Rock drilling is enhanced by neutralizing the rock surface charge with respect to the drilling fluid. The isoelectric condition is obtained by nullifying the zeta potential of the rock surface by chemical additives such as surfactants or any material. Drilling enhancement is maintained as long as the rock zeta potential registers a zero reading. An apparatus and method is disclosed to achieve and maintain this isoelectric condition and provide for the maximal drilling rate and drill bit life. Drilling with the zero zeta potential concentrations of zrcl4, alcl3, cacl2, and nacl were found to extend the bit life by 68, 99, 73, and 76 pct, respectively, compared with drilling with distilled deionized water. This occurred while the drilling rates were enhanced by 96, 97, and 115 pct for zrcl4, cacl2, and nacl, respectively.
U.S. Pat. 4,765,415, Aug. 23, 1988