Asphaltene precipitation from live crude oil

Asphaltene precipitation from live crude oils that occurs due to pressure r eduction can foul and clog oil production equipment, at the well surface, i n the borehole, and even in the subsurface formation, thus is of considerab le interest to oil operating companies. We employ near-infrared (NIR) spect roscopy to characterize this asphaltene precipitation process; in particula r, the independent measurements on asphaltene flocculation of wavelength de pendence of optical scattering and of sedimentation rates are performed. He re, it is established that different asphaltene flocs form during depressur ization 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 proc ess is shown to be lamely reversible in the minutes time frame, but subtle irreversibilities are suggested. Compressibility is measured using NIR tech niques to validate our methods. Optical spectroscopy on optically thin samp les is found to be a powerful and indispensable tool to characterize asphal tene precipitation.