Assessment of Empirical Pressure–Volume–Temperature Correlations in Gas Condensate Reservoir Fluids: Case Studies

Abstract

Measurement and modeling of fluid properties and phase behavior of gas condensate reservoir fluids are challenging tasks. Many researchers proposed various empirical correlations based on either simple measurable field or laboratory data (e.g., gas-to-condensate ratio (GCR), compositions, and plus fraction characteristics) to estimate other PVT (pressure–volume–temperature) properties. In this study, several empirical correlations for estimating gas condensate fluid properties have been selected to be evaluated against available field data gathered from Iranian gas condensate fields. Experimental data from 30 lean gas condensate samples taken from nine gas condensate fields in the south of Iran were collected to examine the reliability of the empirical correlations. A wide range of field data were used for the evaluation: reservoir temperatures of 343.7–385.9 K, gas molecular weights of 17.40–21.13 g/mol, dew point pressures of 21.37–35.64 MPa, gas compressibility factors of 0.84–1.06 at dew point pressure, maximum retrograde condensates of (MRC) 0.09–2.91%, and GCRs of 5964–110,012.6 m3/m3. The estimated empirical correlations were compared to the measured field data, and the accuracy of the correlations was evaluated via error analysis. The parameters included in the assessment of empirical correlations were C7+ mole%, gas molecular weight, MRC, GCR, dew point pressure, and gas compressibility factor at dew point pressure. The results indicate that correlations of parameters with dew point pressure and with MRC have minimum and maximum errors, respectively. In cases where the GCR is high, correlations with C7+ mole% were not suitable for assessment. Also, estimation of gas compressibility factors at dew point pressure based on empirical correlations is not recommended.