Disconnect Sub Tensile Break Design for Downhole Sealing
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Solution Overview
Problem
Existing downhole sealing devices in oil and gas wells require complex and often inefficient methods to disconnect from drill pipes, which can disrupt cement operations and increase the need for additional remedial work.
Innovation Solution
A disconnect sub with a designed disconnection point of lower tensile break value than the rest of the body, allowing for either rotational or tensile disconnection, maintaining an open-ended pipe for further operations like cementing, and optionally featuring a slick outer diameter and internal tapered profile for tool passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical setting tool with large outer diameter components is used to convey and set the bridge plug, then the plug can be reliably positioned and set at the desired depth, but the tool must be completely removed from the well and replaced by a smaller diameter pipe, which disrupts cement operations and requires additional remedial work
Solution Approach 1:
The disconnect sub is segmented into two main parts: a body portion with a smaller outer diameter for efficient cementing operations, and a threaded connection portion that interfaces with the bridge plug. This segmentation allows the tool to function as both a setting tool and a cementing pipe, eliminating the need for complete tool removal and replacement
Solution Approach 2:
The invention transitions from a single large-diameter mechanical setting tool to a composite structure where the disconnect sub provides a smaller outer diameter profile. This dimensional change enables the pipe to remain in the well during cementing operations, improving cement flow and reducing the need for additional remedial operations
2Ease of operation
If the drill pipe is pulled in tension to break a threaded stud and release the plug, then the plug can be released from the drill pipe, but the pipe does not remain open-ended and the upper portion of the plug cannot be retrieved
Solution Approach 1:
The disconnection point is created with local quality differences - it has a lower tensile break value than the rest of the wall of the body. This localized weakness ensures that when tensile force is applied, the disconnection point fails first, creating a clean break that leaves the pipe open-ended while allowing the upper portion of the plug to be retrieved
Solution Approach 2:
The disconnection point is pre-designed with a lower tensile break value before deployment. This preliminary preparation ensures that when tensile force is applied during plug release, the disconnection point will fail at a predictable load, providing both plug release capability and maintaining an open-ended pipe for further operations
3Productivity
If a disconnect sub with a disconnection point of lower tensile break value is used, then rapid disconnection is enabled and clean break for tool passage is achieved, but the wall structure must be intentionally weakened at the disconnection point
Solution Approach 1:
The wall of the body has different properties at the disconnection point compared to the rest of the structure. The disconnection point is intentionally designed with a lower tensile break value through features such as reduced wall thickness, notches, or material property changes at that specific location, while the rest of the wall maintains full strength for normal operations
Solution Approach 2:
The disconnection point is designed as a sacrificial element that is intended to fail under tensile load. This disposable portion of the wall allows the disconnect sub to function as a temporary conveying tool that can be released by breaking a predetermined weak point, enabling rapid disconnection while maintaining overall structural integrity during deployment
Data Source
AI summary
A disconnect sub is connected at one end to a pipe for deployment into a well, where the disconnect sub is then connected to a downhole sealing device such as a plug. The disconnect sub comprises a disconnection point that has a lower tensile break value than the rest of the plug, and has a predetermined tensile break value such that the disconnection point will fail when a threshold value of axial tensile load is applied to the disconnect sub. This offers two methods of disconnection of the pipe from the plug after the plug has set—firstly, rotation of the pipe, or if rotation is not possible, overpull of the pipe in excess of the threshold will cause failure of the disconnection point and separation of the pipe from the plug.