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StressInversion ‑ geomechanical analysis

StressInversion is an effective, autonomous tool that specifies the stress state that best accounts for a set of microearthquake focal mechanisms. The orientations of the principal stress axes σ1, σ2 and σ31 > σ2 > σ3) are determined from passive seismic datasets, adding new value to existing microseismic data. Using the orientation of the stresses, one can optimally place wellbores optimizing the recovery from an reservoir.

StressInversion recovers four parameters of the stress tensor: three angles defining the directions of the three principal stresses, σ1, σ2 and σ3, and the ratio between their differences, Φ = (σ2 - σ3) / (σ1 - σ3). 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.

Stress inversion       Stress inversion
Left: 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: The results of StressInversion. Stress is inverted using the 45 focal mechanisms from input. The optimum position of the directions of the principal stresses σ1, σ2 and σ3 are marked by darker colour symbols. Clusters of same coloured symbols denote the confidence zones of maximum σ1 (red), medium σ2 (grey) and minimum σ3 (blue) stress axes derived from the jack-knife uncertainty test.