Characterization of yield value of waxy crude oil with storage modulus

The yield behavior of waxy crude oil directly affects the safety of pipeline transportation. When the temperature decreases, wax crystals precipitated from waxy crude oil interact with the resin and asphaltene present in the oil, forming a three-dimensional network structure with a certain strength. Under the external shearing force, this structure is yielded and fractured, at a yield value, i.e., yield stress. Rheology tests of Changqing, Daqing, Huanjiang River and Jidong waxy crude oil were carried out through strain sweep experiments. Results show that the storage modulus of the crude oil have remained basically unchanged in linear viscoelasticity region which increases with the increase of temperature, and stress increases linearly with strain. Storage modulus and yield value of waxy crude oil present a linear increase relationship in the log-log graph. The structural yield coefficient, which is equal to the log ratio of storage modulus to yield value, is introduced to represent the strength of the structure when waxy crude oil yields. Compared with other methods, the yield value obtained by this method is more stable, making it easier to form relevant standards.