Performance Evaluation of Demulsifier Using the Optimum Formulation HLD Concept: A Practical Case Using Heavy Crude Oil Diluted in Naphtha or in Synthetic Aromatic Oil

Abstract

Summary Asphaltene-stabilized water-in-oil (W/O) emulsions can cause severe problems during oil production and transportation. These emulsions are broken by adding a demulsifying agent at a suitable concentration (CD*) to obtain the optimal formulation, with minimal emulsion stability (stability*). Herein, we studied, from a phenomenological point of view, the performance of two demulsifiers on W/O emulsion breaking with high asphaltene content. A very simple polyethoxylated nonylphenol demulsifier (6EO) and a complex commercial demulsifier (COD) were studied. The influence of the chemical nature of the oil phase on the performance of the demulsifiers was evaluated. The emulsion stability* and CD* values of W/O systems of heavy crude oil diluted in cyclohexane (Systems A and B) were compared to W/O emulsions composed by a heavy crude oil diluted in heavy naphtha or in an aromatic synthetic crude oil as the oil phase (Systems C and D). The results show that demulsifier performance improves significantly when the crude oil is diluted in heavy naphtha and in aromatic synthetic crude oil, obtaining unstable W/O emulsions (rupture time of 10−2–10−1 minutes). In the latter cases, the CD* value is significantly lower and with a wide area of low emulsion stability compared to systems formulated with crude oil diluted in cyclohexane. The mechanisms that generate this type of behavior are discussed and strategies to increase performance and robustness analyzed.