Experimental Study of Asphaltenes Flocculation Onset in Crude Oils Using the Densitometry Measurement Technique

Abstract

The asphaltenes flocculation proceeds with changes of oil composition and causes significant losses in petroleum industry operations. The main objective of this work is to evaluate the reliability of the densitometry technique in studying experimentally the mechanism of aggregation and flocculation of asphaltenes occurring in crude oils. As asphaltene flocculation threshold in crude oils or mixture can be achieved by addition of n-heptane, various n-heptane concentrations were added to crude oil, and their effects have been investigated trough density measurements. Thereby, measurements were based on mixture of crude oil + toluene and cyclohexane + n-heptane, respectively. While asphaltene aggregates form clusters and flocculate, the mixture volumetric mass change and the reduced density of non-Newtonian fluids under investigation have been pointed out as one of appropriate measures of flocculation process. In particular, the curve representing the reduced density as function of the ratio between n-heptane concentration and concentration of crude oil under study featured a break point that well characterizes the flocculation threshold. Besides the quantity needed to initiate and to aggregate asphaltenes within crude oils, the amount required to completely achieve deposition of asphaltenes has also been identified. A quantity of 4 and 20 g of n-heptane per gram of crude oil was found necessary.