topdrive

Topdrive, usually written as top drive, is a drilling equipment system used on oil and gas rigs to rotate the drill string. Mounted at the top of the derrick or mast, a top drive provides the rotational torque to the drill string and serves as an alternative to the conventional rotary table.

A top drive assembly consists of a motor (electric or hydraulic) connected to a gear train that drives a quill connected to the drill pipe. It travels up and down the derrick on a vertical track and is operated via surface controls or a computerized control system. Pipe stands are fed into the string by a separate pipe-handling system, allowing simultaneous rotation and drilling or tripping.

Advantages include improved safety and efficiency, the ability to rotate and drill while pulling or running pipe, better directional drilling control, and the capacity to handle longer and heavier stands without counterweights required by a rotary table. Top drives are commonly used on offshore and onshore rigs and have become standard on many new installations; they can be electric or hydraulic powered and are controlled by surface PLCs and monitoring systems.

History and adoption: The top drive concept emerged in the late 20th century as an alternative to rotary tables, with widespread adoption from the 1990s through the 2000s as rigs sought to reduce non-productive time and improve drill rates. Today, several major oilfield equipment manufacturers supply top-drive systems, and the approach remains a common method for modern drilling operations.