基于格子Boltzmann方法的孔隙尺度水驱油数值模拟研究

A Pore-Scale Numerical Study of Waterflooding in Oil Reservoirs Based on the Lattice Boltzmann Method

摘要: 针对长期水驱后储层内部剩余油微观分布难以准确表征的问题，本文基于格子Boltzmann方法建立了孔隙尺度水驱油数值模拟模型。采用多组分多松弛时间格子Boltzmann模型描述复杂孔隙介质中油水两相流动，并结合半步反弹边界、Zou-He速度入口和零梯度出口边界实现驱替过程模拟。通过接触角验证和Poiseuille流动验证，证明所建模型具有较好的数值精度与可靠性。在此基础上，利用CT扫描铸体薄片二值化图像构建孔隙介质模型，对水湿和油湿条件下的水驱过程进行了对比分析。结果表明，润湿性显著影响水相推进路径、驱替前缘形态及剩余油赋存特征；与油湿条件相比，水湿条件下水相波及范围更大，剩余油分布更分散，驱替效率更高。研究结果可为孔隙尺度剩余油识别及提高采收率机理研究提供参考。

Abstract: To address the difficulty in accurately characterizing the microscopic distribution of residual oil in reservoirs after long-term water flooding, a pore-scale numerical model for water flooding was established based on the lattice Boltzmann method. A multicomponent multi-relaxation-time lattice Boltzmann model was employed to describe oil-water two-phase flow in complex porous media, and the displacement process was simulated using half-way bounce-back boundaries, a Zou-He velocity inlet, and a zero-gradient outlet boundary. Contact angle validation and Poiseuille flow validation demonstrated that the proposed model has good numerical accuracy and reliability. On this basis, a porous medium model was constructed from binarized CT images of cast thin sections, and comparative simulations of water flooding under water-wet and oil-wet conditions were carried out. The results show that wettability significantly affects the advance path of the water phase, the morphology of the displacement front, and the distribution characteristics of residual oil. Compared with the oil-wet condition, the water-wet condition exhibits a larger sweep area, a more dispersed residual oil distribution, and higher displacement efficiency. The results provide a useful reference for pore-scale residual oil characterization and the study of enhanced oil recovery mechanisms.