A new approach to the analysis of multicomponent EOR processes with interphase mass exchange is proposed. It’s based on the splitting of mass exchange and flow problems corresponding to two-phase displacement in porous media. On the first stage phase and composition behavior of system inside the zone of mass exchange is investigated by means of simulation of various composition paths. All these paths, as it was found, are realized in a very strong narrowing of compositional space for every fixed compositions of displacing and displaced fluids.

This is very useful on the second stage when hydrodynamic calculations are worked out. Such an approach substantially reduces the expenses connected with repeated calculations of phase behavior for compositional models and it extends the application range for analytical methods.

The main features of new approach are illustrated for gas-drive EOR processes. The general form of cubic EOS is used for description of phase behavior in terms of real composition. Hydrodynamic calculations are fulfilled after the reduction of a real system to a three-component one. Generalization of common composition path simulation for immiscible oil displacement by gas agents is proposed. The results for methane and smoke gas injections in Tengiz and Surgut fields are presented.

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