Insights into asphaltene stability, aggregation, deposition and molecular structure

Asphaltenes are the heaviest, most polar, and most surface-active species of crude oils which are fairly stable in the oil; however, a small variation in the pressure, composition, and temperature can cause asphaltene phase instability and alteration in their solubility parameter and can precipitate and aggregate out of the crude oil, leading to expensive deposition problems in pipelines, well, valves, and porous media. The overarching aim of this body of work is to depict the fundamental structure and behaviour of asphaltenes for ultimate application in different operating conditions. In this treatise, asphaltenes are studied over a wide range length scale, ranging from the macro to the molecular scale. Following a literature review, the dissertation begins by reporting the results of a study on the destabilization and deposition of asphaltenes using various experimental techniques. Asphaltenes were destabilised owing to addition of a normal alkane (n-alkane) to the crude oil, and the influence of amphiphilic molecules on asphaltene stabilisation was also illustrated. It is shown that the current techniques that are employed to select the most appropriate asphaltene inhibitor based on their efficiency should be revisited to provide a better methodology for choosing the most suitable strategy for inhibitor/solvent injection. In the study of asphaltene deposition, a new High Pressure-High Temperature Quartz Crystal Microbalance (HPHT-QCM) rig was designed and developed to determine the rates of asphaltene deposition onto the solid surfaces. Also, a reliable procedure is proposed for selection of chemical additives for remediation/prevention strategies to handle gas-induced asphaltene deposition problems. The factors that can play a role in controlling the effect of chemistries on asphaltenes at various conditions are also investigated in this thesis. Furthermore, the differences between the molecular structures of n-alkane and gas induced asphaltenes is explored. Based on the results, it was denoted that the gas induced asphaltenes are structurally, morphologically, and compositionally different from n-alkane precipitated asphaltenes which lead to have different interactions between the asphaltene and inhibitor molecules and diverse rankings of chemistries based on the utilised evaluation techniques. In this thesis, a new two-dimensional dynamic model was developed and validated to simulate asphaltene precipitation, aggregation, and deposition at isothermal and non-isothermal conditions. The effect of the aggregate size on the rate of aggregation and deposition was studied through this simulation study, and it was inferred that the rate of asphaltene deposition increases as a function of concentration of nanoaggregates in the well column. The tendency of smaller aggregates to deposit onto the surfaces could be explained because of the increase in the diffusion coefficient of asphaltene aggregates. For the first time, experimental results of the effect of water with different salinities on gas induced asphaltene aggregation and deposition at elevated pressure and temperature conditions were attained. The roles of ion type on formation of asphaltene stabilised water in oil micro-emulsions, asphaltene deposition, and respective water wettability alteration of solid surface at micro scale were also investigated. Finally, the effects of oil composition changes owing to different gas injection scenarios and addition of paraffin waxes on asphaltene destabilisation and deposition under real field conditions were thoroughly illustrated.James Watt scholarshi

Surface Chemistry Can Unlock Drivers of Surface Stability of SARS-CoV-2 in Variety of Environmental Conditions

The surface stability and resulting transmission of the SARS-CoV-2, specifically in indoor environments, have been identified as a potential pandemic challenge requiring investigation. This novel virus can be found on various surfaces in contaminated sites such as clinical places, however, the behaviour and molecular interactions of the virus with respect to the surfaces are poorly understood. Regarding this, the virus adsorption onto solid surfaces can play a critical role in transmission and survival in various environments. In this article, firstly an overview of existing knowledge concerning viral spread, molecular structure of SARS-CoV-2, and the virus surface stability is presented. Then, we highlight potential drivers of the SARS-CoV-2 surface adsorption and stability in various environmental conditions. This theoretical analysis shows that different surface and environmental conditions including temperature, humidity, and pH are crucial considerations in building fundamental understanding of the virus transmission and thereby improving safety practices

Gas hydrates in sustainable chemistry

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hassanpouryouzband, A., Joonaki, E., Farahani, M. V., Takeya, S., Ruppel, C., Yang, J., English, N. J., Schicks, J. M., Edlmann, K., Mehrabian, H., Aman, Z. M., & Tohidi, B. Gas hydrates in sustainable chemistry. Chemical Society Reviews, 49(15), (2020): 5225-5309, doi:10.1039/c8cs00989a.Gas hydrates have received considerable attention due to their important role in flow assurance for the oil and gas industry, their extensive natural occurrence on Earth and extraterrestrial planets, and their significant applications in sustainable technologies including but not limited to gas and energy storage, gas separation, and water desalination. Given not only their inherent structural flexibility depending on the type of guest gas molecules and formation conditions, but also the synthetic effects of a wide range of chemical additives on their properties, these variabilities could be exploited to optimise the role of gas hydrates. This includes increasing their industrial applications, understanding and utilising their role in Nature, identifying potential methods for safely extracting natural gases stored in naturally occurring hydrates within the Earth, and for developing green technologies. This review summarizes the different properties of gas hydrates as well as their formation and dissociation kinetics and then reviews the fast-growing literature reporting their role and applications in the aforementioned fields, mainly concentrating on advances during the last decade. Challenges, limitations, and future perspectives of each field are briefly discussed. The overall objective of this review is to provide readers with an extensive overview of gas hydrates that we hope will stimulate further work on this riveting field.A. H. and K. E. were partially supported by funding from UKRI-EPSRC (grant number EP/S027815/1). C. R. was partially supported by DOE-USGS Interagency agreement DE-FE0023495. C. R. thanks L. Stern and W. Waite for insights that improved her contributions. E. J. is partially supported by Flow Programme project sponsored by Department for Business, Energy and Industrial Strategy (BEIS), UK. Any use of trade, firm or product name is for descriptive purposes only and does not imply endorsement by the U.S. Government