Preprint A604/2008
MAXIMAL OIL RECOVERY FROM VIRGIN RESERVOIRS UNDER THREE-PHASE FLOW CONDITIONS

Bradley Plohr | Azevedo, Arthur | de Souza, Aparecido | Furtado, Frederico | Marchesin, Dan

**Keywords: **
method of characteristics | Buckley-Leverett solution | immiscible three-phase flow | three-phase permeabilities

If two fluids are available to displace oil from a virgin reservoir, what is the
injection strategy that maximizes recovery? This question is considered here. Suppose that
the densities of the oil in the reservoir and the two injected fluids are similar, so that gravity
segregation can be neglected; and suppose that the injected fluids and the oil form three
immiscible phases with no mass interchanges. What is the mixing proportion for injected
fluid slugs that optimizes the oil recovery?
We derive formulae for the optimal injection proportion and oil recovery for Corey-type
quadratic permeabilities. The optimal quantities are essentially determined by the vis-
cosities of the three phases. The formulae are based on a recently-developed method-of-
characteristics theory for immiscible three-phase flow. We present numerical simulations to
illustrate this theory and the dependence of the saturation profiles and production histories
on the injection proportion. We also show simulations that demonstrate how alternating
injection of pure fluids in this proportion yields the same oil recovery.