The overall strategy for the GEISER project is to start with a collection of representative data for comparison and analysis. On the basis of the analysis and detailed investigations into the mechanisms and processes involved in induced seismicity in geothermal developments, seismic hazard will be assessed and ground shaking scenarios will be calculated. At the end, guidelines for licensing of geothermal project will be prepared and strategies for the mitigation of induced seismicity during geothermal development and operation will be proposed. To reach these goals, the project is broken down into seven workpackages (WP) lead by one of the GEISER partners:
WP1: Project Management. GFZ.
WP2: Compilation of induced seismicity data from geothermal sites. ISOR.
In this WP, data on induced seismicity from representative sites in Europe are collected, to provide an overview of lessons learned from previous experience. This workpackage is designed for the smooth exchange of data between partners and to guarantee sufficient, comparable of these data from the various sources. For this purpose, data are checked and homogenized for comparison and further use in the other workpackages.
WP3: Analysis of Induced Seismicity. GFZ.
Different seismological approaches will be applied and further developed to analyse data sets of induced microseismicity from geothermal areas. Based on the evolution of induced seismic activity in space and time, the interrelation between the specific local geological settings, injection parameters and the occurrence of fluid-injection induced seismic events will be addressed.
WP4: Understanding the Geomechanical Causes and Processes of Induced Seismicity. BRGM.
Different modelling approaches and laboratory experiments will be performed to investigate some of the key factors influencing induced seismicity: The goal is to come to a better understanding of the basic physical mechanisms that induce microseismicity and to deliver management and production scenarios with relative estimates of the stress-state changes for different geothermal settings.
WP5: Seismic Hazard Assessment. ETHZ.
On the basis of the results from WP3 and WP4 and considering natural seismicity, WP5 assembles all the components of hazard assessment to be conducted before the selection and start of operations at an EGS site, to result in Guidelines for best practice. This will include the analysis of the natural background seismicity, an estimate of the ground shaking produced by the microseismicity induced during the initial stimulation phase and the probability of triggering a large earthquake (M>4) ahead of its natural time of occurrence, either during the stimulation phase or during the long-term EGS operation.
WP6: Strategies for EGS operations with respect to Induced Seismicity (Mitigation). TNO.
The objective of WP6 is to provide strategies to operators and regulatory bodies to achieve this. These strategies are targeted at guidelines for regulatory bodies for the selection, licensing and long-term operation of EGS sites in different geological settings, at developing the concept of “soft stimulation”, at proper monitoring of induced seismicity, and at a minimization of the risk.
WP7: Dissemination. BRGM.
The achieved understanding and the recommendation for standardized procedures will be disseminated among stakeholders/industry and public authorities as well as the scientific community.
Interdependencies of workpackages
Following the concept of the project to bring together expertise in geothermal utilization, seismic hazards, and public awareness all workpackages are strongly interconnected. The database generated in WP2 provides the basis for the applied work of all the other workpackages. In addition, a state of the art of induced seismicity in geothermal field development will be defined, based on literature review. The investigation of spatio-temporal characteristics of fluid-injection induced seismicity and the analysis of background and induced seismicity performed in WP3 will provide essential input parameters for the modelling part in WP 4. Understanding the role of large magnitude events (LME) in controlled reservoir stimulations as investigated in WP 3 is important for the modelling in WP4. Results from both WP3 and WP4 will be used for seismic hazard assessment in WP5 as well as for the mitigation concepts to be developed in WP6: a) Design and optimization of seismic network and earthquake monitoring procedures with input from WP3; b) The model of elastic interactions in porous, heterogeneous and fractured media role of existing faults segments and temperature from WP4. The theoretical work in WP4 will also provide the basis for a soft stimulation strategy (targeting at mitigation of induced seismicity) to be proposed in WP6. The guidelines resulting from work in WP5 have a direct impact on the strategies in WP6. Finally, all activities will contribute to the Dissemination in WP7.