Optimizing induced seismicity monitoring for CO2 injection at Trüllikon, Switzerland using risk-informed guidelines

The success of geological carbon storage (GCS) operations depends on the effective management of risks, such as induced seismicity. In this study, we consider prior assessments of induced seismicity risks to guide our Measurement, Monitoring, and Verification (MMV) program for a prospective CO 2 injection test site near Trüllikon, Switzerland. A diverse suite of geophysical analyses including fault identification, fault slip potential, fluid pressure modelling, seismic risk modelling, and traffic light design are synthesized into MMV performance targets, based on recent ‘good practice’ guidelines. These MMV performance targets are then used to guide our MMV optimization process. This optimization process indicates that installing seven new broadband stations would improve the magnitude-of-completeness from M L 0.9 to M L 0.0, while lateral and depth resolutions would be improved to 50–100 m (for a M L 1.0 earthquake). While these optimized designs are expected to meet our MMV performance targets, we also provide contingency plans in the case that our estimates are overly optimistic. This contingency largely considers the quantification of noise attenuation with depth, which we estimate to be between a 10-fold to 30-fold improvement, based on a temporary downhole fibre optic deployment. Overall, this study demonstrates how GCS risks can be embedded into MMV design; our workflow can thus serve as a template to guide future GCS MMV designs, long before CO 2 injection operations commence.