Experimental assessment of well integrity for CO2 geological storage: A numerical study of the geochemical interactions between a CO2-brine mixture and a sandstone-cement-steel sample

Abstract : Geologic storage of CO2 is one option for avoiding CO2 emissions from a large-scale point source such as a thermal power plant and a gas refinery. The alteration of well materials by CO2 under reservoir conditions requires characterization because the wells are the main possible leakage pathways for CO2 from a geological reservoir. This paper presents a numerical modeling of interaction experiments involving a composite well sample formed from steel casing surrounded by Portland cement, itself surrounded by sandstone and CO2-saturated brine at 10 MPa and 50 °C during a period of up to 8 weeks, as reported by Mito et al. (2015). A reactive-transport model was developed to simulate diffusion of the CO2-saturated brine in the well sample and the resulting successive dissolution/precipitation reactions in the sandstone, cement and steel. The observed changes in mineralogy (which primarily consist of dissolution of portlandite and Ca-rich CSH phases and precipitation of calcite, amorphous silica and zeolite) and the associated evolution in brine composition were reproduced by the model. A buffering role of sandstone on the cement degradation was evidenced, thus avoiding the re-dissolution of calcite usually observed in experiments with direct interaction between cement and CO2-saturated brine. Interestingly, the model results also noted a possible perturbation in the measured pH and Ca content due to CO2 outgassing during solution sampling. The Si behavior control linked with the uncertainty in zeolite stability is also discussed.
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Contributeur : Joachim Tremosa <>
Soumis le : lundi 20 février 2017 - 10:14:21
Dernière modification le : mardi 21 février 2017 - 11:34:27

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Joachim Tremosa, Saeko Mito, Pascal Audigane, Ziqiu Xue. Experimental assessment of well integrity for CO2 geological storage: A numerical study of the geochemical interactions between a CO2-brine mixture and a sandstone-cement-steel sample. Applied Geochemistry, Elsevier, 2017, 78, pp.61 - 73. 〈http://www.sciencedirect.com/science/article/pii/S0883292716302013〉. 〈10.1016/j.apgeochem.2016.12.011〉. 〈hal-01471561〉

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