Abstract
Three correlations for retrograde gases have been developed. First, a correlation was developed that relates the composition of a retrograde gas-condensate mixture at any depletion stage to the composition at its dew point pressure. This correlation is as accurate as previous correlations, and in addition, to the composition, it includes the trends for molecular weight of heptanes plus fraction (A4WC7+), specific gravity of heptanes plus fraction (SGC7+), gas produced (GP) and fraction of liquid (FL). Second, a correlation to describe the molar distribution Of C7+ of a gas-condensate mixture as a function of carbon number (CN), the C6 mole fraction and the properties Of C7+ has been developed. For comparison, the Ahmed, et aL, and Whitson methods were evaluated using a data base of 52 extended (from C]5+ and up) retrograde gascondensate samples. The evaluation of the Ahmed, et al. and Whitson methods showed that both methods are better than the new method. The Ahmed, et aL method does a better overall job than the Vvlhitson method. Comparing the relative error, Ahmed, et al. method had an error of 20.6 percent, and Whitson's method had an error of 25.1 percent. Third, a new and improved retrograde dew point pressure correlation has been developed. The new dew point correlation is an improvement of the Kennedy-Nemeth dew point correlation. Contrary to the Kennedy-Nemeth correlation, temperature is not included in the new correlation. The new dew point correlation is based on composition and the C7+ properties, molecular weight and specific gravity of the heptanes plus fraction.
Crogh, Arne (1996). Improved correlations for retrograde gases. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -C77.