This study aims to address the issue of ultra-deep well, high H2S content and the completion of permanent packer string in Yuanba gas field, which leads to difficult recovery of gas wells in Yuanba gas field after flooding. Based on the investigation and analysis on the applicable conditions of conventional drainage gas recovery process, a new combined process of “water injection nitrogen+foam drainage” for the recovery of flooded wells is proposed. Then the calculation model of gas injection pressure is optimized. The quick chart of the relationship between the amount of nitrogen needed to fill the wellbore and the pump pressure and the relationship between the amount of nitrogen injected and the height of nitrogen column for process design is drawn. Furthermore, a new type of high temperature sulfur-resistant foaming agent with good compatibility with corrosion inhibitors and defoamers commonly used in gas fields was developed. The field application of well YB29-1 and well YB121H shows that the new combined process of “water injection nitrogen+foam drainage” can effectively evacuate the wellbore effusion and restore the production of water flooded wells, which can be promoted in the completion wells with high sulfur permanent packer string of the same nature.