Use of Microemulsion Systems in the Solubilization of Petroleum Heavy Fractions for the Prevention of Oil Sludge Waste Formation

In this work, we investigate the use of microemulsions in the solubilization of heavy crude oil fractions, which are responsible for the formation of deposits in petroleum processing operations. Initially, the construction of phase diagrams was addressed, with the intention of determining the area within which microemulsions are formed. Unitol L 90 was used as a non-ionic surfactant. Butan-1-ol and butan-2-ol were tested as co-surfactants. Four different systems were studied: Unitol L 90 + butan-1-ol + water + kerosene (system l), Unitol L 90 + butan-1-ol + water + xylene (system 2), Unitol L 90 + butan-1-ol + water + 90% kerosene/10% xylene (system 3), and Unitol L 90 + butan-2-ol + water + xylene (system 4). Physical adsorption experiments were carried out with the static method, aiming to simulate natural reservoir conditions. Crude oil samples from the Fazenda Belem field (Rio Grande do Norte State, Brazil) were used and dissolved in xylene. Arenite samples from the Assu (Rio Grande do Norte State) and Botucatu (Parana State, Brazil) geological formations were tested as rock reservoirs. The adsorption curves featured the "S" profile. The solubilization process was accomplished via the batch method, by varying the stirring time, microemulsion composition, and the solid/solution ratio. The experiments showed that the microemulsions presented high efficiency in the solubilization of crude oil adsorbed on the arenites. In particular, system 2 presented an efficiency as high as 99% when tested on the Assu arenite and 97% on the Botucatu arenite. No significant differences were detected on the extent of solubilization of heavy fractions, by varying the surfactant concentration in the formulations used in this work. Therefore, for economical reasons, it could be suggested that systems containing only 20% in active matter (surfactant plus co-surfactant) are more suitable for applications involving the use of non-ionic microemulsions on the prevention of oil sludge waste formation.