Implementation of a Comprehensive Mechanistic Prediction Model of Mild Steel Corrosion in Multiphase Oil and Gas Pipelines

In the present study, the implementation of a comprehensive mechanistic predictive model for corrosion of mild steel in the oil and gas transmission pipelines is described. The present model simultaneously accounts for all major corrosion scenarios, including CO₂ corrosion, H₂S corrosion, and corrosion in the presence of organic acid and also incorporates the effect of corrosion product layer formation, including iron carbonate and iron sulfide. With this approach, the present model mechanistically reflects the mainstream understanding of corrosion in such environments and can be readily used to predict the corrosion rates in industrial applications. The model was implemented by using a generalized mathematical and programming approach that has built-in flexibility to add new chemical species and additional reactions in the future. The model was designed to make it easy to extend and cover an even broader range of conditions than it currently does, such as higher temperatures and pressures, nonideal solutions, etc. The mechanistic nature of the model allows it to be readily coupled with other applications such as computational fluid dynamics codes, multiphase flow simulators, process design simulators, etc. In order to demonstrate the capabilities of this model, the calculated corrosion rates were compared with the experimental corrosion rate data across a broad range of environmental conditions and brine chemical compositions.