Secondary Enhanced Recovery
Enhanced recovery of oil or gas from a reservoir beyond the oil or gas that can be recovered by normal flowing and pumping operations under primary recovery scheme. Secondary recovery techniques involve injecting water, gas or other substances into the formation to maintain or enhance the reservoir pressure as a driving force for production of oil or gas to the surface.

Tertiary Enhanced Recovery
Tertiary recovery involves injecting other gases (such as carbon dioxide) or water soluble chemicals (such as polymers and surfactants), or heat (steam or hot water) to stimulate oil and gas flow to produce remaining fluids that were not extracted during primary or secondary recovery phases.

CO₂ Capture and Storage
CO₂ storage is the process through which carbon dioxide (CO₂) from the atmosphere is injected into depleted oil and gas reservoirs and stored indefinitely.