Answer:
Definition of injection well
An injection well is used to place fluid underground into porous geologic formations. These underground formations may range from deep sandstone or limestone, to a shallow soil layer. Injected fluids may include water, wastewater, brine (salt water), or water mixed with chemicals.
The definition of a well is codified in the UIC regulations at 40 CFR 144.3.
Well means: A bored, drilled, or driven shaft whose depth is greater than the largest surface dimension; or, a dug hole whose depth is greater than the largest surface dimension; or, an improved sinkhole; or, a subsurface fluid distribution system.
Injection well construction is based on the type and depth of the fluid injected. For example, wells that inject hazardous wastes or carbon dioxide (CO2) into deep isolated formations have sophisticated construction. These wells are designed to provide multiple layers of protective casing and cement. In contrast, shallow wells are usually of simple construction.
