Interfacial behavior and water solubility of various asphaltenes at high temperature

Estudio de la Viscosidad en un Crudo Aditivado con Dispersantes y Disolventes Asfalténicos

En Ecuador, el aumento de la cantidad de crudo pesado extraído genera preocupación en la industria. Debido a su naturaleza viscosa, presenta dificultades en el transporte y en la refinación. El objetivo de este proyecto es el estudio de la reducción de viscosidad de un crudo pesado, extraído del Oriente Ecuatoriano mediante el uso de compuestos dispersantes y disolventes de asfaltenos, para ser transportado dentro de un oleoducto. Para ello, se selecciona y clasifica a los reductores de viscosidad que tienen un efecto disolvente, dispersante o inhibidor de asfaltenos, por medio de sus espectros FT-IR resultantes. Se analiza el cambio de propiedades físicas y químicas del crudo con los reductores seleccionados por medio de cuatro pruebas: a) prueba para determinar la viscosidad; b) análisis S.A.R.A.; c) prueba de oliensis; d) prueba para determinar la gravedad API. Finalmente, se realiza la evaluación de la facilidad del transporte de crudo en un banco de pruebas de tuberías que presenta comportamientos similares al transporte del crudo por un oleoducto. Por medio de la clasificación y selección de los reductores, se escoge a los tres aditivos usados para las pruebas: M01-X, M02-A y M03-S. Se clasifica, a los dos primeros como disolventes de asfaltenos y el último como dispersante de asfaltenos. En la evaluación del cambio de propiedades del crudo el mejor resultado se obtiene con el aditivo “M01-X” con un porcentaje de reducción de viscosidad de 65,0 % y aumento del caudal del crudo de 1,24 a 2,01 (mL/s). Como alternativa y mejor resultado a este reductor se usó una mezcla formada por dos aditivos (M02-A + M03-S) con un porcentaje de reducción de viscosidad de 69,0 % y un aumento de caudal a 2,72 (mL/s).

Mechanisms, performance optimization and new developments in demulsification processes for oil and gas applications

The present review discusses new developments and optimization of demulsification processes in oil and gas applications, and highlights the critical parameters. Discussed are the primary mechanisms of demulsification, as well as the strategies for developing optimum demulsifiers. Demulsification mechanisms are presented in the context of emulsion stability principles which are equally applicable to the destabilization of crude oil-water emulsions. The present paper is a concise overview of the various surfactant classes and their structure-activity relationship. It correlates demulsification optimization with surfactant properties and their applications. These classes include, but are not limited to pluronic block co-polymers, as well as amine- and siloxane based nonionic surfactants. The emphasis is on providing some strategies for achieving optimum crude oil-water separation efficiency by tuning the demulsifier to the intended application and crude oil properties. A brief overview of unconventional analytical techniques, which reach beyond the standard demulsifier evaluation methods, i.e., Near Infrared Spectroscopy (NIR), and in particular, low resolution NMR relaxometry, highlights their role in monitoring demulsification processes.

Dynamic Asphaltene-Stearic Acid Competition at the Oil-Water Interface

Interfacial tension (IFT) is one of the major parameters which govern the fluid flow in oil production and recovery. This paper investigates the interfacial activity of different natural surfactants found in crude oil. The main objective was to better understand the competition between carboxylic acids and asphaltenes on toluene/water interfaces. Dynamic IFT was measured for water-in-oil pendant drops contrary to most studies using oil-in-water drops. Stearic acid (SA) was used as model compound for surface-active carboxylic acids in crude. The influence of concentration of these species on dynamic IFT between model oil and deionized water was examined. The acid concentrations were of realistic values (total acid number 0.1 to 2 mg KOH/g oil) while asphaltene concentrations were low and set between 10 and 100 ppm. In mixtures, the initial surface pressure was entirely determined by the SA content while asphaltenes showed a slow initial diffusion to the interface followed by increased adsorption at longer times. The final surface pressure was higher for asphaltenes compared to SA, but for binaries, the final surface pressure was always lower than the sum of the individuals. At high SA concentration, surface pressures of mixtures were dominated entirely by the SA, although, Langmuir isotherm analysis shows that asphaltenes bind to the interface 200-250 times stronger than SA. The surface area/molecule for both SA and asphaltenes were found to be larger than the values reported in recent literature. Various approaches to dynamic surface adsorption were tested, showing that apparent diffusivity of asphaltenes is very low, in agreement with other works. Hence, the adsorption is apparently under barrier control. A possible hypothesis is that at the initial phase of the experiment and at lower concentration of asphaltenes, the interface is occupied by stearic acid molecules forming a dense layer of hydrocarbon chains that may repel the asphaltenes.

Phase field modelling of spinodal decomposition in the oil/water/asphaltene system

In this paper the quantitative applicability of van der Sman/van der Graaf type Ginzburg–Landau theories of surfactant assisted phase separation [van der Smanet al.,Rheol. Acta, 2006,46, 3] is studied for real systems displaying high surfactant concentrations at the liquid–liquid interface.