Abstract: Abstract:This paper presents a multi-compositional mathematical model of 3-D and 4-Phase (oil, gas, water and organic solid) and an equilibrium thermodynamic model of 3-Phase. In order to verify and evaluate the multi-compositional model, the numerical simulation study of long-core water alternate gas displacement experiment is conducted after fufilling the PVT phase behavior experiment and 3-Phase fluid phase equilibrium experiment of asphaltene precipitation. The results show that in the process of gas injection for EOR, the organic solids precipitation could occur in the oil-gas reservoir, and thus a negative effect appears on the numerical simulation results. This improved multi-compositional simulator can be used for better description of the reservoir fluid dy namic flow characters and physico-chemical features in the porous media, hence better understanding of the reservoir performance for EOR by gas injection process.

Key words: 3-D and 4-Phase, multi-composition, long core, numerical simulation, organic solid, gas injection