IESE Borehole Seismology and Seismic Networks
At IESE our seismic research interests lie in the study of tectonics, microearthquakes and borehole seismic networks, and the application of this knowledge and technology to geothermal exploration and microseismic monitoring, including monitoring induced seismicity during fracking.
Why study microearthquakes?
Too small to be felt at the surface, the vast majority of earthquakes are tiny. But when carefully measured, these microearthquakes (MEQs) provide a significantly improved view of the subterranean fractures and faults. For geothermal developers, MEQs help to accurately identify the movement of subsurface fluids and therefore give clues for potential drill sites.
Our experience has shown that the best method of detecting and monitoring MEQs is to establish a borehole seismic network. Placing a seismometer down a borehole isolates it from ambient surface noise - including everything from wind to trains – and attenuates the weather layer at the surface. The deeper the borehole the better the results for identifying earthquakes!
Borehole Seismic Networks
The IESE senior scientific team has more than 25 years field experience in designing borehole networks and deploying instrumentation in plate boundaries, fault zones and geothermal fields around the world for national governments and other major industry clients.
IESE’s microearthquake monitoring networks are being used to assist in geothermal development and management by tracking the locations of seismicity that relate to fluid production and injection fracking.
Our team's collective experience in borehole network projects include:
- Geothermal Exploration and Monitoring Projects
Wairakei, New Zealand: installation of a world-class borehole seismic array of 10 stations at a depth of 50 - 200m in the oldest operating geothermal field in New Zealand, providing real-time data about the micro-earthquake activity in the field. The field operator, Contact Energy, will use these data to monitor, manage and possibly expand operations at Wairakei.
Coso Geothermal Field, USA: installation, operation and analysis of the seismic network, lead to the development of S-wave splitting tomography for locating fractures as drilling targets. Subsequent electromagnetic and drilling studies confirmed the locations and size of potential high permeability zones.
Krafla Volcanic Field, Iceland: deployment of a 6 station borehole network in 100m boreholes, surface seismometers and electromagnetic (MT and TEM) soundings. The IESE integrated model of the field provided optimum drilling targets, and subsequent drilling yielded one of the most productive wells in the field.
Puna Geothermal Fields, Hawaii: installation of 8 station networks in 100m boreholes.
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- Enhanced Geothermal Systems projects
EGS is an exciting new high-potential geothermal technology of extracting energy from hot dry rock within the earth by circulating water through hot rock. The process involves fracking the subsurface rock, which generates small seismic events (induced seismicity). By utilising a borehole seismic network at project sites, the location of these microearthquakes can be readily detected and magnitude monitored. This valuable seismic data can then be interpreted for accurate well targeting while also ensuring precautionary safety measures are taken.
IESE staff have been developing advanced, data based models of the complex interactions of hot rocks and fluids, erratic flow pathways, and the deformation effects of temperature and pressure changes.
IESE staff have monitored the following EGS - Fracking projects:
Hot Dry Rock Experiment in Basel, Switzerland: responsible for the construction of a 6 station seismometer and accelerometer borehole monitoring network, including instruments at 1.2 and 2.7km, and the collaborative analysis of induced seismicity.
Paralana, Australia: installation of what is currently the deepest seismometer in Australia down the 1800m well. Supplementing this deep station is an array of shallower ‘post-hole’ seismometers and surface seismometers, which together form a robust seismic monitoring network. This seismic network will provide real-time feedback on the field during drilling and hydrofracking.
Borehole Monitoring Network, Svalbard, Norway: 5 level 300m seismic array; 3 posthole 15m seismic stations; real time CO2 sequestration monitoring
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