ABSTRACT
The simulation of EOR processes characterized by the injection of gases, solvents and/or chemicals with steam into a petroleum reservoir requires a fully implicit, thermal, compositional formulation. The simulator must be able to handle robustly and efficiently all the different types of PVT-composition behavior found in these processes. For reliable predictions, it also must accurately account for the complex physical effects that these additives have on oil, gas and aqueous phase properties such as density and mobility. Finally, the formulation must be able to accommodate future developments in steam additives EOR processes with a minimum of change to the simulator.
This paper describes such a multi-phase multi-component thermal model. The use of global mole fractions as primary variables permits all phase equilibrium calculations to be carried out in an interchangeable flash module which is designed specifically for the type of additive being injected. Two examples of these flash modules are presented. The phase equilibrium constraints are coupled to the flow equations using a novel method which optimizes robustness and efficiency. Phase properties are calculated in another interchangeable module which is tailored to reproduce the desired effects of the additive.
Results show that the simulator can handle a wide range of steam injection processes efficiently. Several examples are used to compare this model with another model that employs a more conventional formulation.
