Cailiao Baohu (Sep 2023)

Research on Internal Corrosion Protection Technology of Corrosion Inhibitor Combined with Cathodic Protection Casing

  • XU Jianguo, CHEN Zuoming, ZHAO Kaifeng, CHEN Wei, ZHANG Xinxin, DENG Jingyu, LI Ning, WANG Chen, LYU Xianghong

DOI
https://doi.org/10.16577/j.issn.1001-1560.2023.0227
Journal volume & issue
Vol. 56, no. 9
pp. 161 – 168

Abstract

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For the internal corrosion problem of oil well casing， high-temperature and high-pressure weight loss tests， polarization curves， AC impedance spectroscopy， and potentiostatic polarization electrochemical testing techniques were used， combined with finite element simulation calculations， to study the casing internal corrosion protection technology of solid corrosion inhibitors combined with cathodic protection and its synergistic promotion mechanism.Results showed that the corrosion inhibition rate of J55 casing was 85.91%when the on-site concentration of solid corrosion inhibitor was 120 mg/L， meeting the standard requirements， but the corrosion rate was relatively high， which was 0.307 9 mm/a.The selected solid corrosion inhibitor belonged to the cathodic corrosion inhibitor.Therefore， cathodic protection could significantly promote the adsorption and retardation effect of corrosion inhibitor particles.After adding－50 mV cathodic polarization potential，the adsorption polarization resistance of corrosion inhibitor increased from 505.59 Ω·cm2 to 1 878.50 Ω·cm2.The protection distance of the high-temperature aluminum anode to the J55 bare steel pipe was calculated by finite element simulation software， which was only 11.104 m.After applying the solid corrosion inhibitor combined with sacrificial anode cathodic protection， solid corrosion inhibitor extended the protection distance of the sacrificial anode.The effective protection distance continued to extend as corrosion inhibitors coverage increased continuously.When the corrosion inhibitor coverage reached 98%， the effective protection distance was above 100 m.The solid corrosion inhibitor and cathodic protection had a synergistic promotion effect.Indoor experiments showed that under the combined action， the uniform corrosion rate of J55 casing decreased to 0.010 2 mm/a， and the corrosion inhibition rate reached 99.53%， demonstrating excellent protective effects.

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