Drilling-Type Underreamer | SLB

Drilling-Type Underreamer

Retractable, retrievable underreamer with application-specific cutting structures

Three Schlumberger workers performing maintenance on a drilling-type underreamer.

The drilling-type underreamer (DTU) is designed to run in conjunction with a drill bit or a bullnose, depending on pilot hole condition or project objectives.

Reliable deployment and retraction

The DTU's three retractable cutting arms are opened and held in position by continuous hydraulic pressure. Cutters are retracted by disengaging the pump, enabling the tool to be repositioned for selective underreaming operations or retrieval from the well. A piston spring assists with arm retraction following interruption of hydraulic pressure.

Diamond underreamer.
Up to 75% graphic.

75% increase in hole diameter

The three-arm design enables the pilot hole diameter to be increased by up to 75% depending on tool size. Cutter arms can be changed quickly on the rig floor. The underreamer design facilitates fluid passage to the bit or jetted bullnose.

Application-specific cutting structures

Milled tooth, tungsten carbide insert (TCI), or polycrystalline diamond compact (PDC) cutters can be used according to the application.

Illustration of a drilling-type underreamer.