What is the difference between water injection and water flooding?

Answer 1

I do not think that there is any difference. Petroleum engineers normally inject water into an oil reservoir to maintain the reservoir pressure (and hence the ability of the reservoir to pump oil to the surface). In the process and if the water injection wells are properly located, the injected water normally sweeps (pushes out) out more oil effectively flooding the reservoir and increasing the amount of oil that is recovered from the reservoir. This incremental oil will otherwise be left behind in the reservoir. Hence, in an oil reservoir where the natural aquifer is large and strong enough to maintain the reservoir pressure, water injection is unlikely to significantly increase the oil recovery from the reservoir.