Underground injection has been the preferred pollution control strategy for oilfield fluid waste since the 1930s. In addition, the same technology is used in secondary oil recovery projects (often called “waterfloods”). In this application, water introduced via injection wells serves to sweep oil through the formation over to nearby producing wells, thus allowing extraction of the last recoverable oil from depleted formations. Until the mid seventies, underground injection was regulated at the state level under regulatory programs that varied widely in their effectiveness. Federal regulation under the Safe Drinking Water Act began in the mid seventies, drawing on the best practices and regulations developed by the states over the previous forty years. The U.S. EPA is responsible for overall management of the regulatory program for some 144,000 wells serving the oil and gas industry, called “Class II” wells. In some states, the agency regulates the practice directly, while in others, such as Ohio, it has delegated the responsibility to state government. Permitting and enforcement of oil and gas injection wells in Ohio, called “Class II” wells, is the responsibility of the Ohio Department of Natural Resources, Division of Mineral Resource Management.
Although incidents of groundwater contamination from oil and gas injection wells were extremely rare even before federal regulations, more rigorous construction standards and operating requirements contained in modern regulations has made incidents from new wells in the modern era of regulation almost unheard of.
As used in the oilfield, the technology has proven itself to be extremely reliable as a pollution control technology that effectively serves to protect groundwater overlying the injection zone.