Oil well fires are extreme fire scenarios characterized by high temperatures, elevated pressures, and complex suppression challenges. In conventional settings, water or inert gases are widely used for fire suppression. However, in arid and semi-arid regions such as deserts and Gobi areas, where water resources are critically limited, sand presents a practical alternative due to its unique physical properties, which can both contain the spread of spilled oil and slow down fire propagation. This study aims to systematically investigate the relationship between sand particle size and its thermal conductivity, as well as the effectiveness of sand in suppressing oil well fires. Thermal conductivity measurements were performed using a Hot Disk thermal constants analyzer under elevated temperature conditions (800 degrees C), targeting sand samples with particle sizes ranging from 0.2 mm to 4 mm. Furthermore, a fire dynamics simulation was conducted using PyroSim to model an oil well fire scenario with a radiative heat flux of 4000 kW/m2, allowing the evaluation of suppression performance across different sand particle sizes. Results demonstrate a positive correlation between sand particle size and effective thermal conductivity. The simulation further revealed that sand with a particle size of 1 mm achieved the most favorable fire suppression effect under the specified conditions. These findings highlight the significance of particle size selection in optimizing the use of sand for passive fire control. The study provides both theoretical support and technical reference for developing emergency fire suppression strategies in water-scarce regions, contributing to enhanced fire safety in oil extraction environments.