rampers please explain, page-12

Exaclty my thinking there Chinguetti.

As for the bit change Abuman, drill bits wear out as you drill, if you don't spend the time changing them, you can spend a week trying to fish the bits out that fall off them. Or even worse, have to pull back up the hole and sidetrack around the bits that you couldn't get out.

Another reason is if the formation you are drilling in changes, or is likely to soon change. Certain bits work better in certain rocks, and the time to change a bit can be made up if the bit you put in drill faster for long enough.

As for the 18hours costing $1m, I think it would more likely be around 150-200k/day for the rig, so I would say it didn't cost them that much.