Heavy Oil Correlation for Liquid Viscosity

Most other liquid viscosity methods produce poor predictions when applied to heavy fractions. This is especially true at lower temperatures where liquid viscosity may change dramatically with small temperature changes. Simulation Sciences developed the heavy oil correlation specifically for the heavy oils and bitumens. It is a hybrid between the LIBRARY and SIMSCI methods.

Library components individually contribute viscosities derived from the saturated liquid (LIBRARY) viscosity correlations. In contrast, constants (Tc, Pc, etc.) for individual PETRO components are mixed according to the SIMSCI method to represent a single lumped (typically heavy) component. This composite (PETRO)component is treated mainly as in the SIMSCI method. However, the SIMSCI method computes NBP by mole averaging. In contrast, the Heavy Oil method determines the NBP as the mean average of the lumped component.

Next, the viscosities of the library components and of the single lumped component are combined using the Mehrotra mixing rule.

Finally, viscosity is estimated at two reference temperatures (100F and 210F), then the viscosity-temperature relationship is extrapolated or interpolated, as required.

For more information, refer to the sub-topic "Heavy Oil Correlation for Liquid Viscosity" in the PRO/II Reference Manual Volume I, Component and thermodynamic Data, Chapter 2, under the section "Special methods for Liquid viscosity".

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