Abstract
Wellbore stability in extreme drilling environments remains a critical challenge. This study advances the understanding of these complexities through a comprehensive numerical modeling approach. By incorporating thermal, chemical, and hydraulic effects, four refined models were developed to simulate wellbore behavior under high pressures and temperatures. A comparative analysis of four failure criteria and a detailed investigation into the impact of fluid properties on pore pressure and stress distribution provide novel insights. The results indicate that pressure distribution and stress variations around the wellbore are significantly influenced by poroelastic, thermal, and chemical effects. The poroelastic effect increases pressure due to overbalanced drilling conditions, while thermal effects vary with fluid temperature, leading to notable pressure changes. Chemical effects are significant, with lower salinity mud increasing pore pressure and higher salinity decreasing it. Thermal effects primarily dominate stress distribution, altering radial, tangential, and axial stresses, with tangential stresses peaking in the direction of minimum horizontal stress. Collapse area predictions suggest that Mohr-Coulomb and Drucker-Prager criteria predict larger collapse areas compared to Mogi-Coulomb and Modified-Lade criteria, indicating a more conservative approach. Poroelastic effects slightly enlarge collapse areas due to increased pore pressure, while thermal effects reduce collapse areas with cooling and increase them with heating. Higher salinity mud improves formation stability by enhancing effective stress and reducing pore pressure. The results demonstrate that using higher salinity mud enhances formation stability and that careful management of temperature can mitigate stress variations and collapse risks. Regular monitoring and adjustments based on wellbore stability models are essential for optimizing performance and safety in drilling operations. The findings reveal that optimizing mud salinity and carefully managing temperature can effectively enhance formation stability, which offers practical guidelines for mitigating wellbore risks and optimizing drilling operations in challenging formations.