The compressional tectonic setting between the Southern Tianshan and Western Kunlun Mountains results in dynamic geological activity in the Tarim Basin. Drilling operations face significant challenges due to the complexity of lithology and stress variations in the Ordovician. This study analyzes well diameter, cave morphology, whole rock mineral and physicochemical properties, and rock strength to investigate the mechanism of Ordovician wellbore instability. The results indicate that fractured carbonate rocks predominate in the Ordovician. These rocks have low linear expansion and high rolling recovery rates. Wellbore instability was caused by extrusion tectonics, fractured formation, and stress concentration. Fractured formations with weak cementation and loose structure are more susceptible to shear failure. Numerous high-angle fractures and weak planes can also contribute to drilling fluid leakage. Therefore, when encountering Ordovician carbonate formations, it is important to use drilling fluids that enhance sealing and consolidating properties to improve formation integrity and rock strength. We recommend increasing the density of the drilling fluid appropriately. Efforts should be made to simplify the drill string, optimize drilling parameters, and adopt a less drilling and more reaming approach when drilling through deep Ordovician carbonate rock to ensure downhole safety.