Effects of Asphaltene Content and Temperature on Viscosity of Iranian Heavy Crude Oil: Experimental and Modeling Study

Heavy and extra heavy crude oils usually have a high weight percentage of asphaltene, which could induce many problems during production to refining processes. Also, asphaltene has the main role on the high viscosity of the heavy and extra heavy crude oils. In this paper, the effects of asphaltene characteristics on the crude oil rheological properties have been experimentally and theoretically investigated using different classes of the suspension models. For experimental investigation, the asphaltene was first precipitated from the original heavy crude oil and then 10 well-defined reconstituted heavy oil samples are made by dispersing the asphaltene into the maltene (i.e., deasphalted heavy crude oil) for measuring viscosity at a wide range of temperatures from 25 to 85 degrees C. Then, the viscosity of the prepared reconstituted heavy oil samples was measured using a rotational rheometer at seven different temperatures. Moreover, for modeling the viscosity behavior of the heavy oil samples versus different asphaltene contents (0-12.22 vol %) at different temperatures (25-85 degrees C), six equations from three groups of suspension models are used, including Pal-Rhodes (with parameters of the shape factor v and solvation constant K), Mooney, Krieger-Dougherty, and Brouwers (with parameters of the intrinsic viscosity [eta] and the maximum packing volume fraction phi(max)), and Bicerano et al. and Santamaria-Holek and Mendoza (with parameters of the intrinsic viscosity [eta] and the critical volume fraction phi(c).The results of experimental study indicate that the viscosity of the reconstituted heavy oil samples increases exponentially as the asphaltene content increases at a constant temperature. Also, the viscosity of the heavy oil samples decreases significantly with increasing the temperatures from 25 to 85 degrees C at a constant asphaltene volume fraction.