Study of an anti-high-temperature and salt-resistance alkyl glycine foaming agent and its foam stabilizing mechanism

The development of high-temperature and salt-resistant foaming agents is critical to the successful drilling of complex and low-pressure reservoirs. In this study, a novel alkyl glycine surfactant (AGS-8) was synthesized by the one-step method. The foam quality of AGS-8 at high temperatures (140–180 °C) and the salt solutions (5–36%wt) was evaluated by the Waring-Blender method to explore its applicability in harsh reservoirs. Results show that: (1) The successful synthesis and chemical structure of AGS-8 was determined by FTIR and 1H-NMR. (2) AGS-8 shows good thermal stability within 330 °C and has high surface activity. (3) AGS-8 generated stable foams after aging at 180 °C for 16 h. The outstanding high-temperature foam stability of AGS-8 is an important feature different from the conventional commercial foaming agents. (4) AGS-8 generated stable foams in saturated salt solution (36%wt NaCl) after 150 °C aged. A synergistic foam stabilization effect was found between high concentrations of NaCl (≥25%wt) and AGS-8. (5) The foam stabilization mechanism of AGS-8 was discussed and can be summarized as the electrostatic attraction effect of head groups and the enhancement of inter-molecular repulsive force. In conclusion, AGS-8 was found to be a promising foaming agent in the drilling of high-temperature salt-gypsum formations.