In EOR, what is the method called that floods from the top or an updip location to push oil toward a producing well?

• A. Water Flood
• B. Foam Flood
• C. Gas Flood
• D. Chemical Flood

Answer: (C)

Gas flooding involves injecting gas, often CO2 or other light gases, from the top or an updip location to push oil toward a producing well. Because gas is buoyant relative to oil, it tends to rise and form a gas cap, which expands and drives the oil downward and toward the producer. This buoyant displacement is a defining feature of this method and can be effective when the gas can contact and mix with the oil at adequate pressures to improve sweep efficiency.

Water flooding, by contrast, uses liquid water to push oil and isn’t characterized mainly by injection from the top to create a buoyant push. Foam flooding uses foam to reduce gas channeling and improve sweep, while chemical flooding uses polymers or surfactants to alter fluid properties and interfacial tension—none of which describe the straightforward buoyant drive from a top/updip gas injection.