Flexible Collet Anchor with Compressive Load Bypass
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Solution Overview
Problem
Existing collet designs for tubular strings are inadequate for supporting tools under high loads, such as 30,000 pounds, as they transmit stress through weak finger structures, and fail to effectively manage differential pressure stresses.
Innovation Solution
A collet assembly with flexible fingers and a surrounding landing sleeve that transmits compressive loads directly to the collet heads, bypassing the finger structure, and features an inward taper to align fingers axially, enhancing tensile loading and facilitating retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional collet design with thin-walled housing and extended dogs is used, then the device can be introduced into the string and selectively extended, but the stress on the housing gets to the dogs that are extended into the recess of the landing nipple, causing failure under high tensile loads
Solution Approach 1:
The housing is divided into thick-walled segments that form a rigid support structure, separating the load-bearing function from the extension mechanism. This segmentation allows the housing to resist stress while the dogs remain selectively extendable through windows in the thick-walled housing.
Solution Approach 2:
The housing combines thick-walled structural segments with integrated dog extension mechanisms, creating a composite structure where the thick walls provide stress resistance and the integrated dogs provide selective extension capability. This composite design resolves the contradiction between operational flexibility and structural strength.
2Strength
If a thick-walled collet design is used to increase strength, then the collet can support higher loads, but the collet loses flexibility for running in and setting when aligned with a groove of a tool
Solution Approach 1:
The collet assembly is segmented into multiple thick-walled collets that can independently flex and align with grooves in the tool. Each collet maintains sufficient thickness for strength while the segmented structure allows individual flexing during running in and setting operations.
Solution Approach 2:
The thick-walled collets are designed with dynamic flexibility, allowing them to flex and align with grooves during insertion and setting, then rigidify to support high loads when engaged. The thick walls provide the necessary dynamic response to transition between flexible and rigid states.
3Strength
If the fingers are oriented radially outward in the set position, then the collets are engaged in the recess, but the collets cannot retract easily when support is removed for retrieval
Solution Approach 1:
Instead of having the fingers oriented radially outward in the set position, the fingers are oriented radially inward, causing the collets to engage the recess from the opposite direction. This inverted orientation creates a retraction force that naturally pulls the collets out of the recess when support is removed, enabling easy retrieval.
Data Source
AI summary
A collet assembly has a housing and the collets disposed on flexible fingers connected to the housing at their opposed ends. A surrounding landing sleeve stops the assembly so that collets are aligned with a recess in a landing collar that is part of a surrounding tubing string. Once set the landing sleeve transmits compressive loads so that compressive stress essentially bypasses the finger structure supporting the collets. The fingers are initially tapered toward a longitudinal axis so that when internally supported they assume an aligned orientation to the housing axis to allow greater tensile loading and to provide a retraction force when the housing is to be removed after the collet support is removed.