Numerical Analysis of Hydro-Mechanical Behavior of Faults: Impact of Hydraulic Conductivity Variation on the Pressure Buildup Due to Co2 Injection

Abstract This study aims to create a advanced numerical model to estimate the effect of fault reactivation caused by carbon dioxide (CO2) injection on the pressure field in nearby rock formations. The study also evaluates the hydro-mechanical stability of adjacent faults under different pressure conditions during underground CO2 injection. The investigation explores the hydro-mechanical response of faults, especially the changes in hydraulic conductivity with fault opening and how they influence fault reactivation. Our methodology uses zero-thickness interface elements in a Finite Element Method, with adequate constitutive model, to precisely simulate single-fault planes behavior during coupled hydro-mechanical processes. This approach improves existing models in rock mechanics by allowing accurate sensitivity analysis of fracture transmissivity to normal stress variations and shear displacement. We incorporate Poiseuille's cubic law and also thin layer model law to account for changes in hydraulic conductivity due to mechanical deformation. The fault mechanical behavior is described using an elasto-plastic nonlinear model, which effectively captures the complex interdependencies between elastic and plastic strains under variable stress and fluid pressure conditions. Using the Finite Element software, our numerical simulations provide important insights into the behavior of faults under seismic and aseismic conditions induced by CO2 injection. The study investigates various injection scenarios, focusing on the pressure buildup and subsequent dissipation during rest periods, with particular emphasis on the interaction between fault and reservoir permeabilities. Our findings reveal significant variations in pressure dissipation patterns, depending on the mechanical properties and initial permeability of the geological formations. These results contribute to a deeper understanding of pressure distribution dynamics and fault reactivation processes, offering valuable implications for managing induced seismicity in CO2 sequestration projects. This study presents a new and comprehensive modeling approach to estimate fault reactivation and its hydro-mechanical consequences within CO2 injection contexts. By integrating mechanical and hydraulic factors in fault behavior analysis, the research enhances our understanding of fault responses to induced pressures, thereby aiding in the development of more effective risk assessment and mitigation strategies. The introduction of advanced numerical techniques and detailed sensitivity analyses provides a robust framework for future studies on fault stability and induced seismicity.