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Flow assurance is one of the main challenges in the oil industry. Many factors can affect the oil fluidity, including the oil °API and the formation of water-in-oil (w/o) emulsions that increase the fluid viscosity. The demulsification process aims to decrease as much as possible the water content in the crude oil. Chemical products known as demulsifiers can be used to aid in this process. In laboratory, the chemicals can be evaluated under temperature and water content conditions similar to those in the oil field. In this work, the effect of demulsifier aging on its performance, simulating oil field storage, was evaluated using synthetic w/o emulsion prepared with a heavy crude oil and brine at 55 000 ppm. The crude oil was characterized and some demulsifier properties were measured along the time. The crude oil was identified as a heavy oil containing 11.6% of asphaltenes, contributing to the w/o emulsion stability. The demulsifier performance increased with aging time, and the results strongly suggested that a mere evaporation of the additive solvent occurs, concentrating its active matter.
Nunes et al. (Fri,) studied this question.