Abstract: The generalized water displacemnent curves can be corresponded with many f_w-R^* relationships. In this paper, 9 types of generalized water displacement curves are presented and corresponded relationships of N_p-f_w,f_w-R^*,$\frac{df_w}{dR^*}-R^*$* and Q_t-t and N_p-t of corresponded decline curves are derived. The changing characteristics of their relationships of fu- R* were mainly studied with the fgures. The curve of equation (32) has good relatinship of f_w-R^*,and has already been used in the oilfield. But it has more complex formulas of water displacement curve. The generalized water displacement curves of equations (24) and (25) are valuable ones. For equation (24),that is $N_p=a-\frac{b}{L_{p}^{b}}$, when m is changed from∞ to 0, Arps' decline indices of corresponding decline curves are just changed from 0 to 1,i.e. exponential, hyperbolic and harmonic decline curves, so it has wide representativety and can be used in the bedded reservoirs with water drive especially. The water displacement curve of equation (25), $N_p=a-\frac{b}{W_{p}^{m}}$. is the protruding curve on the coordinate of f_w-R^*,and can be used in carbonate reservoirs with bottom water drive especially.

Key words: Water drive, Displacement curve, Index, Water cut, Recoverable reserve, Recovery percent, Decline rate