Definition - What does Depleted Reservoir mean?
A depleted reservoir can be defined as a reservoir in sub-surface sand or rock formation that has previously produced oil or gas and is used for storing natural gas.
There are three different types of underground reservoirs namely, depleted gas reservoirs, aquifer reservoirs, and salt cavern reservoirs.
The depleted reservoirs are usually those that have produced all or part of their economically recoverable gas. To maintain working pressure in a depleted reservoir, the formation should have about 50% of the natural gas as a cushion.
Trenchlesspedia explains Depleted Reservoir
A depleted reservoir is capable of storing injected natural gas in the pore spaces between grains without migrating or being lost into surrounding formations and which can later be delivered at economic rates. Since the physical and geological characteristics of depleted reservoirs have already been studied by geologists, they are cheap and easy to develop, operate and maintain.
The rock formation of the depleted reservoir should be capable of withstanding the repeated cycle of pressure increase and pressure drop during natural gas injection and natural gas production respectively.
Other factors that determine the economic viability of a depleted reservoir are its quality of porosity and permeability, its proximity to gas markets and the presence of existing infrastructure suitable for injection and production.