Interfacial Shear Rheology of Calcium Naphthenate at the Oil/Water Interface and the Influence of pH, Calcium, and in Presence of a Model Monoacid

Interfacial Rearrangements of Block Copolymer Micelles Toward Gelled Liquid-Liquid Interfaces with Adjustable Viscoelasticity

Though amphiphiles are ubiquitously used for altering interfaces, interfacial reorganization processes are in many cases obscure. For example, adsorption of micelles to liquid-liquid interfaces is often accompanied by rapid reorganizations toward monolayers. Then, the involved time scales are too short to be followed accurately. A block copolymer system, which comprises poly(ethylene oxide)₁₁₀ -b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride}₁₇₀ (i.e., PEO₁₁₀ -b-qPDPAEMA₁₇₀ with quaternized poly(diisopropylaminoethyl methacrylate)) is presented. Its reorganization kinetics at the water/n-decane interface is slowed down by electrostatic interactions with ferricyanide ([Fe(CN)₆ ]^3- ). This deceleration allows an observation of the restructuring of the adsorbed micelles not only by tracing the interfacial pressure, but also by analyzing the interfacial rheology and structure with help of atomic force microscopy. The observed micellar flattening and subsequent merging toward a physically interconnected monolayer lead to a viscoelastic interface well detectable by interfacial shear rheology (ISR). Furthermore, the "gelled" interface is redox-active, enabling a return to purely viscous interfaces and hence a manipulation of the rheological properties by redox reactions. Additionally, interfacial Prussian blue formation stiffens the interface. Such manipulation and in-depth knowledge of the rheology of complex interfaces can be beneficial for the development of emulsion formulations in industry or medicine, where colloidal stability or adapted permeability is crucial.

A critical update of experimental techniques of bulk and interfacial components for fluid characterization with relevance to well fluid processing and transport

The present article reviews techniques to address central flow assurance and separation issues. It is our purpose to update the need for extended information in order to draw adequate conclusions about the reason for irregularities in production and how this is related to individual components or fractions in the crude oil. Our intention is to show that the mass related analysis (such as SARA, MS etc.) are insufficient for a validation of the early stage predictions concerning irregularities. The review introduces a set of new characterization and fractionation techniques such as interfacial rheology, SANS, and NMR, where the central theme is the functionality of the components and not just their mass. Two crude oil-related issues are addressed: Wax precipitation and deposition, and crude oil/water resolution. First, bulk techniques to characterize wax precipitation are reviewed. The influence of the chemistry of other crude oil components (asphaltenes) and wax inhibitor on the precipitation is highlighted. Secondly, in aqueous systems, interfacial w/o conditions are important for the stability of dispersed systems. Asphaltenes have a crucial and important role in the stability of crude oil emulsions. Here special attention is directed to properties like interfacial viscosity and elasticity as well as the adsorbed layer structure determination. Small molecular changes in these properties will have dramatic influence on the stability of the heterogeneous systems. A good example is inhibitor functionality.

Rechargeable Aqueous Microdroplet

Directional and controllable transportation of microdroplets is critical for emerging micro- and nanotechnology, in which the conventional mechanical energy generation is not applicable. This Letter shows that an aqueous microdroplet can be charged for controlled motion in electrostatic potential, which was created by differentiating pH, between two oil/water interfaces. The directional motion of the droplet, <100 μm in diameter, was obtained with a constant velocity of ∼1 mm/s. The force analysis showed that the droplet surface was charged and recharged oppositely by ion transfer through interfacial layers, without significant mass transfer. The charging and recharging cycles were recorded continuously with a single droplet over 100 times. The energy for motion was generated from pH neutralization, which is the simplest aqueous reaction. This is the first time that the phenomenon is reported. The phenomenon can be employed as an efficient and robust method to convert chemical to mechanical energy for miniaturized devices and microprocesses.

The chemistry of tetrameric acids in petroleum

This article reviews the properties of a novel class of molecules: the tetrameric acids. These molecules have brought a large interest in petroleum science since the discovery of the family of molecules named ARN in 2004. ARN, which is naturally present in oil, is responsible, by reaction with calcium ion, of the formation of calcium naphthenate deposits; organic deposits that cause irregularities in crude oil production and processing. In order to study the properties of ARN, a model tetrameric acid molecule mimicking some of its properties named BP-10 has been developed in 2008 by Nordgård and Sjöblom and has been extensively used since then. After presenting the experimental techniques used to study the tetrameric acids, this review describes in detail the structure, preparation, detection and the bulk and interfacial properties of tetrameric acids ARN and BP-10. Finally the prediction of the operational problems with calcium naphthenate precipitation in new fields is discussed.