Drill rig characteristics and drilling techniques required for maximum borehole depth with directional drilling

Directional drilling has been the established form of in-seam drilling for gas drainage, exploration and water management for the past three decades. Although there has been a desire to achieve longer boreholes to depths similar to that achieved with surface drilling, seam conditions, equipment capacity and drilling methods have limited in-seam drilling depths. Development into a new area of Metropolitan Colliery required boreholes to depths of 2000 m to provide the required gas drainage. This offered an opportunity to use a combination of slide and rotary drilling similar to that used with Surface to Inseam (SIS) drilling to achieve the required depths. This paper presents the results of the drilling, describes the drilling techniques used and defines to equipment specifications required for undertaking a range of in-seam directional drilling projects.