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.
I did read the article, but it's simply wishful thinking to believe that all toxic substances could be flushed from a 3,800m deep hole. They say 1.5 cubic meters of lubricants and antifreeze came to the surface. Where did the rest go?
It'll be exciting to find out what life forms are hiding down there, but by cracking the seal, we've already changed that ecosystem. Pumping hundreds of litres of kerosene into the ice was probably not the best way to introduce ourselves.