Name one of the three main methods of Enhanced Oil Recovery (EOR).

• A. Water Flood
• B. Steam Injection
• C. Gas Injection
• D. Chemical Injection

Answer: (C)

Enhanced oil recovery focuses on changing reservoir conditions to mobilize oil that couldn’t be produced in primary recovery. The three main approaches are thermal methods, gas injection, and chemical methods. Gas injection fits as one of these because it involves introducing a gas (like CO2 or natural gas) into the reservoir to maintain pressure and interact with the oil. This interaction can reduce the oil’s viscosity or cause it to swell, making the oil flow more easily toward production wells. Steam injection is a thermal method that uses heat to lower viscosity, while chemical injection uses polymers or surfactants to improve sweep efficiency and reduce interfacial tension. Water flood is typically considered secondary recovery and not one of the primary EOR categories.