Development and evaluation of foaming agents for high salinity tolerance

Foam flooding cannot only remarkably improve sweep efficiency, but also increase oil displacement efficiency, which has been the most important tertiary oil recovery technique with a bright future. Aiming at high salinity reservoirs, we overcame the weak point of conventional foaming agents with poor ability to salinity tolerance, and developed foam agents with excellent performances by compounding. Through analyzing the influence rules and the reasons for the single factors on the foam performances, and optimizing with orthogonal experiment, the optimum formula is determined, including 0.4% alkyl hydroxyl sulfobetaine, 0.04% dodecanol and 0.1% quaternary ammonium salt surfactant, which have good synergistic effect. The foaming agents have better performances from 40 °C to 60 °C, and can apply in a very wide range of salinity of (1–16) × 104 mg/L. The resistance factor of the optimal formula increases as permeability of sand pack increases, and the lower the permeability of sand pack, the smaller the injection volume of foam needed to achieve stability. We also evaluated oil displacement efficiency in heterogeneous model with permeability ratio of 7.7, and the total recovery for foam flooding increased almost 21% based on conventional water flooding. All the experimental results show that the foam agents have good effects of profile control and incremental oil in high salinity reservoirs, and the compounded experiment is an effective way to improve properties of the foam system. It also provides a train of thought for developing subsequent foaming agents.