The results of field tests proved that PDC anchor bit is ideal in mid hard rock drilling.

现场试验结果表明，PDC锚杆钻头是钻进中硬岩层的理想钻头。

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The revolving-drilling technique is one of the new-type and effective methods for hard rock drilling.

冲旋钻井技术是一种新型、高效钻进硬地层的方法。

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Potter Drilling of California uses jets of superheated fluid to break through granite five times faster than traditional techniques, which don't do well against hard rock types.

加利福尼亚的Potter Drilling5次使用过热液体穿透花岗岩，花费时间比传统工业快很多，不过这种工艺在试用硬质岩石时表现不佳。

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