Black-oil equations
The black-oil equations are a set of partial differential equations that describe fluid flow in a petroleum reservoir, constituting the mathematical framework for a black-oil reservoir simulator.

The term black-oil refers to the fluid model, in which water is modeled explicitly together with two hydrocarbon components, one (pseudo) oil phase and one (pseudo-)gas phase.

This is in contrast with a compositional formulation, in which each hydrocarbon component (arbitrary number) is handled separately
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.