Casing Removal via Perforation and Fluid Displacement
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Solution Overview
Problem
In underground wells, the viscous and settled-out drilling mud creates significant drag on casings, limiting the length of casing that can be removed in a single operation, making it time-consuming and expensive to extract longer sections.
Innovation Solution
A method involving perforating the casing, injecting a high-pressure fluid with lower specific weight through the perforations to displace the mud, and then cutting and lifting the casing in sections, using expandable sealing elements to manage the process efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the casing is removed in a single operation without fluid displacement, then the operation is simple and quick, but the viscous drilling mud creates excessive drag that limits the removable casing length to 5-10 meters
Solution Approach 1:
The patent applies preliminary action by first forming perforations in the casing and then injecting fluid into the annulus before attempting to remove the casing. This preliminary fluid injection displaces the viscous drilling mud and reduces drag on the casing, enabling longer sections to be removed in a single operation. The perforations are formed at a first depth, fluid is injected, and only after this preparation is the casing removal attempted.
Solution Approach 2:
The patent utilizes hydraulics by injecting fluid under pressure through the perforations into the annulus surrounding the casing. This high-pressure fluid displacement mechanism replaces the viscous drilling mud with a less viscous fluid, significantly reducing the drag force on the casing and enabling longer sections to be extracted in one operation without requiring complex mechanical cutting systems.
2Productivity
If multiple lifting operations are used to remove longer casing sections, then the drag from viscous mud is managed, but the process becomes very time-consuming and expensive
Solution Approach 1:
The patent applies preliminary action by first forming perforations in the casing and then injecting fluid into the annulus before attempting to remove the casing. This preliminary fluid injection displaces the viscous drilling mud and reduces drag on the casing, enabling longer sections to be removed in a single operation. The perforations are formed at a first depth, fluid is injected, and only after this preparation is the casing removal attempted.
Solution Approach 2:
The patent utilizes hydraulics by injecting fluid under pressure through the perforations into the annulus surrounding the casing. This high-pressure fluid displacement mechanism replaces the viscous drilling mud with a less viscous fluid, significantly reducing the drag force on the casing and enabling longer sections to be extracted in one operation without requiring complex mechanical cutting systems.
3Reliability
If the annulus is filled with viscous and settled-out drilling mud, then the well is sealed and protected, but the drag on the casing becomes too large to remove longer sections in one operation
Solution Approach 1:
The patent introduces an intermediary fluid that is injected into the annulus through the perforations. This intermediary fluid acts as a mediator between the well sealing requirement and the casing removal operation. The injected fluid displaces the viscous drilling mud and provides a temporary reduction in drag, allowing the casing to be removed more easily while the well remains sealed during the operation.
Solution Approach 2:
The patent utilizes hydraulics by injecting fluid under pressure through the perforations into the annulus surrounding the casing. This high-pressure fluid displacement mechanism replaces the viscous drilling mud with a less viscous fluid, significantly reducing the drag force on the casing and enabling longer sections to be extracted in one operation without requiring complex mechanical cutting systems.
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 sections in a single operation by reducing drag and facilitating the extraction of viscous and settled-out drilling mud, thereby reducing the time and cost associated with casing removal.
Implementation Method 1
The pressurized fluid has a lower specific weight than said viscous and/or settled-out drilling mud, so that the resistance/drag on the inner casing from the surrounding fluid is reduced
Implementation Method 2
passing a fluid at high pressure through the string into the annulus via the perforations, so that the viscous and/or solid mass is displaced up the annulus
Data Source
AI summary
A method is for removing casing from a well. The method includes setting a first sealing element into fluid-sealing engagement with the inside of the casing, lowering a flow-through string into the well, a cutting tool and a second, reversibly expandable sealing element being connected to the string, forming perforations into the casing by means of said cutting tool, expanding the second, expandable sealing element into fluid-sealing engagement with the inside of the casing, passing a pressurized fluid through the string and into the annulus via the perforations, so that the viscous and/or solid mass is displaced up the annulus, cutting the casing around its entire circumference; and pulling a length of the casing up from the well.