Effects of Aqueous Solubility and Geochemistry on CO Injection for Shale Gas Reservoirs.

In shale gas reservoirs, CH and CO have finite aqueous solubilities at high-pressure conditions and their dissolutions in water affect the determination of the original gas in place and the CO sequestration. In addition, the dissolution of CO decreases the pH of connate water, and the geochemical reactions may thus occur in carbonate-rich shale reservoirs. The comprehensive simulations of this work quantify the effects of aqueous solubility and geochemistry on the performance CO huff-n-puff process in shale gas reservoir. Accounting for the aqueous solubility of CH increases the initial natural gas storage and natural gas production. The effect of the aqueous solubility of CO enables to sequester additional CO via solubility trapping. Considering the geochemical reactions, the application of the CO huff-n-puff process causes the dissolution of carbonate minerals and increases the porosity enhancing the gas flow and the gas recovery. Incorporation of geochemistry also predicts the less CO sequestration capacity. Therefore, this study recommends the consideration of aqueous solubility and geochemical reactions for the accurate prediction of gas recovery and CO sequestration in shale gas reservoirs during the CO huff-n-puff process.