## StressInversion ‑ geomechanical analysis

StressInversion is a proprietary effective, autonomous tool that specifies the stress state that accounts the best for a set of microearthquake focal mechanisms.

The orientations of the principal stress axes σ_{1}, σ_{2} and σ_{3} (σ_{1} > σ_{2} > σ_{3}) are determined from passive seismic datasets, adding a new value to the existing microseismic data. Using the orientation of the stresses, one can optimally place wellbores optimizing the recovery from a reservoir.

StressInversion recovers four parameters of the stress tensor: three angles defining the directions of the three principal stresses, σ_{1}, σ_{2} and σ_{3}, and the ratio between their differences, Φ = (σ_{2} - σ_{3}) / (σ_{1} - σ_{3}). StressInversion calculates the effective stress corresponding to a homogeneous tectonic stress in the source region. The uncertainties of the retrieved stress directions are calculated by the jack-knife method.

Left picture: Variability of the input source mechanisms of events recorded during the Soultz injection experiment in 2003. Stacked principal axes: T-axes - triangle apex up, P-axes - triangle apex right. Right picture: The results of StressInversion. Stress is inverted using the 45 focal mechanisms from input. The optimum position of the directions of the principal stresses σ_{1}, σ_{2} and σ_{3} are marked by darker colour symbols. Clusters of same coloured symbols denote the confidence zones of maximum σ_{1} (red), medium σ_{2} (grey) and minimum σ_{3} (blue) stress axes derived from the jack-knife uncertainty test.

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