Mining Wells
(Class III)
A number of minerals are mined by using injection wells. In general the
technology involves the injection of a fluid, usually called lixiviant,
that contacts an ore which contains minerals that dissolve in the fluid.
The pregnant fluid (lixiviant nearly saturated with components
of the ore) is pumped to the surface where the mineral is removed from
the fluid.
EPA protects drinking water from contamination from mining wells by implementing
regulations that set minimum standards. These regulations require mining
well operators to:
- case and cement their wells to prevent the migration of fluids into
an underground drinking water source;
- never inject fluid between the outer-most casing and the well bore;
and
- test the well casing for leaks at least once every five years.
Some of the practices using mining wells are:
- Salt solution mining started in France in
the 9th century. The Chinese used boring techniques to develop wells
and extract brines at the beginning of the 18th century. In the US the
salt industry started recovering brine at the end of the 18th century.
The process consists of pumping water into the salt formation and extracting
the salt from the resulting fluid after retrieval. More than 50%
of the salt used in the US is obtained this way.
- In-situ leaching of Uranium is the practice
of injecting a fluid to leach out the Uranium salts and pumping it back
to the surface where the Uranium is extracted. 80% of the Uranium
extracted in the US is produced this way.
- The production of Sulfur using the Frasch process is one of the earliest
uses of the technology. Traditionally, super heated steam is injected
in order to recover a sulfur solution.
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