Asphaltene particles size and size distribution change at high pressure high temperature conditions: experimental study on a heavy oil sample

The size and size distribution of precipitating asphaltene particles are essential in the study of asphaltene deposition. They affect mass transfer of precipitated from the fluid bulk to the deposition surface (reservoir, wellbore, pipelines, etc) and determine how much deposition accumulates at any specified time and place. In this regard, a question that has not been thoroughly tackled in literature is how asphaltene particle sizes change at different thermodynamic conditions. This paper aims to address this question. In this study, a series of laboratory experiments are performed on a bottom-hole live heavy oil sample to determine its kinetic and thermodynamic properties. These tests include the SARA test for asphaltene instability evaluation, constant composition expansion (CCE) and differential liberation (DL) tests for phase behavior analysis, micro distillation (MD) and gas chromatography (GC) for compositional characterization, high pressure high temperature (HPHT) filtration for asphaltene content measurement and high-pressure microscopy (HPM) for studying particle size and size distribution. Our results show that particle size and distribution are sensitive to temperature and pressure. An empirical model is suggested for correlating the relationship between said parameters. The model's predictions are in good correspondence with lab data. Thermodynamic and microscopic findings also confirm each other. Results of this study can be used for improving transport models for asphaltene deposition.