Pore-Scale Investigation of Waterflooding Based on Experiments and Numerical Simulations Considering the Change in Geometry and Wettability

In order to fully investigate the pore-scale seepage mechanism for a two-phase flow, this study combines pore-scale experiments with lattice Boltzmann simulations to study the effects of geometrical factors and wettability. In this work, first, waterflooding experiments are performed on two water-wet micromodels with/without fractures at different injection rates. Oil recoveries as a function of injected time are determined by using a digital camera and an image-processing system. An optimal injection rate of the micromodel with fractures is 0.15 mL/min and that of the model without fractures is 0.1 mL/min. Then, the lattice Boltzmann method (LBM) is validated by simulating the contact angles and fluid distribution. At last, the LBM is used to further study the effects of different geometrical factors and five wettability conditions on waterflooding. The results reveal that the oil recovery factor of the model with a fracture in the flow direction (theta = 0 degrees) is the lowest due to early water breakthrough. As the fracture becomes longer, the fingering phenomenon becomes obvious. In a circular section model, it is observed that the bridge-type residual oil occupies a small volume, which leads to a high displacement efficiency. In addition, because water-oil-grain contact lines move on a circular grain surface, the displacement pattern becomes more compact and high oil recovery is achieved in the water-wet model. However, oil is attached to the pore wall and forms an oil film in the square section model under oil-wet conditions, and the capillary force is resistant to the non-wetting invading phase to penetrate the blind-end of the pore, leading to low oil recovery.