CORE EXTRACTOR Russian patent published in 2017 - IPC E21B25/08 

FIELD: oil and gas industry.

SUBSTANCE: core extractor comprises a tubular housing, an upper and a lower subs, a drill head, a core receiver comprising rotation support and adjustable suspension at the upper part, and a device for separating core from bottom hole at the lower part. The adjustable suspension is made in the form of a threaded tubular element having end-to-end channels for pumping drilling fluid through the cavity between the tubular housing and the core receiver. The core extractor additionally comprises core receiver isolator consisting of a nipple, a safety coupling, a threaded sleeve with thrust shoulder and thrust washer positioned between the upper sub and the upper part of the tubular housing. The threaded tubular element is made two-threaded with additional internal thread, the thrust washer is positioned in the inner bore of the nipple, placed on the part of the upper sub, the threaded sleeve is provided with a device for thread tensing arranged at the thrust shoulder. The threaded tubular member element is additionally attached to the nipple using the additional internal thread with the threaded sleeve, having the thrust shoulder, and the thrust washer mounted in the internal bore of the metioned nipple. S thread pitch of the safety coupling in conjunction with the nipple, T thread pitch of the safety couling in conjunction with the upper part of the tubular housing and T thread pitch of the nipple in conjunction with the upper sub are connected by ratio S = (3.5÷4.5) T. N thread pitch of the nipple in conjunction with the threaded tubular element and M thread pitch of the threaded tubular element additional internal thread in conjunction with the threaded sleeve are connected by ratio N = (1.4÷1.7) M.

EFFECT: increased salvage operation reliability of drill head, housing and core extractor centralizers, increased reliability of drill string disconnection at the point of core reciever isolator installation.

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