Geothermal energy systems – turning Earth’s heat into electricity - constitute a promising renewable energy source. But they require specific geological conditions that are rarely met in Europe. Thanks to the so-called hydraulic pumping process, Enhanced Geothermal Systems (EGS) can now be implemented in areas which were previously not suited to the thermal conversion of ground heat.
However, the injection of high-pressure water into the rocks may induce seismic activity which, though minor, raises public concern. There is therefore a significant need to mitigate the risk of ‘Induced Seismicity’ in EGS projects so as to increase the public acceptance of such projects.
The Research Centre for Geosciences GFZ based in Potsdam, Germany, gathered a set of 11 R&D European partners with complementary expertise in view of setting up a sustainable strategy to assess and mitigate the induced seismic risk attached to EGS projects.
The GEISER project, completed in mid-2013, developed a set of recommendations and a related software tool providing support for the risk assessment of induced seismicity hazard: the “Advanced Traffic Light System” (ATLS).
This new generation of ATLS will form the seismicity-related safety component of the future systems controlling the hydraulic stimulation process. It includes all calculations beginning with real time date feed in (both seismic and hydraulic data) until near real time seismic risk calculations and forecasts.
The innovative features of this ATL lie in:
- The coupling of a deterministic approach to assess the expected loss value per event magnitude, and of a probabilistic approach to estimate the likelihood of the future induced seismicity;
- distinct output metrics to communicate the risk to different interest groups (public authorities/regulators, operators, public, insurances)
- the quantification of parameter uncertainty through a logic tree approach.
The consortium also developed strategies to:
- create public acceptance of an EGS project at a specific location, relying on the assessment of both technical-spatial and social-economic aspects of the EGS project.
- mitigate the induced seismicity risk, by studying the influence of the key parameters in the injection process such as temperature, pressure, fluid volume and time.
- design the seismic monitoring of EGS projects, including methods for the optimization of microseismic monitoring networks.
Why did it work?
Two main drivers can explain the success of the GEISER project:
- the advanced competences of the team, gathering expertise in geoscience, seismology, environmental risk monitoring and geophysics;
- it was the financial support from the EC Framework Programme (FP7-ENV) of over 5M€, that made this project possible.
The methodology and its software framework were developed based on data collected from representative geothermal reservoirs; on modelling approaches, and on some laboratory experiments: the concept maturity is therefore estimated at 4 on the GML scale.
By developing a sound scientifically-based concept for the mitigation of induced seismicity, the project results have the potential to help accelerate the market introduction of EGS in many parts of Europe and beyond.
Towards real time probabilistic seismic risk assessment of induced seismicity for future enhanced geothermal projects”, Delano Landtwing and Stefan, August 2012