| 摘要 |
A drill collar 10 designed with a fishing neck 20 just behind the pin end 16 of the collar, which has a reduced dimension compared with the box end 14 of the drill collar. This tool is particularly well suited for being oriented with its pin end up in a drill string. The bending strength ratio is increased while the collar retains good "fishability" and "washoverability" characteristics. <IMAGE>
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