Something else that intrigues me is the remoteness of the area and where the drilling rigs come from.
Manaus is a 4 hour flight from Rio.
Assuming they come from the nearest city, Manaus, it's a 17 hour drive to Apui, then on to site. If they come from Belem, it's much further. The highway from Manaus is BR319.
https://www.google.com/maps/@-7.172871,-59.839577,1631m/data=!3m1!1e3?hl=en
http://www.landcruisingadventure.com/the-br319/
Well, I'm not a geologist, so someone will have to help me out with this one.