Visualizing oil displacement with foam in a microfluidic device with permeability contrast

Area of Science:

• Enhanced oil recovery
• Foam flow in porous media
• Surfactant-polymer flooding

Background:

• Mobility control is crucial for efficient oil displacement in heterogeneous reservoirs.
• Foam has shown promise as an enhanced oil recovery (EOR) agent.
• Understanding foam behavior in complex porous structures is essential for optimizing EOR strategies.

Purpose of the Study:

• To investigate foam mobility control and oil displacement mechanisms in a microfluidic model of layered permeability.
• To evaluate the effectiveness of a specific surfactant blend (AOS/LB) for foam generation and oil mobilization.
• To analyze foam behavior and phase separation in response to varying matrix permeability.

Main Methods:

• Pre-generation of foam using a flow-focusing microfluidic device.
• Injection of stable foam into a 2-D oil-wet, oil-saturated PDMS microfluidic device with stratified permeability zones (fracture, high-permeability, low-permeability).
• Measurement of oil saturation and pressure drop over time and injected pore volume.

Main Results:

• A 1:1, 1% blend of alpha olefin sulfonate 14-16 (AOS) and lauryl betaine (LB) surfactants produced stable foam with paraffin oil.
• Foam injection led to increased apparent viscosity and decreased oil saturation, indicating effective oil displacement.
• Foam mobilized trapped oil more effectively than control experiments by increasing flow resistance in high-permeability zones and diverting flow to low-permeability zones.
• Observed foam phase separation into gas-rich and aqueous-rich phases based on matrix permeability.

Conclusions:

• Foam, generated using AOS and LB surfactants, is an effective agent for mobility control and enhanced oil recovery in layered porous media.
• Foam's performance is influenced by the heterogeneity of the porous medium, leading to differential flow diversion.
• Foam should not be treated as a homogeneous dispersion; its phase behavior is critical and dependent on local permeability.