A novel foaming formulation with excellent salt-resistant for foam assisted deliquification of gas wells

In this paper, an excellent foaming formula for natural gas well deliquification was developed, which was based on the synthesized dodecyl ethylethanolamine (DEEA), commercially obtained cocamidopropyl betaine (CAPB) and sodium lauryl glutamate (SLG). The foaming properties and liquid unloading properties were studied, which showed that the optimal molar ratio of DEEA/CAPB/SLG ternary complex turned out to be 14:21:15. At a total concentration of 15 mM in the liquid phase, the optimal DEEA/CAPB/SLG mixture exhibited excellent foaming and liquid unloading capability at various conditions of methanol, condensate oil and salts contents and temperatures. At the methanol content of 45%, the foaming efficiency and liquid unloading efficiency of the DEEA/CAPB/SLG mixture were measured to be 100% and 25.5 ± 2.2%, respectively. When the condensate oil content was 10–30%, the liquid unloading efficiency ranged from 18.0 ± 2.1% to 25.0 ± 2.5%, which was much higher than that (8.3 ± 0.9%) obtained without condensate. The presence of salts retarded the performance of the DEEA/CAPB/SLG mixture, however, the addition of a chelating agent, trisodium nitrilotriacetic acid (NTA), to DEEA/CAPB/SLG could enhance the foaming efficiency and unloading performance at a salinity level of up to 41 × 104 mg/L, which might be the highest salt-resistant level of the gas well foaming mixture. The introduction of 10% methanol exhibited a positive effect on the DEEA/CAPB/SLG mixture's foaming and liquid unloading performance against temperature (up to 90 °C). At 90 °C, the DEEA/CAPB/SLG foam could remove almost all the liquid from the column.