Corrosion behavior and mechanism of P110 casing steel in alkaline-activated persulfate-based preflush fluid

Abstract

Alkaline activated persulfate based preflush fluid has promising potential on mud cake removal in oil and gas well. However, the corrosion on casing steel is rarely investigated. In this work, the corrosion rate of alkaline activated potassium persulfate (KPS) solution on P110 steel was investigated by weight-loss corrosion experiment. The corrosion behavior, changes on surface morphology and corrosion products was characterized by using potentiodynamic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results show that the corrosion rate of P110 steel changes from 0.027 mm/y to 4.076 mm/y with the increase of KPS concentration from 10 mM to 40 mM under 90 °C. But the corrosion rate decreases obviously with the increase of NaOH concentration from 60 to 160 mM with a high KPS concentration (40 mM). Besides, The corrosion degree tends to be stable after 50 °C, which indicates the corrosion rate is less affected by temperature. The corrosion is dominated by charge transfer process through the synergistic effect of acid and oxidation. Corrosion products are mainly composed of Fe2O3, Fe3O4, and FeO(OH). The result is conducive to optimize the preflush fluid and the selection of corrosion inhibitors in the future work.