Neutron Induced Gamma Ray Spectroscopy Background Filtering
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Solution Overview
Problem
Neutron-induced gamma ray spectroscopy in well logging faces challenges in precision and accuracy, particularly when analyzing multiple chemical elements, as the inclusion of additional elements increases statistical noise and introduces biases, leading to a trade-off between accuracy and precision.
Innovation Solution
A method and apparatus that characterize energy detected gamma rays from neutron interactions, select a subset of elemental yields as background yields, filter these yields, and subtract their contribution from the total gamma ray spectrum to determine foreground elemental yields, improving precision without introducing biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If more chemical elements are included in the spectral analysis to improve accuracy, then the accuracy of elemental yield determination improves, but statistical noise increases and precision deteriorates
Solution Approach 1:
The patent segments the spectral analysis into two distinct phases: first analyzing a subset of elements to establish a background spectrum, then removing this background contribution before analyzing the remaining elements. This segmentation allows the background elements (which contribute to statistical noise) to be handled separately, improving precision of the foreground element measurements without sacrificing overall accuracy.
Solution Approach 2:
The patent extracts and removes the background spectrum contribution from the total measured spectrum. By identifying elements that primarily contribute to background radiation and removing their spectral signatures, the method isolates the signals from foreground elements, thereby reducing statistical noise and improving measurement precision without losing the ability to accurately determine all elemental yields.
2Reliability
If more standard spectra are used in multiple elemental analysis to improve accuracy, then accuracy improves, but correlations between spectra amplify statistical noise and precision worsens
Solution Approach 1:
The patent divides the set of standard spectra into two groups: background spectra (from elements that contribute primarily to background radiation) and foreground spectra (from elements of interest). By analyzing background spectra first, removing their contributions, and then analyzing foreground spectra, the method reduces the number of simultaneous correlations needed, thereby reducing noise amplification while maintaining accurate determination of all elements.
Solution Approach 2:
The patent extracts the background spectral contributions from the total spectrum before performing foreground element analysis. This extraction removes the correlated noise components associated with background elements, allowing foreground element yields to be determined with higher precision while still using multiple standard spectra for accurate foreground element determination.
3Measurement precision
If background elements are excluded from analysis to improve precision, then precision improves, but biases are introduced in other calculated elemental yields and accuracy deteriorates
Solution Approach 1:
The patent segments the analysis process into background element analysis and foreground element analysis, but unlike simple exclusion, it systematically removes the background contribution through spectral subtraction. This allows background elements to be properly accounted for in determining foreground element yields, eliminating biases while maintaining the precision benefits of focused analysis.
Solution Approach 2:
The patent extracts the specific contribution of background elements from the total spectrum through spectral subtraction, rather than simply excluding them. This extraction process removes the biased influence of background elements on foreground element calculations while still allowing background elements to be determined accurately, thereby maintaining both precision and accuracy.
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 precision of elemental yield calculations, as demonstrated by a factor of 2 improvement in carbon and oxygen ratio measurements, equivalent to a 4-fold increase in logging speed, by filtering out instrument-related background contributions and reducing statistical noise.
Implementation Method 1
gamma rays that result from inelastic collision of high energy neutrons (approximately 1 million electron volts or more) with certain nuclei in the formations
Implementation Method 2
characterizing by energy detected gamma rays
Data Source
AI summary
A method for determining a composition of a formation, includes characterizing by energy detected gamma rays resulting from interaction of neutrons that irradiated the formation. Elemental yields are determined by spectrally analyzing the energy characterized gamma rays. A subset of the elemental yields is selected as background yields. The background yields are filtered. An apparent contribution of the filtered background yields to the characterized gamma rays is determined. Foreground elemental yields are determined by spectrally analyzing the characterized gamma rays having the apparent contribution removed.