Gelling properties of waxy crude under quiescent and shearing conditions

Gel point or pour point is the temperature indicating the gelling of waxy crude, and is widely used for evaluating the low temperature flowability of a crude oil. While they are not sufficient to describe the gelling properties of waxy crudes under flow conditions, since the rheological properties of waxy crudes are strongly dependent on shear history. The gelling characteristics of waxy crude were investigated by dynamic temperature sweep measurements. At a given dynamic stress, the gelation temperature at which the storage modulus equals the loss modulus almost coincides with the eigen-temperature, the temperature corresponding to the maximum value of the curvature of a non-dimensional viscosity-temperature chart. For the rather low stress, the wax crystal network formation will not be disturbed, and the crude is gelled as under the quiescent conditions, both gelation temperature and eigen-temperature are close to the gel point of the specimen. However, they decrease with the increasing shear stress. This suggests that these two parameters may be appropriate measures of the onset of gelling under static as well as flow conditions.