NMR Echo Train Inversion Using Polarization Cutoffs
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Solution Overview
Problem
Current NMR logging techniques face challenges in accurately determining petrophysical properties of formations, particularly in cases with small contrasts between water and light oil, due to poor signal-to-noise ratio and resolution, and existing methods are not robust or efficient for simultaneous inversion of multiple echo trains.
Innovation Solution
A method and apparatus for characterizing earth formations by obtaining multiple NMR echo trains with different acquisition parameters, using a least squares inversion process that accounts for cutoff times for full polarization, allowing for simultaneous fitting of echo trains to determine characteristics like clay bound water, bulk volume irreducible, and porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional NMR logging techniques are used to determine petrophysical properties, then the measurement process is simple, but the accuracy is poor due to small contrasts between water and light oil and poor signal-to-noise ratio
Solution Approach 1:
The patent segments the NMR signal analysis by dividing the echo trains into multiple segments based on polarization state and acquisition parameters. Each segment is processed separately through inversion to determine specific petrophysical properties, improving accuracy by handling complex signals in manageable portions rather than attempting to process the entire signal at once.
Solution Approach 2:
The patent introduces additional dimensions to the analysis by processing multiple echo trains with different acquisition parameters simultaneously. This multi-dimensional approach allows the system to resolve small contrasts between fluid types that cannot be detected in single-dimension analyses, improving measurement precision through comprehensive multi-parameter inversion.
2Reliability
If multiple echo trains with different acquisition parameters are processed simultaneously, then the robustness and efficiency improve, but the computational complexity increases
Solution Approach 1:
The patent merges multiple echo trains with different acquisition parameters into a unified inversion framework. By combining the processing of fully polarized echo trains, partially polarized echo trains, and non-polarized echo trains within a single computational framework, the system achieves robustness through comprehensive data utilization while managing computational complexity through structured integration rather than separate processing streams.
Solution Approach 2:
The inversion method is designed with universal applicability to handle multiple echo train types under different polarization states. This multi-functional approach allows a single computational algorithm to process diverse acquisition parameters and polarization conditions, improving reliability through unified processing while avoiding the need for multiple specialized inversion processes.
3Manufacturing precision
If echo trains are processed separately without accounting for polarization state, then the processing is simpler, but the data quality and resolution are poor
Solution Approach 1:
The patent applies local quality by processing different portions of the echo train data with appropriate consideration of their polarization states. Fully polarized echo trains are processed with one set of inversion parameters, while partially and non-polarized trains use adjusted parameters, improving resolution by tailoring the processing approach to the specific characteristics of each data segment rather than applying a uniform simplification.
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 and efficiency of determining petrophysical properties by accounting for different acquisition parameters and polarization states, providing a robust method for processing multiple echo trains and enhancing data quality in challenging logging conditions.
Implementation Method 1
Nuclear magnetic resonance is used in the oil industry, among others, and particularly in certain oil well logging tools. NMR instruments may be used for determining, among other things, the fractional volume of pore space and the fractional volume of mobile fluid filling the pore space of earth formations.
Implementation Method 2
A static magnetic field is produced in the formation using permanent or electro-magnets. The static field aligns nuclear spins within the formation parallel to the static field. A pulsed RF field is applied using a transmitter on the logging tool and the nuclear magnetization signals produced by the pulsed RF field are analyzed to determine formation properties.
Data Source
AI summary
A method for inversion of multiple echo trains with different wait times uses a cutoff times for each of the echo trains for full polarization. Simultaneous inversion is carried out for T2 bins where full polarization exists. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.