or drill string threads. (To this end, rotary subs are sometimes referred to as "kelly savers.") Lift subs are used to handle bottom hole assembly (BHA) components such as drilling motors, jars, and ...

A BHA often includes a downhill motor and rotary steering system in addition to MWD and LWD systems. Mechanical and electrical power is often provided by a downhole turbine. MWD strictly quantifies ...