Modification of Hall-Yarborough Equation of State For Predicting GasCompressibility Factors

摘要

This investigation demonstrates the use of acentric factor as the third parameter in a corresponding statescorrelation for compressibility factors and a discussion of their application to three different types of gasreservoir. A correlation is presented which provides compressibility factors based on Hall - Yarborough equationof states for use in both two - phase and single-phase hydrocarbon systems. The modified Hall - Yarboroughequation employs the acentric factor as an additional parameter to improve its accuracy. This modifiedequation is as simple as the original form, yet achieves substantially better prediction accuracy, especiallyat higher pressure. The correlation is based on hydrocarbon compressibility determinations from twenty-two hydrocarbonsamples taken from three different types of reservoir systems. Out of the data used 67 percent were fromdew point or retrograde gas condensate and bubble point or dissolved gas reservoir, 33 percent were fromsingle phase gas reservoir. Results from the modified Hall - Yarborough equation, the original Hall - Yarborough equation andpractically obtained were compared with natural gas components data for three different reservoirs todemonstrate its accuracy and increased application range. The improvement of the modified equation, overthe original Hall - Yarborough equation ranges from 0.98% to 7.017% on the average.