Reservoir lithology in block Y is sandstone, carbonate rock, and basement fractured granite-metamorphic rock. Through statistical analysis, the well diameter expansion rates of complex lithology sections are more than 35% . Through analysis of comprehensive factors such as composition, micro-structure, physical and chemical characteristics, formation pressure, drilling fluid application, and on-site construction technology, an inhibitor was selected, and blocking materials such as film-forming agents were added to form an optimized anti-collapse drilling fluid system. The indoor suppression performance evaluation shows that the optimized anti-collapse drilling fluid system has stronger anti-collapse suppression performance than the drilling fluid used in the field, the expansion rate is reduced by 2. 3% , and the recovery rate is increased by 10-30% . According to the core hydration law With regard to the relevant geological parameters of the unstable well section, the wall collapse cycle map under the action of the current drilling fluid and the optimized drilling fluid was drawn, and the collapse period was predicted. The collapse period was extended by 7 days. The wall stabilization problem provides a strong guarantee.