Magnetic Assemblies For Downhole NMR Tools
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Solution Overview
Problem
Downhole NMR tools face challenges in maintaining a stable, symmetric magnetic field due to imperfections in permanent magnets, which affect the accuracy of subsurface material characterization during logging operations.
Innovation Solution
Incorporating magnetically permeable structures interleaved with permanent magnets to correct deviations in magnetic field orientations and enhance field symmetry, reducing radial field inhomogeneity and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent magnets are used to generate magnetic field, then magnetic field is produced, but magnetic field symmetry and stability deteriorate due to manufacturing imperfections
Solution Approach 1:
A magnetically permeable structure is introduced as an intermediary between permanent magnets to correct orientation deviations. The permeable structure has higher magnetic permeability than the permanent magnets, allowing it to redirect and realign magnetic flux lines, thereby correcting symmetry errors caused by manufacturing imperfections in the permanent magnets without requiring perfect manufacturing precision
Solution Approach 2:
The invention changes the magnetic permeability parameter by introducing a magnetically permeable structure with higher permeability than the permanent magnets. This parameter change enables the system to compensate for orientation deviations by utilizing the permeability difference to redirect magnetic flux, transforming a manufacturing precision problem into a manageable magnetic circuit design problem
2Measurement precision
If individual magnet testing and placement is performed to ensure field symmetry, then measurement precision improves, but device complexity and time increase
Solution Approach 1:
The magnetically permeable structure serves as a passive correction element that automatically compensates for magnet orientation errors without requiring complex testing and placement procedures. This intermediary structure simplifies the assembly process by eliminating the need for precise individual magnet alignment while maintaining measurement precision through magnetic flux redirection
Solution Approach 2:
The magnetically permeable structure provides self-correcting functionality by automatically redirecting magnetic flux lines to compensate for orientation deviations. This self-service mechanism eliminates the need for external intervention through complex testing and adjustment procedures, thereby reducing device complexity while maintaining measurement accuracy
3Stability of the object's composition
If magnetically permeable structures are added to correct field symmetry, then magnetic field symmetry improves, but device complexity increases
Solution Approach 1:
The invention creates a composite magnetic assembly combining permanent magnets with magnetically permeable structures. This composite structure leverages the different magnetic properties of the two materials - the permanent magnets provide the magnetic field while the permeable structure corrects symmetry - achieving field symmetry improvement through material composition rather than complex geometric arrangements
Solution Approach 2:
The magnetically permeable structure is strategically positioned in specific locations where orientation deviations occur, providing localized correction rather than requiring complex overall restructuring. This local quality approach allows symmetry correction at critical points without increasing overall device complexity significantly
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 use of magnetically permeable structures in magnet assemblies for downhole NMR tools stabilizes the magnetic field, reducing the need for individual magnet testing and placement, thereby enhancing the reliability and efficiency of NMR measurements.
Implementation Method 1
Incorporating magnetically permeable structures interleaved with permanent magnets to correct deviations in magnetic field orientations and enhance field symmetry
Implementation Method 2
Some downhole NMR tools include a magnet assembly that produces a static magnetic field
Data Source
AI summary
Magnetic assemblies for downhole nuclear magnetic resonance tools are provided. A magnetic assembly includes one or more permanent magnets and one or more magnetically permeable structures. The magnetically permeable structures generate an induced magnetic field responsive to the magnetic field of the permanent magnets. The induced magnetic field corrects axial asymmetries in the magnetic field of the permanent magnets. The one or more permanent magnets may be interleaved, in the magnet assembly, with the one or more permanent magnets.