Drilling. Wednesday , August 02nd , 2017 - 21:39:40 PM
The well had a particularly small mouth, "as small as a small bowl." Archaeological evidence of the drilling tools used in deep-well dwelling are kept and displayed in the Zigong Salt Industry Museum. According to Salt: A World History, a Qing Dynasty well, also located in Zigong, "continued down to 3,300 feet [1,000 m] making it at the time the deepest drilled well in the world." Mechanised versions of this system persisted until about 1970, using a cam to rapidly raise and drop what, by then, was a steel cable up to 3 mm.
In the 1970s, outside of the oil and gas industry, roller bits using mud circulation were replaced by the first pneumatic reciprocating piston Reverse Circulation (RC) drills, and became essentially obsolete for most shallow drilling, and are now only used in certain situations where rocks preclude other methods.
Drilling rigs can sample sub-surface mineral deposits, test rock, soil and groundwater physical properties, and also can be used to install sub-surface fabrications, such as underground utilities, instrumentation, tunnels or wells.
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