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Improved Downhole Tool Cutter Arm/Anchoring Blade Opening Mechanics Using a “Geared” Linkage and Other Methods

IP.com Disclosure Number: IPCOM000239225D
Publication Date: 2014-Oct-22
Document File: 10 page(s) / 4M

Publishing Venue

The IP.com Prior Art Database

Abstract

Reamer cutter arm deployment can sometimes be challenging in certain extreme applications, influenced by the specific cutter arm design employed as well as the operational downhole environment. Solutions are proposed below to mitigate these issues.

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Improved Downhole Tool Cutter Arm/Anchoring Blade Opening Mechanics Using a “Geared” Linkage and Other Methods

ABSTRACT

Reamer cutter arm deployment can sometimes be challenging in certain extreme applications, influenced by the specific cutter arm design employed as well as the operational downhole environment. Solutions are proposed below to mitigate these issues.

DISCUSSION

Reamer cutter arm deployment can sometimes be challenging in certain extreme applications, influenced by the specific cutter arm design employed as well as the operational downhole environment. The latter primarily driven by, but not limited to, the mud system employed (affecting mud lubricity, the potential of clay adherence to steel surfaces, etc.).

In some reamers, cutter arm actuation/deployment (or similar functionality of equivalent downhole tool, i.e. anchoring blade) resembles the basic make-up of a centric “crank-slider” linkage mechanism where the crank, coupler and slider respectively correspond to the upper-arm, lower-arm and traveling block.

Whereas “crank-slider” linkages actively load their hinge/pivot pins (thereby providing consistent force/contact locations), certain reamer cutter arm deployment loads have historically been applied to equivalent “bearing” surfaces (2x examples shown below). Although numerous pins are used within the cutter arm design it’s emphasized that they facilitate retraction and prevent parts from being lost-in-hole. Said “bearing” surfaces reflect a circle-/arc- segment rather than a true link and as such the well understood friction axis behavior of turning pairs no longer applies.

Prevalent Reamer cutter arm design implementation:

(no pin loading, only “bearing” surfaces stressed)

Recent (although infrequent)cutter arm design implementation:

(bottom pin loaded & top-/middle- “bearing” surfaces stressed)

Positive cutter arm deployment is achieved once the lower arm (~coupler) transfers a sufficiently large amount of force onto the upper arm (~crank) after overcoming internal friction, thereby producing the necessary opening moment to overcome rock strength (following activation) and/or BHA side-forces (during continued hole enlargement, i.e. after making a connection). During normal reamer tool operation, said net equivalent (middle hinge) force location is sufficiently offset from the top- and bottom- hinges producing actuation when applying sufficient pressure to the drive rod (= traveling block “driving” force, ~slider).

Stressing the middle hinge interface surface (instead of the actual pin) can furthermore have a significant impact on the required traveling block (~slider) “driving” force (as illustrated by the simplified example on the right).

Specifically, the middle hinge interface consists of both a lower- and upper- “bearing” surface and depending on manufacturing tolerances (as well as other operational factors) the less advantageous “bearing” surface may initially becom...