NMR Logging Tool Motion Detection Using Multiple Echo Spacing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
NMR logging tools experience lateral motion during operations, leading to inaccurate measurements of formation properties like porosity and permeability due to signal decay, which is difficult to distinguish from intrinsic decay, resulting in faulty characterizations.
Innovation Solution
Implementing a Carr-Purcell-Meiboom-Gill (CPMG) echo train with multiple echo spacing (tE) and a single excitation pulse to detect motion, combined with signal processing techniques to distinguish motion effects using multiple echo spacing sequences, allowing for real-time motion evaluation and adjustments in drilling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If NMR logging tool measures relaxation times during lateral motion, then measurement speed is improved, but measurement precision deteriorates due to signal decay
Solution Approach 1:
The patent segments the NMR echo train into multiple segments with different echo spacings (tE). By dividing the measurement into segments with varying tE values, the system can detect motion-induced signal decay patterns that differ from intrinsic relaxation, thereby maintaining measurement accuracy during lateral motion while preserving fast measurement capability
Solution Approach 2:
The patent changes the echo spacing parameter (tE) across different segments of the CPMG echo train. By varying tE rather than keeping it constant, the system creates distinguishable signal decay patterns that allow differentiation between motion effects and intrinsic relaxation, resolving the accuracy-speed contradiction
2Device complexity
If NMR logging tool uses single echo spacing sequence, then device complexity is reduced, but difficulty of detecting and measuring motion effects increases
Solution Approach 1:
The patent divides the CPMG echo train into multiple segments, each with a distinct echo spacing (tE). This segmentation allows the system to detect motion effects by comparing signal decay patterns across segments, thereby improving motion detection capability while maintaining relatively simple pulse sequence implementation
Solution Approach 2:
The patent applies partial action by using only a few segments with different tE values rather than continuously varying tE throughout the entire echo train. This provides sufficient motion detection capability while keeping the pulse sequence complexity manageable
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
Enables accurate differentiation between motion-induced and intrinsic signal decay, ensuring reliable formation attribute measurements by minimizing the impact of lateral tool motion on NMR logging tools.
Implementation Method 1
NMR logging tools that measure induced magnetic moment of hydrogen nuclei (i.e., protons) contained within the fluid-filled pore space of formation media
Implementation Method 2
Implementing a Carr-Purcell-Meiboom-Gill (CPMG) echo train with multiple echo spacing (tE) and a single excitation pulse to detect motion
Data Source
AI summary
Techniques and systems for motion detection of a logging tool. A system includes a nuclear magnetic resonance (NMR) logging tool configured to perform at least one Carr-Purcell-Meiboom-Gill (CPMG) scan utilizing a plurality of distinct echo times (tE) in conjunction with a single excitation pulse and a single wait time as a multiple echo spacing sequence to acquire NMR logging measurements and a processing system coupled to the NMR logging tool, wherein the processing system is configured to process the NMR logging measurements acquired by the NMR logging tool to determine whether the NMR logging measurements were affected by lateral motion of the NMR logging tool.