Study of an ESP's performance handling liquid-liquid flow and unstable O-W emulsions Part I: Experimental

•Unstable emulsions are formed due to surface-active compounds and small drop sizes.•High water cuts lead to a loss of the emulsion's microscopic structure and rheology.•Phase morphology and non-Newtonian rheology directly determine the pump performance.•Performance improves with a shear-thinning emulsion, despite its higher viscosity.•When the emulsion structure is lost, higher water cuts do not affect the performance. This article is the first part of a study which analyzes the performance and internal flow of an ESP when handling oil-water flow, focusing on the characterization of the two-phase flow/emulsions observed and their influence on the ESP's global performance. The testing facility consisted of a four-stage ESP located in a closed-loop arrangement. W/O emulsions are formed at high oil fractions, due to the presence of surface-active compounds and small droplet sizes. At the inversion, an increase in the viscosity and shear-thinning characteristics of the emulsion is noticed. At higher water cuts, the emulsion's microscopic structure is lost, transitioning to a dispersed two-phase flow. The head rise increased noticeably at the inversion point thanks to the shear-thinning trend observed. The ESP's performance improves at higher water fractions due to lower viscosities with a shear-thinning nature. As the non-Newtonian behavior is lost, higher water cuts do not affect the pump's operation.