Downhole Flow Pulsing Device for Casing Recovery
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Solution Overview
Problem
The existing methods for well abandonment and casing recovery face challenges in pulling long lengths of cut casing due to binding materials like drilling fluid sediments and settled solids, which limit the pulling capacity of drilling rigs, requiring multiple trips and potentially damaging the casing with impact forces or vibrations.
Innovation Solution
An apparatus comprising a string with a hydraulic jack, a downhole flow pulsing device, and a pressure drop sub, which creates a cyclic pressure variation to dislodge sediments and increase the vibratory pull, allowing longer casing lengths to be removed efficiently without splitting the casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional impact force methods (hydraulic jar) are used to free stuck casing, then the casing may be freed from binding materials, but the casing may be damaged by the impact forces
Solution Approach 1:
The patent applies periodic vibratory motion through a downhole flow pulsing device that creates cyclic pressure variations in the drilling fluid. This periodic action loosens binding materials (sediments, partial cement, sand) between the casing and surrounding body, enabling gradual extraction without impact damage. The vibratory pull is applied continuously in a controlled manner rather than through sudden impacts.
2Productivity
If drilling rig pulling capacity is increased to recover longer casing lengths, then fewer trips are required, but the friction losses in the drill string increase, reducing power at the casing spear
Solution Approach 1:
The patent employs mechanical vibration generated by a downhole flow pulsing device that creates cyclic pressure variations. This vibration reduces friction between the casing and binding materials in the annulus, and also reduces friction in the drill string itself, allowing more power to reach the casing spear over longer distances. The vibratory motion breaks the static friction that develops in the drill string, enabling efficient power transmission over longer casing lengths.
Solution Approach 2:
The patent uses hydraulic pressure variations transmitted through the drilling fluid to generate vibratory motion downhole. A flow pulsing device creates cyclic pressure changes that propagate through the fluid column, delivering mechanical energy to the casing without requiring increased surface pulling capacity. This hydraulic mechanism overcomes drill string friction losses by generating force directly at the casing location.
3Force
If multiple trips are made to cut casing into shorter lengths for recovery, then the drilling rig's limited pulling capacity is not exceeded, but the time and cost of the operation increase
Solution Approach 1:
The downhole flow pulsing device generates vibratory motion that reduces friction between the casing and binding materials, enabling the recovery of longer casing lengths (e.g., 100-200 meters or more) in a single trip. This eliminates or reduces the need for multiple trips to cut and recover shorter sections, significantly reducing operation time and cost while staying within the drilling rig's pulling capacity limits.
Solution Approach 2:
The patent changes the physical state and properties of the binding materials through vibratory action and pressure variations. By applying cyclic pressure and vibration, the binding strength between sediments, partial cement, and sand is reduced, transforming the friction characteristics to enable longer casing extraction. This parameter change allows recovery of casing lengths that would otherwise require multiple trips.
4Productivity
If vibratory pull is applied to dislodge sediments and free the casing, then longer casing lengths can be recovered, but the complexity of the apparatus increases
Solution Approach 1:
The downhole flow pulsing device serves multiple functions: it creates vibratory motion to dislodge sediments, generates cyclic pressure variations to loosen binding materials, and transmits power through the drilling fluid. By combining these functions in a single downhole apparatus, the patent achieves long casing recovery without requiring multiple separate tools or complex surface equipment modifications.
Solution Approach 2:
The vibratory pull mechanism is self-contained downhole, using the drilling fluid itself as the power transmission medium. The flow pulsing device utilizes the existing drilling fluid circulation system to generate vibratory motion, eliminating the need for separate power sources or complex mechanical linkages. The system serves itself by using the fluid already present in the wellbore to transmit the vibratory energy to the casing.
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
Enables the removal of longer casing lengths with reduced risk of sticking, utilizing a combination of hydraulic and vibratory forces to overcome binding materials, thus enhancing the efficiency of casing recovery while minimizing damage.
Implementation Method 1
a downhole flow pulsing device for varying fluid flow in the throughbore and thereby superimpose a cyclic pressure on the first pressure
Implementation Method 2
a hydraulic jack, the hydraulic jack comprising an anchor for axially fixing the apparatus to a tubular in the well, and an inner mandrel axially moveable relative to the anchor in response to the fluid at a first pressure in the throughbore
Implementation Method 3
fluid at the first pressure superimposed with the cyclic pressure operates the hydraulic jack so that the inner mandrel oscillates as it moves axially and pulls the length of casing
Data Source
Figure 1a~1f
Figure 2a~2b
Figure 3a~3b
AI summary
A method and apparatus for casing recovery for well abandonment. A string is run-in, the string including a hydraulic jack (18), an anchor (28), a casing spear (20), a downhole flow pulsing device (22) and a pressure drop sub (24). The casing spear grips an upper end of the length of casing to be pulled. The anchor is set in casing of a greater diameter above the length of cut casing. Fluid pumped through the string and through the pressure drop sub will increase fluid pressure at the hydraulic jack to a first fluid pressure (78). Fluid pumped through the downhole flow pulsing device will vary the fluid flow superimposing a cyclic pressure (82) on the first pressure (78), causing oscillation of an inner mandrel (30) of the hydraulic jack. The jack moves the oscillating inner mandrel upwards relative to the anchor to pull the length of casing.