Foam Dynamics in Limestone Carbonate Cores.

Area of Science:

• Petroleum Engineering
• Reservoir Engineering
• Enhanced Oil Recovery

Background:

• Foam applications are increasingly studied for heterogeneous carbonate reservoirs to enhance gas sweep and manage high gas-oil ratios (GOR).
• Limited experimental data exists on foam matrix transport properties in carbonates compared to sandstones.
• Understanding foam behavior in carbonates, especially with residual oil, is crucial for effective field applications.

Purpose of the Study:

• To investigate foam generation and transport mechanisms in carbonate rocks.
• To evaluate the impact of remaining oil on foam performance.
• To assess the potential of foam as a gas shut-off technique in high-GOR wells.

Main Methods:

• Co-injection of Alpha Olefin Sulfonate (AOS) solution and nitrogen (N2) gas into outcrop Indiana Limestone cores.
• Experiments conducted at high pressure and temperature after surfactant adsorption.
• Foam generation and transport evaluated in both oil-free and residual oil conditions across various gas fractions.

Main Results:

• In oil-free cores, foam generation was rapid, with the strongest foam observed at a 90% gas fraction.
• Foam generation and propagation were significantly delayed in the presence of residual oil, requiring higher AOS concentrations (5 wt%).
• Persistent foams were generated and maintained stability against significant nitrogen pressure gradients (up to 0.5 bar/m) in both scenarios.

Conclusions:

• Foam, particularly using AOS, demonstrates effectiveness in carbonate reservoirs, even with residual oil present.
• Designed foam treatments can be a cost-effective and low-risk method to mitigate high GOR, improve gas handling, and reduce gas reinjection issues.
• Further research into foam transport in carbonates can optimize EOR strategies and well productivity.