| 摘要 |
A downhole abrading tool (10) has a body (20) with a first end (12) for c onnection to a drill string, a cutting end (14), an exterior surf ace (21), a drilling fluid passageway (26), a valve (80), and a chamber (18). Upon exp osure of the chamber to a wellbore fluid pressure due to excessive wear on t he cutting end, the valve opens. The opening of the valve permits drilling f luid to flow from the drilling fluid passageway, through the exterior surfac e and into the wellbore. The flow of drilling fluid through the exterior sur face causes a pressure drop that is detected at the surface by an operator o f the downhole abrading tool. The valve movement may also cause the release of taggants, or indicators, into the drilling fluid that may also be detecte d by the operator, either visually or with the aid of detection equipment.</ SDOAB>
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