纳米颗粒在岩石表面吸附-脱附规律研究

Adsorption and desorption behavior of nanoparticles on rock surfaces

低渗透油气藏是我国油气田开发的主体,其特点是孔喉细小、连通性差、毛细作用强,而纳米颗粒由于其尺寸较小,已被应用于提高采收率油田矿场。但是,纳米颗粒在多孔介质中具有较强的吸附性,因此,探索纳米颗粒在多孔介质中的吸附对其在油田开发的应用至关重要。为评价不同类型纳米颗粒在岩石固体表面的吸附损耗程度,本文采用密封振荡平衡法研究了亲水性、疏水性纳米颗粒在石英砂与露头砂表面的静态吸附和脱附规律。实验结果表明:亲水性、疏水性纳米颗粒在岩石表面以物理吸附为主,且为单层吸附,其等温吸附曲线均符合"S"型特征,与Freundlich等温吸附模型拟合度高;亲水性纳米颗粒在岩石表面的吸附能力较弱,脱附后的最终吸附量更小,而疏水性纳米颗粒的吸附-脱附行为与之相反。通过研究纳米颗粒在固体岩石表面的吸附-脱附规律,可为油田现场合理认识与应用纳米驱油技术提供理论指导。

Low permeability reservoirs play a major part in China’s oil and gas exploitation. They feature small pore throats, poor connectivity and strong capillary effects, while nanoparticles have been applied to enhance oil recovery due to their small size. However, nanoparticles present strong adsorption ability in porous media, so it is imperative to examine the adsorption and desorption behavior of nanoparticles to improve their applications in oilfields. In order to study the adsorption and desorption behavior of nanoparticles on rock surfaces, the static adsorption loss of hydrophilic and hydrophobic nanoparticles on quartz sand and outcrop sand surfaces was quantified using the sealed oscillation equilibrium method. Experimental results showed that hydrophilic and hydrophobic nanoparticles were mainly physically adsorbed on the rock surface and exhibited characteristics of single-layer adsorption. Their isothermal adsorption curves had the characteristics of an "S" isothermal adsorption curve and could achieve good agreement with the Freundlich isothermal adsorption model. Hydrophilic nanoparticles had relatively poor adsorption capacity and the final adsorption loss after desorption was smaller, while hydrophobic nanoparticles presented the opposite adsorption and desorption behavior. This experimental study can provide theoretical guidance for a better understanding of nanofluid technology and its application in oilfields.