Abstract

Wellbore instability frequently leads to substantial nonproductive time and increased operational costs in both drilling and production phases. Traditionally, analytical models have been employed to assess the stress state around wellbores and predict failure conditions. However, these models are often constrained by simplifying assumptions that limit their effectiveness in addressing the complexities inherent in modern wellbore stability analyses. To address these limitations, a fully coupled model has been developed based on the governing equations of motion, heat transfer, and multiphase fluid flow. This model integrates the transport dynamics of two-phase fluids (water and oil) and thermal exchange near the wellbore, enabling a more comprehensive evaluation of time-dependent wellbore stability. It accounts for thermal effects, fluid-rock interactions, and the formation's petrophysical and transport properties.

In this study, the developed model is applied to investigate the influence of fluid-rock interactions on wellbore integrity. The primary objective is to assess the impact of rock weakening due to drilling fluid invasion on the stability of the borehole wall and to propose appropriate mitigation strategies. Results demonstrate that fluid-rock interaction is a critical factor influencing wellbore integrity, particularly in formations with water-sensitive mechanical properties. Mitigating the invasion of drilling fluids into the formation significantly enhances wellbore stability. Specifically, shifting formation wettability towards a more hydrophobic state improves the structural integrity of the rock surrounding the wellbore. This finding highlights the importance of considering not only mud weight but also the physicochemical properties of drilling fluids in mitigating wellbore instability issues, introducing a novel approach to wellbore instability management.

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