Viscoelastic and thermodynamic properties of highviscosity oil with different water cut

Abstract

Dependencies of the viscoelastic and thermodynamic properties of high-viscosity oil from the oil-gathering reservoir of the N-Korenevskoye and Denisovskoye fields on the degree of water cut and temperature have been established. Under the conditions of shear deformations and at comparable temperatures, the nature of the processes of structure formation of oil at a low degree of water cut is due to phase transitions of paraffins, which is consistent with the experimental data described in the literature for non-watered oils, indicating the identity of the nature of intermolecular interactions between non-watered oil and oil with a low degree of water cut. The maximum effect of the thermal method for reducing the viscosity of oil with a low degree of water cut can be achieved when it is heated to the paraffin melting point T m *, determined using the ln(η) = f (1/T) dependence. The peculiarity of the rheological behavior of high-water-cut oil is due to an increase in the energy of intermolecular interaction, which in the entire temperature range is practically comparable to E act1 of low-water cut oil at T <T m *, which is associated with the formationn of invert emulsions stabilized by interphase layers of asphaltene molecules. It is shown that an increase in temperature and shear deformations contribute to a decrease in the values of the effective viscosity of low and high water cut oil; however, the destruction of their colloidal structure does not occur in the entire range investigated. The loss of aggregate and kinetic stability of high-viscosity watered oil is achieved in the presence of a surfactant composition based on Sorbital C-20 and a sodium salt of alkylbenzenesulfonic acid, which causes the desorption of “natural stabilizers” from the oil-water interface and, as a consequence, the coalescence of water droplets.