Segmented Cement Plug to Prevent Annular Ring Interference
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Solution Overview
Problem
Conventional cement displacement plugs (CDPs) with a large outer diameter create annular rings during milling, leading to interference with fluid circulation and cutting transport, and are difficult to install and costly due to large rubber molds, especially in smaller casing strings.
Innovation Solution
A segmented cement plug with annular wiper fins and gaps that break apart during milling, allowing for a smaller drill bit to be used, and features optimized outer diameter and apertures for easy installation and fluid flow, with a sealing element for rotational locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cement displacement plugs with large outer diameter are used, then they can form effective barriers between fluids, but they create annular rings during milling that interfere with fluid circulation and cutting transport
Solution Approach 1:
The wiper fins are divided into multiple segments by introducing radial gaps, allowing the fins to break into small pieces during milling rather than forming annular rings. This segmentation enables effective fluid barrier functionality while eliminating the harmful annular ring byproduct that interferes with circulation and cutting transport.
2Reliability
If conventional cement displacement plugs with large outer diameter are used, then they can provide adequate sealing, but they are difficult to install and costly due to large rubber molds
Solution Approach 1:
The plug is designed with segmented wiper fins containing radial gaps, which allows the overall outer diameter to be reduced while maintaining sealing capability through the flexible fin segments. This reduction in size makes the plug easier to install and reduces manufacturing costs by enabling smaller rubber molds to be used.
Solution Approach 2:
The wiper fins are designed as flexible segments that can deform and adapt to the casing inner surface, providing effective sealing even with a reduced outer diameter. This flexibility compensates for the smaller size while maintaining the barrier function, thereby easing installation and reducing mold requirements.
3Reliability
If conventional cement displacement plugs with thick wiper fins are used, then they can provide adequate sealing, but they create strong annular remnant rings that become lodged on equipment
Solution Approach 1:
The wiper fins are segmented into multiple sections by radial gaps, transforming thick continuous fins into thinner discrete segments. This segmentation maintains sealing effectiveness through the cumulative contact of multiple segments while ensuring that during milling, the segments break into small manageable pieces rather than forming thick annular remnant rings that could lodge on equipment.
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 segmented cement plug effectively mills without creating annular rings, reduces installation friction, and allows for efficient fluid flow and secure locking, minimizing wear and cost, while enabling quick removal with a smaller drill bit.
Implementation Method 1
allowing the at least one segmented annular wiper fin to frictionally engage with and wipe the inner surface of the casing string as the at least one plug travels through the casing string
Implementation Method 2
the cement slurry sets to form an annular sheath of hardened, substantially impermeable cement that bonds and stabilizes the casing string to the wellbore
Data Source
AI summary
An improved cement plug and methods of use for wiping the inner surface of a casing string positioned within a subterranean wellbore are provided, the plug having at least one annular wiper fin having at least one gap therethrough, the gap forming at least one wiper fin segment.