Study on the adsorption and deformation laws of multi-components in shale oil with nanopores——insights from the molecular simulation

Abstract

The development of shale oil reservoirs is significant for the petroleum industry. Fluids in shale oil play exist in nanoscale pores, and the interaction between fluids and shale rock surface walls can lead to the expansion and deformation of the entire pore medium thus affecting the development and production of oil reservoirs. We used an organic matter (graphene) pore model to represent the nanopore structure of shale reservoir. Methane, n-hexane and n-dodecane multi-component fluids were used to characterize shale oil. The adsorption and deformation law of multi-component shale oil in the nanopore was systematically studied by using the molecular simulation method. The results showed that the adsorption of multi-component shale oil in organic nanopores was positively correlated with pressure. The total adsorption amount increased with the increase of pressure. Firstly, when the ratio of CO₂ was higher, it was more favorable for the development of crude oil and the large amount of CO₂ sequestration. The adsorption amount was negatively correlated with temperature. Secondly, the adsorption amount of multicomponent shale oil is proportional to the pore size; The adsorption amount of large-size pore model is more sensitive to pressure changes than that of small-size pore model. Finally, the trend of adsorption deformation volume is similar to that of adsorption volume, which decreases with the increase of temperature. The shale deformation caused by CO₂ injection at this time is much smaller than the other component ratios, indicating that the magnitude of deformation is positively related to the adsorption volume.