Underground Injection Control (UIC)

Definition - What does Underground Injection Control (UIC) mean?

Underground Injection Control, abbreviated as UIC is a program by the United States Environmental Protection Agency that contains a set of instructions and regulations which protect water sources and aquifers from the large amount of oil and gas drilling activities. The regulations also ensure that any toxic fluids produced are injected into underground zones that do not pollute the groundwater.

Petropedia explains Underground Injection Control (UIC)

Underground Injection Control policies developed by most countries define the depth of disposal of waste or treatment fluids used or developed during the drilling of oil or gas wells. Most of the policies are in line with the policies recommended by EPA. As per the U.S. Environmental Protection Agency (EPA), underground injection control is done by defining six classes of injection wells, i.e., Class I, Class II, Class III, Class IV, Class V and Class VI.

  • Class I injection well – It is used for injecting either hazardous or non-hazardous industrial and municipal waste into deep confined rock formations which are drilled thousands of feet below the lowermost underground source of drinking water.
  • Class II injection well – It is primarily used for injecting fluids produced during oil and gas activities.
  • Class III injection well – It is used to inject fluids that are used in mineral solution mining.
  • Class IV injection well – This is basically a shallow well used for the disposal of hazardous or radioactive wastes above a geologic formation that contains an underground source of drinking water.
  • Class V injection well – This well is used for the disposal of non-hazardous waste into or above an underground source of drinking water.
  • Class VI injection well – This well is used to inject carbon dioxide (CO2) into deep rock formations. This long-term underground storage is called geologic sequestration and helps in lowering the carbon dioxide emissions in the environment thereby reducing greenhouse effect.
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