The Limitations of the Cloud Point Measurement Techniques and the Influence of the Oil Composition on Its Detection

Cloud points are in the petroleum industry one of the main guides to evaluate the wax precipitation potential of a fluid. The planning of the exploration of a reservoir or the design of its pipelines are based on the measured cloud points for the reservoir oil. It is known that each measuring technique will provide a different cloud point temperature, yet although some of these techniques seem to be more accurate than others no definite conclusion has been established on how cloud points should be measured. On this work several cloud point measurement techniques are discussed and compared. It will be shown that some of these techniques such as viscosity, filter plugging and DSC can only be used under very favourable circumstances but it will be argued that since every technique requires some finite, often large, amount of solid to detect the presence of a new phase, the cloud point, defined as the temperature for which the first solid appears in the oil, is not accessible experimentally and, unless a very detailed compositional analysis is available, it is also impossible to predict it accurately with a thermodynamic model. The effect of the paraffin distribution in the oils on the cloud point detection will be discussed and it will be shown how the compositional information can be used to assess the uncertainty of the measured cloud points.