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}(\delta t) = \frac{ \left<p_e(t+\delta t) \right>-\left<p_e(t)\right>}{Q_{WI}(t+\delta t) -  Q_{WI}(t) }

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

See Also