External Magnet NMR Tool for Drilling
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Solution Overview
Problem
Conventional logging-while-drilling (LWD) nuclear magnetic resonance (NMR) tools face limitations due to the placement of permanent magnets within the drill collar, which reduces the magnetic field strength, increases the risk of damage, and complicates accessibility, affecting the Signal to Noise Ratio (SNR) and overall performance.
Innovation Solution
The solution involves placing magnets external to the drill collar and using magnetically permeable members to control the magnetic field gradient, allowing for increased magnetic field strength and flexibility in magnetic field shaping, thereby enhancing NMR measurements during drilling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent magnets are placed within the drill collar, then the magnets are protected from damage, but the magnetic field strength decreases and the Signal to Noise Ratio deteriorates
Solution Approach 1:
The patent extracts the permanent magnets from the drill collar and positions them externally on the outer surface of the drill collar. This extraction resolves the contradiction by allowing the magnets to generate stronger magnetic fields outside the drill collar while the drill collar itself provides protective support. The magnets are no longer confined within the limited space of the drill collar, enabling increased magnetic field strength and improved SNR while maintaining protection through the external mounting structure.
2Device complexity
If permanent magnets are placed within the drill collar, then the structure is compact, but accessibility to magnets and components becomes cumbersome
Solution Approach 1:
By extracting the magnets from the internal configuration and mounting them externally on the drill collar surface, the patent improves accessibility to the magnets and other NMR tool components. This external positioning allows easier access for maintenance, adjustment, and replacement operations while the overall structural compactness is maintained through the integrated external mounting design on the drill collar.
3Strength
If magnets are placed external to the drill collar, then magnetic field strength increases, but the magnets become more exposed to damage risks
Solution Approach 1:
The extraction of magnets to external positioning on the drill collar enables stronger magnetic fields while the drill collar structure itself serves as a protective framework. The external mounting is designed to leverage the drill collar's inherent strength and protection capabilities, allowing the magnets to operate in a position that maximizes field strength while still benefiting from the protective environment provided by the drill collar structure.
Solution Approach 2:
The patent incorporates preliminary protective design in the external mounting structure, where the magnets are pre-positioned and secured on the external surface of the drill collar with protective fixtures and mounting mechanisms that are installed before drilling operations begin. This preliminary protective arrangement ensures the magnets are safeguarded against drilling-related shocks and wear while maintaining their external position for optimal magnetic field generation.
4Reliability
If framework housing is used for magnets, then magnets are protected, but the volume of magnetic material is reduced
Solution Approach 1:
By extracting the magnets from an internal framework housing configuration and positioning them externally on the drill collar surface, the patent eliminates the space-consuming framework structure. This external positioning allows for significantly increased volume of magnetic material to be used, as the magnets are no longer constrained by the limited internal space of a housing framework. The protection function is transferred to the external mounting structure on the drill collar, enabling greater magnetic material volume for enhanced SNR and field strength.
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
This configuration improves the magnetic field strength and gradient, reducing sensitivity to tool motion and enabling more robust NMR measurements, including better fluid typing and porosity analysis, while allowing for interchangeable components for easier maintenance and improved accessibility.
Implementation Method 1
The axis about which the nuclei precess may be established by applying a strong, polarizing, static magnetic field Bo to the formation, such as through the use of permanent magnets.
Implementation Method 2
NMR measurements, in general, are accomplished by causing the magnetic moments of nuclei in a formation to precess about an axis.
Implementation Method 3
magnets external to the drill collar and magnetically permeable members to control the magnetic field gradient
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Methods and systems are provided that enable logging while drilling NMR measurements to be made with magnets placed outside of the drill collar and magnetically permeable members to control the magnetic field gradient. A set of magnets can be disposed on and/or embedded on a drill collar, with an antenna disposed axially therebetween. Alternatively, a set of magnets and an antenna disposed therebetween can be disposed on a sleeve that is slid onto a recess in a drill collar. Additionally, a permeable member can be axially positioned between the set of magnets for affecting the depth of investigation.