The Petratherm geothermal exploration experiment began in Australia and the Paralana “hot-rock" project, located 11 kilometres from the Beverley Uranium Mine in South Australia, is to be jointly developed by Petratherm, Beach Petroleum Ltd and TRUenergy. The initial drilling and stimulation of the two wells will create an underground heat exchanger involving circulation of water between the wells through rock fractures – to demonstrate a commercial “hot rock" energy resource.
Petratherm geothermal aims to initially provide electricity to the local growing needs of the Beverley Uranium Mine, from around 7.5 MW building to 30 MW – and then to expand to around 520 MW and supplying the Australina National Electrcity Market, via two entry points, namely, Port Augusta and Olympic Dam.
In May 2009, Petratherm and its joint venture partners – Beach Petroleum and TRUenergy Geothermal signed a Geothermal Drilling Program Grant Funding Agreement with the Australian Government for $7M.
The company also has a geothermal exploration permit in east Gippsland (Victoria), and two more permits in Renmark (South Australia).
The Renmark tenements cover the Renmark Trough and if successful plants would be ideally situated to two major transmission lines capable of carrying in excess of 220 MW of power.
The Petratherm geothermal company announced on 1 November 20006, that it was successful in obtaining Project endorsement from the Asia Pacific Partnership on Climate and Clean Development (AP6) to undertake a study to “Identify high prospect geothermal energy projects in China". The Project proposal involves a study of the geothermal prospectivity of China over the next nine months, utilising Petratherm’s innovative Exploration Model to identify high quality, commercial geothermal projects.
Petratherm has commenced securing geothermal energy sites in Spain. An application for Geothermal Exploration Licences (GEL’s) has been made in an area 50 kilometres northeast of Madrid and in close proximity to two major high voltage transmission lines capable of carrying in excess of 1000 MW. Through a newly formed company – Petratherm España – a process of securing key project sites is under way. Petratherm has applied its innovative approach to “exploring for shallow hot rocks, close to market" and has initially identified four areas that meet the Company’s commercial criteria.
“Naturally occurring heat from the earth is a massive, environmentally friendly energy resource. As the earth is constantly generating heat, the energy is classified as a renewable resource. One of the processes of extracting heat, which is then used to generate electricity, is outlined above. In this process water is pumped down a borehole into a hot rock source where temperatures are typically between 200°C and 280°C.
The water flows away from the injection well through a network of tiny fractures, either naturally occurring and/or by hydraulic stimulation of the natural system. As the water passes through the fracture reservoir it is rapidly heated to a high temperature by contact with the hot rock – this is known as the underground heat exchanger. Under pressure the heated water then returns to the surface via a production well located several hundred metres away from the original injection well. Although the water is at temperatures in excess of 200°C, the high pressures associated with the closed loop system prevent it from turning to steam."
“At the surface the superheated water is passed through a heat exchanger where most of the heat is extracted. The heat extracted from the water in turn heats a low boiling-point liquid, which boils, producing high-pressure steam used to drive electricity turbines. The surface heat exchanger is another closed-loop fluid system. The cooled water is then re-injected back down the injection borehole to be reheated and used again. A “farm” of injection and production wells could be used to produce large-scale, constant and renewable power." (from Petratherm Pty Ltd)
More information can be obtained from the Petratherm geothermal web site.