A study of the effect of gas condesate on the viscosity and storage stability of Omani heavy crude oil

Heavy crude oil (density of 0.9571 g/cm³ at 288 K and kinematic viscosity of 7160 mm²/s at 303 K) and natural gas condensate (density of 0.7848 g/cm³ at 288 K and kinematic viscosity of 0.764 mm²/s at 303 K) were sampled from Omani oil fields. The oil was mixed with condensate (5-50 vol %), and the mixture viscosities were measured at the temperature range of 293-348 K. A drastic decrease in kinematic viscosity was achieved. An addition of about 12 vol % of condensate gave a viscosity of 265 mm²/s at 303 K. This made it easier to transport the heavy oil mixtures. The experimental data for the kinematic viscosity [v(mm²/s)] as a function of the gas-condensate fraction (φ) and temperature [T (K)] could be described by an equation: In(In(v)) = (k₁ + k₂·T) + (k₃ + k₄·7)·φ, with a high accuracy. Blends of the heavy oil and the gas condensate were stored to evaluate their stability. Results showed less than 0.05 wt % sludge formation after 2 months.