Asphaltene Precipitation, Aggregation and Deposition

H. Scott Fogler^* and Claudio Vilas Boas Favero

Chemical Engineering Department, The University of Michigan, USA

Asphaltene are heavy and aromatic crude oil components that precipitate and deposit on pipeline walls during production. Assessing risk of asphaltene deposition in a production facility is a crucial step when designing a new facility. Risk assessment at production condition, i.e., high pressure and temperature, are cost prohibitive, leading oil companies to use model systems to assess asphaltene deposition risks for given oil. The most common method to study asphaltene precipitation and deposition in the laboratory is by adding n-alkanes to crude oils at room temperature and room pressure. When n-alkane, such as heptane, is added to crude oil, asphaltenes precipitate and undergo an aggregation process. Using state-of-the art microscopy, centrifugation, and scattering techniques the aggregation kinetics of asphaltenes was investigated. It was observed that upon heptane addition oil, asphaltene experience an increase in their fractal dimension as they precipitate and undergo a reaction-limited aggregation process. A geometric form of the population balance was used to model the asphaltene aggregation data obtained by time-resolved centrifugation, indicating that for every 1 million collisions between asphaltenes suspended in the oil-heptane mixture, 1 collision will result in aggregation. In turn, the experimental results of time-resolved microscopy have shown that there is no such thing as a onset volume of asphaltene precipitation. If heptane is added to oil as concentration below the so-called onset volume, if one waits for long enough precipitation will be detected under optical microscopy. The long time for detecting asphaltene precipitation is due to the slow aggregation process due to a low collision efficiency. By postulating a relationship between the collision efficiency and the difference in solubility parameter of asphaltenes and oil-heptane mixture, a universal aggregation line for asphaltenes was obtained. The universality of the aggregation model was demonstrated by testing over 50 different crude oils and model oils and showing that they matched the aggregation line.

The asphaltene deposition was also studied using capillary and packed bed apparatus. Experimental results of asphaltene deposition rate show that for nanometer-sized asphaltenes at low Reynolds flow, the rate by which asphaltenes deposit is dictate by the diffusion time of asphaltenes nanoparticles from the bulk to the depositing surface. These findings provide solid ground for modeling asphaltene deposition in pipelines and predicting asphaltene deposition risk in a new facility based on lab-scale experiment and parameter estimations. The packed bed asphaltene deposition apparatus has also been used to evaluate performance of chemicals that are commercialized to alleviate asphaltene deposition in oil fields.

Biography:
H. Scott Fogler is the Ame and Catherine Vennema Professor of Chemical Engineering and the Arthur F. Thurnau Professor at the University of Michigan in Ann Arbor and was the 2009 National President of the American Institute of Chemical Engineers. He received his B.S. from the University of Illinois and his M.S. and Ph.D. from the University of Colorado. Scott recently received a doctor honoris causa degree from the Universitat Rovira i Virgili, Tarragona, Spain. He is the author of the Elements of Chemical Reaction Engineering and Essentials of Chemical Reaction Engineering which are the dominant books in this area worldwide. Scott has graduated 45 PhDs and they have published over 240 research articles and 12 books, in areas such as acidization of petroleum wells, gelation kinetics wax deposition in subsea pipelines and asphaltene flocculation and deposition kinetics. Scott is an associate editor of Energy & Fuels.

Some New Approaches in Petrochemical Industries: from Methane to Carbon and Hydrogen and from Crude Oil to Chemicals

Jean-Marie Basset

KAUST Catalysis Center and Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Saudi Arabia

The world evolution in petroleum and petrochemicals is changing rapidly. The demand for energy is increasing quite drastically but diversification of energy resources is a parameter that can no longer be ignored. Simultaneously the demand for chemicals (especially propylene, ethylene, and aromatics) is increasing even more rapidly.

In this context the only source of carbon is still crude oil and the best source of clean energy is natural gas decomposition products like hydrogen and C.

In this lecture we will present our recent results on two main topics that we have developed in the Kaust Catalysis Centre (KCC) in relation with ARAMCO and AIR LIQUIDE: from crude oil to olefins and from natural gas to carbon and hydrogen.

Biography:
Jean-Marie Basset is the Distinguished Professor for Chemical Science in the Physical Science and Engineering Division at King Abdullah University of Science & Technology. Prof Basset, who has authored more than 500 scientific papers 50 patents, pioneered the field of “Surface Organometallic Chemistry”, which focuses on possible relationships between homogeneous and heterogeneous catalysis. Professor Basset received his PhD in 1969 from the University of Lyon, France. After a postdoctoral position in Toronto he moved to the Institute of Catalysis in Lyon where he became vice-director. In 1987, he founded the Laboratory of Surface Organometallic Chemistry that became later the laboratory of Chemistry, Catalysis, Polymer, Process (C2P2). Professor Bassetʼs Lyon lab was home to 100 scientists, including Nobel Laureate Yves Chauvin who got his Nobel in 2005. In 2009 he moved to the King Abdulla University of Science and Technology in Saudi Arabia as director of the KAUST Catalysis Center.