11376 Effect of Debonded Interfaces on Corrosion of Mild Steel Composites in Supercritical CO2-Saturated Brines

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Product Number: 51300-11376-SG

ISBN: 11376 2011 CP

Author: Jiabin Han, J. William Carey and Jinsuo Zhang

Publication Date: 2011

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The geologic sequestration of CO2 is a proposed method to reduce greenhouse gas emissions and has been the subject of many studies in the last decade. Wellbore systems achieve isolation of the sequestration reservoir through a combination of steel (generally carbon steel) and Portland cement. CO2 and brine leakage along the steel-cement interface has the potential to accelerate corrosion. We conducted experiments to assess the corrosion risk at the cement-steel interface under in situ wellbore conditions. In this study, we focus on the mass-transfer limits of corrosion by simulating wellbore interfaces with assemblies constructed of J55 mild steel and epoxy. Corrosion was investigated in supercritical CO2 saturated brines (NaCl=1 wt%) at T = 50 °C, pCO2=1 MPa with an interface gap between steel and epoxy of 20 and100 µm as well as an open steel surface. The corrosion kinetics were measured by electrochemical techniques including linear polarization resistance and electrochemical impedance spectroscopy. The corrosion scales were analyzed using scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction. Corrosion rates decreased with time with or without an interface gap. The initial corrosion rates were controlled by mass transfer barrier through the interface gap while the final steady corrosion rates were limited by the mass transfer barrier of scale formation. Corrosion rates of steel with scale were two orders of magnitude less than fresh steel. The corrosion scale was composed of iron carbonates and was pseudo-crystalline at the open steel surface. Well-crystallized scale was observed with epoxy-steel interface gaps of 20-100 µm.

Key words: Carbon dioxide, cement, corrosion, interface, surface analysis