Asphaltene Densities and Solubility Parameter Distributions: Impact on Asphaltene Gradients

Abstract

Analysis of spatial gradients of the concentration of asphaltenes in reservoir crude oils has become an important tool for oilfield reservoir characterization. Modeling these gradients requires knowledge of asphaltene properties. For example, the commonly employed Flory–Huggins–Zuo (FHZ) equation requires the asphaltene particle size, solubility parameter, and density. Asphaltenes from various sources, particularly including sources beyond conventional crude oil, can have widely varying compositions such as the H/C ratio. Here, we measured the solubility parameters and densities of five asphaltenes that span a large range of H/C ratios, including asphaltenes from coal, petroleum, and shale, and then performed a sensitivity analysis to examine how that range of compositions impacts the magnitude of asphaltene gradients as predicted by the FHZ equation. Two case studies are included in the sensitivity analysis, one in which the asphaltene gradient is driven primarily by gravity, and another in which the asp...