(under the class definition) Process or apparatus including a step or means for changing the physical state of a material from solid to liquid or gaseous in a location in the earth where it naturally occurs.
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17, for a process of obtaining valuable solid material from the earth as solid particles in a fluent state.
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166, Wells, appropriate subclass for a process or apparatus for converting solid hydrocarbon to a fluid in situ and recovering the valuable hydrocarbon through a well solely in the fluid state. If any of the valuable material is recovered through a well as a solid, or a valuable material other than hydrocarbon is converted to fluid and recovered, classification is in Class 299.
405, Hydraulic and Earth Engineering,
58, for subject matter relating to the construction of an underground fluid storage cavity by dissolving earth material; and subclass 131 for a process or apparatus for thawing the earth.
