A unified volume translation model in SRK EOS for dry gas constituents

Abstract

Dry gas, mainly made of light hydrocarbons (such as methane and ethane), is an important type of natural gases. The PVT properties of dry gas constituents (e.g., compressibility factor) play an important role in the various stages of dry gas recovery. In this study, we develop an improved distance-function-based volume translation model in Soave-Redlich-Kwong equation of state (SRK EOS) for dry gas constituents (including carbon dioxide, nitrogen, methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, and neopentane). This model not only accurately replicates the critical compressibility factor for a specific dry gas component but also maintains strong performance across a broad range of pressures and temperatures (i.e., pressure range: from triple-point pressure to 300 MPa; temperature range: from triple-point temperature to 600 K). For the 10 dry gas constituents considered in this study, the new volume-translated SRK EOS yields an %AAD of 1.27 in reproducing saturation pressure, while it yields %AADs of 0.73, 0.38, 0.69, 1.72, and 1.55 in reproducing the liquid-phase, vapor-phase, saturated-liquid-phase, saturated-vapor-phase, and supercritical-phase compressibility factors, respectively. Moreover, the new volume-translated rescaled SRK EOS (VTR-SRK EOS) does not lead to crossover of pressure-volume isotherms within the tested pressure/temperature ranges.