CHARACTERIZATION AND MULTIPHASE EQUILIBRIUM PREDICTION OF CRUDE-OIL HEAVY COMPONENTS

For compositional simulation purposes, a new method has been developed for estimating the specific gravities of pseudo-components that are r equired to characterize the heavy components of crude oils. This metho d makes use of the always available data for the heavy components of c rude oils: average molecular weight and specific gravity of the heptan es-plus (C-7+) fraction. To evaluate the new method and compare it wit h the existing estimation methods, a procedure has been implemented fo r the phase equilibrium predictions of crude oil/carbon dioxide system s without using any tuning techniques. The phase equilibrium predictio ns, based on the specific gravities estimated by the new method and th e existing methods proposed by Whitson et al. (1989) and Yarborough (1 979), were all reasonably accurate and of the same magnitude. The spec ific gravities estimated by the new method and the method proposed by Whitson et al. (1989) always provided similar predictions. The satisfa ctory results reported here also indicate that a simple truncated expo nential distribution for the heavy components of crude oils is adequat e.