Ratio of the variation of the field-average formation pressure in producers to the total field cumulative water injection for the same time period :

{\rm PIR} = \frac{<p_e(t=T)>-<p_e(t=0)>}{Q_{WI}(t=T)}

It measures how efficiently waterflood supports the pressure in producers and represents one of the key Waterflood Diagnostics.

See Also