Corrosion behavior of N80 steel in CO₂-saturated formation water

Abstract

Purpose

This paper aims to explore the influence of CO₂ partial pressure, flow rate and water cut on N80 steel corrosion behaviors in the displacement process of oil in glutenite reservoir by CO₂ injection.

Design/methodology/approach

A self-made 3 L high-temperature and high-pressure autoclave was used to conduct corrosion simulation experiments of N80 steel in different CO₂ partial pressures, flow rates and water cut (the independently developed oil and water mixing approach can ensure the uniform mixing of oil and water in experiments). Techniques like weight loss and surface analysis were used to analyze the corrosion behaviors of N80 steel under different conditions.

Findings

Results showed that the average corrosion rate of N80 steel accelerated at varying degrees with the increase of CO₂ partial pressure, flow rate and water cut. Excluding that the samples showed uniform corrosion under the two conditions of 0.5MPa CO₂ partial pressure and static corrosion, they displayed mesa attack corrosion under other conditions. Besides, with the increase of CO₂ partial pressure, the pH value of solution dropped and the matrix corrosion speed rose, hence leading to the increased Fe²⁺ and CO₃²⁻ concentration. Meanwhile, a lowered pH value improved the FeCO₃ critical supersaturation, thereby leading to an increased nucleation rate/growth rate and ultimately causing the decrease of the dimension of FeCO₃ crystallites formed on the surface of the samples.

Originality/value

The results can be helpful in targeted anti-corrosion measures for CO₂/oil/water corrosive environment.

Citation

Qiu, Z., Xiong, C., Ye, Z., Zhou, X., Wang, R., Lin, X. and Sui, P. (2019), "Corrosion behavior of N80 steel in CO₂-saturated formation water", Anti-Corrosion Methods and Materials, Vol. 66 No. 4, pp. 464-470. https://doi.org/10.1108/ACMM-10-2018-2005