In the last quarter of 2003, a hydraulic stimulation was carried out at Cooper Basin HDR field, South Australia. More than 30,000 microseismic events were detected and over 11,000 events have been located by SED(Single Event Determination)/JHD(Joint Hypocenter Determination). The source distribution was showing sub-horizontal structure which has a size of 3.2 km by 2.5 km with a thickness of 200 m, and was consistent with the tectonic stress field at the site. However, the fine scale structures of the fracture system in the reservoir has not been clear, because the source location accuracy is not enough to distinguish the fine scale structures in the microseismic cloud due to the location error. In this paper, we have used the induced microseismic multiplet to reveal the detailed reservoir structure. The microseismic multiplet is a group of microseismic events with similar wave-forms, and they are considered to be induced by shear slips of the same fracture plane or structure. Using the coherency function to search for multiplets indicates that 96% of located events are multiplet events. The source locations of multiplets have been determined by solving DD (Double-Differential) equation. The results suggest that the microseismic source distribution is composed of sub-horizontal planer clusters that are sub-parallel to each other and dipping to West with low inclination, and the thickness of each seismic cluster is less than 50m.
- Cooper Basin
- Enhanced Geothermal System
- Hot Dry Rock
- Microseismic multiplet
ASJC Scopus subject areas
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering