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Failsafe Mechanism for Reaming Blades

IP.com Disclosure Number: IPCOM000249093D
Publication Date: 2017-Feb-03
Document File: 1 page(s) / 101K

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention comprises a new failsafe mechanism for expandable reamer blades. Current reamer designs require an angled blade track (typically between 10° and 15° relative to the tool axis) in order to allow the blades to be pushed back into the tool body in case of a system failure. In this case the blades are typically pushed back by pulling the tool into the casing. The invention allows different blade and blade track designs by incorporating a failsafe mechanism into the blade itself. The blade is made out of at least two parts which are connected with a certain feature, e.g. a dove tail guidance. The parts are movable along this guidance. In one direction the parts can be moved without limitation allowing the assembly and disassembly of the parts. In the other direction the movement in limited by a shoulder. This allows to transmit the complete reaming force without disengaging the blade parts. In case the blade is not being retracted properly, the outer part of the blade can be pushed against the casing and will disengage from the inner part. This allows the retrieval of the tool. In order to avoid the accidental disengagement of the blade parts a locking mechanism can be implemented (e.g. shear screws). This mechanism will release the outer part of the blade only after applying a certain force. In order to avoid the disengaged blade parts remaining in the bore hole a feature in the tool body can be designed to catch the lose parts. Current reamer designs require an angled blade track (typically between 10° and 15° relative to the tool axis) in order to allow the blades to be pushed back into the tool body in case of a system failure. In this case the blades are typically pushed back by pulling the tool into the casing. This mechanism allows blades to be expanded radially from the tool body without an axial movement. This can reduce the length of the reaming tool which is especially important for near-bit applications.

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Reaming Force

Inner blade part

Outer blade part

Tool Body

Pull-back Force

Inner blade part

Tool Body

Blade Movement

Shear Pin

Outer blade part Broken Shear Pin

Normal reaming operation

Failsafe mode (outer blade part detached) Casing