Abstract
This study introduces and demonstrates a new type of drilling tool that can be used to drill small-diameter deflection holes in hard rock and steel. It principally is a fluid-operated micro drilling turbine which actively generates thrust by using built-in thrust nozzles and attached to a flexible hose, automatically pulls itself into the drilled material. To validate the new technology and its performance under different conditions, a parametric study was performed. Using the micro drilling turbine straight and deflected test boreholes were drilled into granite, quartzite, sandstone and steel. Three newly developed impregnated diamond bits with different geometries were used at different operating pressures and flowrates. It was found that two of the three bits were not suitable for the drilling process. With the other, however, holes could be drilled reliably into all of the samples. With increasing operating pressure, the rate of penetration could be increased to 1.5 m/h in granite at 20 MPa pump pressure. Although the experiments were performed at ambient surface conditions, the results can give recommendations for even downhole applications in deep wells.