One of the Productivity Diagnostics methods based on correlation between pressure drawdown and total sandface flowrate , where:

	drain-area formation pressure as function of time
	bottomhole pressure as function of time

It shows unit slope on log-log plot for stabilized reservoir flow:

\Delta p(t) = J^{-1} \bar q_t(t)

where

constant productivity index

In case pressure data is available for a fair interpolation it is recommended to plot sandface cumulatives rather than surface which provides better linearity for stabilized reservoir flow.

Although it is equally applicable to producers and injectors, due to lack of BHP and formation pressure data availability for producers in most practical cases in the past the normalized Hall plot analysis was mostly applied for water injectors.

Since the BHP and formation pressure data are not readily available for the same time moment the interpolation is required, which usually lead to a high degree of uncertainty.

More practical solutions are achieved via group of cumulative-based Productivity Diagnostics methods: t-weighted J-plot, q-weighted J-plot and Hall Plot.

See Also