Abstract: Apparatus for drilling operations in underground boreholes, comprises: a drilling assembly that can be located in a borehole and is moved along the borehole during the drilling operation; a flexible fluid supply line connected to and in fluid communication with the drilling assembly and extending from the drilling assembly to the surface when the drilling assembly is in the borehole; and an electric cable for providing electric power to the drilling assembly and extending from the drilling assembly to the surface when the drilling assembly is in the borehole; the fluid line and the electric cable are separate, and the electric cable being outside the fluid line. A method for conducting drilling operations using an apparatus as defined above, comprises operating the drilling assembly and directing fluid between the surface and the drilling assembly via the flexible fluid line.