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Use of in-seam mining techniques allow Pike River to see ahead
4 September 2009 - The use of in-seam drilling technology has already proved its worth at Pike River Coal’s underground West Coast mine.
Peter Whittall, the general manager of the Pike River mine, told the AusIMM minerals conference in Queenstown that in-seam drilling had detected ahead of mining an unknown fault which dropped the coal seam by some 20 m.
He said that this allowed changes to mine design and would help create greater certainty in mine planning.
The technology would potentially save many millions of dollars over the life of the mine, Mr Whittall said.
Directional drilling had been developed in Australia and now used in mines in a number of countries, mainly for drainage of in-seam gas.
But at Pike, because of the need to limit environmental impacts and difficult access within a highly tectonized zone, routine surface drilling has so far been limited to 46 boreholes.
Pike River decided on more use of seam directional drilling, primarily for coal seam and structure definition, but also for gas drainage ahead of operations.
The company contracted Valley Longwall Drilling using a track-mounted Boart Longyear drill rig with 1,300 m penetration capability and guided by a Advanced Mining Technologies directional guidance system.
Mr Whittall said the technology was the most accurate in-seam guidance tool available in the world for underground coal mines.
The equipment could be ‘steered’ so that the roof and floor of a coal seam could be ‘touched’, usually at 40 m intervals, to give progressive accurate measurements of coal seam depths.
In-seam drilling would also help minimise outbursts of underground water as well as gas. Coal seam gas from the in-seam holes will be collected into the mine’s gas drainage system or directed into the return air system.
Mr Whittall said in-seam drilling was an exploration tool that should form part of every risk mitigation programme in structurally complex coal seams.
Pike River Coal earlier announced a three month delay in the first 60,000 tonnes coal shipment from the mine until the first quarter of next year.
Delays in mining development roadways, which would have allowed earlier use of the large output hydro monitors, plus commissioning problems with its three coal cutting machines, have slowed the ramp up to full production at the Pike River mine.
Sources: Pike River Coal and Lindsay Clark
