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Hot Fractured Rock Update

Page history last edited by PBworks 15 years, 6 months ago

Geothermal Energy in Australia.

 

Update Hot Fractured Rock Geothermal Australia . 13 th September 2008-09-14

 

The concept of obtaining power from hot fractured rocks is to pump water down an injection bore , pass it through hot fractured rocks usually granites and recover the very hot water +2000C up a production bore. The water loop returns it to the injection bore via a heat exchanger to transfer the heat to a secondary circuit which drives a turbine generator.

 

Progress in the production of electricity in Australia by using the energy available from hot fractured rocks is taking a little longer than first anticipated. Drilling to depths of 5 kilometres in very hot rocks is taking drillers into new territory. It is slow, tough on drill bits , and a drill bit change can take 24 hours. A down the hole drive turbine was used successfully . Geodynamics the company operating in South Australia and furthest ahead bought a Lightning 100 drilling rig from USA to overcome difficulties it had experienced drilling its second bore down to 4500 metres. A third hole has been completed down to 4250 metres using the new rig. It penetrated the hot granite for approximately 600 metres and as expected , the granite was suitably fractured and this was enhanced by pumping fluid at very high pressures down the bore and expanding the fractures to allow good circulation of water between the injection well (first hole bored and the third bore hole, the production well sited 500 metres away . The temperature at the bottom of the hole was 244 degrees centigrade . The company is in the process of testing the continuity of the circulation between the two holes for a six weeks duration to confirm the proof of their concept. The company is expecting , in early 2009 , to have one megawatt of power available which has been produced from a turbine driven with exchanged heat in a Kalina cycle. In the meantime a fourth borehole sited 9 kilometres from the third , has reached a depth of 4900m and will be terminated at 5000 metres its target depth.. After testing, another 5000metre bore is planned 10 kilometres further away .The target granite has been radiogenetically heated and is very well insulated from the surface. It is envisioned that six bores would be needed to be sunk to the deep heat exchange zone to power a 50 megawatt power plant.

 

Another company Petratherm , operating about 200 kilometres away expects to develop an underground heat exchanger in very hot sediments due heated by uranium decay at a depth less than 4 000 metres. It is waiting to receive a big Lightning 100 drill rig before commencing drilling to penetrate to its target and test its concept .

 

Other companies , mostly in South Australia , are drilling shallower exploration bore holes to confirm high heat flow gradients and these are all nearer consumers than the Geodynamics site.

 

posted by Dick in Australia

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