Xu Hui, Su Zhiqing, Li Yingcheng, Yang Guang, Pu Xue, Sun Hui, Jin Jun, Xia Yanmin
SINOPEC Shanghai Research Institute of Petrochemical Technology, Shanghai 201208, China.
ACS Omega. 2021 Sep 22;6(39):25782-25790. doi: 10.1021/acsomega.1c04214. eCollection 2021 Oct 5.
Core-shell micro-spheres (MS) with both negative and positive charges in the core and only negative charges in the shell were developed as adaptive plugging agents for in-depth conformance control for enhanced oil recovery. The MS were designed to propagate deeply into the reservoir due to the small particle size and electrostatic repulsion between the MS and the sandstone at the initial stage of injection and form aggregates by electrostatic attraction between the cores with mixed charges when the shells degraded at a given time during transportation, leading to an effective plugging of the highly permeable layers with low residual oil saturation. The self-assembling and plugging behaviors of the MS have been studied by Monte Carlo simulation. The results show that charge density ( ), fraction of positive charge ( ), MS concentration, temperature, and salinity are the key factors influencing the self-assembling behaviors. The electrostatic interaction would become stronger with the increase in when it is larger than 0.5. The MS are more likely to form aggregates when approaches 0.5. The higher the concentration of the MS, the stronger the electrostatic interaction between the MS. In addition, electrostatic interactions between the MS become stronger with the increase in temperature and decrease in salinity. Simulation results prove that the MS with mixed charges can effectively and adaptively plug highly permeable layers with low residual oil saturation through self-assembling by combination of electrostatic interactions along with physical bridging, leading to the improvement of oil recovery. Furthermore, block charge distribution will be helpful for the MS with mixed charges to form larger aggregates than that of the random mode to effectively plug the highly permeable layers.
开发了一种核壳微球（MS），其核中同时带有正负电荷，而壳中仅带负电荷，作为用于深度调剖以提高采收率的自适应封堵剂。由于粒径小以及在注入初期MS与砂岩之间的静电排斥作用，MS被设计用于深入地层，并且在运输过程中的给定时间壳降解时，通过带混合电荷的核之间的静电吸引形成聚集体，从而有效封堵残余油饱和度低的高渗透层。通过蒙特卡罗模拟研究了MS的自组装和封堵行为。结果表明，电荷密度（ ）、正电荷分数（ ）、MS浓度、温度和盐度是影响自组装行为的关键因素。当 大于0.5时，随着 增加，静电相互作用会变强。当 接近0.5时，MS更有可能形成聚集体。MS浓度越高，MS之间的静电相互作用越强。此外，随着温度升高和盐度降低，MS之间的静电相互作用变强。模拟结果证明，带混合电荷的MS可以通过静电相互作用与物理桥接相结合进行自组装，有效且自适应地封堵残余油饱和度低的高渗透层，从而提高采收率。此外，块状电荷分布有助于带混合电荷的MS形成比随机模式更大的聚集体，以有效封堵高渗透层。
