hp what is the depth, page-19

TP,
yes there is quite a bit of time to change a drill bit.
Any driller is reluctant to pull 4km of pipe unless necessary.
The best indication is an increase in torque (among other things), and then based on experience a decision to pull the bit is made. On the Hab-2 intervention program there was an initial reluctance to pull the bit at signs of increasing torque and the result was a loss of cones. The reluctance was the due to the time involved to pull out the drill string using the subbing unit. This time it is different. With this rig tripping time is a lot less, and very efficient so the time to pull the bit will not be a consideration. This time prudence will dictate that at the first signs of bit wear, it will be pulled out without hesitation. It may seem excessive but it's excellent insurance. I'm sure that's the way they will do it.
I'm punting on a completion of drilling at Christmas and a test in Jan.