这张未标日期的图片上的钻纹龟有两个头。
The diamondback terrapin in this undated photo has two heads.
预先评价未打开地层的岩石可钻性分布规律，对钻井施工提供指导是有实际意义的。
Evaluating rock drillability distribution rule before strata has been opened has practical significance to guidance of drilling construction.
就位接头与止动环用螺纹联结并上紧扣和钻柱连接下入井内，在未投入止回阀时作为钻柱上的一个接头。
The landing is thread connected with stop ring and tightened on and put into downhole with drill string. The landing sub is used as a sub above drill string before check valve is run in downhole.
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