NMR Logging Motion Correction via Inversion Kernel
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Solution Overview
Problem
NMR logging tools face challenges in accurately measuring formation properties due to motion-induced signal decay caused by lateral motion during drilling, which results in underestimation of permeability and other formation parameters.
Innovation Solution
A method and system that determine relative motion of a downhole logging tool, calculate motion-induced signal decay, and use a motion-effect kernel to process measurements and correct for motion effects, thereby obtaining motion-corrected data representative of formation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If NMR logging tool moves during operation to enable drilling progress, then drilling productivity is improved, but measurement precision deteriorates due to motion-induced signal decay
Solution Approach 1:
The system uses motion sensors to detect tool motion in real-time and feeds this information back to the signal processing system. The feedback loop enables dynamic compensation of motion-induced errors by adjusting the inversion kernel based on actual motion parameters, thereby maintaining measurement precision while allowing continuous drilling operation
Solution Approach 2:
The invention changes the parameters used in signal inversion by incorporating motion-induced decay (MID) corrections into the inversion kernel. By modifying the kernel parameters to account for tool motion effects, the system compensates for signal decay and maintains accurate formation property measurements even during tool movement
2Measurement precision
If tool motion is reduced to improve measurement accuracy, then measurement precision is improved, but drilling speed deteriorates
Solution Approach 1:
Instead of using mechanical methods to stabilize the tool (which would reduce drilling speed), the invention substitutes a signal processing approach. By replacing mechanical stabilization with computational correction using motion sensors and modified inversion algorithms, the system achieves high measurement precision without compromising drilling speed
3Measurement precision
If motion correction processing is added to compensate for tool motion, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary action by pre-calculating and storing motion-effect kernels for various motion conditions before actual logging operations. During measurement, the appropriate pre-computed kernel is selected and applied, avoiding the need for complex real-time calculations and reducing processing complexity while maintaining high measurement precision
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 solution effectively compensates for motion-induced errors in NMR measurements, improving the accuracy of permeability and other formation parameter estimates by isolating intrinsic signal decay from motion-induced decay, leading to more reliable formation evaluations.
Implementation Method 1
nuclear magnetic resonance (NMR) logging tools typically measure, among other things, relaxation times, such as transverse relaxation times (T2), of formation fluids
Implementation Method 2
determining a motion induced signal decay (MID) based upon the determined relative motion, determining a motion-effect inversion kernel (MEK) based upon the determined MID
Data Source
AI summary
A method for correcting motion-effects from a downhole measurement includes, in one embodiment, determining relative motion of a downhole logging tool for a given logging operation in a borehole formed in an earth formation, determining a motion induced signal decay (MID) based upon the determined relative motion, determining a motion-effect inversion kernel (MEK) based upon the determined MID, using the downhole logging tool to acquire measurements that are affected by motion of the downhole logging tool during the logging operation, and using the MEK to process the acquired motion-affected measurements to obtain motion-corrected data. Corresponding systems, devices, and apparatuses are also disclosed herein.