A novel salt and condensate–resistant foam co-stabilized by mixtures of surfactants and citric acid for gas well deliquification

Abstract

Aged gas wells are often blocked by the accumulation of liquids, which can be removed by the injection of foaming surfactant mixtures. In this study, a compound foam stabilized by a quaternary mixture (alkyl amidoamine (amine), citric acid (acid), α–olefin sulfonate (AOS) and lauramidopropyl betaines (LAPB)) was firstly developed with the Waring blender method. The liquid unloading performance of this compound foam was then investigated to estimate its application potential under various condensate fraction, salinity and temperature conditions. At a condensate content range of 20 %–40 %, the amine/acid/AOS/LAPB foam is particularly effective in unloading the liquids. However, salinity was found to reduce the foaming efficiency (referred to as the ratio of the mass of the formed foam to that of the original liquid) and liquid unloading performance of the amine/acid/AOS/LAPB foam, which could be overcome through the addition of a chelator, namely nitrilotriacetic acid trisodium salt (NTA). Temperatures higher than 60 °C enhanced the performance of the amine/acid/AOS/LAPB foam. Synergistic effects within the quaternary mixture were confirmed by surface tension measurements, morphological observation, interaction energy calculation and the electrostatic potential analysis. The present results suggested that the amine/acid/AOS/LAPB mixture may be of use in relieving liquid loading of gas wells.