Collapsible Bow Centralizer for Tight Clearance Retention
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Solution Overview
Problem
In oilfield operations, centralizers fail to maintain effective stand-off from the borehole wall in tight clearance sections, leading to incomplete cement encirclement and potential well failure due to the inability of collapsible bows to elastically return to their pre-collapsed state after passing through restrictions.
Innovation Solution
A centralizer design featuring a first collar with an inner diameter larger than the stop collar, a second collar with a smaller inner diameter, and a retainer with a bore smaller than the stop collar's outer diameter, along with collapsible bows connecting the collars, allows for proper assembly and retention on the tubular, ensuring effective centralization by collapsing the bows when passing through restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If collapsible bows are used to allow passage through restrictions, then the centralizer can navigate tight clearance sections, but the bows fail to elastically return to their pre-collapsed state causing centralization failure
Solution Approach 1:
The centralizer is divided into multiple collapsible bow segments that can independently deform during passage through restrictions. Each bow acts as a separate unit that can collapse and then recover, distributing the mechanical stress and improving the overall ability to navigate tight clearances while maintaining reliability.
Solution Approach 2:
The centralizer transitions from a static structure to a dynamic one where the bows can change shape and configuration. The bows are designed to be flexible and movable, allowing them to collapse during restriction passage and then elastically return to their original state, ensuring both adaptability and reliable centralization.
2Ease of operation
If the first collar has a larger inner diameter to allow stop collar passage, then assembly is simplified, but the retainer must have a smaller bore to block passage, adding complexity
Solution Approach 1:
The retainer is designed with non-uniform bore geometry, featuring different diameter sections along its length. The smaller bore section strategically positioned to block stop collar passage while the larger sections allow other components to pass through, enabling both simplified assembly and reliable retention without excessive complexity.
3Reliability
If the second collar has a smaller inner diameter to retain the centralizer, then centralizer retention is improved, but passage through restrictions becomes more difficult
Solution Approach 1:
The second collar is designed to work in conjunction with the collapsible bows, allowing it to effectively retain the centralizer during normal operation while the bows can collapse to reduce the overall profile during restriction passage. This dynamic interaction ensures both reliable retention and adaptability.
Solution Approach 2:
The retention function is distributed between the second collar and the collapsible bow structure. The second collar provides primary retention while the bows provide secondary retention and flexibility, allowing the system to maintain reliability without compromising the ability to pass through restrictions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design ensures the centralizer maintains the necessary stand-off and allows for the complete encirclement of cement around the tubular, preventing well failure by ensuring the bows elastically return to their pre-collapsed state post-restriction, thus ensuring effective cement placement and well integrity.
Implementation Method 1
it is generally desired for the collapsed bows to elastically return to their pre-collapsed state
Data Source
AI summary
A centralizer having a plurality of collapsible bows interconnecting a first collar and a second collar, with the centralizer disposed on a tubular with a stop collar, and an attachable retainer(s) of the centralizer blocking passage of the stop collar therethrough. The bows may have a yield strength of at least about 200,000 psi. Outer surface of the bows may have a coefficient of friction equal or less than about 0.02. Maximum radial thickness of centralizer when the plurality of collapsible bows is fully collapsed may be equal to or less than 3/16″. Centralizer may be rotatable relative to tubular. Centralizer having a split tubular body forming first and second collars connected by collapsible bows and a retainer to retain the split tubular body on the tubular, and the retainer, the first collar and/or the second collar providing a recess therein to receive a stop collar of the tubular.