Foams have been widely used in oilfields for effective profile control and displacement. However, foams stabilized by surfactants lack long-term stability, especially in an oil reservoir. Here, we have studied the in situ modification of positively charged AlOOH nanoparticles via the adsorption of the anionic surfactant sodium dodecyl sulfate (SDS) and the characterization of foam stabilized by AlOOH nanoparticles in synergy with SDS under different conditions. Changes in the zeta potential and adsorption isotherm of the AlOOH nanoparticles confirmed their modification. The most stable foam was obtained with an SDS/AlOOH concentration ratio of 5:1; further increases of the SDS concentration led to a decrease and subsequent increase in foam stability. The relationships between the zeta potential, three-phase contact angle, nanoparticle aggregate size, and foam stability were comprehensively analyzed, revealing that foam stability was affected by all of these factors. We concluded that nanoparticles with partial hydrophobicity, a positive or slightly negative charge, and small aggregate size can be adsorbed tightly to foam surfaces and form compact networks in the foam’s film, thereby resulting in a stable foam. The SDS/AlOOH-stabilized foam also shows good stability under high temperatures and in the presence of oil. Sandpack flooding experiments showed that the SDS/AlOOH foam can increase and maintain the differential pressure more effectively than the SDS foam. This study provides additional options for using nanoparticles to stabilize foams for enhanced oil recovery.

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A novel air flooding technology based on catalyst-activated low-temperature oxidation (CLTO) has been researched by static and dynamic oxidation experiments and can be applied in light crude oil reservoirs under reservoir conditions to improve the safety and oil recovery of air flooding. The catalytic effect of additives on the oxidation behavior of three crude oils was researched. The changes in oil recovery, oxygen distribution, and oil characteristics caused by additives were researched by dynamic oxidation experiments, and the influences of crude oil types, additive injection pattern, injection volume, and injection time on the catalytic effect were also researched. The results show that metallic additives can improve the oxygen consumption capacity of crude oils. Furthermore, the addition of additives can delay the oxygen breakthrough time and reduce the oxygen content in the gas produced. During the catalytic air flooding, the oxygen injected reacts mainly with the residual oil near the injection wells, and the influence of CLTO on the properties of oil produced from light oil reservoirs is minor. The key point to guarantee the success of catalytic air flooding is to select the optimal catalyst for the reservoir oil. The preferred catalyst injection pattern is catalyst alternating air injection, and the recommended catalyst injection volume is 0.03–0.05 PV. Catalytic air flooding technology can improve the safety and widen the application of air flooding technology.

Tea saponin (TS) is a relatively inexpensive natural nonionic surfactant extracted from parts of tea plants, which can be modified into an anionic surfactant to achieve better surface activity. In this paper, the synthesis of TS‐based succinic acid sulfonate as an anionic foaming agent is described. TS used as the hydrophobic source was modified by maleic anhydride (MAH) and then reacted with sodium bisulfite. Orthogonal experiment of a 2‐step reaction was designed and performed, resulting in 9 kinds of succinic acid tea‐saponin sulfonate (STS). 4‐Dimethylaminopyridine and tetrabutylammonium bromide were, respectively, used as catalyst for the esterification with MAH and the sulfonation with sodium bisulfite. During the synthesis process, N,N‐dimethylformamide was employed as the solvent and ethyl acetate as the extractant. The molecular structure of STS was confirmed by infrared spectroscopy and mass spectrometry. The foaming property of STS was investigated through comparison with different kinds of common surfactants. The results show great prospects of these environmentally friendly anionic surfactants.