Impact of Crude Oil Emulsion on Pipeline Corrosion

Abstract

The objective of this work is to study the effect of emulsion formation on steel corrosion in a sweet environment in a laboratory scale. Field experience shows that improper sizing of pipelines in the petroleum industry is often caused by a lack of understanding of three-phase flows which are characterized by a gas phase flowing together with a brine-oil liquid phase. The emulsion formation in these systems plays an important role on the corrosion rates of steel pipelines. Therefore, the corrosiveness and stability of the brine-oil mixtures with different water cuts are systematically studied. The necessity to reduce costs in handling fluids requires a high flow rate with an inherent risk for turbulence influencing the stability of the brine-oil mixtures and the corrosion process of steel pipes. These conditions occur especially in offshore environments, in oil and gas productions, in chemical processes and in energy production industries. In previous work, multiphase-flow-loop tests were conducted for thirty hours using a centrifugal pump for promoting a mixture of 20% of light oil crude oil or heavy crude oil + 80% of deionized water, containing 15% of sodium chloride, at 40 °C under a CO2 partial pressure of 2.0 bar. In this work, emulsion tests were conducted with heavy, medium, and light crude oil with a water cut of 80% at 40 °C for thirty hours, under 1200 rpm stirring, in the presence of CO2. The emulsion stability evaluation was performed by Turbiscan Stability Index (TSI) based on multiple light scattering methods. A comparison between the obtained results in the multiphase-loop and in the Turbiscan Stability Index (TSI) tests showed that the higher emulsion stability contributed to the increase in the corrosion rates.