In Situ Stress in Switzerland – From Pointwise Field Data to a 3D Continuous Quantification
International Workshop on Geomechanics and Energy
Motivation The 3D in situ stress state is an important field variable to assess the reactivation potential of tectonic faults and to predict the future structural evolution over geological time spans. Furthermore, it is a critical parameter for a wide range of underground engineering activities addressing questions with respect to stability aspects as well as productivity for georeservoirs [Fuchs and Müller, 2001; Moeck and Backers, 2011] . Stability refers e.g. for safe drill path, long-term
... ability of nuclear waste disposal sites or CO 2 sequestration in the underground. For the depletion of georeservoirs, re-injection of waste water and hydraulic fracturing to enhance permeability, the in situ stress is critical as it determines how much stress changes the reservoir can sustain before e.g. sealing faults are reactivated or cap rock integrity is affected. Knowledge of the in situ stress state is also required in order to forecast the effectiveness of hydraulic fracturing performed to enhance the permeability and thus productivity. However, data of the in situ stress are in general very sparse and incomplete as only a subset of the six components of the 3D stress tensor is available. E.g. the World Stress Map (WSM) Project compiles globally the contemporary orientation of maximum horizontal stress S H , but it has only 21,750 data records in the upper 40 km . A compilation of stress magnitude data is in progress, but the global dataset has so far only ~1200 data records [Zang et al., 2012] . In order to determine all components of the 3D stress tensor spatially continuous, a geomechanical-numerical model has to be set up and calibrated against the stress information.