Drilling a 700m hole would take weeks under normal circumstances. Drilling a 500mm shaft wide enough for man access whilst ensuring minimal disturbance (so as not to cause further collapse) in a fractured rock adds much complexity. Throw in the fact that the world is watching your every move and you can see why it would take so long. Constructing a borehole isnt simply a case of 'just drilling a hole'. You have to use casing to support the sides of the hole and even with all the care in the world gear can get trapped halfway down the hole. Imagine what it must be like to be one of the drillers knowing that the lives of so many people depend on you. That must be quite a high pressured job.
It's hard to tell from the photos exactly what rig they're using, but basically what I'm saying is that it is not a unreasonable amount of time to construct this borehole. Mining companies and oil exploration companies have access to the best drilling rigs (they are the main market for rigs) so it is reasonable to assume that the rig they are using is suitable.
Slow and steady is definitely the way to go here. There are no shortcuts.
Hope that helps.
Gar (officially a geologist, but an environmental consultant by trade)
Edit: Who am I kidding? Officially I'm a waster and I'm lucky to have a job :-)
Last edited by garmei; 9 Sep 2010 at 23:41.