The document discusses various methods for measuring and predicting productivity and inflow performance relationships (IPRs) for oil wells. It defines productivity index J as the ratio of total liquid flow rate to pressure drawdown. Vogel's, Standing's, and Fetkovich's methods are empirical models for generating current and future IPRs. Vogel normalized IPRs using dimensionless parameters. Standing extended Vogel's method to predict future IPRs based on changes in reservoir pressure and productivity index over time. Fetkovich accounted for nonlinear well flow behavior in calculating theoretical productivity indices.