SPWLA Glossary

Recovery of petroleum oil from underground reservoirs by using secondary sources of energy, such as injected natural gas or water to increase producing rates and to improve ultimate oil recovery. Water injection, commonly known as water flooding, usually affords higher recovery than gas injection. Gas injection is generally limited to those reservoirs which have a gas cap and in which gas cap expansion is expected to be an efficient natural drive mechanism.

Although the terms “primary” and “secondary” imply a sequence of use, both mechanisms might work concurrently once secondary recovery is implemented. See also primary recovery and tertiary recovery.