Coring Shaft Inner Surface Features for Sample Retention
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Solution Overview
Problem
Existing coring tools face challenges in effectively retaining and retrieving core samples from subterranean formations due to insufficient sample retention force and difficulty in removing stuck coring shafts from the sidewall of boreholes.
Innovation Solution
The development of coring shafts with raised features such as knurls, helical ridges, and serrations on the inner surface to increase sample retention force, and a circumferential groove on the exterior surface to facilitate controlled fracture and removal, along with adaptable leading edge configurations and operational modes based on formation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a smooth inner surface is used in the coring shaft, then the device complexity is reduced, but the sample retention force is insufficient
Solution Approach 1:
The inner surface of the coring shaft is equipped with raised features (knurls, ridges, serrations) at specific locations rather than being uniformly smooth. These localized textured regions provide enhanced friction and mechanical interlocking with the core sample, increasing retention force without requiring the entire surface to be complex.
Solution Approach 2:
The raised features on the inner surface incorporate curved and helical geometries (such as helical ridges and rounded knurls) that better conform to the cylindrical shape of the core sample. These curved surfaces provide continuous contact and progressive engagement with the sample, improving retention through geometric interlocking rather than flat surface friction.
2Reliability
If the coring shaft is made strong and rigid, then the reliability of sample collection is improved, but the difficulty of removing stuck coring shafts increases
Solution Approach 1:
The coring shaft is designed with a circumferential groove that creates a distinct separation between the main shaft body and the tip section. This segmentation allows the tip (which engages the formation) to be fractured or separated from the main shaft, enabling retrieval of the shaft while leaving the sampled tip section in the formation or allowing controlled breakout.
Solution Approach 2:
The material properties or cross-sectional parameters of the coring shaft are varied along its length, with the tip section having different mechanical properties (such as reduced wall thickness or different material composition) compared to the main shaft body. This parameter change allows the tip to fracture at a predetermined location while the main shaft remains intact for retrieval.
3Adaptability or versatility
If the coring shaft is designed for high strength formations, then the manufacturing precision requirements increase, but the adaptability to different formation types decreases
Solution Approach 1:
The coring shaft incorporates an adaptable leading edge that can change its effective geometry during operation. The leading edge may include movable components, adjustable cutting elements, or a design that allows deformation and reconfiguration based on the resistance encountered, enabling the same shaft to effectively handle different formation types from soft to hard.
Solution Approach 2:
The coring shaft is designed with a multi-functional leading edge that can perform multiple functions: cutting through hard formations, penetrating softer formations, and self-sharpening or self-adjusting during operation. This universal design allows a single shaft configuration to adapt to various formation types without requiring precise manufacturing for each specific formation type.
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
Enhanced sample retention force and improved ability to retrieve core samples, even from formations with high strength or tar sand, and efficient withdrawal of the coring tool from stuck situations, optimizing the coring operation.
Implementation Method 1
the raised features are shaped so that at least one of the raised features or an exterior surface of the sample in the cavity deforms to increase a force required to remove the sample from the cavity
Implementation Method 2
raised features such as knurls, helical ridges, and serrations on the inner surface to increase sample retention force
Implementation Method 3
a circumferential groove on the exterior surface to facilitate controlled fracture and removal
Data Source
AI summary
A coring method includes disposing a coring tool in a borehole adjacent a subterranean formation to be sampled. The method further includes determining a property of the formation and selecting a coring tool operational mode based on the property of the formation. The method also includes obtaining a sample from the formation using the coring tool operational mode. A type of coring shaft also may be selected based on the property of the formation.