Drilcorp has recently completed a large diameter borehole using reverse circulation air lift drilling techniques.
The borehole targeted mine workings 170mtr below ground level and needed to be very straight and accurate to enable it to hit the 4mtr wide target roadway.
The drilling rig used was a Comax 800 specially designed for Drilcorp by Conrad Stanen (www.conrad-stanen.com) in the Netherlands.
Comax 800
| Superficial deposits were cased off to 21mtr with a 1220mm (48”) mild steel casingand the annulus was fully grouted. The borehole was then drilled through coal measures to 150mtr at 300mm (12”). It was then reamed at 457mm (18”), 635mm (25”), 889mm (35”) and finally 1066mm (42”). |
Preparing for the 42" Pass
Selection of Hole Openers
42" Hole Opener
A 914mm mild steel casing was installed to 150mtr and the annulus was fully grouted.
The air lift reverse circulation drilling technique left the borehole clear of any drill cuttings allowing the casing to seat perfectly on the bottom of the borehole.
Finally the borehole was successfully drilled to 160mtr into the mine workings on target at 880mm (34.5”) and a 610mm (24”) stainless steel casing and screen was dropset to cover the bottom section of the borehole.
Preparing to install the 36” casing
Drilcorp Contract Manager John Gowans said ‘This is a major achievement for Drilcorp; the actual borehole we drilled was considerably larger, if not as deep, as the borehole that released the Chilean Miners’
Borehole Headworks in place
