Nanopore-Scale Study on CO₂-Oil Differential Miscibility, Competitive Adsorption, Cross-Interphase Mass Transfer, and...

Area of Science:

• Petroleum Engineering
• Nanotechnology
• Chemical Engineering

Background:

• Tight oil reservoirs, common in shale formations, present unique challenges for enhanced oil recovery due to their micronanopore structure.
• Carbon dioxide (CO2) miscible flooding is a promising technique for improving oil recovery in these unconventional reservoirs.
• The effects of nanoconfinement on CO2-oil miscibility are critical and require detailed investigation.

Purpose of the Study:

• To investigate the competitive adsorption, interfacial mass transfer, and dynamic flooding behaviors of CO2-oil systems within nanoporous media.
• To understand how CO2 concentration influences miscibility and the minimum miscible pressure (MMP) in tight reservoirs.
• To evaluate the extraction capabilities of CO2 flooding on both light and heavy crude oil components.

Main Methods:

• Molecular dynamics (MD) simulations were employed to model CO2-oil interactions at the nanoscale.
• Experimental studies were conducted to validate simulation results and observe macroscopic behaviors.
• Analysis focused on adsorption layers, interfacial mass transfer, and dynamic flooding under varying CO2 concentrations.

Main Results:

• CO2 preferentially adsorbs onto quartz surfaces in nanopores, forming an adsorption layer that strips lighter hydrocarbons (C10).
• Increasing CO2 concentration enhances stripping, but excessive CO2 can form a second adsorption layer, increasing the effective MMP.
• CO2 concentration significantly impacts the degree of miscibility and overall flooding behavior, with a minimum MMP observed at 60 wt% CO2.

Conclusions:

• Nanoconfinement critically affects CO2 miscibility in tight reservoirs, influencing adsorption and mass transfer.
• CO2 concentration is a key parameter controlling miscibility and recovery efficiency, with an optimal range identified.
• CO2 flooding demonstrates effective extraction of both light and heavy oil components, offering valuable insights for tight oil development.