Ratio of oil production rate $\begin{array}{l}q_O\end{array}$ to water injection rate $\begin{array}{l}q_{WI}\end{array}$ :

(1)	$\begin{array}{l}\displaystyle {\rm PIR} = \frac{q_O}{q_{WI}}\end{array}$

It measures how efficiently waterflood supports the oil production and represent one of the key Waterflood Diagnostics.

The PIR can be related to the current VRR as:

(2)	$\begin{array}{l}\displaystyle {\rm PIR}= \frac{1}{\rm VRR} \cdot \frac{1-Y_w}{Y_w + (1-Y_w) \, \left[ \frac{B_o}{B_w} + \frac{B_g}{B_w} \, ( {\rm GOR} - R_s) \right] }\end{array}$

(see

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for derivation)

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