Effect of acidic returned fluid on the electric demulsification of crude oil emulsions

Abstract

The main objective of this work is to investigate the effect of acidic returned fluid (ARF) on the electric demulsification of crude oil emulsion produced by acid fracturing technology. It was found that the pH and the iron ions of the ARF had a huge influence on the electric demulsification. The pH value could affect the strength of the interfacial film to result in the short circuit of the electric dehydrator. The short circuit only happened in basic conditions when water content (WC) was low, but when WC reached 15%, the short circuit happened both in the acidic and basic conditions. In addition, it needed less time to happen in acidic conditions due to the strength difference of the interfacial film in the acidic and basic conditions. Because of the polar interactions between asphaltenes, resins and iron ions, the iron ions had a great tendency to interact with them, thereby easily changing the adsorption structures of asphaltenes and resins on the oil–water interface to enhance the strength and thickness of the interface film, which resulted in the short circuit of the electric dehydrator.