Numerical Simulation of Spontaneous Imbibition under Different Boundary Conditions in Tight Reservoirs

[Image: see text] Based on the spontaneous imbibition phenomenon and seepage mechanism of the tight core, a spontaneous imbibition model of the tight reservoir was established. The imbibition experiment was used to verify the reliability of the model and reverse the parameters. The relative error between the experimental and model recovery is within 5%. The model is used to calculate the oil recovery and oil saturation distribution characteristics of spontaneous imbibition in tight reservoirs under different boundary conditions. The model results show that the imbibition area and imbibition recovery are different under different boundary conditions [one-end-open, two-end-open, two-end-close (TEC), and all-face-open (AFO)]. If the imbibition area increases, imbibition recovery increases. If the side is closed, the spontaneous imbibition occurring at two end faces does not interfere with each other in the initial stage. When the imbibition process under TEC conditions is advanced to the middle and late stage, the superimposed effect occurs between the two imbibition leading edges. Under the AFO condition, the imbibition process has a superimposed effect at the corner between the end face and the side face. The superimposed effect of the end face is more obvious than that of the side face. The superimposed effect not only improves the oil washing efficiency but also inhibits the imbibition area.