Gas condensate reservoirs: Characterization and calculation of dew-point pressure

Abstract

A large data bank of more than 700 gas-condensate samples collected from literature and experiments was established. On this basis, empirical correlations and equations of state commonly used to calculate dew-point pressure (DPP) were evaluated. A new model for estimating DPP was proposed. All the empirical correlations and the Peng-Robinson state equation were compared, and sensitivity of parameters was analyzed. The current standards used to identify gas condensate were evaluated and found to be not accurate enough. The Peng-Robinson state equation has no unique solution and is affected by multiple factors such as the characterization of C7+ components and the splitting scheme. The Nemeth-Kennedy correlation has the highest accuracy when applied to the data bank established in this study, followed by Elsharkawy correlation and Godwin correlation. While Shokir correlation cannot be used for samples without C7+ components, it is therefore the lowest in accuracy. The newly proposed model has an average absolute error, root mean square error and coefficient of determination of 7.5%, 588, and 0.87, respectively, and is better than the above four correlations statistically. The proposed model proved to be more accurate and valid when compared to experimental results and simulation with the Peng-Robinson state equation.