Coupling Flow-Geomechanical Model for Stimulation of Fractured Geothermal Fields

Geothermal energy, with its combination of very low CO₂ emission rates and the possibility of providing electricity, has the potential of being a key factor in the global greenhouse gas emission reduction. Some geothermal systems, however, require stimulation to achieve economic production. To simulate the effectiveness of stimulation techniques, a synergy between dynamic flow simulators and geomechanical models is crucial. Especially in volcanic environments. Such systems are characterized by a high fracture density, fluids are generally stored in the pores of the rock mass, but the fracture network, rather than the connectivity of the pores, provides the conduits for fluids and heat to flow through the reservoir. Injecting fluid alters the stress field in the area. If the induced extra pressure is larger than the rock strength, it propagates tensile fractures in the rock, enhancing the conductivity and permeability. For smaller pressures, the reduction of the effective stress might cause hydro-shearing of existing fractures. Moreover, injecting fluid colder than the in situ temperature will generate thermal stresses, with similar effect on the fractures. To tackle all those aspects, we linked numerical simulators and analytical solutions to connect the evolving fluid properties and temperature with the changes in the stress field.