Using the Migration of the Induced Seismicity as a Constraint for Fractured Hot Dry Rock Reservoir Modeling

Heat extraction from deep 'engineered' fractured formations is currently under investigation at many places in the world. The challenge is to develop a reservoir in deep rock masses, to circulate a fluid and to recover heat for clean electricity production at the surface. In most cases, the promoted technology is to force cracks that pre-exist in deep rocks by injection of pressurised water as the effect of a pore pressure increase is to weaken fracture strength. Failure in fractures is explained by a linear relation in between shear stress at failure and normal stress, with two parameters, the internal friction μ and the internal cohesive strength C. When failure develops along particular fractures, frictional slip occurs. The triggered dislocations are accompanied by AE which are recorded and processed for the evaluation of the success of the hydraulic treatment. However many uncontrolled events with unwanted seismic magnitude are reported that may trouble public acceptance for this CO2 free source of energy.