High-pressure phase equilibrium and volumetric properties of pseudo-binary mixtures of stock tank oil + methane up to 463K

High-pressure phase equilibrium and volumetric properties of highly asymmetric mixtures related to reservoir fluids are critical the development high-pressure high-temperature (HPHT) reservoirs. However, there is a lack relevant data accurate modeling tools. In this work, we prepared pseudo-binary methane (CH4) + stock tank oil (STO) systematically measured their densities at temperatures from (298.15 463.15) K pressures up 140 MPa. The mole fraction in these range 0.20 0.61 for density measurement, 0.81 measurement. From experimental densities, isothermal compressibility values, as well pseudo-excess volumes, were determined. Moreover, envelopes, relative liquid volume fractions below saturation point also measured. These valuable evaluating improving thermodynamic models HPHT fluids. results modeled by Soave-Redlich-Kwong (SRK) equation state (EoS), Peng-Robinson (PR) state, translated versions SRK-VT PR-VT, Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT). For density, SRK PR gave large deviations ~18% ~8%, respectively, compared with ~3% PC-SAFT. Inclusion translation reduced same level that compressibility, all 20-30%, PC-SAFT, PR-VT being slightly better. excess volumes calculated SRK, PC-SAFT similar close values. resulted only ~1% if experimentally determined STO used. It was illustrated small could be utilized method accurately estimate live densities. This deviation on average models, giving smallest maximum deviation. ~5% overall smaller.