NMR Logging Motion Correction Matrix
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Solution Overview
Problem
Nuclear magnetic resonance (NMR) logging tools face challenges in accurately measuring porosity and relaxation times due to motion-induced distortions and B1 inhomogeneities, leading to incorrect inversion of NMR data and reduced measurement precision.
Innovation Solution
A method involving the use of a motion-dependent matrix to correct for distortions caused by tool motion and B1 inhomogeneities, which simulates the echo train mathematically using knowledge of the B0 and B1 fields, allowing for accurate inversion of NMR data and improved precision in porosity and relaxation time measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low-gradient magnet configurations are used to reduce axis motion effects, then the sensitive volume is reduced vertically, but the tool becomes more sensitive to vertical motion and rate of penetration
Solution Approach 1:
The patent applies parameter changes by modifying the inversion process to account for motion effects. Specifically, it changes the parameters used in data inversion to compensate for tool motion and B1 inhomogeneities, allowing accurate measurement despite the reduced sensitive volume and increased motion sensitivity inherent in low-gradient configurations
Solution Approach 2:
The patent introduces an intermediary computational step between data acquisition and final interpretation. A motion correction matrix is calculated as an intermediary element that mediates between the raw NMR signals and the formation properties, correcting for the adverse effects of vertical motion sensitivity before deriving porosity and T1 spectra
2Device complexity
If traditional inversion methods are used for NMR data, then processing is simpler, but motion effects and B1 inhomogeneities cause incorrect inversion results
Solution Approach 1:
The patent applies preliminary action by pre-calculating a motion correction matrix before the actual inversion process. This matrix, which accounts for tool motion and B1 inhomogeneities, is prepared in advance and then applied to correct the NMR signals before inversion, ensuring accurate results without significantly complicating the overall workflow
Solution Approach 2:
The patent replaces the traditional mechanical inversion approach with a computational solution. Instead of using simple inversion algorithms that assume stationary conditions, it substitutes a motion-aware computational model that uses matrix operations to correct for dynamic effects, achieving higher accuracy through mathematical transformation rather than physical measurement adjustments
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 enhances the accuracy and precision of NMR logging by accounting for motion effects and B1 inhomogeneities, providing reliable porosity and relaxation time spectra, even in fast-drilling scenarios where traditional methods fail.
Implementation Method 1
Nuclear magnetic resonance (NMR) is used as a tool in a number of different technology areas to investigate different types of mediums. NMR can occur when the medium is subjected to a static magnetic field, B0, and to an oscillating magnetic field, B1.
Implementation Method 2
When subjected to an applied static magnetic field, polarization of nuclear magnetic spins of the medium occurs based on spin number of the medium and magnetic field strength.
Implementation Method 3
Applying an electromagnetic field to the medium in the static magnetic field can perturb the polarization established by the static magnetic field.
Implementation Method 4
Nuclear magnetic resonance measurements are created by the oscillation of excited nuclear magnetic spins in the transverse plane, that is, the direction perpendicular to the magnetic field.
Implementation Method 5
A widely used NMR measurement technique, designed by Carr, Purcell, Meiboom, and Gill and, hence, referred to as CPMG, uses a sequence of radio frequency pulses to produce spin echoes and counteract dephasing of the magnetization in the medium investigated.
Implementation Method 6
another pulse, a recovery pulse, commonly a 180° or other angle tipping pulse, is applied to return to phase, which produces a signal called an echo from the medium
Data Source
AI summary
Various embodiments include apparatus and methods to acquire echo signals associated with operation of a nuclear magnetic resonance logging tool to evaluate a formation and process the echo signals taking into account motion of the nuclear magnetic resonance logging tool. Coefficients may 5 be generated that are correlated to porosity of the formation. Additional apparatus, systems, and methods are disclosed.