Cement system for CO2 injection and sequestration in mafic/ultramafic rock and method of use

A method of cementing a CO2 injection well bored in an underground geological formation formed of mafic and/or ultramafic rock, comprising:

• injecting a cementitious slurry mixture into an annulus between a well casing and an injection well wall,
• wherein the cementitious slurry mixture comprises:
• 60-80 wt. % of a class G cement;
• 10-35 wt. % of a fly ash;
• 1-5 wt. % of a microsilica;
• 1-5 wt. % of a plurality of additives;
• 10-15 wt. % of an epoxy resin blend,
• wherein wt % is based on the total weight of the class G cement, the fly ash, the microsilica, the additives and the epoxy resin blend,
• curing the cementitious slurry mixture to form a cured cement to bond the injection well casing to the injection well wall,
• after the curing, injecting a CO2-containing fluid into the CO2 injection well below the first depth, and
• reacting CO2 in the CO2-containing fluid with the mafic and/or ultramafic rock in the underground geological formation to sequester the CO2 in the underground geological formation,
• wherein the epoxy resin blend in the cementitious slurry mixture comprises a bisphenol A-based diglycidyl ether, an amine, and 1,4-butanediol diglycidyl ether,
• wherein the curing is performed at a temperature of 50 to 70° C. for a period of 4-10 hours, and
• wherein the cured cement has a bonding strength of 350 to 400 bar after 7 days of curing according to ASTM C109 standard and a durability with a strength retention of at least 97% after up to 7 days exposure to CO2 containing fluid.