borehole vs oil well

borehole

noun
  • A hole bored into the ground to collect samples for analysis or to extract oil or water. 

verb
  • To bore a hole of this kind (in). 

oil well

noun
  • A hole drilled into the earth from which petroleum is pumped. 

How often have the words borehole and oil well occurred in a corpus of books? (source: Google Ngram Viewer )