High Speed Cross Panel Drilling System

Gas drainage is a major issue currently affecting underground coal mines. The difficulties associated with underground gas drainage are partly responsible for poor development rates for longwall coal blocks; this in turn limits coal production from underground operations. In an effort to improve longwall productivity, and address current safety issues associated with methane drainage, the CMTE has been investigating the applicability of high pressure waterjet drilling for gas drainage in underground mines. The technology has the capability for high productivity and with steering could significantly reduce gas drainage drilling costs.

The overall aim of the this project was to produce a high speed cross panel drilling system which has productivity characteristics and a drilling accuracy exceeding that of current drilling systems. This work is a carry on from the ACARP (C7024) project. The work program was split into two stages;

• Stage 1 develops the guidance (surveying and steerage) of the drilling tool
• Stage 2 takes the technology to the underground demonstration stage (the focus of this report).

From trials conducted at German Creek (Anglo Coal) and Elouera Colliery (BHP), a dead reckoning navigation tool has been further refined for commercialisation. Significant work has been undertaken to improve survey tool accuracy and vibration resistance. The position of the drilling tool is reported out of the hole in real time while drilling. This is the first time this has been achieved as conventional drilling techniques require drilling to be stopped when a survey point taken. This adversely affects productivity and the working continuity of drilling. Jet thruster steerage has also been demonstrated to change the borehole trajectory in a controlled and predictable fashion. Steerage has yet to be activated in real time, however a positional motor to orientate the jet thruster has been tested. Further testing has also investigated the resultant drilling build curves generated by a side thrusting jet.

The findings from Stage 2 indicate that a waterjet drilling tool for producing underground gas drainage boreholes is technically feasible and readily achievable. Commercialisation partners are presently being approached to fund an underground demonstration of the equipment. The technology has the potential to have significant productivity gains, which could halve underground gas drainage drilling costs.