Effect of enhanced oil recovery on the composition and rheological properties of heavy crude oil

The composition and rheological properties of ten samples of heavy crude oil from five different wells were investigated before and after integrated oilfield treatment with gel-forming and oil-displacing systems for increasing oil recovery. The study of the viscosity and viscoelastic properties of oil samples in a wide temperature range (from −30 to 70 °C) made it possible to determine their gelation and glass transition temperatures and also to establish the effect of enhanced oil recovery treatment on these characteristics. It was found that the treatment can either increase or decrease the viscosity of oil, and the same applies to the gelation and glass transition temperatures as well as to the contents of saturates, resins, and asphaltenes. The rheological properties of oil samples were closely related to their group composition, while the changes in the latter as a result of oilfield treatment were dependent on the relative position of the injection and production wells. The work allowed finding universal correlations between the group composition of heavy oil, its viscosity, and test temperature.