COUPLING FOR DUAL MEMBER PIPE

摘要

A coupling assembly (100) to interconnect an inner member (40) and an outer member (42) of a dual member drill string in torque transmitting engagement is disclosed. The coupling assembly (100) is adapted to transmit torque input from both members (40, 42) to a downhole tool. In one embodiment, the coupling assembly comprises a connector sub (102) that fixedly and non-fixedly couples both members. In another embodiment, the coupling assembly comprises a clutch mechanism (138) to interconnect both members when the rotational speed of the outer member exceeds the rotational speed of the inner member. In another embodiment, the coupling assembly comprises a mechanism to couple both members (40, 42) by axial downhole movement of the inner member (40) relative to the outer member (42). In another embodiment, the coupling assembly comprises a planetary gear system (556, 562, 558) that interconnects both members to provide high torque to the downhole tool at relatively low output speed of the dual member drill string.