Core Barrel Sleeve and Piston Assembly for Reliable Core Ejection
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Solution Overview
Problem
Existing core extraction methods face challenges in efficiently retrieving cores from deep boreholes due to issues with mud and debris inhibiting the sealing and ejection process, particularly in triple-tube core barrel assemblies, which can lead to difficulties in disengaging downhole tools and expelling cores to the surface.
Innovation Solution
A downhole tool assembly is provided with sleeves and a core ejection piston that inhibit radial and axial movement of split tubes, allowing for fluid flow and facilitating core ejection by sealing the bore with a plug, while incorporating features like bypass channels and engaging structures to ensure reliable core retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a triple-tube core barrel assembly is used with split tubes to receive core, then the core can be securely contained during drilling, but mud and debris accumulate on the inner tube and piston making plug engagement difficult
Solution Approach 1:
The invention extracts the harmful accumulation of mud and debris from the critical engagement area by providing bypass channels that allow fluid to flow past the piston. This prevents the buildup that would otherwise interfere with plug engagement, thereby maintaining ease of operation while preserving core containment reliability
Solution Approach 2:
The bypass channels act as an intermediary pathway that allows drilling fluid to flow around the piston without accumulating on surfaces that need to remain clean for proper plug engagement. This mediator pathway protects the engagement surfaces from contamination while maintaining the core containment function
2Ease of operation
If the core barrel is designed to allow axial movement of the inner tube for core retrieval, then the core can be easily extracted, but radial movement of split tubes may occur causing overlap and blocking
Solution Approach 1:
The invention segments the constraint function by providing separate elements: the retaining portion that prevents radial movement of split tubes, and the axial movement capability that enables core extraction. This segmentation allows each function to be optimized independently without interfering with the other
Solution Approach 2:
The invention applies asymmetric constraints to the split tubes - restricting radial movement through the retaining portion while allowing axial movement for core extraction. This asymmetric design enables the system to simultaneously achieve reliable tube positioning and easy core extraction by applying constraints only in the directions where they are needed
3Reliability
If the downhole tool extends axially away from the core barrel to be interposed between the core barrel and back-end assembly, then the tool can function during drilling, but the assembly length increases descent time
Solution Approach 1:
The invention nests the downhole tool within the core barrel assembly structure, positioning it to extend axially from the core barrel while maintaining compact overall dimensions. This nesting approach allows the tool to be interposed between the core barrel and back-end assembly for functional operation during drilling, while minimizing the overall assembly length to reduce descent time
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 enhances the efficiency of core extraction by preventing tube overlap and ensuring seamless core ejection, even in challenging borehole conditions, thereby improving the reliability and ease of retrieving cores for analysis.
Implementation Method 1
The piston defines at least one bypass channel arranged to allow fluid to flow axially past the piston when arranged in the core tube
Implementation Method 2
mounting a piston plug within the core barrel assembly to seal the bore
Implementation Method 3
pumping fluid into the inner tube and against the plug. This causes the plug and/or piston to urge against and push the split tubes and core out of the core barrel
Data Source
Figure 1~3
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Figure 6~8
AI summary
Downhole tool assembly (10) for mounting to a core barrel assembly (12) including a core tube (14) and a pair of split tubes (16). The downhole tool assembly (10) includes a downhole tool (18) and at least one sleeve (20) dimensioned to slidingly engage the split tubes (16) to inhibit radial movement of the split tubes (16) and receive and retain the downhole tool (18) coaxially with the core tube (14). Core ejection pistons (72), and methods for extracting a core from bedrock are also disclosed. A housing assembly (120) for a downhole tool, downhole assemblies (180, 200), and methods of assembling such assemblies are also disclosed.