Which EOR method uses polymers or detergent-like surfactants to help lower the surface tension that often prevents oil droplets from moving through a reservoir?

Which EOR method uses polymers or detergent-like surfactants to help lower the surface tension that often prevents oil droplets from moving through a reservoir?

• A. Gas Injection
• B. Thermal Recovery
• C. Chemical Injection
• D. Waterflood

Answer: (C)

This question tests how interfacial properties are manipulated in enhanced oil recovery to mobilize trapped oil. Chemical injection uses formulations that include detergents (surfactants) and polymers. Surfactants accumulate at the oil–water interface and lower the interfacial tension, helping oil droplets overcome capillary pinning in pore throats and begin moving toward the production wells. Polymers are added to the injected water to increase its viscosity, improving sweep efficiency and reducing fingering so the oil displaced by the lowered tension can be more effectively recovered. Gas injection relies on pushing oil through a displacing gas and thermal recovery uses heat to lower oil viscosity; neither primarily relies on lowering interfacial tension with detergents or polymers. Waterflood displaces oil with water but does not focus on chemical modification of interfacial properties.

This question tests how interfacial properties are manipulated in enhanced oil recovery to mobilize trapped oil. Chemical injection uses formulations that include detergents (surfactants) and polymers. Surfactants accumulate at the oil–water interface and lower the interfacial tension, helping oil droplets overcome capillary pinning in pore throats and begin moving toward the production wells. Polymers are added to the injected water to increase its viscosity, improving sweep efficiency and reducing fingering so the oil displaced by the lowered tension can be more effectively recovered. Gas injection relies on pushing oil through a displacing gas and thermal recovery uses heat to lower oil viscosity; neither primarily relies on lowering interfacial tension with detergents or polymers. Waterflood displaces oil with water but does not focus on chemical modification of interfacial properties.