Two-phase isentropic compressibility and two-phase sonic velocity for multicomponent-hydrocarbon mixtures

Two-phase compressibility and two-phase sonic velocity of hydrocarbon mixtu res are needed for a variety of applications in well testing, metering, and seismic exploration. In this work, a thermodynamic model is presented to e stimate the two-phase isentropic compressibility and two-phase sonic veloci ty. The model accounts for the mass transfer between the equilibrium phases and the effect of capillary pressure. The results reveal that isothermal a nd isentropic compressibilities can be different by a factor of 20 in the t wo-phase near the retrograde dewpoint. With the exception of the retrograde dewpoint, the difference between the isentropic compressibility in the sin gle phase and two phase is less than the corresponding difference for the i sothermal compressibility. The sonic velocity in the two phase can be either less or more than the sin gle phase. For the hydrocarbon mixtures that the sonic velocity decreases i n the two phase, the decrease is much less pronounced than in nonhydrocarbo n systems such as water-steam and water-air.