothermal gradients have been reported which imply temperatures in excess of 150ºC lie at depths of approximately 3500 metres. The Lakes Entrance coastal fringe region appears to be particularly promising. The Wellington Park 1 well drilled at 3660 metres is the deepest in the region (Figure 1). Several temperatures were measured in the well. The temperature recorded from logging tools at 3660 metres was 136ºC and the estimated equilibrium bottom hole temperature is estimated to be 163ºC in the absence of the cooling effects of drilling.
The target reservoir rocks in the Lakes Wellington/Lakes Entrance area are the Tyers Conglomerate and the Rintouls Creek Sandstone, which unconformably overlie the Paleozoic basement in the license area. These have not been intersected in the license area, however outcrop samples to the west demonstrate some primary permeability and high porosity. In the vicinity of the Wellington Park 1 well, seismic data indicates that the favourable horizon is at 3500-4500 metre depth.
Another potential reservoir horizon is situated in the top section of Paleozoic basement rock and along the basin floor surface. The topmost basement (possibly palaeo-weathered) may yield high secondary fracture permeability as demonstrated in operating Engineered Geothermal Systems at Soultz and Landau in the Rhine Graben of Europe.
The first stage of works will involve delineation of target sites based on re-evaluation of existing seismic data and targeted magneto-telluric and possibly further seismic ground survey work. As there is an established understanding of the regional temperature gradient at depth and good geological control from historical drilling and seismic survey work, there is no requirement to undertake shallow gradient test wells. The work program comprises the drilling of a production grade deep well (3.5-4.0 kilometres) in year three of the licensing period, reservoir development and then a second deep production grade well in year five in order to test closed loop circulation of the potential geothermal system.
Keep up to date with what is happening around Petratherm by subscribing to the alerting service below.