Low cost slim hole drilling system

Interest in reducing the cost of exploration in frontier areas and in areas of special environmental concern has given rise to a variety of initiatives to develop slim hole drilling systems and down hole tools. The market over capacity of conventional rigs offered at unrealistic commercial rates masks the real cost of operating heavy drilling equipment. This acts as a disincentive to the development of smaller innovative drilling rigs and associated equipment and the development of a smaller scale drilling system that has wide acceptance in the industry. Furthermore, funding for development of such systems has been sadly lacking. In response to a contractual commitment, an opportunity arose to design and construct a small, low cost drilling system suitable for a range of slim hole and downsized drilling scenarios. In this particular case, the equipment was required to drill both vertical and slant boreholes with slant angles up to 45°. The drilling unit and associated equipment combine a blend of oilfield and mining ideas with the objective of demonstrating that a low cost unit could satisfy the requirements of the industry for frontier drilling. The drilling unit is capable of both conventional destructive drilling up to 17-1/2 in diameter and continuous coring using heavy duty sytems up to 6-1/4 in hole size. The singles rig is 100 ton capacity with a rotary capability from the top drive system of up to 400 rpm which gives a slim hole capability of over 3500m. This paper describes the background philosophy, the equipment and the initial operations since commissioning the equipment in June 1994.