Solution behavior of asphaltic residues and deasphalted oil prepared by extraction of heavy oil

Abstract An experimental setup to mix crude oil with propane or other gases at high pressure and high temperature is described. The system permitted the injection of predefined volumes of oil and pressurized gas above its saturation pressure to get a homogeneous mixture and subsequent fractionation of the sample into a solid residue and a liquid extract. For propane, the solubility parameter prevailing in the mixing cell was estimated in the range of 13.0 and 12.6 MPa 0.5 which is lower than the values usually used for asphaltenes separation with n-heptane (15.3 MPa 0.5 ) or n-pentane (14.5 MPa 0.5 ). As expected, this experimental procedure reduces to a largely the asphaltic materials from the crude oil and incorporates to the solid residue part of the component usually separated in the resins fraction. These components in spite of their lower solubility parameter seem to enhance in some way the stability of the residue solution in toluene. Elemental analysis indicates that the heteroatoms accumulate in the solid residue but some polar compounds still remain in the liquid extract which presents a relatively high solubility parameter (20.3 MPa 0.5 ), comparable to the value obtained for the crude oil (21.2 MPa 0.5 ). The deasphaltation process reduces the crude oil viscosity from 30,320 cP in the crude oil to 2510 cP in the extract and a re-extraction of the liquid extract with n-propane further reduces the viscosity to 720 cP. These results are interpreted as an indication that components not necessarily included in the asphaltenes fraction may significantly contribute to crude viscosity.