Screening and Evaluation of CO₂ Thickening Agents Based on Molecular Dynamics Simulation Technology

Area of Science:

• Petroleum Engineering
• Materials Science
• Computational Chemistry

Background:

• Carbon dioxide (CO2) flooding is a key enhanced oil recovery (EOR) technique.
• Low CO2 viscosity causes viscous fingering and gravitational override, reducing sweep and displacement efficiencies.
• Enhancing CO2 viscosity is critical for improving CO2 flooding performance.

Purpose of the Study:

• To investigate the feasibility of using polymers to increase CO2 viscosity.
• To analyze CO2 + polymer systems using molecular dynamics simulations.
• To identify polymer structures that effectively enhance CO2 viscosity for EOR.

Main Methods:

• Molecular dynamics simulations were employed.
• Five CO2 + polymer systems were modeled: P-1-D, PVEE, PVAEE, Piso-BVE, and four-armed PVAc.
• Intermolecular interactions and viscosity changes were analyzed.

Main Results:

• Polymers with ether, acetate, and ester functional groups enhance CO2 viscosity.
• These functional groups restrict CO2 molecule movement and reduce intermolecular forces.
• Four-armed PVAc increased CO2 viscosity by 5.29 times; P-1-D increased it by 4.75 times.

Conclusions:

• Polymers can effectively increase the viscosity of supercritical CO2.
• Polymer structure and functional groups significantly influence viscosity enhancement.
• Optimizing polymer selection is crucial for improving CO2 flooding efficiency in reservoirs.