The Vapour-Vapour Interface Observation and Appraisement of a Gas-Condensate/Supercritical CO2 System

Abstract

Injecting supercritical CO2 into gas reservoir is a novel trial to improve condensate gas recovery and decrease the hydrocarbon liquid dropout. A good understanding of the effect of supercritical CO2 on the phase behavior properties of these hydrocarbons is essential for accurately forecasting the displacing performance and storing process of the reservoirs with numerical simulators. This paper presents novel phase behavior experimental procedures and phase equilibrium evaluation methodology for gas-condensate phase system mixed with supercritical CO2 over a wide range of temperatures and pressures. A unique phase behavior phenomena was also reported. The mass transfer between two vapour phases was also measured. In order to interpret and identify the interface property between condensate gas and supercritical CO2, a multiphase thermodynamic VLV equilibrium model was established. Finally, taken YKL condensate gas in Northwest China as an example, the region where the conditions in terms of pressure, temperature and CO2 concentration can yield VLV equilibrium was found. The calculation results of multiphase thermodynamic model for condensate-CO2 system in this paper are close to the experimental data and can truthfully reflect the phase behavior of interface between CO2 and condensate gas. The research results indicate that it is the existence of the interface between CO2 and condensate gas that makes CO2 possible be an attractive option to successfully displace condensate gas and decrease CO2 emissions.