Initiation and propagation of fracture shearing during hydraulic stimulation in enhanced geothermal system

•Develop generic model to estimate shearing growth direction in EGS stimulation.•Perform generic study on effects of stress condition on shearing.•Propose idea to compute orientations with high tendency for shearing in practice.•Perform case study of shearing growth for Soultz EGS site.

This paper develops a generic model to estimate the location of shearing onset, the required pressure, and the overall shearing growth direction during the hydraulic stimulation in Enhanced Geothermal System, for which massive volume of fluid is injected into the fractured rockmass through a long open hole section. General studies on the effects of the stress condition on the shearing initiation and propagation captured some basic features related to the observed induced seismicity. Upward growth of shearing prevails for most stress conditions and a dense fluid favors downward shearing. Performed case studies demonstrate the developed method is potentially applicable to provide first order assessment of shearing initiation and propagation during hydraulic stimulation in a fractured EGS reservoir.