Abstract: High pressure oil and gas formation were contained in the producing zone of Zhao-46 in Huabei oilfield. Gas cutting and well kicking occurred if the density of drilling fluid is lighter than 1. 10g/cm3, and mud losing occurred if the density is heavier than 1. 18g/cm3. By using external casing packer and corollary tools, special threaded aliphatic in the free section of the casings and optimized performance of cement slurry, the casings can be run safely, the well can be cemented with high grade and the casing threads of free section can be prevented from leaking.