Abstract:

A self?made long?chain cationic surfactant (SFC111) and a low interfacial energy substance (SFC115) were used to prepare a cationic emulsion for further application as surfactant for low permeability oil and gas reservoirs. The dispersion of the emulsion in water, the contact angle of the core before and after the emulsion treatment and the surface tension were investigated by particle size analyzer, contact angle meter, and rotating drop interfacial tension meter, respectively. The thermodynamic parameters of the emulsion at 20 ℃ and 70 ℃ were calculated. Particle size of 0.5% concentration emulsion is D₅₀=420.8 nm at 20 ℃, D₅₀=728.0 nm at 70 ℃.The contact angle of clear water on the surface of the core increases from 10° to 120°. The emulsion could reduce the surface tension of water to 24 mN/m at 70 ℃, indicating the good waterproof lock performance. The adsorption characteristic of emulsion conforms to the langmuir adsorption theory. The thermodynamic results show that as the temperature increases, the amount of adsorption on the surface of the emulsion decreases, the area occupied by the molecules on the surface of the emulsion goes down, and the thickness of the adsorption layer decreases.

Key words: Low permeability reservoir, Emulsion, Surface tension, Contact angle, Thermodynamic calculation

摘要：

以自制的一种长链阳离子表面活性剂(SFC111)和低界面能物质(SFC115)构建出阳离子型乳液，研究其作为低渗透油气藏用表面活性剂性能。通过粒度仪考察乳液在水中的分散性，通过接触角测定仪考察经乳液处理前后岩心的接触角，通过旋转滴界面张力仪测试表面张力；通过计算得到乳液在20、70 ℃的热力学参数。结果表明，质量分数为0.5%的乳液在20 ℃时D₅₀=420.8 nm，70 ℃时D₅₀=728.0 nm；清水在岩心表面上的接触角从10°最大可增至120°；70 ℃下乳液可将清水的表面张力降至24 mN/m，表现出良好的防水锁性能。乳液符合langmuir吸附理论，其热力学结果表明，随着温度的升高，乳液表面吸附量降低，乳液表面分子所占面积减小，吸附层厚度降低。

关键词: 低渗透油藏, 乳液, 表面张力, 接触角, 热力学计算