Asphaltenes and Asphaltene model compounds: Adsorption, Desorption and Interfacial Rheology.

摘要

There are numerous problems encountered during extraction, production, transportation andudrefining of crude oil. Most of these problems are typically oil-specific, meaning that theyuddepend upon the source of the oil, and sometimes they are reservoir-specific, meaning thatudthey depend on the stage of extraction (primary, secondary or enhanced recovery).udNevertheless, a great part of the problems are related to the indigenous surface-active speciesudsuch as asphaltenes, naphthenates and resins.udThe definition of asphaltenes rather than being a single molecule is instead based on audsolubility class. This means that they are polydisperse in nature which leads to differences inudproperties and composition. Asphaltenes are responsible for stabilizing water-in-oiludemulsions by forming a mechanically strong gel at the interface that prevents dropletudcoalescence. Asphaltenes are also known to precipitate and under certain conditionsud(pressure, temperature, composition) form deposit layers which could lead to plug formation.udAll this issues generate deficits in flow assurance and evidently, increases in the operationaludcosts.udTwo strategies might be implemented to further advance in the understanding of theudmechanisms involved in asphaltene adsorption onto various interfaces (liquid-liquid or solidliquid).ud(i) Fractionation or (ii) model compounds. The first strategy explores the differentudsub-fractions that are obtained at different solvent/precipitant ratios using indigenousudasphaltenes. The second strategy is to design a molecule, or group of molecules with definedudfunctionalities that mimic the main known asphaltene properties, for instance self-associationudin solution and interfacial behavior.udIn this thesis, the different publications were aimed to study and explore possible solutions toudthe several problems stated. In the first and second publications, adsorption and desorptionudaspects of asphaltenes and demulsifiers at the liquid-liquid interface were explored.udFurthermore, interactions between asphaltenes and demulsifiers were studied via interfacialudtension measurements and interfacial dilatational rheology. The results shed light on theudmechanisms involved during chemical demulsification of water-in-crude oil emulsions. In theudthird publication, rheology and sorption aspects of asphaltene model compounds at the liquidliquidudinterface were studied. The main goal of this publication was to establish the interfacialudproperties inherent to asphaltenes captured by a set of asphaltene model compoundsuddeveloped at the Ugelstad laboratory. Similarly, in the fourth publication adsorption of asphaltenes and asphaltene model compounds onto the solid-liquid surface was studied. Inudthis study, the determination of the adsorption enthalpy via microcalorimetry allowed toudelucidate the type of bond and the driving force for adsorption onto surfaces of differentudnature.udWith these publications, a complete study at the liquid-liquid interface and the solid-liquidudsurface was developed for asphaltenes and asphaltene model compounds. This provides audfundamental framework for model systems that can be used to understand the behavior in realudapplications.