The localized corrosion of mild steel in carbonated cement pore solution under supercritical carbon-dioxide in a simulated geothermal environment

Cement carbonation, one of the main causes of the reinforced concrete corrosion, is also inevitable in the geological environment of carbon sequestration, possibly destroying the integrity of well/cement system. To evaluate the corrosion risk of casing pipe in a geothermal well environment, the corrosion behavior of P110 steel was investigated in carbonated cement pore solutions under carbon dioxide supercritical conditions. It was found that a dense FeCO3 layer was generally formed and it could effectively prevent the steel from corrosion. However, above the threshold concentrations of chloride ion and dissolved oxygen, localized corrosion protrusions could be observed, which might continuously grow larger and higher until its outer shell ruptured during the exposure of the steel substrate in the simulated environment. The expansive growth of the protrusion could be attributed to the active dissolution accelerated by chloride ion at the bottom and the cooperative formation of iron oxide and carbonate in the core region. Such a localized corrosion damage could occur at the casing/cement interface in practice and may become a fatal threat to casing pipes for carbon sequestration in the oil/gas industry. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study found that localized corrosion protrusions could be observed in environments with chloride ions and dissolved oxygen, which may pose a fatal threat to the integrity of casing pipes.