- A method of drilling whereby an impact tool or bit, suspended in the well from a steel cable, is dropped repeatedly on the bottom of the hole to crush the rock. The tool is usually fitted with some sort of cuttingsbasket to trap the cuttings along the side of the tool. After a few impacts on the bottom of the hole, the cable is reeled in and the cuttings basket emptied, or a bailer is used to remove cuttings from the well. The tool is reeled back to the bottom of the hole and the process repeated. Due to the increasing time required to retrieve and deploy the bit as the well is deepened, the cable-tool method is limited to shallow depths. Though largely obsolete, cable-tool operations are still used to drill holes for explosive charge placement (such as for acquisition of surface seismic data) and water wells.
- rotary drilling