An enlarged pipe at the top of a casing string that serves as a funnel to guide drilling tools into the top of a well.

套管柱顶部的一根大口径管，形如漏斗，以引导钻井工具进入到井眼的顶部。

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The adapter between the first casing string and either the BOP stack (during drilling) or the wellhead (after completion).

在第一根套管柱和防喷器组(钻井时)或完井后的井口之间的一个接头。

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