Rate of CO2 Attack on Hydrated Class H Well Cement under Geologic Sequestration Conditions

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• 作者：Barbara G. Kutchko ; Brian R. Strazisar ; Gregory V. Lowry ; David A. Dzombak ; Niels Thaulow
• 刊名：Environmental Science & Technology
• 出版年：2008
• 出版时间：August 15, 2008
• 年：2008
• 卷：42
• 期：16
• 页码：6237-6242
• 全文大小：413K
• 年卷期：v.42,no.16(August 15, 2008)
• ISSN：1520-5851

文摘

Experiments were conducted to study the degradation of hardened cement paste due to exposure to CO₂ and brine under geologic sequestration conditions (T = 50 °C and 30.3 MPa). The goal was to determine the rate of reaction of hydrated cement exposed to supercritical CO₂ and to CO₂-saturated brine to assess the potential impact of degradation in existing wells on CO₂ storage integrity. Two different forms of chemical alteration were observed. The supercritical CO₂ alteration of cement was similar in process to cement in contact with atmospheric CO₂ (ordinary carbonation), while alteration of cement exposed to CO₂-saturated brine was typical of acid attack on cement. Extrapolation of the hydrated cement alteration rate measured for 1 year indicates a penetration depth range of 1.00 ± 0.07 mm for the CO₂-saturated brine and 1.68 ± 0.24 mm for the supercritical CO₂ after 30 years. These penetration depths are consistent with observations of field samples from an enhanced oil recovery site after 30 years of exposure to CO₂-saturated brine under similar temperature and pressure conditions. These results suggest that significant degradation due to matrix diffusion of CO₂ in intact Class H neat hydrated cement is unlikely on time scales of decades.