Pad-Mounted Atomic Magnetometers for NMR Logging
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Solution Overview
Problem
Traditional NMR tools face significant energy losses and limited adaptability in large boreholes with conductive fluids, requiring custom designs for specific borehole sizes due to their large sensing region and distance from the tool.
Innovation Solution
The development of a nuclear magnetic resonance (NMR) tool with multiple pad-mounted atomic magnetometers, which employ a static magnetic field and RF atomic magnetometers to reduce energy requirements and adapt to various borehole sizes, using either permanent magnets or the Earth's magnetic field for polarization, and varying the number of pads based on borehole size for optimal coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional NMR tools use a large sensing region to improve measurement coverage, then the sensing capability is enhanced, but energy losses increase significantly in large boreholes with conductive fluids
Solution Approach 1:
The patent divides the sensing system into multiple discrete pads mounted on the tool body, each pad containing its own atomic magnetometer. This segmentation allows the sensing function to be distributed across multiple locations, improving coverage while reducing the energy burden on any single sensing region and minimizing interference from conductive fluids at any one location.
Solution Approach 2:
The patent transitions from a single large sensing region to multiple smaller sensing pads distributed in three-dimensional space around the tool. This spatial distribution across multiple dimensions allows the system to achieve comprehensive measurement coverage while reducing the energy losses associated with any single large sensing area in conductive fluids.
2Measurement precision
If traditional NMR tools are designed for specific borehole sizes to optimize performance, then measurement accuracy is improved, but adaptability to various borehole sizes is reduced
Solution Approach 1:
The patent designs a universal tool configuration where multiple pads with atomic magnetometers can be adapted to various borehole sizes. The same basic tool design can be configured for different borehole diameters by adjusting pad placement and number, eliminating the need for custom-designed tools for each borehole size while maintaining measurement accuracy.
Solution Approach 2:
The patent enables dynamic adaptation of the sensing system to different borehole conditions. The multiple pads can be selectively activated or positioned based on the specific borehole size and formation characteristics, allowing the tool to optimize its performance for each unique logging environment rather than being fixed for a single borehole size.
3Reliability
If traditional NMR tools use conventional RF detection methods to achieve sufficient signal detection, then measurement capability is maintained, but power requirements increase
Solution Approach 1:
The patent replaces conventional RF detection methods with atomic magnetometers that directly detect magnetic field variations. This substitution eliminates the need for high-power RF transmission and reception systems, dramatically reducing power requirements while maintaining or improving signal detection capability through direct quantum mechanical detection of nuclear magnetic resonance signals.
Solution Approach 2:
The patent changes the fundamental detection parameter from RF electromagnetic field detection to direct magnetic field detection using atomic magnetometers. This parameter change allows for highly sensitive detection of NMR signals with minimal power consumption, as atomic magnetometers can detect extremely weak magnetic fields without requiring the high power levels needed for conventional RF 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
This design enhances signal-to-noise ratio and reduces power requirements, allowing the tool to operate effectively across a range of borehole sizes with minimal interference from conductive fluids, while maintaining measurement accuracy and adaptability.
Implementation Method 1
NMR tools operate by using an imposed static magnetic field, B0, to preferentially polarize the nuclear spins of the formation nuclei parallel to the imposed field
Implementation Method 2
the tool applies a perturbing field. Usually the perturbing field takes the form of a radio frequency (RF) pulse whose magnetic component, B1, is perpendicular to the static field B0
Implementation Method 3
the precessing nuclei (which are phase-aligned by the perturbing field) lose their phase alignments with each other. The relaxation time constant of this coherence loss is the spin-spin or transverse relaxation time constant T2
Data Source
AI summary
Various disclosed nuclear magnetic resonance (NMR) logging systems and methods employ a plurality of NMR sensors, including atomic magnetometers, mounted on pads. Certain method embodiments include: utilizing the Earth magnetic field to pre-polarize the protons in a formation; utilizing a plurality of atomic magnetometers to obtain NMR measurements; and determining at least one characteristic relaxation time of the formation. The NMR sensor may optionally include a permanent magnet assembly.