What is a Class II well? Class II wells inject fluids associated with oil and natural gas production. Most of the injected fluid is salt water (brine), which is brought to the surface in the process of producing (extracting) oil and gas. In addition, brine and other fluids are injected to enhance (improve) oil and gas production. The approximately 144,000 Class II wells in operation in the United States inject over 2 billion gallons of brine every day. Most oil and gas injection wells are in Texas, California, Oklahoma, and Kansas.
Three types of Class II injection wells are associated with oil and natural gas production:
1) Enhanced Recovery Wells inject brine, water, steam, polymers, or carbon dioxide into oil-bearing formations to recover residual oil and—in some limited applications—natural gas. This is also known as secondary or tertiary recovery. The injected fluid thins (decreases the viscosity) or displaces small amounts of extractable oil and gas, which is then available for recovery. In a typical configuration, a single injection well is surrounded by multiple production wells. Production wells bring oil and gas to the surface; the UIC Program does not regulate production wells. Enhanced recovery wells are the most numerous type of Class II wells, representing as much as 80 percent of all Class II wells.
2) Disposal Wells inject brines and other fluids associated with the production of oil and natural gas or natural gas storage operations. When oil and gas are produced, brine is also brought to the surface. The brine is segregated from the oil and is then injected into the same underground formation or a similar formation. Class II disposal wells can only be used to dispose of fluids associated with oil and gas production. Disposal wells represent about 20 percent of Class II wells.
3) Hydrocarbon Storage Wells inject liquid hydrocarbons in underground formations (such as salt caverns) where they are stored, generally, as part of the U.S. Strategic Petroleum Reserve. There are over 100 liquid hydrocarbon storage wells in operation.
What are the requirements for Class II wells? A state has the option of requesting primacy* for Class II wells under either section 1422 or 1425 of the Safe Drinking Water Act:
Section 1422 requires states to meet EPA’s minimum requirements for UIC programs. Programs authorized under section 1422 must include construction, operating, monitoring and testing, reporting, and closure requirements for well owners or operators. Enhanced oil and gas recovery wells may either be issued permits or be authorized by rule. Disposal wells are issued permits. The owners or operators of the wells must meet all applicable requirements, including strict construction and conversion standards and regular testing and inspection.
Section 1425 allows states to demonstrate that their existing standards are effective in preventing endangerment of USDWs. These programs must include permitting, inspection, monitoring, and record-keeping and reporting that demonstrates the effectiveness of their requirements.
The Center takes issue with the EPA policy position related to disposal of brine, particularly as it relates to hydraulic fracturing. EPA states:
How do Class II wells protect drinking water resources? When oil and gas are extracted, large amounts of brine are typically brought to the surface. Often saltier than seawater, this brine can also contain toxic metals and radioactive substances. It can be very damaging to the environment and public health if it is discharged to surface water or the land surface. By injecting the brine deep underground, Class II wells prevent surface contamination of soil and water. When states began to implement rules preventing disposal of brine to surface water bodies and soils, injection became the preferred way to dispose of this waste fluid. All oil and gas producing states require the injection of brine into the originating formation or into formations that are similar to those from which it was extracted.This technique would seem to put groundwater at risk. Moreover, evidently EPA's UIC Program does not regulate production wells. This is confusing because isn't hydraulic fracturing (see illustration above) enhanced recovery?
Regardless, hydraulic fracturing was exempted from federal oversight by the Energy Policy Act of 2005:
SEC. 322. HYDRAULIC FRACTURING.
Paragraph (1) of section 1421(d) of the Safe Drinking Water Act (42 U.S.C. 300h(d)) is amended to read as follows:
(1) UNDERGROUND INJECTION- The term `underground injection'--
(A) means the subsurface emplacement of fluids by well injection; and
(i) the underground injection of natural gas for purposes of storage; and
(ii) the underground injection of fluids or propping agents (other than diesel fuels) pursuant to hydraulic fracturing operations related to oil, gas, or geothermal production activities.'.
* Primacy: primary enforcement authority. The authority to implement the UIC Program. To receive primacy, a state, territory, or tribe must demonstrate to EPA that its UIC program is at least as stringent as the federal standards; the state, territory, or tribal UIC requirements may be more stringent than the federal requirements. (For Class II, states must demonstrate that their programs are effective in preventing pollution of USDWs.) EPA may grant primacy for all or part of the UIC program, e.g., for certain classes of injection wells.
(EPA, Underground Injection Control Program)