Correlation of Excess Volume of Oil Stocks

Thura Nasrat Abd Al-Haddy
Prof. Dr. Jabir Shanshool

Binary mixtures of three, selected Iraqi crude oils had been subjected to density measurements at temperatures 15, 25, 30C and precise data had been acquired on the volumetric behavior of these systems. The results are reported in terms of equations for excess specific volumes of the mixtures. The crude oil types used were of good varity, they ranged from light crude with API value of 44.3 (khana) to medium crude (Basrah) of API 31.4 reaching the heavy crude (Shark Baghdad) of API 24.2.Temperatures in the range of 15-30C0 have a minor effect on excess volume of crude binary mixtures thus, low decrease of
expansion or low increase of shrinkage is observed by increasing the temperature.Mixture of crudes with aromatic oil-stocks shows positive excess volume. This expansion effect is greatest for the lowest boiling point spike as in the case of toluene. While, the presence of methyl groups in aromatic rings results in a lower positive excess volume.The API gravity of crude oil has predominated effect on the
expansion of aromatic spiked crude oils. Those, khana crude, as a typical light type gives the maximum positive excess volumes of 2.68 when spiked with toluene. While the spiked heavy crude,shark Baghdad resulted in the lowest excess value of 0.7.Spiking of the considered Iraqi crudes with either kerosene or gas oil resulted in negative excess volume. This shrinkage is greatest for the lowest-boiling spike as in the case of kerosene. The gravity of crude oil has an effect on excess volume when the crude was spiked with petroleum fraction. Those, shark Baghdad as typical heavy type resulted in minimum negative excess volume of -4.81 and -3.29, when it was spiked with the petroleum fraction (Kerosene and Gas Oil respectively), while the spiked light crude and Khana gave maximum negative excess volume of -7.56 and 6.38 respectively.Density prediction was calculated using a generalized Costaldequation of state through –Hankinson-Brobst-Thomson (HBT) technique for binary crude oil mixtures studied.The
over all average absolute percent error for 54 data point is 0.874.Ageneralized density-temperature-composition correlation for undefined liquid petroleum fractions was developed to represent the data at      temperatures 15-30C0 over a range of weight percent (0-100), as follows: