Phase Behaviour of Fluids in Multiple Contact Processes with CO2, N2 and their Mixture

Abstract

Abstract The thermodynamic behaviour of hydrocarbon fluids in multiple contact processes with non-hydrocarbon gases (N2, CO2 and their mixtures) has been studied experimentally. A gas condensate PVT cell has been used to simulate the process of multiple contact gas injection in the vicinity of an injection well. Measured quantities at each contact include volumes and compositions of gas and liquid phases at cell conditions of pressure and temperature and the number of moles of each component in the discharged gas. Attention has mainly been given to gas condensates, although the results are equally applicable to oil fluids. The tested fluids are well defined mixtures of paraffinic hydrocarbons and the injectant gases were pure CO2, N2 and their mixtures. Dynamic miscibility was achieved by CO2 injection, while the process with N2 injection was of the immiscible evaporating type, vaporizing light, intermediate and fractions of heavy hydrocarbons. Lean mixtures of CO2 in N2 (5–15% by mole), similar to those in flue gases, had the same evaporation behaviour as the N2, but caused liquid phase swelling effect due to the CO2 solution.