Directional control in longhole drilling

Directional drilling has provided the coal mining industry with a means to position in-seam boreholes to achieve goals such as gas drainage, exploration and inrush protection. The evolution of the technology has progressed to a point where most drilling operators use the standard down-hole drilling configuration which has proven effective in most applications. Survey techniques have been modified to reduce the distance between bit and survey point without consideration of the effects on survey accuracy, driller skills and data collection. Data from two long in-seam boreholes is analysed to show the response curves of the standard down-hole configuration. An indication of the effects of in-hole friction, of feed pressures and limitations put on the eventual borehole depths is shown