Numerical Modeling of Geological Fault Reactivation Using Sequential Coupling Strategies

ABSTRACT The interaction between fluid flow and mechanical deformation in fault zones can lead to processes of fault reactivation, triggering potential geomechanical problems such as seismicity, well collapse, fluid migration to shallower layers, and aggravated surface subsidence. During the production phase, fluid injection/production alters the stress state near a geological fault, which may compromise the integrity of initially sealed faults. Some approaches based on either one‐way or fully implicit analyses have been used to predict the reactivation of geological faults. Fully‐implicit approaches are, in theory, the most accurate because the governing equations are solved conservatively in a single system. However, their application is restricted owing to several issues, such as convergence and computational effort. On the other hand, one‐way analyses are easy to implement and provide solutions at lower computational costs. Unfortunately, they trigger inaccurate results depending on the coupling level between fluid flow and geomechanics. This work proposes two‐way sequential coupling strategies based on fixed stress rates for forecasting fault reactivation and leakage. Such strategies are implemented through explicit and iterative techniques between fluid flow and geomechanics. The implemented coupling strategies are verified against relevant numerical solutions by simulating a reservoir production problem and the fault reactivation analyses. Then, all strategies are compared in terms of accuracy, stability, and computational time. The results show that the proposed two‐way sequential strategies overcome the drawbacks of the one‐way and the fully implicit approaches and can be used for practical engineering applications.