Lattice Boltzmann Modeling of Spontaneous Imbibition in Variable-Diameter Capillaries

Previous micro-scale studies of the effect pore structure on spontaneous imbibition are mainly limited to invariable-diameter capillaries. However, in real oil and gas reservoir formations, capillary diameters changing interconnected. Applying lattice Boltzmann color gradient two-phase flow model parallel computation CPUs, we simulated variable-diameter We explored reasons for nonwetting phase snap-off systematically studied critical conditions imbibition. The effects pore-throat aspect ratio, throat diameter, tortuosity were studied. Through analyzing results, found that variation diameter produces an additional resistance, which increases with increase ratio a capillary. Under action this phenomenon sometimes occurs imbibition, makes recovery efficiency non-wetting extremely low. In addition, main factors affecting tortuosity, is different from conventional concept tortuosity. When does not occur, velocity when fixed, period increases, i.e., rate decreases, also increases. bigger smaller sine function both inhibit speed