Unlocking the potential of hydraulic fracturing flowback and produced water for CO2 removal via mineral carbonation

• Published in: Applied geochemistry Vol. 142; p. 105345
• Main Authors: Zhu, Bizhou, Wilson, Sasha, Zeyen, Nina, Raudsepp, Maija J., Zolfaghari, Ashkan, Wang, Baolin, Rostron, Ben J., Snihur, Katherine N., von Gunten, Konstantin, Harrison, Anna L., Alessi, Daniel S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-07-2022; Elsevier
• Subjects: Applied geology; Carbon dioxide removal; Carbon mineralization; Earth Sciences; Environment and Society; Environmental Sciences; Geochemistry; Hydraulic fracturing flowback and produced waters; Mineral carbonation; Mineralogy; Sciences of the Universe; Wastewater management; Carbon mineralization; Mineral carbonation; Hydraulic fracturing flowback and produced waters; Carbon dioxide removal; Wastewater management
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2022.105345

Flowback and produced water (FPW) generated by hydraulic fracturing operations is highly saline and contains elevated concentrations of ions including calcium and magnesium. Here, we investigate the use of FPW as a source of calcium and magnesium for carbon dioxide (CO2) removal and storage in carbonate minerals. We performed pH titration experiments to precipitate calcium and magnesium from three FPW samples from Alberta and Saskatchewan, Canada. Depending on the pH (8.5–12), calcite (CaCO3) and brucite [Mg(OH)2], with occasional aragonite (CaCO3) and portlandite [Ca(OH)2] precipitate from FPW within 24 h of exposure to atmospheric pCO2 at ∼18 °C. Our experiments demonstrate that pH adjustments are an effective means of precipitating calcium and magnesium carbonates and hydroxides from FPW, but that relying solely upon passive removal of CO2 from air is limiting to carbonation. We estimate that carbonation of all calcium and magnesium from brines produced in conventional and hydraulic fracturing operations in Canada could store up to 1,010 Mt CO2 annually. Carbonation rates could be improved by using higher pCO2 gases, such as flue gases from fossil energy generation (via CO2 capture), gas streams produced by Direct Air Capture plants or using novel looping technologies.
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•Waste waters from oil and gas production can be used to bind CO2 in minerals.•Addition of base precipitates Ca carbonates and Ca and Mg hydroxides.•Ca carbonates precipitated from brines are stable stores for atmospheric CO2.•Up to 12.2–22.5 g CO2/L can be stored in the flowback and produced waters tested.•The carbonation potential of oil and gas brines in Canada alone is 1.010 Gt CO2/year.