BOHRLOCHWERKZEUG

A downhole tool for providing a thrust force to an elongate body extending in a borehole formed in an earth formation is provided. The tool comprises at least one rotatable body provided with a plurality of rollers, each roller being expandable against the borehole wall at a selected contact force between the roller and the borehole wall. The rollers are oriented when expanded against the borehole wall so as to roll along a helical path on the borehole wall, and a motor is provided to rotate each rotatable body. The tool further comprises a device to measure the thrust force provided by the tool and a control system to control the thrust force provided by the tool by regulating the rotative torque of the rotatable body, in response to the measured thrust force.