1) American invention 2) Drilling technology
Found on
https://www.crosswordclues.com/clue/well-drilling
Well drilling is the process of drilling a hole in the ground for the extraction of a natural resource such as ground water, brine, natural gas, or petroleum, for the injection of a fluid from surface to a subsurface reservoir or for subsurface formations evaluation or monitoring. Drilling for the exploration of the nature of the material undergro...
Found on
http://en.wikipedia.org/wiki/Well_drilling
No exact match found.
