Abstract:

Foam-based deliquification is important to ensure the production of gas wells, therefore, there is no doubt that the development of high-performance foaming agents is extremely critical for the gas wells with high salinity, high condensate oil content and high temperature. For this reason, a highly efficient and environmentally friendly ternary foaming mixture was prepared by coconut oil amide propyl hydroxy sulfobetaine （CHSB）, sodium α-olefin sulfonate （AOS） and synthetic Gemini cationic surfactant （CAGB） in this study. The results showed that the AOS/CAGB/CHSB mixture had the best performance when the molar ratio was 12∶3∶35 at the total amount of 20 mmol/L. The foam volume and half-life reached 360 mL and 30.27 min, respectively. In the foaming agent solution containing 30% methanol, the measured liquid unloading efficiency was 31%, and the foaming efficiency was 95%. With 0%-50% condensate oil, the ternary foaming mixture showed good performance. With 20% condensate oil, the liquid unloading efficiency was up to 38% and the foaming efficiency was 95%. The optimized AOS/CAGB/CHSB exhibited poor tolerance to salt ions. However, with trisodium aminotriacetate （NTA）, the ternary complex system was still effective at a salinity of 150 g/L. At temperatures higher than 50 ℃, the liquid unloading efficiency of the foam also gradually increased, and the liquid unloading efficiency was above 95% at 90 ℃. In addition, the surface tension test and foam microstructure observation also confirmed the presence of synergy in foaming, foam stabilization and foam liquid unloading.

Key words: gas well deliquification for gas recovery, betaine surfactant, Gemini surfactant, foaming performance, liquid unloading efficiency