Equilibrium Vaporization Ratios for Nitrogen, Methane, Carbon Dioxide, Ethane, and Hydrogen Sulfide in a Natural Gas-Condensate System

Experimental equilibrium vaporization ratios were obtained for nitrogen, methane, carbon dioxide, ethane, and hydrogen sulfide in natural gas-condensatesystems. Two different overall mixture compositions were investigated over thepressure range 500 to 4,000 psia at 100?, 150?, and 200?F. Partial phasediagrams of the mixtures were obtained; one of these showed a critical point at204?F and 3,875 psia. These and earlier data were compared with the Kelloggcorrelation at 100?F and 1,000 psia. Introduction The authors have presented equilibrium vaporization ratios for nitrogen, methane, carbon dioxide, ethane, and hydrogen sulfide in complex mixtures, suchas natural gas-crude oil and natural gas-absorber oil. Since mixtures of thenatural gas-condensate type also occur widely in petroleum reservoirs and oftencontain the non-hydrocarbons mentioned, it would be useful to have appropriateK data for calculating equilibrium vaporization conditions. Roland, Smith, andKaveler obtained K's for methane and the light hydrocarbons in gas-condensatemixtures; and Poettmann and Katz obtained K's for carbon dioxide in agas-condensate system. The data presented in this paper extend this coverage toinclude K's for nitrogen and hydrogen sulfide and phase diagrams for theexperimental mixtures. Experimental Work The equipment and experimental procedure was essentially as describedpreviously except for analysis of the vapor samples. The vapor sample bombswere filled at the pressure and temperature of the run. Immediately aftersampling, a portion of this sample was flushed from the bomb into a 650 ccglass bulb, filling it to near atmospheric pressure. The sample in the glassbulb was then analyzed by the mass spectrometer. Some checks were made on thisanalytical procedure to find the accuracy of measurement of the C5+ content ofthe vapor samples. The modifications tried were complete fractionation of thevapor sample and the use of several liquids (depropanized condensate andretrograde liquid from several vapor samples) as calibrating materials for themass spectrometer. The results obtained from these various checks differed byabout 10 per cent relative and this is believed to be the order of accuracy ofthe vapor C5+ concentrations. T.P. 3652