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

Journal Article · Fri Aug 01 00:00:00 EDT 2008 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es800049r· OSTI ID:1014750

Kutchko, Barbara G. ^[1]; Strazisar, Brian R. ^[2]; Lowry, Gregory V. ^[3]; Dzombak, David A. ^[3]; Thaulow, Niels ^[4]

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1. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Civil and Environmental Engineering
2. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)
3. Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Civil and Environmental Engineering
4. RJ Lee Group, Inc., Monroeville, PA (United States)

Experiments were conducted to study the degradation of hardened cement paste due to exposure to CO₂ and brine under geologic sequestration conditions (T = 50 degrees 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 I 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.

• Research Organization: National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
• Sponsoring Organization: USDOE Assistant Secretary for Fossil Energy (FE)
• OSTI ID: 1014750
• Report Number(s): NETL-TPR-2308
• Journal Information: Environmental Science and Technology, Vol. 42, Issue 16; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
54 ENVIRONMENTAL SCIENCES