Densities and Excess Volumes of CO2 + Decane Solution from 12 to 18 MPa and 313.15 to 343.15 K

摘要

It has been widely considered that the global warming was induced by the increasing atmospheric concentrations of carbon dioxide, which has a significant impact on the sustainable development of the human society. Injecting carbon dioxide into depleted oil / gas reservoir has been developed to reduce carbon dioxide emission by the sequestration of CO2 underground, which is also considered as one promising approach to enhance oil recovery simultaneously. The evaluating of CO2 sequestration in oil reservoir needs highly accurate experimental data and models about the thermodynamic characters of CO2 + oil mixture. Density is one of key physical characters for simulating the diffusion and migration of carbon dioxide under the oil / gas reservoir. Research on volumetric behaviour is helpful to understand the expansion of the liquid phases in CO2 + oil mixture. In this paper, decane is investigated instead of petroleum because of the similar thermal physical property. The measurements have been performed at pressures from 12 MPa to 18 MPa and temperatures from 313.15 K to 343.15 K at four compositions X1 (x1 is the mole fraction of carbon dioxide) = 0.8690, 0.9135, 0.9430 and 0.9818 by a magnetic suspension balance (MSB). The accuracy of the experimental quantities presented in this work are 77 K = ± 0.01, m I g = ± 10~(-5) respectively. One circulation pump (AKICO, Japan) is equipped to accelerate the dissolution of CO2 in decane. Some conclusions can be obtained from the experiment as follow: (1) the dissolution of CO2 increases the density of decane, the density of CO2 + decane solution increases with increasing pressure and decreases with increasing temperature. (2) the slope of density with respect to pressure increases with increasing CO2 mole fractions while the slope with respect to temperature decreases with increasing CO2 mole fractions. (3) the crossover phenomenon appears at different compositions and the crossover pressure increases with temperature. (4) the excess molar volumes of this binary mixture are negative and show negative increasing with temperature for the data reported in this work. The GERG-2008 model is used to predict density of CO2 + decane solution, which takes temperature, pressure, and CO2 concentration into account. An empirical equation is also used to predict the density of this binary mixture. The predictions show that the empirical equation is in good agreement with the experimental data over the experimental range. The measurement and the model used in this work supplies the basic experimental data and theoretical analysis to CO2 sequestration and enhance oil recovery.