It would seem that there might be a lot of potential pressure under all that ice. Wouldn't breaching that cause a pretty impressive geyser?
No:
You:(1) case the hole (metal piping as you go);(2) have what is called a pressure control stack on the surface (blow out preventers and a annular) in the event you become underbalanced; and (3) most importantly, you have a colum of drilling fluid of some kind weighing down the formation (lake, in this instance) . . water being the lightest, to brine (all you'd need here), or even some sort of heavier petroleum based mud.
Yes, I am a drilling engineer.