The Well Tractor functions with an electric over hydraulic power unit which feeds the drive sections. The power to generate the hydraulic pressure is supplied by the attached cable or e-line which also is used for control and communication purposes. All mechanical functions are hydraulic. The modular structure of the drive sections makes it possible to change the traction by reducing or increasing the number of active wheels.
Traction is provided by wheels pressed against the casing or borehole wall. When the Well Tractor is powered up, the wheels in each drive section are hydraulically extended out of the tool body and activated automatically as the tractor centralizes itself. Each wheel contains its own independent hydraulic motor, which drives the wheel and provides the forward motion of the tractor.
The Well Tractor overcomes the limitations of traditional e-line operations by being able to reach the toe of a deviated or horizontal well and carry out operations throughout the entire length of the wellbore.
The passive and immediate fail-safe features prevent the Well Tractor from getting stuck in the well bore with the arms and wheels extended. In the event of a power failure or shut-down the arms and wheels will automatically retract leaving a flush tool string which can be retrieved by winching in the e-line.
The e-line Well Tractor is currently available in three sizes: 2 1/8", 3 1/8" and 4 1/2" outside diameter.
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