Electropulse Drilling

a drilling method in which rock is broken by a powerful high-voltage (up to 200 kilovolts) electric discharge—that is, by electrical breakdown—in the rock face at the bottom of a hole filled with a liquid dielectric, such as oil or diesel fuel. The method was developed in the late 1960’s in the USSR by A. A. Vorob’ev and others.

The drill consists of a serrated annular electrode and a central electrode. During drilling, the electrodes are pressed against the bottom of the hole and the central electrode is rotated to produce successive electrical breakdowns at a specific rate over the entire area of the hole. The rock is broken because of the stresses that develop in it during electrical breakdown. Cuttings are removed by circulating the liquid dielectric.

The drilling efficiency does not depend on the hardness of the rock or on the depth of the hole but is determined by the electrical-breakdown parameters and the conditions under which the cuttings are removed. The drilling rate may be as high as 6–10 m/hr.

Electropulse drilling is used to drill holes in dense rock that has a high resistivity and that does not absorb the liquid dielectric circulating in the hole.