10.: Producer/Injector Ratio

The Main Pattern Types section noted that the commonly used waterflood patterns have producer/injector ratios that range from 1:1 to 3:1. Apart from the impact that the geology might have on sweep and the general reluctance that is often displayed in the drilling of injection wells as opposed to producers, how might the optimal producer/injector ratio be decided?

This question has been considered for a homogeneous reservoir using the concept of the total mobility ratio M_T (Hansen and Fanchi 2002). The effective total mobility ratio is the single mobility value k_r/μ that represents the average mobility that exists from the well to the average reservoir pressure contour: