Displacement Efficiency (ED)

Displacement efficiency defines the fraction of the initial pore-saturating fluid displaced in a the piston sweep by invaded fluid:

$\begin{array}{l}\displaystyle E_D = 1- \frac{V_{HC, \ LEFT}}{V_{HC, \ INITITAL}} = \frac{1-s_{wi}-s_{orw}}{1-s_{wi}}\end{array}$

where $\begin{array}{l}s_{wi}\end{array}$ – inititial water in oil pay, $\begin{array}{l}s_{orw}\end{array}$ – residual oil to water sweep.