ASPHALTENE CHARACTERISATION USING SPECTRAL ANALYSIS SYSTEM

Abstract

Asphaltenes are the heaviest hydrocarbon component of crude oil and remain in colloidal suspension under reservoir temperature and pressure conditions. These materials may flocculate and deposit as a result of pressure, temperature and compositional changes, and consequently, disrupt production operations. This disruption can have severe implications, particularly in an offshore subsea environment. In these circumstances, it is imperative to understand the fundamental behaviour of asphaltenes prior to the development phase of any field under consideration.

In this paper, we present a novel methodology to understand the thermodynamic asphaltene instability conditions using near infrared and spectral analysis system (SAS) techniques. Using the SAS technique, we were able to estimate the asphaltene particle size and growth behaviour as functions of pressure and time. Asphaltene particle size determined at the onset of asphaltene flocculation is in the order of 0.25 μm for a pressure-compensated sample. On the other hand, the asphaltene particle size is determined to be about 0.8 μm at the onset pressure using a conventional sample. Results also indicate that the particles from the pressure-compensated sample had a slower initial growth rate compared to the particles growth rate estimated from the non-pressure compensated sample. These results demonstrate the importance of representative sampling on asphaltene characterisation.