(96c) Computational Study of Oil-Water Wetting Regimes Established in Horizontal Flows: Wettability Maps and Corrosion

Wettability effects in pipelines carrying oil-water phases at varying proportions are crucial in undermining the net effects of corrosion in the system. Prediction of phase distribution, especially the information whether oil or water wets the pipe wall is an important factor, which can affect the corrosion mitigation strategy and increase confidence in the integrity of the pipeline. There are large knowledge gaps in this area of research and consequently only empirical criteria are used in the industry.

In the present work, detailed computational study involving, a turbulent oil-water multiphase flow system in a horizontal carbon steel pipeline, is carried out to predict different water wetting regimes as well as corrosion kinetics of emanating from the fluid-metal interaction. Computational Fluid Dynamics simulations include Eulerian multiphase models with appropriate sub-models for interfacial forces, turbulent interaction and population balance equations. Population balance techniques identify and follow the dispersed (water) phase dynamics such as droplet breakage and agglomeration in a detailed fashion. In addition, concentration equation for ferrous ion (Fe2+) is modeled to capture corrosion kinetics. The current study focuses on flow pattern computations for water cut ranging from 0 - 20%.

Our simulations captured various water wetting regimes inclusive of intermittent, fully wetting, dispersed and semi-dispersed water-in-oil behavior. Results were in good agreement with the experimental observation. Simulations clearly predicted that for given superficial water velocity, elevating the superficial oil velocity leads to transition of regimes from stable water wetting to intermittent water wetting and subsequently stable oil wetting scenario. Phasic fraction and velocity distribution at different flow cross-section reveal the flow modulations as a function of the turbulence inherent to the two-phase system. Corrosion computations clearly indicate a substantial generation of Fe2+ ion under stable water wetting regime while the concentration and corrosion levels deteriorate with intermittent water wetting, an effect well characterized in flow loop tests.