Estimation of Natural Gas Compressibility Factors Using Mathematical Correlations For Sirte Oil Fields

Abstract

Knowledge of the pressure-volume-temperature (PVT) behavior of natural gases is necessary to solve many petroleum engineering problems. Gas reserves, gas metering, gas pressure gradients, pipeline flow and compression of gases are some of the problems requiring the gas compressibility factor, or Z factor. Typically, the Z factor is determined by laboratory measurement. However, laboratory data is only applicable for the conditions and condition investigated. When conditions of interest are different from those of the laboratory studies or data is not available, correlations must be used. This study has been conducted on four gas fields of Sirte Oil Company, namely Zeltinfield, Al Ragouba field, Al Hotayba field and Al Braiga field. The Z factor has been calculated for the different fields using mathematical correlations and charts through the calculations of pseudocritical and pseudoreducedtemperatureT_pr and pressureP_pr. The values obtained are corrected because the natural gases contain impurities(H2S, CO2, N2) that caused factor deviation. The results exhibit some variation due the different constituents of gas mixture.