Being a sort of acidic gas,carbon dioxide(CO2)grows into another type of acidic fluid with extreme corrosion when run-ning into either water or aqueous media,which allows it prone to chemical reaction with cement in wellbore annulus of oil producers.Especially there exist the worst cases of high pressure and temperature for this fluid in the wellbore under operating modes such as CO2 capture,utilization,and storage(CCUS),CO2-enhanced oil recovery(CO2-EOR),and carbon storage,creating immense risks of CO2 corrosion and failure in wellbore packers.Thus,this paper discusses corrosion mechanisms,conditions and influences on ce-ment,explores CO2-resistant materials and cement slurry systems,analyzes this CO2 corrosion on cement under carbon storage and its impacts on wellbore integrity,and tries to find the next research interests.Results show that(ⅰ)four zones including CO2 dissolution zone,Ca(OH)2 depletion zone,CaCO3 precipitation zone,and silica gel zone degraded due to both Ca2+leaching and CSH decompo-sition are arose in the entire process of CO2 dissolving in water,intruding into cement and reacting with it,each of whose behaviors should be quantitatively evaluated;(ⅱ)an in-depth study is required on the quantitative relation of various controls to corrosion rate in the context of CCUS;and(ⅲ)existing materials to improve the resistance are mainly composed of volcanic ash,exclusive additives and non-Portland cement.However,for the last one among them,its packers are in long encapsulation,leading to performance defects under harsh conditions,which is a burning issue.
CO2Cement in oil producersCorrosionCCUSCarbon storageCarbonation
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