What are Asphaltenes?

They are crude oil molecules with great tendency to self-associate into clusters.

Why do we study them?

Production and operation condition can cause the asphaltenes clusters in solution to destabilize and aggregate. When aggregation occurs on surfaces, a deposit builds us and hinders oil production. Understanding when and how asphaltene deposit forms is of great industrial interest.

Current Work

We are currently investigating the phenomenon of asphaltene deposition. An apparatus was designed, built, validated, and is currently being used. The apparatus allow us to measure the amount of deposit formed as a function of time for different crude oil and model and at different alkane concentrations.

For more information on this project you can contact Claudio Vilas Boas Favero (cfavero@umich.edu).

Highlights of recent asphaltene research in our group

Nasim Haji-Akbari, who recently earned her PhD working in our research group, figured out the physics underlying the slow aggregation of asphaltenes.

At low heptane concentration in oil the asphaltenes destabilization cannot be immediately detected by optical microscopy. The time for detection of destabilization, however, can be measured as a function of heptane concentration. A linear relation is observed in the plot log tdet (detection time) vs. heptane concentration in crude. This line was found to be characteristic of crude oil, in other words, different crude oil have different lines.

By using the population balance model and proposing a relation between collision efficiency and solution properties, Nasim came up with a scaling law that can explain the behavior of 20+ different crude oils. The complete work can be read in the article published in Energy and Fuels.

Wax Research

Why do we study crude oil waxes?

Wax deposition is a billion-dollar problem in the oil industry. When the temperature of the oil in the pipeline drops low enough, wax molecules tend to crystallize an deposit on the pipe wall. The accumulated wax deposit can cause several operation problems including complete blockage and extreme circumstances, can lead to abandonment of a platform.

Current Work

Water-in-oil dispersed flow is common in the transportation of deep-water petroleum fluids. In water-in-oil dispersions, the continuous oil phase is in direct contact with the pipe wall. Consequently, dissolved wax molecules can diffuse through the continuous oil phase towards wall to form a wax deposit. Dispersed water droplets can impede the molecular diffusion path of wax molecules because wax molecules are insoluble in water and therefore cannot penetrate water droplets and consequently must diffuse around them.

In this study, the inhibitive effect of the dispersed water droplets on wax molecular diffusion in water-in-oil dispersion is confirmed and quantified using NMR diffusometry. Based on experimental characterization, two existing empirical approaches for the calculation of the effective wax diffusivity in water-in-oil dispersion are evaluated. It is discovered that neither of the current empirical approaches provides consistent predictions for the wax effective diffusivity with experimental measurements.

For more information on this project you can contact Sheng Mark Zheng (shzheng@umich.edu).

MWP - The Michigan Wax Predictor

Through the course of the last 15 years, our research group has developed the only model that predicts the deposition of wax in pipelines by solving fundamental transport equation. The model predicts the trends of deposition rates with varying operating condition, and contains no tuning parameter for upper and lower limits of deposit thickness. Additionally, our model has been verified with 50+ flow-loop experiments from different facilities around the world. For more information on the Michigan Wax Predictor, please contact Sheng Mark Zheng (shzheng@umich.edu).