新型纳米活性流体协同改变油湿性砂岩表面润湿性的机理

Mechanism of synergistically changing the surface wettability of oil-wet sandstone by a novel nano-active fluid

摘要:

以带正电的碳酸钙纳米颗粒和阳-非离子双子表面活性剂为原料，制备了一种纳米活性流体。通过Zeta电位、红外光谱（IR）、石英晶体微天平（QCM）、接触角测量和自发渗吸实验等方法研究了制得纳米活性流体中碳酸钙纳米颗粒和阳-非离子双子表面活性剂协同改变油湿性砂岩表面润湿性的机理。结果表明，纳米活性流体处理后的油湿性砂岩表面红外光谱中，原油的羰基吸收峰强度低于阳-非离子双子表面活性剂处理后的砂岩表面羰基吸收峰强度；当阳-非离子双子表活剂质量分数均较高时（>0.003%），纳米活性流体中的碳酸钙颗粒促进了双子表面活性剂和原油羧基离子对的形成和解吸附过程，使得纳米活性流体处理过的砂岩表面共振频率变化量（Δf）比阳-非离子双子表面活性剂处理过的砂岩表面Δf小；接触角测定结果进一步确认，纳米活性流体改变油湿性砂岩表面润湿性的效果比单一阳-非离子双子表面活性剂和碳酸钙纳米颗粒效果更好，纳米活性流体中的两种组分起到协同效应。

Abstract:

A nano-active fluid was prepared using positively charged calcium carbonate nanoparticles and cationic-nonionic gemini surfactants as raw materials. The mechanism of synergistic modification of surface wettability of oil-wet sandstone by calcium carbonate nanoparticles and cationic-nonionic gemini surfactants in a novel nano-active fluid was investigated by zeta potential, infrared (IR), quartz crystal microbalance (QCM), contact angle measurements and spontaneous imbibition experiments in this paper. The results showed that the intensity of carbonyl absorption peak of infrared spectrum for the surface of sandstone treated with the novel nano-active fluid was lower than that treated with the gemini surfactant. When the mass fraction of cationic-nonionic gemini surfactants was high (>0.003 %), the formation and desorption of the ion pairs produced by the cationic-nonionic gemini surfactants and carboxyl groups of crude oil are promoted by the calcium carbonate particles in the nano-active fluid, resulting in a higher reduction of the Δf (the amount of resonance frequency change) for the sandstone surface treated by the nano-active fluid than that for the cationic-nonionic gemini surfactant. The fact that the novel nano-active fluids are more effective than the single gemini surfactants and calcium carbonate nanoparticles in altering the wettability of oil-wet sandstone surfaces is confirmed by the contact angle measurements. The two components in the nano-active fluid act synergistically.