Title: Effects of sulfate and magnesium on cement degradation under geologic CO₂ sequestration conditions

Abstract

For safer geologic CO₂ sequestration (GCS), it is important to understand CO₂-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 CO₂) 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 CO₂ 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 magnesium calcite did not form,more » due to the low pH at cement surface and the limited diffusion of Mg into cement inner layers.« less

Authors:

Guo, Jilong ^[1]; Cao, Bo ^[2]; Steefel, Carl I. ^[3]; Chen, Jiawei ^[4]; Hu, Yandi ^[2]

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+ Show Author Affiliations

1. China University of Geosciences, Beijing (China)y; University of Houston, TX (United States)
2. University of Houston, TX (United States)
3. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
4. China University of Geosciences, Beijing (China)

Publication Date:

Thu May 25 00:00:00 EDT 2017

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Natural Science Foundation of China (NSFC); Science and Technology Innovation Fund of the China Univ. of Geosciences

OSTI Identifier:

1475007

Alternate Identifier(s):

OSTI ID: 1459454

Grant/Contract Number:  

AC02-05CH11231; 41272061; 41472232

Resource Type:

Accepted Manuscript

Journal Name:

International Journal of Greenhouse Gas Control

Additional Journal Information:

Journal Volume: 63; Journal ID: ISSN 1750-5836

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; geologic CO2 sequestration (GCS); cement degradation; sulfate; magnesium; gypsum; calcite