Shear instability in geothermal fields under hydromechanical feedback

Abstract

A recent trend in improving the seismic safety and economic efficiency of enhanced geothermal systems in deep rock formation has led to an interest in the underlying mechanisms of shear stimulation. This contribution investigates the formation of shear localization patterns around an injection hole in deep geothermal reservoirs considering thermo-hydro-mechanical coupled processes. The constitutive formulation treats the target rock layer as an elasto-visco-plastic material with an Arrhenius dependence taking into account the effect of pore fluid pressure. Considering the thermal pressurization effect resulting from frictional heating, the role of system heterogeneity and the influence of injected fluid temperature are investigated. The findings of this study indicate that a deeper layer and a hotter injection would favor localized shear deformation around a deep borehole and hence an effective network of fluid pathways.