Tasmania is our flagship Enhanced Geothermal Systems (EGS) project.
Why Tasmania?
Based on their long experience in the geological and geophysical characteristics of Tasmania, and being aware of the criteria for the successful exploitation of geothermal energy, company founders Dr John Bishop and Dr Roger Lewis thoroughly reviewed the available data pertaining to possible geothermal systems in Tasmania. They found promising data surrounding the presence of geological structures that would infer the existence of favourable enhanced geothermal energy inputs, primarily a large radiogenic heat source and strong thermal insulation.
Tasmania contains several large granite masses and the granites associated with tin mineralisation are enriched in the radioactive elements and generate high heat fluxes. Eastern Tasmania contains buried extensions of granitic bodies which, based on surface scintillometer measurements, and elevated heat flow measurements from several boreholes, were known to be thermally anomalous and where temperatures may be high enough to support electricity generation.
Published modelling of the measured gravity field throughout eastern Tasmania clearly indicated that the exposed granitic bodies in eastern Tasmania dip under sedimentary and other rock cover, such that significant areas may lie between the prospective 3 to 5 km vertical depth zone. Furthermore, MRT and exploration company investigations demonstrate that the sedimentary rock package overlying the granitic bodies include a widespread sequence of coal measures and other carbonaceous sediments. Rocks containing carbonaceous material, such as coal, have elevated thermal insulation properties, so any heat generated beneath the coal will have a smaller proportion transmitted through, compared to rock sequences of higher thermal conductivity. In effect providing a high quality thermal blanket provided by three to six kilometres of sedimentary rocks.
In addition to the target of the Thermally Anomalous Granites, a particular target was the known zone of relatively high electrical conductivity known as the Tamar Conductivity Zone. University Studies have shown that a large, deep zone striking parallel and adjacent to the Tamar Valley from Bass Straight to the central midlands area is anomalously electrically conductive. The most likely cause of this electrical conductivity is a brine filled fracture zone. If this is the case, then should that fracture zone intersect a thermally anomalous granite at depth, the fracturing component of a deep geothermal system (which usually needs to be artificially enhanced) may be, at least in part, already present.