Gas Drainage for Anglo American Featured

Written by John Harms and Ashley Peters

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While it’s not uncommon to spot one of the district’s finest Brahmans wandering dopily across the surface at the site, much is happening underground.

The horizontal hole is drilled by the very powerful Gallagher 600, which has 600,000 pounds (280 tonnes) of push-pull.  Rig3, as she is called, can operate with entry angles of 10-60 degree holes (off horizontal).  It operates in a similar manner to Rig 1 operating at the Grasstree site.  Holes of up to 2,500 metres long have been drilled at this mine.  Generally each lateral well intersects a vertical well near the end of the lateral well.

The drill head is steered along its path using MWD (Measurement While Drilling) technology together with other tools such as Rotating Magnets and Dynamic Rotating Gamma, which are utilised to assist with the steering process.  The MWD system records the location of a probe located behind the drill bit and sends this data back to an operator (the Steerer) located in the drill cabin.  The Steerer plots the desired path and provides this information to the driller who then implements this plan by directing the drill head along the desired path.

Geotech Drilling uses National Oilwell A600PT mud pumps that are crucial to the operation.  The speed of the drill bit in Rig 3 is dependent on the rate at which water can be pumped along the hole.  The A600PT has the capacity to pump up to 700 gallons per minute (gpm).

The water also returns the cuttings back along the hole to the surface where it is fed through a four-station recycling system.  The recycling system separates the cuttings from the drilling fluids which are subsequently recycled and pumped back down the well being drilled and the process is repeated.

The operation is continuous.  Two crews of five men work twelve hour shifts.

As the jobs progress, Ashley Peters and Geotech Drilling are determining the best way of achieving the necessary results for Anglo American, which is contributing significantly to an understanding of what is possible in response to the circumstances and conditions of the situation.

Innovative thinking is driving the development and refining of these processes.