water well drilling hard layer does not take the core, what drill bit is best (how much is a deep water well drilling machine)

装运水井钻机，要进行安全检查，钻机各部件要齐全电缆无漏电钻杆钻具等五损坏现象 进入施工场地，钻机钻塔要固定好，钻场面积要大于钻机...