(352e) Modeling of Asphaltene Deposition in Pipelines: Accounting for a Chemical Inhibitor Effect

Asphaltene deposition occurs in production flow lines when pressure drops below the asphaltene onset precipitation pressure, which is determined by oil chemical composition. The deposit layer can, eventually, become thick enough to significantly reduce production rate. Asphaltene deposition can be prevented or reduced by chemical inhibitors. To decide whether using an inhibitor is necessary or not, a reliable deposition model is required. The deposition process includes a number of phenomena, such as precipitation of asphaltene nanoparticles from a fluid, growth of agglomerates, their transport to the wall and agglomerate-wall interaction. The deposit layer formed on the wall can be also partially removed with a fluid flow (the shear removal effect). A deposition model that we developed assumes that both particle agglomeration and particle transport to the wall are governed by Brownian motion. Agglomerate growth is modeled by Population Balance technique. Sticking of a particle to the wall is assumed to be a probabilistic process. Shear removal is described by a purely empirical sub-model.  To identify model coefficients for a specific oil, experiments are conducted utilizing a laboratory Taylor-Couette device in which the inner cylinder rotates whereas and the outer cylinder remains immobile. Deposition occurs on the outer cylinder wall. The model developed allows relatively accurate matching of modeling results to experimental data obtained in the laboratory Taylor-Couette device. Since the model is derived from a physical basis, accounting for the effect of asphaltene inhibitors does not require the introduction of an additional model or terms. Inhibitor effects are accounted for through tuning of the existing model coefficients. A model of asphaltene deposition in pipe flow, based on the same principles as that for a Taylor-Couette device, is used for forecasting deposit layer formation on a field scale.