In the application of Beggs and Robinson dead oil viscosity-temperature empirical correlation to several hundred dead oil systems we have found consistently significant deviation between measured and calculated viscosity values. This paper presents a modified Beggs and Robinson empirical viscosity correlation. The proposed new correlation has been verified using a data base of about four hundred oil analysis reports (oil systems), and it shows a significantly better correlation, with a standard deviation and average error of at least 12% and 55% respectively, better than the existing correlation of Beggs and Robinson. We have also expanded the applicability of this correlation further by the inclusion of pour point temperature in the empirical equations. The new correlation also appears to apply to a wide range of oil specific gravities and pour point temperatures.
One of the most important physical properties of crude oils is viscosity, which is a critical parameter required in various aspects of petroleum engineering analysis. A laboratory PVT analysis of a crude oil provides viscosity information at reservoir temperature and pressure. However, difficulties arise when viscosities are required at other temperatures. Therefore, if viscosity at a desired temperature can be predicted by less expensive laboratory measurement technique, it will be extremely useful in the reservoir performance prediction. particularly for thermal recovery processes.
Until recently the most widely used methods for predicting oil viscosity were those of Beal (i) for dead oil and Chen and Connally (2) for live oil systems. While Beal correlated dead oil viscosity as a function of API gravity and temperature, Chen and Connally presented a correlation for the effect of dissolved gas on oil viscosity. More recently, Beggs and Robinson, (3) presented an empirical viscosity correlation equation for dead or gas-free crude oil as a function of API gravity and temperature. The correlation for dead oil viscosity which was developed by plotting log10 (T) vs log10 log10 (µOD + 1) on cartesian co-ordinates, enjoys extremely wide application in the petroleum industry.
We have examined the correlation equation presented by Beggs and Robinson and found a significant deviation betNeen measured and calculated viscosity values. There is a strong belief in the industry that the chemical composition of a crude oil may be important in its viscosity characteristics.
The inclusion into the correlation of any parameter related to crude oil composition (4–6) may improve the viscosity correlation. This i5 particularly 50 when considering the current developments in a wide range of heavy oil reservoirs where viscosity behaviour is extremely Important. Therefore, the need for a better viscosity correlation is apparent.
In this study, a new parameter, pour point temperature, is introduced into the viscosity correlation. Pour point temperature, (Tp), by definition, is the lowest temperature at which the oil is observed to flow when cooled and examined under conditions prescribed in ASTM 097. Pour point temperature of crude oil appears to be related to the paraffin content; the pour Point temperature increases with crude oil paraffin content.
