Effects of stress and oscillatory frequency on the structural properties of Daqing gelled crude oil at different temperatures

The structural properties of Daqing gelled waxy crude oil were studied with a controlled-stress rheometer under oscillatory shear mode. Our results demonstrate that the gelled waxy crude oil shows viscoelastic properties. The linear viscoelastic region and yielding of crude oil can be determined not only by the critical linear shear stress (tau(cl)) and yield stress (tau(y)), but also by the critical linear shear strain (gamma(cl)) and yield strain (gamma(y)) respectively. With the decrease of test temperature, tau(cl) and tau(y) increased greatly while gamma(cl) and gamma(y) decreased gradually. The crude oil showed more elastic at lower temperatures. The frequency had little effect on the structure of crude oils in the measured range. (c) 2009 Elsevier B.V. All rights reserved.