| A novel application of Fourier Transform Infrared (FT-IR) Spectroscopy was used to measure the wax precipitation temperature and estimate the weight percent precipitated solid versus temperature, of a sample of the combined stream Alaska North Slope crude oil, transported by the Trans Alaska Pipeline System. The wax precipitation temperature, and weight percent precipitated solid determined by FT-IR for the Alaska North Slope crude oil sample were compared with wax precipitation and weight percent precipitated solid versus temperature values generated from conventional analysis methods, including cross-polarized microscopy, viscometry, differential scanning calorimetry, and centrifugation. The capability of the FT-IR method to determine the wax precipitation temperature and weight percent precipitated solid versus temperature was demonstrated by analysis of a Model Oil system with known solid-liquid equilibria.; The experimental values for Alaska North Slope crude oil wax precipitation temperature, weight percent precipitated solid versus temperature, and precipitated solids composition were compared with results of predictive modeling. True Boiling Point and Single Carbon Number characterizations of the ANS crude oil and derived crude oil solids were developed from distillation and chromatographic analyses for input to predictive models, which included an equation of state, and an activity coefficient model. Poor agreement were observed between experimental and predicted values for weight percent precipitated solid versus temperature, and precipitated crude oil solids composition for the combined stream Alaska North Slope crude oil analyzed.; Blending of gas condensate (C4 through C8) liquids (10 vol %) with an individual North Slope crude oil delivered to the Trans Alaska Pipeline produced a 7°C decrease in the wax precipitation temperature measured by FT-IR, and increased precipitation of solids at temperatures below 0°C estimated by both FT-IR and centrifugation. Investigation of asphaltene contents of precipitated solids shows that co-precipitation of asphaltene solids is suggested to occur in the combined stream Alaska North Slope crude oil since the experimentally determined asphaltene content of the precipitated crude oil solids do not decrease with decreasing occluded oil content. |
