Interpretation of Reservoir Creation Process at Cooper Basin, Australia by Acoustic Emission‪.‬

Abstract Hydraulic stimulation of an engineered geothermal reservoir has been carried out at Cooper Basin hot-dry-rock (HDR) field, Australia in 2003. AE monitoring network, which consists of four near surface and one downhole stations, detected approximately 32,000 triggers during the stimulation and approximately 12,000 of them have been located on-site by the single-event determination method (SED). The location of AE showed a sub-horizontal structure that is consistent with the state of tectonic stress and the orientation of existing fractures in the corresponding field. We have estimated the composite focal mechanism, and it showed a reverse fault with a low inclination to West. The plane of the nodal plane agrees well with the structure by the locations of AE. We found that the plane from the focal mechanism is nearly under the critical stress state for shear slip at Cooper Basin. The AE activity was higher than that at Soultz field, where EU and other organizations are carrying out an HDR project, suggesting that the stress state in Cooper Basin site is closer to critical.