Packer Back-Up System Using Iris Mechanism for Extrusion Control
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Solution Overview
Problem
Packer elements in subterranean formations face issues with extrusion under high differential pressures and temperatures, leading to compromised seal integrity, especially in larger diameter applications where back-up rings fail to provide sufficient resistance against unwanted extrusion.
Innovation Solution
An annular seal assembly with expandable elements and pivot blade back-up elements that expand radially to prevent extrusion, utilizing guide rings and ramps to move the back-up elements from a retracted to an expanded position, ensuring the expandable element remains contained and maintaining seal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If larger diameter packer elements are used in high pressure and temperature environments, then the sealing capability and pressure resistance are improved, but the risk of extrusion through gaps between packer OD and tubing/casing ID increases
Solution Approach 1:
The back-up element is divided into multiple pivot blades that can independently pivot and expand. This segmentation allows the back-up element to conform to the tubing or casing ID and provide effective resistance against extrusion forces while maintaining seal integrity in high pressure and temperature environments.
Solution Approach 2:
The back-up element transitions from a static structure to a dynamic one through the pivot mechanism. The pivot blades can rotate about pivot points to expand radially outward when extrusion forces are applied, providing adaptive resistance that maintains reliability under varying pressure conditions.
2Device complexity
If traditional back-up rings are used in high expansion applications, then the device complexity is kept simple, but the resistance to extrusion of elastomeric element is insufficient
Solution Approach 1:
The pivot blade mechanism transforms a simple static ring into a dynamic structure that can expand radially when needed. The blades pivot about fixed points to increase their radial extent, providing enhanced extrusion resistance only when extrusion forces are present, thus maintaining simplicity when not in use while providing strength when needed.
Solution Approach 2:
The pivot blades are nested within the back-up element housing in a retracted state, occupying minimal space. When expanded, they protrude radially to provide extrusion resistance. This nesting allows the back-up element to maintain a compact profile during normal operations while providing full protective function when required.
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
The solution effectively prevents extrusion of packer elements into the annulus, enhancing the structural integrity of the seal and maintaining the seal's effectiveness even in high-pressure and high-temperature environments.
Implementation Method 1
The guide ramps are configured to receive the back-up element in a retracted position and move the back-up element to an expanded position wherein the outer diameter of the back-up element substantially contacts the inner diameter of the tubing string or casing
Data Source
AI summary
An annular sealing assembly and method are disclosed. The assembly includes a mandrel and an expandable element disposed around the mandrel which expands to seal against the inner diameter of a tubing or casing string. The expandable element seals the mandrel from the annulus between the mandrel and the tubing string. The assembly includes at least one back¬up element having a plurality of pivoting blades circumferentially secured in a ring around the mandrel. The back-up element is capable of radially expanding and contracting upon longitudinal movement along, and engagement with, a generally ring-shaped ramp. A guide ring guides the back-up element along the guide ramp. The method is directed to expanding the expandable element to seal the annulus and the back-up element so the blades come in contact with the inner diameter of the tubing string preventing the expandable element from extruding outward into the annulus beyond the back-up element.