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Oil, Gas & Geothermal - Inject' _ Wells Paget of 3 State of California Department of Conservation DOGGR > General Information Oil, Gas & Geothermal - Injection ... ells Injection wells have been an integral part of California's oil and gas operations for over 50 years. Currently, over 25,000 oilfield injection wells are operating in the state. Injection wells are used to increase oil recovery and to safely dispose of the salt and fresh water produced with oil and natural gas. Injection wells are classified by the U.S. Environmental Protection Agency into five classes according to the type of fluid they inject and where the fluid is injected, as follows: Class I wells - inject hazardous and non -hazardous wastes below the lowermost underground source of drinking water (USDW). Injection occurs into deep, isolated rock formations that are separated from the lowermost USDW by layers of impermeable clay and rock. Class II wells - inject fluids associated with oil and natural gas production operations. Most of the injected fluid is brine that is produced when oil and gas are extracted from the earth. Class III wells - inject super -heated steam, water, or other fluids into formations to extract minerals. The injected fluids are then pumped to the surface and the minerals in solution are extracted. Generally, the fluid is treated and re -injected into the same formation. >>' Class IV wells - inject hazardous or radioactive wastes into underground sources of drinking water. These wells are banned under the Underground Injection Control (UIC) program because they directly threaten public health. %> Class V wells - are injection wells that are not included in the other 4 classes. Some Class V wells are wastewater disposal wells used by the geothermal industry, but most are wells such as septic systems and cesspools. Generally, they are shallow and depend upon gravity to drain or "inject" liquid waste into the ground. In California, all Class II injection wells are regulated by the Department of Conservation, Division of Oil, Gas, and Geothermal Resources, under provisions of the state Public Resources Code and the federal Safe Drinking Water Act. Class II injection wells fall under the Division's UIC program, which is monitored and audited by the U.S. Environmental Protection Agency. In 1983, the Division received EPA primary authority, primacy, to regulate Class II wells. The main features of the UIC program include permitting, inspection, enforcement, mechanical integrity testing, plugging and abandonment oversight, data management, and public outreach. How Many Injection Wells Are Used in Oil and Gas Operations In California? About 25,000 injection wells are used for waterflood, steamflood, cyclic steam, and water disposal. These wells are referred to as Class II http://www.conservation.ca.gov/dog/general_information/Pages/class_iniection_wells.aspx 6/29/2009