Introduction to Injection Wells

After the Second World War, as chemical manufacturing expanded in the United States, companies began using deep well injection to dispose of industrial and toxic waste. In response to the expansion of the practice, the U.S. Environmental Protection Agency received a mandate from Congress to report these waste disposal practices and to develop minimum requirements for underground waste injection. In 1974 this mandate culminated in the passage of the Safe Drinking Water Act, and the Underground Injection Control program is outlined in that act.

Why It Matters

Understanding all of the classes of underground injection wells, both those that relate specifically to oil and gas and those that do not, enables an understanding of the relationship between fluids injected into the subsurface and underground sources of drinking water.  This knowledge allows inspectors and regulatory staff to provide guidance to the public and regulated communities on complex issues regarding appropriate well classification and permitting process based on specific functions, operations, injected fluids and construction.   

Learning Objectives

  • Identify all EPA classes of injection wells and describe the main purpose of each
  • Describe the geology needed to facilitate an efficient injection well
  • Describe two regulatory processes that states may follow when developing a Class II UIC program
  • Explain the differences between primary, secondary and tertiary recovery
  • Describe some examples of enhanced oil recovery
  • Describe the difference between injection wells for deep geothermal and heat pump use
  • Briefly explain the difference between the classification of CO2 injection wells for enhanced oil recovery vs. storage.

Images: “Graphic” by Top Energy Training