Studies on the Structural Characteristics of Gelled Waxy Crude Oils Based on Scaling Model

The structural characteristics of three gelled waxy crude oils were studied through DSC analysis, rheological test, and a scaling model for colloidal gels. The total wax content is 8.1 wt % for crude oil A, 11.5 wt % for crude oil B, and 17.3 wt % for crude oil C. The concentration of precipitated wax crystals, phi(W) increases gradually with the decrease of temperature. The gelation point, which increases with the increase of wax content, is 16.5 degrees C for crude oil A, 26 degrees C for crude oil B, and 41 degrees C for crude oil C. The elastic modulus in linear region, G'(E) of the gelled crude oils always increases with decreasing temperature while the critical linear elastic strain, gamma(E) of the gelled crude oils first decreases with decreasing temperature, then increases with the further decrease of temperature. The microstructure of gelled crude oils, which can be divided into strong-link region and weak-link region, is similar to that of colloidal gels. In the strong-link region, the G'(E) increases but the gamma(E) decreases with increasing phi(W), and the microstructure of the gelled crude oils is porous and loose due to the small value of phi(W). In the weak-link region, the G'(E) and gamma(E) both increases with increasing phi(W) and the microstructure of the gelled crude oils is relatively compact because of the high value of phi(W). The fractal dimension D increases with increasing phi(W) indicating the continuous development of the microstructure of the gelled crude oils with increasing phi(W).