Diachronic viscosity increase in waxy crude oils

During the study of paraffin wax deposition from crude oil in flow lines, it was observed that after exposure to air the viscosity of the oil increased continuously with time. The cause of this diachronic viscosity change has been investigated and evidence is presented to show that, for the crude oil used in this study, it is primarily due to the evaporation of lighter ends. Infrared spectroscopy was used to ascertain the type of changes that occurred in the oil under two conditions, oxidation and evaporation. The oil used came from the cretaceous Dakota reservoir in the Fourteen Mile field in Wyoming. The Gas Chromatograph–Mass Spectrometer (GC–MS), Gas Chromatograph–Flame Ionization Detector (GC–FID) analysis and other relevant property data pertaining to the oil are also presented.