The Effects of Compositional Uncertainties on Phase Behavior Calculations

Abstract Accurate estimates of reservoir mole compositions are important for developing accurate fluid models and fluid initialization. However, because of the limitations of the methods used for compositional analysis, a complex mathematical procedure is used to estimate the reservoir from several other measured and estimated properties. The method for compositional analysis has several potential sources of uncertainties, from measurement errors and calculational errors. Compositional variations can have a significant impact on phase behavior calculations, which can have impacts on downstream estimates. Examples of processes that can be impacted include fluid model development, composition initialization (resulting wrong in place estimates), to surface oil volumetric rates. This article systematically introduces the sources of compositional errors for a wide range of fluid types and shows the impact on the phase behavior calculations. Based on this analysis, qualitative guidelines can be made on what compositional uncertainties have the biggest impact on the different fluid types and phase behavior properties.