First Optical Log!
Another day, another borehole log. Things went smoothly this morning,
and after warming up the gear a little, we were ready to log. The
optical televiewer (OPTV) has to run a little more slowly than the
temperature logger, since we log both down and up at about 2 m/min.
So logging 700 meters (we start the log below the fluid level in the
hole, which is around 60 meters) takes about 350 minutes, or just
about 6 hours. With the OPTV we log on the way up as well, so the
total trip time in-hole is about 12 hours. For this reason it's
important to get an early start! Things like making coffee, having
breakfast, they can be done while logging, but getting underway is the
highest priority since that puts a hard limit on your finishing time
for the day, and if we go too late (I've logged until 4-6am many times
in the past) it makes it difficult to put in a good day the next day.
[David and me about to remove the instrument from the borehole. As you can see, I'm standing in a 'well' we'd dug in the snow, to access the borehole more easily from inside the tent. David and I are both wearing gloves to protect our hands from the borehole fluid, Estisol-240, which has about the volatility of diesel fuel...]