Borehole Plug Retrieval via Lower Slip Assembly and Pressure Differential
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Solution Overview
Problem
Borehole plug designs face challenges with high shear loading on ratcheting patterns, leading to breakage under operating pressure, especially in applications like fracturing, where quick milling is required for zone treatment and multiple plug removals, and existing solutions fail to efficiently retrieve plugs to the surface without prolonging milling time.
Innovation Solution
A borehole plug design featuring a split lock ring with a wedge or triangular sectional shape and downhole-oriented surface treatment, allowing for differential pressure handling and plug retrieval by lowering pressure from above, enabling slips to disengage and flow back to surface equipment for safe removal, and incorporating sensors for data collection and analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ratcheting lock ring assembly is used to maintain plug set position, then the plug can hold differential pressure from above, but the ratchet teeth break under high shear loading within the operating pressure range
Solution Approach 1:
The patent removes the upper slip assembly from the plug design, eliminating the ratcheting lock ring assembly that was prone to failure. The plug relies solely on the lower slip assembly anchored in the lower cone for maintaining set position and holding differential pressure, thereby extracting the problematic ratcheting mechanism that caused ratchet tooth breakage under shear loading.
Solution Approach 2:
Instead of using a ratcheting mechanism that locks in one direction and releases in the other, the patent inverts the approach by using a simple cone-and-slip anchoring system that can be released by applying pressure in the opposite direction. The lower slip assembly anchored in the lower cone provides the locking function, while pressure applied from above releases it, eliminating the need for fragile ratchet teeth.
2Loss of time
If upper slips are eliminated to simplify design and shorten milling time, then milling time is reduced, but the plug may not reliably maintain set position under differential pressure
Solution Approach 1:
The patent concentrates the plug holding function entirely in the lower slip assembly anchored in the lower cone, rather than distributing it between upper and lower slips. This localized anchoring provides sufficient reliability for maintaining set position under differential pressure while eliminating the upper slips, thereby reducing milling time without compromising holding capability.
3Productivity
If plugs are flowed back to surface by lowering pressure from above, then plugs can be retrieved without milling, but plugs may slow down or fail to reach surface equipment in wells with increasing tubular size
Solution Approach 1:
The patent introduces a wiper assembly as an intermediary device that actively pushes plugs up the wellbore. The wiper, positioned above the plug, uses formation pressure differential to drive itself and the plug upward through the increasing tubular sizes, ensuring reliable delivery to surface equipment while maintaining high retrieval efficiency.
4Reliability
If multiple plugs are used for zone treatment, then zone isolation is improved, but removal time increases if milling is required
Solution Approach 1:
The patent eliminates the need for milling by removing the upper slips and ratcheting mechanism, allowing all plugs to be retrieved simply by lowering pressure from above and using formation pressure to flow them back to surface equipment. This extraction of the problematic upper slip assembly enables rapid removal of multiple plugs while maintaining zone isolation capability during treatment.
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
This design reduces the need for milling, lowers operational costs, and facilitates efficient plug retrieval and data collection, ensuring quick removal and analysis of plugs without prolonging treatment processes, while maintaining pressure integrity during treatment.
Implementation Method 1
a surface treatment on the lock ring that provides minimal resistance in the setting direction and resists reaction force from the compressed sealing element in the set position
Implementation Method 2
When the treatment is concluded pressure from above is relieved or lowered so that the plug or plugs disengage at the slips
Implementation Method 3
The plug is set with a setting tool that creates relative movement between a setting sleeve that is outside the mandrel and the plug mandrel
Data Source
AI summary
A borehole plug or packer for treating is designed to be flowed back to a surface location after use. When the treatment is concluded pressure from above is relieved or lowered, and well fluid is flowed back, so that the plug or plugs disengages at slips designed to resist differential pressure from above. The application of differential pressure from below causes the lower slips to release one or more of such plugs in the hole into specialized sub surface or surface capture equipment so that well pressure is relieved before removal of the plugs from specialized subsurface or surface capture equipment. Sensors to obtain and store data can be incorporated into the plugs or into objects landed on the plugs so that when brought to the surface the data can be processed and used in aid of production.