NMR Tool Motion Compensation via Dual Acquisition Windows
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Solution Overview
Problem
NMR well logging data are sensitive to lateral motion of the NMR tool, causing distortion and inability to acquire spin echo signals representing transversal NMR relaxation, especially in LWD or MWD contexts, where rotational sensitivity is reduced but longitudinal and lateral displacement due to vibration remains problematic.
Innovation Solution
The NMR tool acquires first and second NMR signals using different acquisition window durations, with a processor determining motion effects by comparing these signals and generating NMR relaxation data with reduced motion effects by applying lateral displacement through numerical simulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the NMR tool is used in LWD or MWD contexts with vibration, then logging operations can be performed in challenging environments, but lateral displacement causes distortion and inability to acquire accurate spin echo signals
Solution Approach 1:
The system dynamically adjusts the acquisition window duration based on detected motion conditions. When motion is detected, the system switches between a first acquisition window duration for motion-free conditions and a second acquisition window duration for motion-affected conditions, allowing adaptive operation in varying environmental conditions while maintaining measurement accuracy
Solution Approach 2:
The system changes the acquisition window duration parameter in response to detected lateral displacement. By modifying this temporal parameter, the system compensates for motion-induced signal distortion and enables accurate NMR measurements even when the tool experiences vibration and lateral movement during logging operations
2Ease of operation
If a fixed acquisition window duration is used, then the system operation is simple, but motion effects cannot be distinguished from relaxation signals
Solution Approach 1:
The system segments the NMR signal acquisition into multiple phases by using different acquisition window durations. By acquiring signals with both a first and second acquisition window, the system separates motion-induced artifacts from true relaxation signals, enabling identification and removal of motion components while preserving genuine NMR data
Solution Approach 2:
The system uses feedback from comparing signals acquired with different window durations to detect motion effects. When motion is detected through this comparison, the system adjusts the acquisition strategy accordingly, creating a closed-loop system that maintains data quality by adapting to real-time motion conditions
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 allows for the identification and reduction of motion components in NMR signals, enabling accurate NMR relaxation data acquisition even in conditions of lateral tool motion, thereby improving data quality and reliability in logging operations.
Implementation Method 1
an assembly of magnetic moments, such as those of hydrogen nuclei, are exposed to a static magnetic field they tend to align along the direction of the magnetic field, resulting in bulk magnetization
Implementation Method 2
a coil assembly that generates radio frequency (RF) control signals and detects magnetic resonance phenomena in the subsurface material
Implementation Method 3
the coil assembly that generates radio frequency (RF) control signals and detects magnetic resonance phenomena
Data Source
AI summary
A nuclear magnetic resonance (NMR) tool for use in a subterranean region, the NMR tool comprising a magnet assembly to produce a magnetic field in a volume in the region, an antenna assembly to produce an excitation in the volume, and to receive NMR signals from the volume, and an acquisition system coupled to the antenna assembly and configured to acquire a first NMR signal using a first acquisition window having a first duration, and acquire a second NMR signal using a second acquisition window having a second duration, wherein the second duration is different than the first duration, and a processor coupled to the acquisition system and configured to determine a lateral displacement of the NMR tool as a function of time based on the first and second NMR signals, and apply the lateral displacement to the first NMR signal to generate NMR relaxation data with reduced motion effects.