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Chile mine rescue hole underway

Chile mine rescue hole underwayA Strata 950 raise borer capable of reaming up to 6 m-diameter holes over lengths of up to 1 km is drilling a 38 cm-diameter pilot hole some 702 m to a safe holing point accessible to the San Jose miners. The hole, which had reached 171 m on 09.09.2010, should be complete by end-September, by which time the contractors, an affiliate of Murray & Roberts, will have decided whether to downream at 72 cm-diameter, or to lower a specially-designed upreaming head through the pilot hole for the miners to attach to the drill string. Upreaming is twice as fast as downreaming, because the reaction forces are more favourable for the rig. However, the downreaming operation is more manageable, can start immediately the pilot hole is completed, and is not subject to the inevitable operational risks that upreaming with a hybrid reamer will involve. Around 20-25 m/day can be expected when downreaming with this machine. For rig specification visit www.ruc.com.au/fleet/fleet-raise-950.html. The backup plan comprises a multiple-pass hole drilled by a waterwell rig which has hit snags, and a large diameter hole drilled by an oilwell rig which has not yet started. 36/10.