Correlating the chemical and physical properties of a set of heavy oils from around the world

Variations in the viscosity and other physical properties of heavy oils are poorly understood. The viscosities measured for different heavy oils can vary by orders of magnitude even at the same API gravity, which is the standard metric for lighter oils. Heavy oils are viscoelastic materials, and the shear modulus and the viscosity are coupled. Understanding what controls heavy oil viscosity will provide insight into what controls heavy oil shear modulus. Therefore, using rheology, ultrasonic measurements and molecular beam mass spectroscopy (MBMS) the physical and chemical properties of seven heavy oils from around the globe are explored. The viscoelastic nature of the oils is quantified as a function of temperature. Overall, the heavy oil samples show little correlation between the viscosity or shear modulus and the API gravity, separate resin content or separate asphaltene content as measured from SARA analysis. However, the total resin plus asphaltene content collapses the viscosity and modulus values to provide empirical relations between these quantities. Also, a partial least squares regression analysis provides tight correlations for the chemical signatures from the MBMS. The rapid and quantitative nature of the MBMS make it an attractive substitute for the inconsistencies endemic to SARA analysis. (C) 2008 Elsevier Ltd. All rights reserved.