Importance

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Abstract

A retrievable drill bit and cutter or reamer assembly includes a fluid-drive motor, an eccentric cutter part and a concentric bit in assembly and insertable in and retrievable from the interior of a drill stem without removing the drillstem from a wellbore. The eccentric cutter is disposed on a shaft connected to the output shaft of the motor and journals an accentric cylindrical bearing member mounted on the shaft. In response to rotation of the shaft in one direction, the cutter part is displaced into a position to enlarge the wellbore to permit progress of the drillstem therethrough and in response to rotation in the opposite direction, the cutter centers itself to permit retrieval of the bit assembly throught the drillstem. The fluid-driven motor engages locking splines on a sub at the lower end of the drillstem and may be inserted in and retrieved from the drillstem by drilling fluid in forward and reverse circulation, respectively.

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First Claim