During waterflooding, spontaneous imbibition is a fundamental recovery mechanism in fractured reservoirs. A large number of numerical and experimental studies have been devoted to understand the interaction mechanism between the matrix and the fractures at the core scale under various boundary conditions. Little attention has been paid, however, to the effect of microfractures on pore-scale spontaneous imbibition. In this study, five models with various types of microfractures, embedded in the same porous matrix, are used to investigate their role in counter-current spontaneous imbibition, using an optimized color-gradient lattice Boltzmann method. During the entire counter-current imbibition, the influence of the microfractures on the macro-recovery of the non-wetting fluid and the two-fluid interfaces, including the initial and local dynamics of the interfaces, and the evolution of the interface morphology, is analyzed in detail. The results indicate that microfractures have little influence on both the interfacial dynamics at the initial stage and the local interface dynamics in the matrix. The evolution of the interface morphology is, however, controlled by the geometric shape of the microfractures. In addition, the microfractures improve significantly the recovery of oil. The length of a single microfracture and the bifurcation angle of a microfracture bifurcated into two other microfractures affect significantly the recovery curve by influencing the evolution of the two-phase interface.

中文翻译：

---

通过格子玻尔兹曼模拟研究微裂缝在逆流自吸中的作用

在注水过程中，自吸是裂缝性油藏的基本恢复机制。大量的数值和实验研究致力于了解各种边界条件下岩心尺度下基质与裂缝之间的相互作用机制。然而，很少关注微裂缝对孔隙尺度自吸的影响。在这项研究中，使用优化的颜色梯度晶格 Boltzmann 方法，将具有不同类型微裂缝的五个模型嵌入相同的多孔基质中，用于研究它们在逆流自吸中的作用。在整个逆流渗吸过程中，微裂缝对非润湿流体和两流体界面宏观回收的影响，包括界面的初始和局部动力学，以及界面形态的演变，进行了详细分析。结果表明，微裂缝对初始阶段的界面动力学和基质中的局部界面动力学几乎没有影响。然而，界面形态的演变由微裂缝的几何形状控制。此外，微裂缝显着提高了石油的采收率。单个微裂缝的长度和分叉成另外两条微裂缝的微裂缝的分叉角度通过影响两相界面的演化显着影响采收曲线。结果表明，微裂缝对初始阶段的界面动力学和基质中的局部界面动力学几乎没有影响。然而，界面形态的演变由微裂缝的几何形状控制。此外，微裂缝显着提高了石油的采收率。单个微裂缝的长度和分叉成另外两条微裂缝的微裂缝的分叉角度通过影响两相界面的演化显着影响采收曲线。结果表明，微裂缝对初始阶段的界面动力学和基质中的局部界面动力学几乎没有影响。然而，界面形态的演变由微裂缝的几何形状控制。此外，微裂缝显着提高了石油的采收率。单个微裂缝的长度和分叉成另外两条微裂缝的微裂缝的分叉角度通过影响两相界面的演化显着影响采收曲线。