Application of mixed aerated drilling technilogy in deep well saltwater interval

Formation was encountered during drilling of Well 126 which produced large volume of water, so single fluid drilling technology could not proceed with drilling. Research and analysis was conducted to the characteristics and implementation conditions of mist, foam and aerated drilling techniques. In the gravel layer interval of ?311.2 mm hole the depth is 3 900-5 000 m in Luntai Well 126, the mixed gas phase flow regime drilling technology was employed, which overcame the difficulty of being unable to proceed with drilling using single mist or foam drilling fluid due to complex formation construction conditions, solved the problem that the pressure rating of supercharger could not meet the requirement of aerated drilling technology in deep wells, avoided the non-production time due to handling of complex accidents, successfully realized the goal of safe and fast drilling in gravel layer and proved that the mixed gas phase fluid regime drilling technology is the most effective method to solve the difficulty of drilling in high water-production formaitons in deep wells.