Evaluating Crude Oils by SARA Analysis

Abstract

Abstract The effectiveness of some improved oil recovery schemes can depend on the composition of the target oil. Crude oils can be described compositionally by a number of methods. SARA analysis divides crude oil components according to their polarizability and polarity using a family of related analytical techniques. Problems arise because several of the analytical techniques in use do not produce identical results, although the users of the data rarely distinguish between them, assuming that SARA fraction values generated by any of the common techniques are essentially interchangeable. We examine this assumption for three SARA analysis methods: gravity-driven chromatographic separation, thin layer chromatography (TLC), and high pressure liquid chromatography (HPLC). Results for a suite of six crude oil samples show that a significant volume of volatile material that contains both saturates and aromatics is lost in the TLC analysis. Application of SARA fraction data to assessment of asphaltene stability is demonstrated.