Comprehensive modeling of CO2 Huff-n-Puff in asphaltene-damaged shale reservoir with aqueous solubility and nano-confinement

Abstract

The CO2 Huff-n-Puff process enhances the shale oil production and it could incur a risk of forming asphaltene, causing damage to the formation. During the process, the effects of aqueous solubility of CO2 and nano-confinement affect the amount of CO2 interacting with asphaltene-bearing oil, phase behavior of fluid determining the asphaltene deposition, CO2 storage, and oil production. Therefore, this study quantifies the effects of the aqueous solubility of CO2 and the nano-confinement on the performance of the CO2 Huff-n-Puff process and the asphaltene formation in a tight formation. When the aqueous solubility of CO2 is considered in the CO2 Huff-n-Puff process, a fraction of the injected CO2 dissolves in the brine, indicating the CO2 sequestration through solubility trapping. Decreasing oil production by 4% is also obtained with a reduction in asphaltene deposition. When the process undergoes the nano-confinement effect, higher oil production by up to 14% and more asphaltene deposition are observed. This study emphasizes that the aqueous solubility of CO2 and the nanoconfinement effects are necessary factors in accurate predictions of the oil production, CO2 sequestration, and asphaltene formation during the CO2 Huff-n-Puff in confined formations.