Mechanistic-Chemometrics Prediction Model with Multi-degree of Freedom for the Pitting Corrosion Damage of HP-13Cr Stainless Steel under the Complex Oilfield Environment Coupling with Temperature, CO₂ Pressure, Flow and Stress

Tao Zhang*, Yang Zhao

Shenyang National Laboratory for Materials Science, Northeastern University, 3-11 Wenhua Road, Shenyang, 110819, China

ABSTRACT: The exploitation of the oil and gas in the Tarim area displays extremely aggressive geothermal environment. The most pressing problems in oil and gas exploration is to develop theories and models that allow the prediction of corrosion damage of HP-13Cr SS. In recent years, CO₂ corrosion of steels had been extensively investigated to understand its mechanism and some prediction models have been developed. However, the present prediction models, including empirical models, semi-empirical models, and comprehensive mechanistic models, primarily focused on progress in predicting CO₂ general corrosion damage of mild steel. Notably, the failure of the wells is not generally caused by general corrosion but by pitting corrosion. Many scientists have devoted much effort to predict the pitting damage from the stochastic model and deterministic model. However, modelling for corrosion under complex coupling environment is a very challenging topic, and this model needs to be reconstructed for the application in such complex corrosive environment. A multi-degree freedom prediction model for pitting corrosion damage of HP-13Cr stainless steel under the oilfield environment coupling with high temperature, high CO₂ pressure, various flow rates and complex stress distribution was presented by means of combining mechanistic-models of single factor and chemometrics method. The mechanistic-model is reconstructed based on Zhang’s Model by considering the effect of single factors. The weight coefficients of single factors and their interaction effects were determined by chemometrics method. Finally, the prediction results were compared with the six-year-served field data, which indicates that the mechanistic-chemometrics model has high validity and high accuracy.

Keywords: Pitting corrosion; mechanistic-chemometrics model; high throughput experimental method;