典型表活剂与稠油在蒙脱石表面吸附行为的分子动力学模拟

Adsorption Behavior of Heavy Oil on Montmorillonite Surface by Typical Surfactant:Molecular Dynamics Simulation

为探究蒸汽与表面活性剂复合驱对稠油与黏土矿物表面吸附稳定性的影响,建立表活剂溶液、稠油和蒙脱石的三元吸附体系,采用分子动力学方法阐释稠油与表活剂在蒙脱石表面的微观竞争吸附机理。计算结果表明:非离子型表活剂难以与蒙脱石表面接触,但在高温吸附质环境中具有较强的扩散能力;阳离子型表活剂在较低温度下占据蒙脱石表面吸附位点并使稠油分子脱离蒙脱石;而阴离子表活剂在高温条件下容易使稠油分子远离蒙脱石。高温促使沥青质聚集核离散,从而促进稠油的流动,但会导致部分表活剂更加亲附蒙脱石而造成非必要的损失。本研究为合理调整温度与表活剂的匹配性,为敏感性稠油油藏的开发提供了良好的应用前景及推广意义。

To investigate the adsorption mechanism of heavy oil on clay mineral surface during surfactant flooding,the microscopic mechanism of heavy oil and surfactant on montmorillonite surface under different temperatures can be explained by molecular dynamics simulation.Based on the four components(SARA)of heavy oil and sodium montmorillonite,the molecular dynamics simulation of the adsorption process is carried out after the water phase adsorbent containing surfactant molecules is added into the adsorption system.It shows that cationic surfactant tends to adsorb on the surface of montmorillonite and occupy more adsorption area,which makes the heavy oil molecules tend to separate from the surface of montmorillonite.The non-ionic surfactant does not show a tendency to adsorb towards the surface of montmorillonite during the relaxation process.Non-ionic surfactant has a high self-diffusion coefficient and thus diffuses in the adsorbent environment.High temperature disperses asphaltene aggregation nuclei in heavy oil,which facilitates heavy oil to flow away from the montmorillonite surface.However,high temperatures can also cause some surfactants more adhesion to the montmorillonite surface,resulting in surfactant loss.This study provides theoretical support for adjusting temperature and surfactant types during surfactant development and enhancing oil recovery of sensitive heavy oil reservoirs.