MEASUREMENT OF ASPHALTENE PARTICLE-SIZE DISTRIBUTIONS IN CRUDE OILS DILUTED WITH N-HEPTANE

The formation and growth of asphaltene particles from heavy crude oils diluted with n-heptane at 22-degrees-C and atmospheric pressure was s tudied using a laser particle analyzer. The results obtained with six crude oil samples indicate that the asphaltene precipitation is an ins tantaneous process leading to a unimodal, log-normal distribution. At typical laboratory conditions, the particles remained essentially unal tered in size and population density. A vast majority of the particles were noted to be far from round in shape, with the mean particle size ranging from 4.5 to 291 mum. It was found that the oil-to-diluent rat io is an important parameter in determining the size of the generated asphaltene particles; higher dilution ratios yielded larger particles. The mean asphaltene particle size was also found to increase with the average molar mass and the asphaltene content of crude oils.