Underreamer with Radial Expandable Cutting Blocks

Abstract

A cutting tool (1) for widening the diameter of a borehole and method thereof is disclosed. The cutting tool (1) comprises a housing (2) having cavity (10) in which a moveable activation element (6) is arranged. The activation element (6) is moved in an axial direction and is connected to one or more cutting blocks via a mechanical coupling (15). The mechanical coupling (15) transfers the axial movement of the action element into a radial movement of the cutting blocks. An activation unit (24) pushes the activation element (6) towards a stopping position which in turn causes the cutting blocks (11) to move out of the housing. The activation unit (24) further pulls the activation element back towards its starting position which in turn causes the cutting blocks to move back into the housing. The cutting blocks (11) extend into one or more cavities formed in the activation element, thereby increasing the travel-to-expansion ratio. The cutting blocks can be replaced by stabiliser blades (20) which are used to stabilise the drilling in the expanded borehole.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a cutting tool for widening the diameter of a borehole and a method for operating the cutting tool. The cutting tool comprises a housing in which a cutting block and an activation element are arranged. Upon activation, the activation element is driven in an axial direction which in turn moves the cutting block in a radial direction from a retracted position to an expanded position via a mechanical coupling.BACKGROUND OF THE INVENTION[0002]Today, it is well-known within the oil, gas and water industries to widen the diameter of a borehole after the initial drilling using an underreamer having expendable blocks with a plurality of cutting elements, such as teeth or cutters. The initial drilling is done by using a cutting tool or drill bit without any expendable cutting blocks, also called a hole opener. The borehole is normally lined with one or more casing elements before the underreamer is inserted into the borehole. The u...

AI Technical Summary

Benefits of technology

The invention is a cutting tool that has improved torsion properties during use. It allows for a greater range of expansion and has a longer lifespan with more cutting elements. This results in more efficient cutting with less wear and tear on the tool.

Problems solved by technology

This solution is sensitive to torsion forces caused by the rotating movement of the tool due to the length of the slots.

This solution has a very limited radial movement since range of movement is limited to the thickness of the housing and thus the tool has a shorter lifespan compared to other underreamer tools.

However, this mechanism requires long elongated slots to expand and contract the arms making it sensitive to torsion forces.

Furthermore, the arms have limited space for the cutting elements thus increasing the wear and reducing the lifespan of the tool.

This solution is sensitive to torsion forces caused by the rotation of the tool due to the long elongated slots.

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