CO2复合驱油分子动力学模拟及微观机理研究

为了探索较大幅度提高高含水期复杂断块油田剩余油采收率，提出了CO₂复合驱方式进行剩余油开采对策并在矿场先导试验井组取得了显著的增油降水效果，但对CO₂复合驱油体系微观增油机理的相关研究较少，亟需开展这方面的基础研究。基于CT扫描结果，结合油藏开发实际，明确了滴状和膜状剩余油为难以动用的2种剩余油类型；构建了溶解油滴模型和剥离油膜模型，利用分子动力学方法进行模拟。溶解油滴模拟结果表明，CO₂扩散至油滴中，增加其体积，然后油滴分子逐渐溶解在驱油体系中；剥离油膜分子动力学模拟结果表明，CO₂在油相中先形成扩散通道，随后CO₂优先通过扩散通道至岩石表面，CO₂在表面上形成氢键而产生吸附。

Molecular dynamics simulation and microscopic mechanism of CO2 composite flooding

A CO₂ composite flooding method was proposed for remaining oil exploitation and achieved significant effects in pilot well tests in order to improve residual oil recovery efficiency in complex fault block oilfields during high water cut period. There are few related studies on the microscopic mechanism of CO₂ composite flooding, and the basic research in this field is urgently demanded. Based on the CT scanning results, combined with the actual development of reservoir, it was clear that the drop-like and film-like residual oil are two types of remain-ing oil that were difficult to recover. A dissolved oil droplet model and a stripped oil film model were constructed and simulated using a molecular dynamics method. The simulation results of the dissolved oil droplet method showed that CO₂ first diffused into oil droplets and increased their volume, and then the oil droplet molecules gradually dissolved into the oil displacement system. The molecular dynamics simulation results of the stripped oil film showed that CO₂ first formed diffusion channels in the oil phase, and then preferentially passed through the diffusion channels to the rock surface. CO₂ formed hydrogen bonds on the surface and generated adsorption.