Abstract: Described here in the essay are the technical difficulties as encountered with in the well completion operations of Sinopec Sichuan Natural Gas Exploration Block, involving such two key issues, i.e., the design of production casings for the marine gas well, and selecting of suitable materials for casing/tubing for the hightemperature and high-pressure CO2-containing gas well. For the contradiction between high strength and sulfideresistance, a solution of combination of different casings is used. For the critical issue concerning cost-effective design of safe wellbore of the CO2-corrosing gas well, the non-API HP1-13Cr material is used for production pipe string and packer seated pre-selected section in extremely serious corrosive gas well, while an solution of ordinary material-made OCTG + premium connection + packer completion is adopted for lightly corrosive gas well. These solutions have been successfully applied to the operations in the well site.