Centralizer for Refracturing Without Liner Hanger
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Solution Overview
Problem
Current refracturing methods require the use of a liner hanger that is time-intensive and expensive to deploy, and can cause stress points that may fail the liner or parent casing.
Innovation Solution
A centralizer system that is configured to land on the existing casing without anchoring, allowing for a cementing operation and slack weight to seal between the centralizer and the existing casing, eliminating the need for a liner hanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liner hanger is used to grip the inner diameter of the existing casing, then the liner hanger can be anchored in place, but substantial stress points are created between the liner hanger and the existing casing that can fail the liner or parent casing
Solution Approach 1:
The patent removes the liner hanger from the system entirely and replaces it with a centralizer that lands on the outer surface of the casing. This extraction eliminates the stress concentration points created by the liner hanger gripping the casing inner diameter, while still providing the necessary positioning and sealing functions through the centralizer's alternative mechanism of landing on the casing outer surface and using a packer for sealing.
Solution Approach 2:
The patent introduces a packer as an intermediary sealing element between the centralizer and the casing. The packer creates the necessary seal without requiring the centralizer to grip or anchor onto the casing, thereby eliminating the stress concentration points while maintaining the sealing function that would otherwise require the liner hanger to grip the casing.
2Reliability
If a liner hanger is positioned flush within the existing casing and mechanically slips grip inside the casing, then the liner hanger can be anchored, but the operation becomes time-intensive and expensive
Solution Approach 1:
The patent extracts the complex liner hanger anchoring operation from the refracturing process and replaces it with a simpler centralizer landing operation. The centralizer is run on a running tool to a desired depth and tagged, aligned with, or positioned on the proximal end of the existing casing, then raised and slacked to land on the casing. This eliminates the time-intensive mechanical slip gripping operation while maintaining the necessary positioning function.
Solution Approach 2:
The patent segments the refracturing operation into distinct functional components: the centralizer handles positioning and sealing, while the packer handles the sealing function separately. This segmentation allows each component to perform its function more efficiently without the time-consuming anchoring operations required by the integrated liner hanger system.
3Reliability
If the outer diameter of the liner hanger is made substantially similar to the inner diameter of the existing casing to enable anchoring, then the liner hanger can be secured, but the device complexity increases and more components are required
Solution Approach 1:
The patent extracts the anchoring function from the centralizer-casing interface and transfers it to the packer-casing interface. The centralizer only needs to land on the casing outer surface, requiring no precise dimensional matching between centralizer OD and casing ID. The packer provides the sealing and anchoring function separately, simplifying the overall device complexity while maintaining reliability.
Solution Approach 2:
The patent segments the sealing and anchoring functions into separate components: the centralizer provides positioning by landing on the casing, while the packer provides sealing and anchoring. This segmentation eliminates the need for the centralizer to have dimensions precisely matched to the casing, reducing manufacturing complexity and allowing for easier assembly and replacement.
4Reliability
If a packer is used to provide liner top integrity and prevent cement from dropping in the backside, then the operation becomes more expensive, but the centralizer with one-way valve can eliminate the need for the packer
Solution Approach 1:
The patent merges the sealing function into the centralizer by equipping it with a one-way valve that prevents cement from falling back before it sets. This integration eliminates the need for a separate packer component, reducing device complexity and component count while maintaining liner top integrity and preventing cement backflow.
Solution Approach 2:
The centralizer is designed to perform multiple functions: positioning by landing on the casing, sealing through the one-way valve mechanism, and preventing cement backflow. This multi-functionality replaces what would traditionally require separate components (centralizer plus packer), simplifying the overall system while maintaining all necessary functions for reliable refracturing operations.
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 centralizer system reduces the need for expensive anchoring and packer systems, minimizes stress on the casing during refracturing, and ensures effective cement placement, enhancing the integrity of the well.
Implementation Method 1
the centralizer may slack weight to be once again positioned on the proximal end of the existing casing to form a seal against the proximal end of the existing casing
Implementation Method 2
seal or prevent flow through in the first direction while allowing flow through the second direction via a check valve, flapper, or any other device that would allow one-way circulation
Data Source
AI summary
A downhole tool with a centralizer that is configured to land on the existing casing, be disconnected, pick up the centralizer, perform a cementing operation, and slack weight to seal between the centralizing and the existing casing, which will eliminate the need to utilize another linear hanger