"Density and Phase Equilibria of Binary and Ternary Alkane Mixtures under High Temperature and Pressure Conditions"
Abstract
The worldwide trend in oil and gas industry is towards exploitation of high pressure high temperature (HPHT) reservoirs due to dwindling conventional resources. Development of such reservoirs requires accurate knowledge of termophysical properties of the reservoir fluids under HPHT conditions in order to lower the economic and technical risks in the exploitation. As the first step to get insight into the thermophysical properties of HPHT reservoir fluids, well-defined hydrocarbon mixtures are used as model reservoir fluids. This avoids the problem of acquiring expensive HPHT reservoir fluid samples. Furthermore, the data for these mixtures under HPHT conditions are far from systematic, especially for highly asymmetric binaries, and for ternaries and multicomponent mixtures, experimental measurement of these mixtures is clearly needed for development and validation of models for HPHT fluids.
In this work we have focused on the experimental determination of two thermodynamic properties, which are density in the temperature range from (278.15 to 463.15)K and pressures up to 140 MPa and phase equilibrium in the temperature range from (283.15 to 473.15)K, through a high pressure vibrating tube densimeter and a full visibility variable volume cell, respectively.
Density of the binary systems methane+n-decane, n-hexane+n-decane, n-hexane+n-hexadecane, as well as a ternary system methane+n-butane+n-decane was determined. As concerns phase equilibrium, the system methane + decane, as well as a ternary mixture methane+n-butane+n-decane were studied.
The ability of several EoSs (Soave-Redlich-Kwong [1], Peng-Robinson [2] and PC-SAFT [3]) to predict densities and phase envelope for these systems was tested.
[1] G. Soave “Equilibrium constants from a modified Redlich-Kwong equation of state” Chemical Engineering Science, 1972, 27: 1197-1203.
[2] D. Y. Peng, D. B. Robinson “A new two-constant equation of state” Industrial & Engineering Chemistry Fundamentals, 1976, 15: 59-64.
[3] J. Gross, G. Sadowski “Perturbed-Chain SAFT: An equation of state based on a perturbation theory for chain molecules” Industrial & Engineering Chemistry Research, 2001, 40: 1244-1260.