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Title: Effects of sulfate and magnesium on cement degradation under geologic CO 2 sequestration conditions

For safer geologic CO 2 sequestration (GCS), it is important to understand CO 2-brine-cement interactions, which affect wellbore integrity. However, potential effects of sulfate and magnesium ions on cement degradation under GCS conditions are not well understood. Class H Portland cement were reacted in brines containing 0.05 M sulfate and/or magnesium ions under both GCS (50 °C and 100 atm CO 2) and control (50 °C and atmospheric pressure) conditions. Using optical microscopy and scanning electron microscope coupled with energy dispersive spectrometry and electron back scattered electron (SEM-EDS/BSE), slower cement carbonation rates were observed in the presence of sulfate under GCS conditions, because of gypsum precipitation on cement surfaces. Calcite rather than gypsum formed in both the inner layers of cement samples reacted under GCS conditions, and on cement surfaces reacted under atmospheric pressure conditions. Under GCS conditions, the dissolved CO 2 lowered the pH of the solution surrounding cement surfaces, thus favoring the formation of gypsum over calcite on cement surfaces; while the high pH condition in pore solution inside cement favors the formation of calcite over gypsum. Finally, the presence of magnesium had no significant effect on cement degradation under GCS conditions, as brucite, magnesium carbonates and magnesiummore » calcite did not form, due to the low pH at cement surface and the limited diffusion of Mg into cement inner layers.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [2]
  1. China Univ. of Geosciences, Beijing (China). State Key Lab. of Biogeology and Environmental Geology; Univ. of Houston, TX (United States). Dept. of Civil & Environmental Engineering
  2. Univ. of Houston, TX (United States). Dept. of Civil & Environmental Engineering
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Geochemistry Dept.
  4. China Univ. of Geosciences, Beijing (China). State Key Lab. of Biogeology and Environmental Geology
Publication Date:
Grant/Contract Number:
AC02-05CH11231; 41272061; 41472232
Type:
Accepted Manuscript
Journal Name:
International Journal of Greenhouse Gas Control
Additional Journal Information:
Journal Volume: 63; Journal ID: ISSN 1750-5836
Publisher:
Elsevier
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); China Univ. of Geosciences, Beijing (China)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Natural Science Foundation of China (NNSFC); Science and Technology Innovation Fund of the China Univ. of Geosciences
Country of Publication:
United States
Language:
English
Subject:
geologic CO2 sequestration (GCS); cement degradation; sulfate; magnesium; gypsum; calcite
OSTI Identifier:
1475007
Alternate Identifier(s):
OSTI ID: 1459454