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Underground Injection Control Program |  |
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Oil and Gas Injection Wells (Class II)The oil and gas production industry accounts for a large proportion of the fluids injected into the subsurface. Typically, when oil and gas are extracted, large amounts of salt water (brine) are also brought to the surface. This salt water can be very damaging if it is discharged into surface water. Instead, all states require that this brine be injected into formations similar to those from which it was extracted. Over 2 billion gallons of brine are injected daily into injection wells in the US. The largest proportion of these brines are injected into formations that contain trace portions of extractable oil and gas. Injection of the brine can have the effect of enhancing production of oil and gas from the formations, thus secondary recovery of oil and gas depends heavily on injection. Furthermore, when States started to implement rules that prevented the disposal of brine to surface water bodies and soils, injection of this waste fluid became the prevalent form of disposal. Class II wells exist wherever there is production of oil and gas. There are approximately 167,000 oil and gas injection wells in the US, most of which are used for the secondary recovery of oil. In this process water is pumped into the formation that contains some residual hydrocarbons. A portion of the hydorcarbons are recovered, along with the injected water, by extraction or production wells. In a common configuration, one injection well is surrounded by 4 or more extraction wells. The recovered fluid is treated to remove most of the hydrocarbons in a device called a separator. The other type of oil and gas injection well is a disposal well. In this type of well, excess fluids from production and some other activities directly related to the production process are injected solely for the purpose of disposal. Class II wells have to follow strict construction and conversion standards except when historical practices in the State and geology allow for different standards. A Class II well that follows EPA federal standards is built very much the same as a deep or Class I well. In 1980 Congress added Section 1425 to the Safe Drinking Water Act, that controls underground injection, relieving Class II well programs in the States from having to meet the technical requirements in the UIC regulations. Instead, they can make a demonstration that the State has an "... effective program (including adequate record-keeping and reporting) to prevent underground injection which endangers drinking water sources." Most of the oil and gas injection wells are located in the Southwest, with Texas having the largest number (53,000) and California, Oklahoma and Kansas following some distance behind with 25,000, 22,000 and 15,000 wells respectively.
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