If this was anything like a typical process, drilling fluid would be pumped under pressure down the drill pipe. Not a few drops - rather hundreds (or thousands) of liters. Obviously, this is not hard-rock drilling so I'd assume the volume of drilling fluid would be reduced. It would still have to be a substantial amount, definitely more that 1.5 cubic meters.
So now that the drilling hole is flushed of antifreeze and its filled with prehistoric lake water... what's to stop it from freezing and closing off the hole again?
It is not much like a typical drilling process. The article includes a pretty decent infographic abt 2/3 way down, which shows the drilling principle on the last slide. Worth a look.