Preparation And Properties Of Petroleum Sulfonate/SiO₂ Nanoparticle Systems

Chemical flooding has been intensively researched and applied in China,especially the ternary composite flooding（ASP）has been used in most oil fields,but the alkali-containing composite flooding can bring a series of problems to the environment and the oil flooding facilities.With the vision of carbon neutrality and carbon peaking in China,the green development of oil and gas fields has become the focus of research.Alkali-free binary composite flooding eliminates the problems caused by alkali and has become a hot spot in composite flooding research.Petroleum sulfonate（PS）is a widely used anionic surfactant,and its oil flooding performance has been recognized by major oil fields.However,PS is strongly influenced by alkali in ASP,and whether alkali is used or not seriously affects its ability to reduce interfacial tension.Based on the findings that hydrophobic nano-SiO₂ can assist surfactants to improve oil-repellent efficiency,the oil-repellent performance of the PS/hydrophobic nano-SiO₂ composite system was investigated by introducing hydrophobic nano-SiO₂ into PS under alkali-free conditions.Firstly,minus two and minus three lines of PS were synthesized by sulfonation reaction using furfural extract oil as raw material,and the synthesis effect of minus two and minus three lines of PS was analyzed using infrared spectroscopy.Using the minimum alkane carbon number and the ability to reduce interfacial tension,the best surfactants were selected from the minus two and minus three lines of PS and Daqing PS.C8-SiO₂ and C12-SiO₂ were then prepared from nano-SiO₂ with a specific surface area of 200 m2/g,using octyltrimethoxysilane and dodecyltrimethoxysilane as coupling agents and ethanol as solvent.Fourier infrared spectroscopy,particle size measurement,transmission electron microscopy,and surface hydroxyl number determination were used to characterize the modification effect of nano-SiO₂.Contact angles were tested to analyze the ability of nano-SiO₂ to alter the wettability of the solid surface and to investigate the relevant influencing factors.Finally,petroleum sulfonates and nano-SiO₂were compounded in a certain ratio to study the interfacial properties of the composite system.The experimental results show that the highest interfacial activity and the highest minimum alkane carbon number of Daqing PS were found to be the most suitable for Daqing crude oil in the process of petroleum sulfonate preparation and screening.In the preparation of modified nano-SiO₂,the determination of surface hydroxyl number showed that the number of hydroxyl groups decreased after modification,and octyltrimethoxysilane was better than dodecyltrimethoxysilane;IR spectral analysis showed that the surname change was successful;TEM analysis showed that the desirability of nano-SiO₂ was improved after modification;particle size analysis showed that the particle size of nano-SiO₂ was affected by the addition of coupling agent after octyl or dodecyl modification.The wettability test shows that the wettability of nano-SiO₂ can be controlled.The compounding of Daqing PS and nano-SiO₂ shows that the compounding ratio of Daqing PS to C8-SiO₂ can be as low as 6:4,and the compounding ratio of Daqing PS to C12-SiO₂ can be as low as 5:5.20%of C8-SiO₂ has the highest interfacial activity in the compounding system;30%and 50%of C8-SiO₂ have the highest interfacial activity in the compounding system.The highest interfacial activity is achieved with 30%and 50%C8-SiO₂.The alkyl chain length affects the interfacial properties of the composite system,with the longer the chain length,the better the effect.Petroleum sulfonate/SiO₂ nanofluids show great potential for recovery enhancement applications.