(under subclass 65) Processes comprising the use of liquid and gaseous materials as the fluid circulated in the borehole.
(1) Note. Processes in which a gas under pressure is provided over a liquid drilling fluid wherein the gas is not circulated through the drill or through fluid in the bottom of the borehole are not included. See this class subclass 71.
SEE OR SEARCH THIS CLASS, SUBCLASS:
205, for apparatus in which a liquid drilling fluid is in contact with a pressurized gas.
212, for above ground drill fluid handling or supply means for supplying a pressurized gas.
