Assessing the effect of cement-steel interface on well casing corrosion in aqueous CO2 environments

Conference · Fri Jan 01 04:00:00 EST 2010

OSTI ID:1009543

Han, Jiabin ^[1]; Carey, James W ^[1]; Zhang, Jinsuo ^[1]

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1. Los Alamos National Laboratory

CO{sub 2} leakage is a critical safety concern for geologic storage. In wellbore environments, important leakage paths include the rock-cement and cement-casing interfaces. If the cement-casing interface is filled with escaping CO{sub 2}, the well casing directly contacts the CO{sub 2}. This can cause severe corrosion in the presence of water. This paper studies the effect of steel-cement interface gaps, ranging from 1 mm to 0 um, on casing corrosion. Corrosion kinetics were measured employing electrochemical techniques including linear polarization resistance, open circuit potential and electrochemical impedance spectroscopy. The experimental results showed that the corrosion of steel is not significant where the gap between steel and cement is small ({le} 100 {micro}m). Corrosion rates are controlled by the diffusion of corrosive species (H{sub 2}CO{sub 3} and H{sup +}) along the interface. In contrast, steel corrosion is severe in a broad gap where the corrosion process is limited only by the reaction kinetics of steel and corrosive species. The threshold leading to severe corrosion in terms of the cement-steel interface size (100 {micro}m) was determined. Our research clarifies a corrosion scenario at the cement-steel interface. Casing steel corrosion is initiated when attacked by corrosive species at the cement-steel interface. For relatively tight interfaces, this results in a slow thinning of the casing and expansion of the interface width. If the gap increases beyond the critical threshold size, the corrosion rate increases significantly, and a potentially damaging cycle of corrosion and interface expansion is developed.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: DOE
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1009543
• Report Number(s): LA-UR-10-02608; LA-UR-10-2608
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CARBON
CARBON DIOXIDE
CEMENTS
CORROSION
DIFFUSION
ELECTROCHEMISTRY
IMPEDANCE
KINETICS
POLARIZATION
REACTION KINETICS
SAFETY
SPECTROSCOPY
STEELS
STORAGE
WATER
WELL CASINGS