Riemann Problem for Two-Phase Four- and Morecomponent Displacement (Ideal Mixtures)

This paper considers the two-phase multicomponent displacement in porous media. We focus on the ideal systems (mixture volume and entropy are additive). This assumption is extensively used for oil-gas and gas-condensate systems at low pressure. For the actual n-component system the problem of the approximation by ideal mixture is solved - density and entropy of every component is found as a phenomenological parameter from the equation of state. Explicit formulae for the Riemann invariants, shock and rarefaction waves are found. Invariant solutions for one-dimensional displacement problem is obtained. Description of the displacement of oil by gases is given.