Petroleum data: leading the search for geothermal resources in Western Australia

Abstract

In Western Australian basins, subsurface drill-hole data, primarily from petroleum exploration, allows the identification of regions of high temperature at depth that may be potential geothermal resources. The extent and economic viability of such resources remain poorly known and require further study. Observed temperatures at depths up to 4.5 km reach 150°C in parts of the Canning, Carnarvon and Perth basins, indicating low-enthalpy resources related to regional heat flow. The greatest potential for hydrothermal resources is in the Perth Basin where subsurface temperatures of 65–85°C are reached at 2–3.5 km depth. Heat-flow modelling of 170 Perth Basin wells shows a range of 30–140 mW/m2, with the highest surface heat-flow values in the northern part of the basin. The median value of 76.5 mW/m2 for this basin exceeds the average reported for the Australian continent—64.5 mW/m2. Potential hot rocks resources are present in parts of the Canning, Carnarvon and Perth basins where the depth to 200°C is less than 5 km. Knowledge of high subhorizontal stress conditions that can enhance geothermal water flow from engineered reservoirs are based on data mostly from petroleum wells in the Perth Basin. A systematic quantitative assessment of geological, hydrogeological, geophysical, stress orientation and geochemical conditions is required to further delineate and prove these resources. Progressive compilation, validation and interpretation of subsurface data from more than 800 wells is underway, and includes temperature logs of 47 shallow water bores and 30 new thermal conductivity measurements of Perth Basin wells. Data compilation from 580 wells in the Canning, Carnarvon and Perth basins is complete. To date the greatest number of wells indicating high geothermal gradients and temperatures are in the Carnarvon Basin.

Radiogenic Heat Generation in Western Australia — Implications for Geothermal Energy

“…The Northampton Complex (see Figure 1 for location), which is part of the Pinjarra Orogen, has been mapped on the Geological Survey of Western Australia's Geraldton and Ajana 1:250,000 geological sheets [48]. The Northampton Complex forms the pre-sedimentary "basement" of the northern part of the Perth Basin, which is considered to possess appreciable geothermal energy potential, due to high temperatures observed within the sediments of the adjacent basin [12,50]. The high temperatures are presumed to be caused by elevated heat generation in the underlying Northampton Complex rocks.…”

“…Laboratory-based values of concentration reported by Sanders and McGuiness [50] suggest that some localities may be significantly higher (i.e., > 39 ppm) than the aero-radiometric threshold maximum of 19.5 ppm. Rocks from the Northampton Complex are very likely to extend under the north Perth Basin, and they probably contribute to the high temperatures observed in petroleum wells in that region [12,35]. Little definitive work has been carried out to date on the influence of radiogenic elements in the basement rocks upon elevated temperatures in the sediments of the north Perth Basin.…”

“…In his study, Bestow [11] recognized parallels of Western Australian basins to the Paris Basin and the need to achieve temperatures in the vicinity of 65-85 °C. At this early stage, Bestow also clearly recognized that the geothermal potential in Western Australia was best based around the concept of hot sedimentary aquifers, rather than either the engineered geothermal systems (EGSs) being advocated elsewhere in Australia [12,13] or the more commonly exploited volcanogenic heat sources.…”

Temperature and Heat Flow Information for Geothermal Energy Exploration in Western Australia

“…Although these observations are based on a limited number of wells it indicates that the area north of Onslow has the highest temperatures ( Figure 2). Given its shallow high-temperature areas the Carnarvon Basin has a high potential for geothermal energy development, provided other factors are also found favourable for developing HR and HSA (Chopra and Holgate, 2007;Driscoll et al, 2009;Ghori, 2009;Ghori, 2010).…”

“…AUGUST 2011 (Bestow, 1982). Geothermal exploration and exploitation was formalized in 2008, after a two-decade long break (Ghori, 2009). Presently, the Perth Basin is the most attractive target for geothermal energy research, exploration and development with six companies and two research institutions exploring in 31 GEPs (Middleton and Bruce, 2010).…”