Asphaltene Precipitation from Live Crude Oil

Abstract

Asphaltene precipitation from live crude oils that occurs due to pressure reduction can foul and clog oil production equipment, at the well surface, in the borehole, and even in the subsurface formation, thus is of considerable interest to oil operating companies. We employ near-infrared (NIR) spectroscopy to characterize this asphaltene precipitation process; in particular, the independent measurements on asphaltene flocculation of wavelength dependence of optical scattering and of sedimentation rates are performed. Here, it is established that different asphaltene flocs form during depressurization of crude oil. Furthermore, the initial precipitate is probably not problematic in the production of crude oil, relaxing constraints imposed by asphaltene considerations. Additionally, the asphaltene precipitation process is shown to be largely reversible in the minutes time frame, but subtle irreversibilities are suggested. Compressibility is measured using NIR techniques to validate our methods. Optical spectroscopy on optically thin samples is found to be a powerful and indispensable tool to characterize asphaltene precipitation.