&EPA
Office of
United States	Ground Water and
Environmental Protection Agency	Drinking Water
CLASS V UIC STUDY FACT SHEET
IN-SITU FOSSIL FUEL RECOVERY WELLS
What is an in-situ fossil fuel recovery	In-situ fossil fuel recovery wells are used to facilitate in-situ conversion of a hydrocarbon
well?	resource into a gaseous or liquid form that can be extracted through production wells.
Specifically, in-situ fossil fuel recovery wells are used to initiate and then to maintain and
control combustion through injection of gases or ignition agents. There are three types of
processes that may use in-situ fossil fuel recovery wells: in-situ combustion of tar sand
deposits, underground coal gasification, and in-situ oil shale retorting. In-situ
combustion of tar sand deposits has not been employed in the United States.
What types of fluids are injected into	The injectate may include air, oxygen, steam, carbon dioxide, or ignition agents,
in-situ fossil fuel recovery wells?
Do injectate constituents exceed	Most of the injected materials are gases that are not likely to show exceedances of
drinking water standards at the point	drinking water standards or health advisory levels. When ignition agents such as
of injection?	ammonium nitrate are injected, exceedances of drinking water standards and health
advisory levels would be expected, but has not been documented.
What are the characteristics of the	In-situ fossil fuel recovery wells inject into a hydrocarbon-containing unit, which is often
injection zone of an in-situ fossil fuel	a steeply inclined coal seam or oil shale deposit that is not practical to mine with
recovery well?	conventional methods. Although injected gases generally do not introduce contaminants
into the subsurface, injection may alter the characteristics of an underground source of
drinking water (USDW), if the gases are allowed to contact a USDW, by changing the
USDW's temperature or increasing the level of gas saturation.
Contamination of ground water resulting from in-situ fossil fuel recovery operations is
well documented, to the extent that most, if not all, in-situ fossil fuel recovery operations
initiated in the last 20 years appear to have caused some ground water contamination.
The ground water is not contaminated with the injected materials, however. Rather, it is
contaminated with combustion byproducts, such as benzene. At some sites, water
containing benzene and other combustion byproducts, such as phenols, has migrated via
fractures or other means from the reaction zone into nearby ground water.
Are in-situ fossil fuel recovery wells
Overall, in-situ fossil fuel recovery wells are not likely to receive spills or illicit
vulnerable to spills or illicit
discharges. The observed contamination problems are associated with in-situ fossil fuel
discharges?
recovery operations, rather than rare spills or accidents.
How many in-situ fossil fuel recovery
There are no known active in-situ fossil fuel recovery wells in the United States.
wells exist in the United States?

Where are in-situ fossil fuel recovery
As stated above, there are no active in-situ fossil fuel recovery wells in the United States.
wells located within the United States?
In the past, such wells have operated primarily in WY and CO.
How are in-situ fossil fuel recovery
Individual permit: WY, CO
wells regulated in states with the

largest number of this type of well?

Where can I obtain additional	For general information, contact the Safe Drinking Water Hotline, toll-free 800-426-
information on in-situ fossil fuel	4791. The Safe Drinking Water Hotline is open Monday through Friday, excluding
recovery wells?	federal holidays, from 9:00 a.m. to 5:30 p.m. Eastern Standard Time. For technical
inquiries, contact Amber Moreen, Underground Injection Control Program, Office of
Ground Water and Drinking Water (mail code 4606), EPA, 401 M Street, SW,
Washington D.C., 20460. Phone: 202-260-4891. E-mail: moreen.amber(@epa.gov. The
complete Class V UIC Study (EPA/816-R-99-014, September 1999), which includes a
volume addressing in-situ fossil fuel recovery wells (Volume 13), can be found at
http://www.epa.gov/OGWDW/uic/cl5study.html.
Are there any contamination incidents
associated with in-situ fossil fuel
recovery wells?

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