<p>The Yingqiong Basin in the South China Sea poses significant challenges for well control operations due to its high-temperature and high-pressure (HTHP) geological conditions, complex structures, and narrow pressure windows. This study investigates the adaptability of unconventional well-killing techniques in the HTHP environment of the northern slope of the Lingshui Depression in the Qiongdongnan Basin. Using numerical simulation software (FLUENT and Drillbench), a wellbore gas-liquid multiphase flow model was developed, incorporating the thermodynamic properties of drilling fluids and dynamic pressure changes during well shut-in. The model elucidates the mechanisms of bottomhole pressure variations during the shut-in process. Comparative analyses of conventional well-killing methods (e.g., the Driller’s Method and the Engineer’s Method) and unconventional methods (e.g., the Displacement Method and the Bullheading Method) revealed that the Displacement Method, with optimized parameters (drilling fluid density: 1.97 g/cm³, displacement rate: 500-800 L/min), effectively stabilizes wellbore pressure and mitigates risks in narrow pressure windows. In contrast, the Bullheading Method exhibited limited applicability due to formation permeability constraints and excessively high pumping pressures. Orthogonal experimental analysis demonstrated that the displacement rate of the kill fluid has the most significant impact on well-killing effectiveness, followed by density and viscosity (displacement rate &gt; density &gt; viscosity). This study established an adaptability evaluation and sensitivity analysis of unconventional well-killing methods in the Yingqiong Basin based on orthogonal experimental methodology. The findings provide theoretical and technical support for well control safety in HTHP basins, emphasizing the importance of adaptive well-killing strategies and advanced simulation tools.</p>