Injection well

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An injection well is an underground well into which water, other liquids, or gases are injected instead of being pumped out.

Injection wells are used for many purposes. One of these is waste water dumping, in which waste water is injected into the ground between impermeable layers of rocks to avoid polluting fresh water supplies. In this case, when the injection well is full, it would be cemented to seal it to avoid leakage from the injection point.

Another use of injection wells is in petroleum production. Steam, carbon dioxide, water, and other substances can be injected into an oil-producing unit in order to heat the oil and/or lower its viscosity, allowing it to flow to a producing well nearby.

Yet another use for injection wells is in environmental remediation, for cleanup of either soil or groundwater contamination. Injection wells can insert clean water into an aquifer, thereby changing the direction and speed of groundwater flow, perhaps towards extraction wells downgradient, which could then more speedily and efficiently remove the contaminated groundwater. Injection wells can also be used in cleanup of soil contamination, for example by use of an ozonation system. Complex hydrocarbons and other contaminants trapped in soil and otherwise inaccessible can be broken down by ozone, a highly reactive gas, often with greater cost-effectiveness than could be had by digging out the affected area. Such systems are particularly useful in built-up urban environments where digging may be impractical due to overlying buildings.^[1]

Theoretically, a injection well is a safe way to dump waste waters as wastes are injected into layer of rocks where water can't go through and building an injection well is strictly controlled, however injection wells are known to be prone to leaking because of earthquakes and fractures in the rock structure.