NMR Frequency Control for Multiple Sensitive Volumes in Formation Evaluation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
NMR logging tools face challenges in maintaining accurate measurements due to temperature-dependent changes in magnetic fields, which affect the sensitive volume and require tedious calibration processes, especially in downhole environments.
Innovation Solution
The method involves adjusting the NMR frequency based on temperature changes using a temperature conversion function to maintain the same radial and axial location of the sensitive volume, accounting for the temperature dependency of the NMR signal by selecting the appropriate frequency to ensure consistent signal reporting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If NMR measurements are performed in downhole environments with varying temperatures, then the NMR tool can operate in diverse geological conditions, but the magnetic field strength and sensitive volume location change due to temperature dependency
Solution Approach 1:
The patent adjusts the NMR frequency parameter based on temperature changes to compensate for magnetic field strength variations. By dynamically changing the operating frequency according to temperature, the system maintains accurate NMR measurements despite temperature-dependent changes in magnetic field strength and sensitive volume location.
Solution Approach 2:
The system uses temperature sensors to monitor downhole temperature and feeds this information back to adjust the NMR frequency. This closed-loop feedback mechanism ensures that frequency adjustments are made in real-time based on actual temperature conditions, maintaining measurement accuracy in varying thermal environments.
2Measurement precision
If the NMR frequency is adjusted to maintain sensitive volume location across temperature changes, then measurement accuracy is improved, but additional temperature monitoring and frequency adjustment mechanisms are required
Solution Approach 1:
The patent introduces temperature sensors as intermediary devices that bridge the gap between temperature changes and frequency adjustments. These sensors monitor temperature and enable the system to indirectly compensate for magnetic field variations through frequency adjustment, rather than directly measuring or controlling magnetic field strength.
Solution Approach 2:
The system changes the frequency parameter in response to temperature variations, using a relatively simple adjustable frequency mechanism rather than complex magnetic field control systems. This approach maintains measurement accuracy while avoiding the need for elaborate temperature compensation hardware.
3Measurement precision
If traditional calibration methods are used for each transmitter, then individual performance variations can be identified, but the calibration process becomes tedious and complicated
Solution Approach 1:
The patent combines multiple transmitter calibrations into a single integrated calibration process. By using a phased array configuration where transmitters are calibrated collectively rather than individually, the system reduces calibration time while maintaining accuracy through the cooperative interaction of multiple transmitters.
Solution Approach 2:
The calibration system is designed to calibrate multiple transmitters simultaneously using a universal calibration procedure. This multi-functional calibration approach allows the same calibration process to handle all transmitters in the array, eliminating the need for separate calibration routines for each transmitter.
4Stability of the object's composition
If the sensitive volume location shifts due to temperature changes, then the radial and axial positioning changes affect measurement consistency, but frequency adjustment can maintain stable sensitive volume geometry
Solution Approach 1:
The patent adjusts the frequency parameter to compensate for temperature-induced changes in sensitive volume location. By changing the operating frequency in response to temperature variations, the system maintains a stable sensitive volume geometry and consistent radial and axial positioning, ensuring reliable measurements despite thermal effects.
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 approach improves the accuracy of NMR measurements by maintaining the sensitive volume's geometry and signal consistency across varying temperatures, reducing the complexity of calibration processes.
Implementation Method 1
NMR measurements can occur when the medium is subjected to a static magnetic field, B0, using a permanent magnet
Implementation Method 2
polarization of nuclear magnetic spins of the medium occurs based on the spin number of the medium and magnetic field strength
Implementation Method 3
Applying an electromagnetic field with proper frequencies and directions to the medium in the static magnetic field, can perturb the polarization established by the static magnetic field
Implementation Method 4
Nuclear magnetic resonance (NMR) is used as a tool in a number of different technology areas to investigate different types of mediums
Implementation Method 5
Collected responses received from the medium related to the total magnetization of nuclear spins in the medium, in response to these applied fields
Data Source
AI summary
A method of performing a nuclear magnetic resonance (NMR) measurement of a subterranean formation includes calibrating an NMR tool at a calibration formation operational frequency (ωgƒ@RT) and a calibration borehole operational frequency (ωgbh@RT) to determine calibration parameters for both the borehole and the formation sensitive volumes. The NMR tool is then operated in the borehole to determine, in the borehole sensitive volume, a downhole borehole operational frequency (ωgbh@T) at which the downhole borehole sensitive volume is substantially unchanged from the calibration borehole sensitive volume. A processor determines a downhole formation operational frequency (ωgƒ@T) at which the downhole formation sensitive volume is substantially unchanged from the calibration formation sensitive volume relative to the NMR tool based on ωgbh@T, ωgbh@RT, and ωgƒ@RT. The processor also determines an optimal amplitude modulation (AMopt) for ωgƒ@T. The NMR tool measures a property of the formation at ωgƒ@T and AMopt.