It frequently occurs during exploitation in some oilfields thatthe oil pipes were jammed by cement slurry. The jammed pipes were usually discarded as useless, which caused a big loss of economy.Based on systematically studyingthe flowlawand dynamic properties of high pressure water jet, the mechanism of rock cutting with hy-draulic and mechanical method was analyzed in detail, water jet parameters were adjusted accordingto conditions and applications, furthermore, the cutters and the nozzles were suitably locate d in the bit. A new technology to cleaning jammed oil pipes with high pres-
sure water jet was presented in the paper, and that special cleaning
equipment and tools were worked and turned out. The technology is a great breakthrough in field.