Precipitated Asphaltene Amount at High-Pressure and High-Temperature Conditions

In the upstream asphaltene flow assurance community, both academics and industries are actively involved to predict the asphaltene deposit profile in wellbores and pipelines. Essential information for such a study is the amount of asphaltenes that can precipitate and, hence, deposit. In this work, the perturbed chain form of the statistical associating fluid theory (PC-SAFT) is applied to predict the asphaltene precipitation onset condition as well as the amount of precipitate under pressure depletion and high-pressure and high-temperature gas injection conditions. Previous PC-SAFT asphaltene studies in crude oil required the compositional data for both flashed gas and flashed liquid. This work shows a PC-SAFT crude oil characterization procedure when only the composition of the monophasic reservoir fluid is available. After the model parameters for asphaltene onset pressure are estimated, the fitted parameters are used to predict the amount of asphaltene precipitation. The modeling results represent a good match for both upper and lower onset pressures. However, the precipitated asphaltene amount shows an overprediction by PC-SAFT with respect to experimental data obtained from different techniques. The study in this paper discusses the accuracy of these experimental techniques at high-pressure and high-temperature conditions. It shows how a small experimental error during the measurement of precipitated asphaltene amount can result in a significant difference between modeled and experimental values. We invite discussion on the possibility of such errors and suggestions of experimental procedures or a new experimental tool for measuring the amount of precipitated asphaltene at high-pressure and high-temperature conditions.