Agitator Vibration for Cement Plugging in Well Abandonment
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Solution Overview
Problem
Existing methods for plugging oil and gas wells without removing the production tubing and Xmas tree often result in inadequate cement barriers due to the tubing's non-central positioning and smooth contact with the casing, preventing a full radial bond and leading to insufficient cement plug formation.
Innovation Solution
An agitator assembly is deployed through the production tubing, which vibrates the tubing to create movement and allow cement to form a full plug across the wellbore diameter by oscillating discs generating pressure pulses and causing the tubing to move, ensuring cement can pass between the tubing and casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cement is injected through production tubing without removing tubing and Xmas tree, then cost and time are reduced, but cement barrier quality becomes inadequate
Solution Approach 1:
The patent applies mechanical vibration to the production tubing during cement injection to prevent the tubing from remaining in static contact with the casing. The vibration causes the tubing to oscillate and move slightly, creating gaps that allow cement to flow radially outward and form a complete barrier around the tubing, thereby resolving the contradiction between maintaining tubing in place and achieving adequate cement bonding.
2Loss of time
If production tubing is left in position during plugging, then removal cost and time are saved, but tubing contacts casing preventing full radial cement bond
Solution Approach 1:
Vibration is applied to the production tubing to create dynamic movement that prevents continuous contact with the casing interior surface. This mechanical oscillation allows cement to access the annular space between tubing and casing, forming a radial bond that would otherwise be impossible when tubing remains static and in contact with the casing.
Solution Approach 2:
The vibration creates periodic motion in the tubing, causing it to oscillate back and forth around its central position. This periodic action intermittently opens the gap between tubing and casing, allowing cement to flow outward in pulses and establish a complete radial barrier, thereby achieving high-quality cement plug formation without tubing removal.
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 technique significantly improves the length and quality of the cement plug, potentially doubling its effective length compared to static tubing methods, providing a reliable and cost-effective solution for well abandonment without the need to remove the Xmas tree and production tubing.
Implementation Method 1
An agitator assembly is deployed through the production tubing, which vibrates the tubing to create movement and allow cement to form a full plug across the wellbore diameter
Implementation Method 2
oscillating discs generating pressure pulses and causing the tubing to move
Data Source
Figure 1
Figure 2
AI summary
A method of cementing an oil or gas well for abandonment comprises cutting the production tubing 6 above the production packer 8, setting a tubing plug 9 in the tubing and then cutting the tubing. A bridge plug may be installed at the level of the cut, which spans the full diameter of the well casing 3. An agitator assembly 20 comprising an agitator 24, packer 21 and burst sub 23, with a running tool fitted to the top, is run down the tubing on wire line. Cement is then injected into the tubing 6, which flows through the agitator assembly and causes the tubing to vibrate. The cement fills the tubing but also flows back up the A annulus between the casing and production tubing. Vibration of the tubing assists the formation of a good quality cement plug extending all around the annulus over a substantial length of the well.