We have a requirement to make a 2 metre diameter lined borehole to a depth of 200 metres to provide access to an underground mined area. Ground conditions are generally soft, not hard rock.
I am unable to find a drill rig manufacturer or source equipment able meet this requirement
Any ideas or advice will be much appreciated!
I'm not sure what eventually happened to all the large diameter drilling tools we were using on the Government Nuclear Repository project in Washington State in the 80's. On that project we were drilling a 144" hole to +-6500'. The Washington State project never really got going because of environmental group activities. However, the rig did stay on Std-By for around 6 years on the Government's dime. The rig in Washington was Loffland Bro's Rig #32 which had been retro-fitted to handle the bigger/heavier loads expected, after it had just finished the Deepest Hole in the World (at that time). We did get the BHA assembled and everything prepared to spud but that was the extent of the drilling operations. The project I worked on in the early 70's we drilled a 96" hole to ~ 2600' then ran 90" casing as part of a oil shale mining project here in Colorado (if I remember dates correctly). On the projects we used reverse circulation/air assist methods using 13 5/8" drill-pipe with bit's having replaceable roller cutters, stacked 90" X 4' diameter "Doughnuts" for weight (instead of Drill Collars) placed on a "Mandrel" assembly which the bit was bolted onto. I remember reading somewhere in my memory about how some mining operators actually "drilled-up" to create a shaft, instead of drilling down to do so. I have a feeling this too is highly specialized operational equipment and have no idea where to go for companies that do this work. Over my career in typical O&G drilling operations I've drilled pilot wells then opened them up to 36" using hole openers and that type of off-the-shelf equipment, but once you get much bigger than that then the tools become pretty scarce. I will do a little research and see what I can find and hopefully get back later--Good Luck
In Germany we do a lot of large diameter drilling in ahead of the open cast mines for soft coal to dewater aquifers down to +/ 400 m deep. So that is a very common technology.
If you wish you can drop me a line and I put you in contact with a former manager at RWE for those operations (promoted higher now). I am sure he can help you.
Hole openers and reamers