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 nano-confinement 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.