Bi-Directional Wellhead Packoff Locking for De-Energized Seal Retrieval
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Solution Overview
Problem
In wellhead annulus packoffs, the lowest seal, such as a lower energizing ring, often gets retrieved in an energized position, leading to increased retrieval loads and issues like wedge pinch points, which prevent complete recovery and require additional de-energizing force, especially with recessed seal pockets in the wellhead housing.
Innovation Solution
A retainer lock mechanism is introduced that anchors the lowest seal component, allowing it to de-energize before retrieval, reducing the required force and preventing pinching by maintaining the seal's elevation and stability during de-energization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lowest seal is retrieved in an energized position, then the seal maintains its sealing function, but retrieval loads increase and complete recovery is prevented
Solution Approach 1:
The retainer lock mechanism is engaged before retrieval to preliminarily secure the lowest seal in place. This preliminary action prevents the seal from moving into a position where it would create wedge pinch points, allowing for easier subsequent retrieval while maintaining sealing integrity during the operation.
Solution Approach 2:
The retainer lock mechanism acts as an intermediary between the lowest seal and the retrieval system. It provides a controlled interface that allows the seal to be securely held during energization while facilitating smooth retrieval by preventing direct contact between the seal and tapered surfaces that would create pinching forces.
2Ease of operation
If de-energizing force is increased to retrieve the seal, then the seal can be removed from the pocket, but radial squeeze increases through the tapered interface
Solution Approach 1:
The retainer lock mechanism serves as an intermediary device that decouples the retrieval force from the seal. By engaging the retainer lock, the seal is held securely while the retrieval force is applied to the retainer lock mechanism itself, preventing direct transmission of high radial squeeze forces through the tapered interface of the seal pocket.
Solution Approach 2:
The retainer lock mechanism is engaged in advance to establish a secure connection with the lowest seal. This preliminary engagement creates a controlled release mechanism that allows the seal to be retrieved without requiring excessive de-energizing force, thereby preventing harmful radial squeeze through the tapered interface.
3Force
If the retainer lock mechanism is engaged, then the lowest seal is secured and retrieval force is reduced, but the mechanism complexity increases
Solution Approach 1:
The retainer lock mechanism is designed to nest within the existing wellhead annulus packoff structure. It integrates with the lowest seal and the wellhead housing, utilizing existing spaces and interfaces. This nesting approach minimizes the addition of external components and reduces overall mechanism complexity while still providing the force reduction benefits.
Solution Approach 2:
The retainer lock mechanism is designed to perform multiple functions: securing the lowest seal during energization, facilitating controlled retrieval, and preventing wedge pinch point formation. By consolidating these functions into a single integrated mechanism rather than multiple separate components, the overall device complexity is minimized while achieving the desired force reduction.
Data Source
AI summary
A wellhead annulus packoff and an associated method is disclosed. A retainer lock mechanism of the wellhead annulus packoff is to sit at least partly within a first indentation of a hanger. The retainer lock mechanism includes a bottom surface and a side surface so that the bottom surface is to be associated with a lower energizing ring and the side surface is to be engaged in an energized state with a first side of the seal element. A second side of the seal element is to abut with a surface of a housing and a slot of the seal element is to abut with the lower energizing ring in the energized state of the wellhead annulus packoff.