Equalizer Valve Assembly for Cementing Plug Pressure Relief
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Solution Overview
Problem
Existing cementing assemblies fail to reliably relieve fluid pressure in the trapped volume between the casing string and the work string during well cementing operations, which can lead to damage or premature release of cementing plugs, especially when the trapped volume is large.
Innovation Solution
A cementing assembly with a sealing device that isolates a portion of the trapped fluid volume and relieves pressure at a controlled rate, using a combination of equalizer valves and a sealing device that separates the annular space into upper and lower regions, allowing pressure to be relieved quickly and preventing damage to the cementing plugs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If equalizer valves are included in the work string to relieve pressure in the trapped volume, then pressure relief is achieved, but the relief rate is insufficient to prevent damage to cementing plugs when the trapped volume is large
Solution Approach 1:
The patent divides the trapped fluid volume into two separate regions using a sealing device: an upper region and a lower region. The lower region, which is in direct communication with the cementing plug, is isolated from the upper region. This segmentation allows the equalizer valve to relieve pressure only from the lower region, ensuring rapid pressure relief at the critical interface with the cementing plug, while the upper region can maintain higher pressure to balance forces on the plug.
Solution Approach 2:
The patent applies different pressure conditions to different parts of the trapped fluid volume. The lower region adjacent to the cementing plug is maintained at a lower pressure through active relief by the equalizer valve, while the upper region maintains higher pressure. This local differentiation of pressure quality ensures that the critical area (lower region) experiences controlled pressure relief to prevent plug damage, while the upper region provides force balance.
2Volume of stationary object
If the trapped volume of fluid is large, then the cementing operation can accommodate larger casing strings, but the pressure buildup exerts excessive downward force on cementing plugs causing damage or premature release
Solution Approach 1:
The sealing device segments the large trapped volume into upper and lower regions, allowing the system to accommodate large overall volumes while controlling the pressure in the critical lower region. The equalizer valve relieves pressure only from the lower region, maintaining force balance on the cementing plug even when the total trapped volume is large.
Solution Approach 2:
The patent creates local pressure differentiation within the trapped volume: the lower region experiences reduced pressure through active relief to minimize downward force on the cementing plug, while the upper region maintains higher pressure to provide overall force balance. This local quality control allows large trapped volumes to coexist with protected cementing plugs.
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 solution effectively prevents damage and inadvertent release of cementing plugs by rapidly relieving fluid pressure, ensuring the plugs remain secure and functional, even with large trapped volumes of fluid.
Implementation Method 1
relieving the fluid pressure within the isolated volume of fluid at a first rate sufficient to prevent damage to or inadvertent release of the cementing plug
Implementation Method 2
a sealing device that isolates a portion of the trapped volume of fluid
Data Source
AI summary
A method for controlling a fluid pressure applied to a cementing plug comprises disposing the cementing plug within a casing string to define a trapped volume of fluid within the casing string, isolating a portion of the trapped volume of fluid adjacent the cementing plug to define an isolated volume of fluid, and relieving the fluid pressure within the isolated volume of fluid at a first rate sufficient to prevent damage to or inadvertent release of the cementing plug. An apparatus for relieving fluid pressure within a casing string being run into a well bore comprises at least one equalizer valve connected to a work string extending into the casing string, and a sealing device disposed above the equalizer valve to seal an annular space formed between the work string and the casing string.