Significance of Regulatory Constraints on the operation of Packerless Waste Injection Wells

Abstract

Summary U.S. federal regulations for groundwater protection require all hazardous-waste disposal wells to be constructed so that casing leaks can be reliably monitored. Wells constructed with static-fluid seals instead of packers are incapable of meeting this requirement and are therefore not in compliance with the regulations. Introduction Though fluids (liquids) have been injected into the subsurface to recover minerals and to dispose of oilfield brine in the U.S. for many years, deep-well disposal has been an approved means of industrial waste management for only a few decades. This method now accounts for the subsurface disposal of increasingly large volumes of industrial liquid waste. If not property controlled, the injected waste could threaten the safety of our drinking water supplies. In the past, subsurface waste disposal was generally regulated by state programs, which varied widely in technical detail. The need for uniform standards for groundwater protection has been obvious for some time. In recognition of this need, the U.S. Congress enacted the Safe Drinking Water Act in 1974 and the Hazardous and Solid Waste Amendments (HSWA) in 1984. The Underground Injection Control (UIC) regulations, which are a part of the HSWA, set minimum standards for the siting, construction, and operation of injection wells in the U.S. The U.S. Environmental Protection Agency (EPA) administers this program directly or through the states to meet the Congressional mandate. UIC regulations require all injection wells to be constructed with tubing set in packers. This feature allows the well operator to use the tubing/casing annulus for monitoring well casing leaks that could endanger the safety of adjacent underground sources of drinking water (USDW's). As of 1984, only 80% of all hazardous-waste disposal (Class I) wells in the U.S. were completed with packers. The regulations permit the operation of packerless wells only if the operator can demonstrate that the mechanical integrity of these wells can be reliably monitored at a level comparable with that of the well with packer. The most common type of the packerless well currently approved by the EPA features a "static-fluid seal" in the annulus-i.e., annulus filled with a mineral oil, in place of the packer, which totally isolates the annulus from the injected waste. This paper examines the extent that the packerless well with the static- fluid seal is comparable with a conventional well with packer in providing reliable protection to groundwater. Considerations of theory and available operating-well data from the Great Lakes region facilities suggest that packerless wells do not meet applicable requirements and therefore do not comply with UIC regulations.