Asphaltene precipitation is a necessary but not a sufficient condition for deposition. Additional work has been conducted to develop experimental and modeling tools to understand and predict asphaltene deposition in the production tubing (Vargas, 2010; Kurup, 2011; Akbarzadeh, 2011; Eskin, 2011).
Figure 1 shows a schematic of the multi-step mechanism for asphaltene precipitation, aggregation and deposition that is believed to occur in the wellbore. According to Vargas (2010) when asphaltenes first precipitate, they can form small aggregates called primary particles, which, in turn, can further aggregate or travel to the inner surface of the production tubing and deposit. The rate of asphaltene precipitation depends on the solubility of asphaltenes at a given pressure, temperature and composition, which can be calculated using the PC-SAFT equation of state. Additional parameters are required to establish the magnitude of asphaltene precipitation, aggregation and deposition rates, which are usually tuned to available data, either from the laboratory or the field.
Figure 1. Schematic for the multi-step mechanism for asphaltene precipitation, aggregation and deposition in a production well (Vargas, 2010).
Kurup et al. (2011) further developed the concepts proposed by Vargas (2010) to establish a one dimensional simulation tool called Asphaltene Deposition Tool (ADEPT), which was successfully used to forecast the occurrence and calculate the magnitude and profile of asphaltene deposition in the some case studies. ADEPT can be an excellent simulator to enable operators to perform quick sensitivity studies and map out operating conditions to better identify potential asphaltene deposition risks.
References
- Akbarzadeh, K., Eskin, D., Ratulowski, J., et al. (2011). Asphaltene Deposition Measurement and Modeling for Flow Assurance of Subsea Tubings and Pipelines. Presented at the OTC Brasil, Offshore Technology Conference. http://doi.org/10.4043/22316-MS
- Eskin, D., Ratulowski, J., Akbarzadeh, K., et al. (2011). Modelling asphaltene deposition in turbulent pipeline flows. Can. J. Chem. Eng., 89 (3), 421–441.
- Khaleel, A., Rashed, M. A., Mathew, N. T., et al. (2013). Novel Approach to Study the Instability of Asphaltenes in Crude Oil. Presented at the ADNOC Res. Dev. Acad. Conf. ARDAC, Abu Dhabi, United Arab Emirates.
- Kurup, A. S., Vargas, F. M., Wang, J., et al. (2011). Development and application of an asphaltene deposition tool (ADEPT) for well bores. Energy Fuels, 25 (10), 4506–4516.
- Vargas, F.M., Creek, J.L., & Chapman, W.G. (2010), On the Development of an Asphaltene Deposition Simulator, Energy & Fuels, 24 (4), pp 2294-2299. http://doi.org/10.1021/ef900951n
