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Betaine surfactants are used widely in oil field chemistry as well as other industrial applications, but their foaming ability is very poor so that it cannot be used in foaming. In this work, the effect of octadecyl ammonium oxide on the foam properties of oleate amide propyl betaine, a new compound foaming reagent, is studied based on foam performance. Then, a foam drainage reagent of 0.5 wt% oleate amide propyl betaine and 0.1 wt% octadecyl ammonium oxide is developed for natural gas production. Its salt resistance, methanol resistance, high temperature resistance, anti-condensate oil performance, and emulsification ability are systematically evaluated. Furthermore, the factors affecting foam performance are analyzed. The results show that the compound foaming reagent has good anti-salt, anti-methanol, and anti-condensate oil properties for meeting application requirements. The microstructures of foams derived from different reagents reveal the stability mechanism. All results reflect the fact that compounding can expand their application range in different environments to various extents, which benefits the design and use of compound surfactants.

In this study, to optimize the foaming activity of sodium dodecyl sulfate (SDS), modified sodium dodecyl sulfate surfactants (MSDS-1 and MSDS-2) are prepared by using methanol and diethanol amine as modifiers by the Mannich reaction. The foaming properties and foam stability of the products are evaluated by the Ross–Miles method and the Waring blender method. The microstructures of the foams produced by three surfactants are compared. The effects of temperature, inorganic salt, methanol, and condensate oil on the foaming activity of SDS, MSDS-1, and MSDS-2 are studied. The results obtained show that the best foaming concentration of all three products is 0.5%. Compared with SDS, the temperature resistance, methanol resistance, salt resistance and anti-condensate oil performance of MSDS-1 and MSDS-2 are improved. Among them, the temperature resistance, salt resistance, and methanol resistance of the MSDS-1 solution are the best. The MSDS-2 solution has the best anti-condensate performance. Besides, the foam size becomes smaller, the foam wall thickens, and the foam stability is improved after modification. The overall performance of SDS as a foaming agent can be improved by the Mannich modification.