Schlumberger

Drilling-Type Underreamer

Run in conjunction with a drill bit or bullnose

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, allowing 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.

75% increase in hole diameter

The three-arm design allows 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 may be used according to the application.

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Large Wellbore Solution Offshore the UK

Drilling-type underreamer (DTU)
To facilitate efficiently building a large wellbore, a 54-in DTU was chosen, featuring a three-arm design that allows the pilot hole size to be increased up to 75%. Read case study

DTU and Bullnose Specifications

Bullnose
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