Abstract: On the basis of study of literature (1), the paper established the transitional water-displacement curve and derived the corresponding oil-water percolation characteristics. From these theoretical studies,it is indicated that the W_p+C and L_p+C water displacement curves are the exceptional cases when the parameter values of the transitional water displacement curves are defined at 0 and 1 respectively. However, for most water-flooding sandstone oil fields, their water-drive features are generally between the piston-like displacement and non-piston-like displacement, so we should select the transitional water displacement curve to carry out evaluation and prediction, Othewise, the predicted recoverable reserves would be lower when using W_p+C water displacement curve while higher when using the L_p+C water displacement curve and the W_p+C water displacement curve would go up and L_p+C water displacement curve would slump down at high water-cut stage.

Key words: water drive, displacement curve, percolation, characteristics, prediction