Numerical Modeling for the Characterization of Fractured Damage Zones in Geological Faults

Resumo

Geological faults play a crucial role in the compartmentalization of reservoirs within rock formations due to the presence of impermeable fault cores. However, faults are not exclusively characterized by impermeable surfaces; they are also accompanied by adjacent damage zones formed by fracture networks. These damage zones may function as preferential pathways for fluid migration in cases where a high concentration of fractures is present. Consequently, an appropriate representation of these zones is imperative for the definition of more effective production strategies in oil fields. A variety of approaches have been proposed, including numerical modeling utilizing the finite element method and elastoplastic constitutive models through classical continuum mechanics. However, the depiction of damage zones as continuous domains often fails to adequately represent dominant fracture networks. Other methodologies employ fracture mechanics theory with elastic models to assess the formation, orientation, and propagation of fractures. However, the complex fracture networks frequently observed in fault damage zones cannot be accurately modeled using these approaches. The continuum model is not capable of explicitly representing fractures, leaving both their orientation and propagation path uncertain. In contrast, cohesive models employ a tailored finite element mesh that can simulate the nucleation and evolution of cracks within the continuum, allowing for an explicit representation of fractures. In light of this, the present study proposes the development of numerical models applied to geological faults, focusing on the representation of fractures through cohesive interface elements capable of explicitly simulating the propagation of discontinuities within the damage zone. The results obtained allow for the evaluation of fracture networks in wall and tip damage zones, highlighting some correlations with outcrop data.