Publication Name: PESA's Eastern Australasian Basin Symposium II
Authors: D. Wyborn, L. de Graaf, S. Davidson and S. Hann
Date Published: December 2004
Number of Pages: 25
Reference Type: Book Section
Abstract:
Geodynamics Limited has successfully completed the first half of its 'Proof of Concept' hot fractured rock (HFR)program to extract hot water for electricity generation from granite buried beneath the Cooper Basin, South Australia. Difficult drilling conditions were discovered in the target granite when the Habanero-1 well penetrated permeable subhorizontal fractures at more than 4,000 m depth. The well was completed at 4,421 m with overpressures in the fractures exceeding the hydrostatic pressure by over 5,000 psi. The static rock temperature at the bottom of the well is expected to be more than 250?C.
The overpressures assisted in the development of the world's largest zone of artificially enhanced permeability, a volume of rock more than 0. 7 km' defined by more than 11,700 microseismic events. The stimulated volume resulted from the injection of 20ML of fresh water into the granite fracture network at pumping pressures up to 9,500 psi. The stimulated volume is more than 2 km NS, 1 km EW and 300 m thick. During its development it showed no evidence of upwards growth towards the sedimentary cover located at around 3,700 m.
The development so far indicates that there is a very good potential for economic energy extraction in the future. This potential has been considerably enhanced by the discovery of the overpressures in the granite fracture network which could add a large convective heat component into the original design which was based purely on conductive heat transfer within the heat exchanger volume.