Abstract: The middle shallow gas well in the old part of Sichuan Basin has been in the low pressure and low production stage. The gas wells with wellhead pressure lower than 1 MPa accounted for 76.13%, and the production lower than 0.2$\times$10$^4$ m$^3$/d accounted for 57.14%; 80.62% of the gas wells have been involved in the bubble discharge process, but the effect of bubbling process is gradually getting worse. In view of the poor bubble drainage effect of high condensate oil and gas wells, the low bubble drainage efficiency of low-pressure and low production gas wells, and the difficulty of gas well treatment caused by the coexistence of effusion and emulsification, three new SCU series foam discharge agents have been developed. By establishing CHSB-SDS-PFBS ternary surfactant system, we developed a high anticoagulant oil bubble drainage agent SCU-2, which could reduce the gas-liquid surface tension to 26.73 mN/m and hold 50% content of anticoagulant condensate. Through the optimization of reaction system and catalyst, we developed self generated energy type foam discharge agent SCU-3, which could generate N$_2$ and heat in the wellbore and increase the foam lifting efficiency in low pressure and low production wells. Optimizing the combination of compound acid and oil resistant surfactant, we developed the purification and drainage integrated foaming agent SCU-6, which is better than conventional foaming agent for gas drainage in the properties of reducing viscosity and foaming ability with same concentration. Currently, SCU series foaming agent have been applied in 138 gas wells with 89.73% effective rate and 774$\times$10$^4$ m$^3$ gas production increase. The new foaming agent gas drainage expand the application scope of foam drainage technology and have excellent prospect of popularization and application.

Key words: foaming agent for gas drainage, high condensate content, autogenous energy, purification and drainage integration, surfactant, SCU series foaming agent