Gamma Ray Elemental Yield Correction for Zero-Yield Bias
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Solution Overview
Problem
Existing gamma ray spectroscopy methods in the oilfield industry suffer from statistical fluctuations leading to negative elemental yields, which result in unphysical negative concentrations and positive bias when corrected, necessitating a method to eliminate negative yields without causing a positive bias.
Innovation Solution
A method involving the summation and resetting of elemental yields with accumulated negative yields to compute corrected yields, using forward and reverse processing to eliminate negative yields and reduce positive bias, with optional averaging to synchronize the corrected yields with the true values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If negative yields are simply set to zero, then negative elemental concentrations are eliminated, but a positive average yield bias is introduced when averaged over an interval with zero average yield
Solution Approach 1:
The patent applies preliminary anti-action by accumulating negative yields before they can cause bias. The system maintains a running sum of negative yields and subtracts this accumulated amount from subsequent yields, proactively counteracting the bias that would otherwise be introduced by simple zero-clipping. This preemptive correction ensures that both individual negative values and their aggregate effect on averages are eliminated.
Solution Approach 2:
The patent implements feedback by using the accumulated negative yield information to adjust subsequent yield calculations. The system continuously monitors and accumulates negative yields, then feeds this accumulated information back into the correction process by subtracting it from future yields. This feedback mechanism dynamically adjusts the correction amount based on the actual negative yield history, ensuring accurate bias compensation.
2Reliability
If a fitting procedure penalizes yields close to zero to avoid negative values, then negative yields are prevented, but a positive bias is introduced in the zero yield elements
Solution Approach 1:
Instead of penalizing yields close to zero (which causes positive bias), the patent applies preliminary anti-action by accumulating the actual negative yields that occur and subtracting this accumulation from future yields. This approach allows yields to naturally fluctuate around zero without artificial penalties, then corrects the aggregate bias through the accumulated negative yield subtraction, maintaining both reliability and precision.
3Measurement precision
If statistical fitting is used to decompose gamma ray spectra, then elemental contributions are estimated, but statistical fluctuations cause negative yields for absent elements
Solution Approach 1:
The patent applies feedback by using the statistical fluctuations themselves as correction information. The system accumulates negative yields that arise from statistical fitting variations, then feeds this accumulated information back to correct future estimates. This transforms the problematic statistical noise into useful correction data, maintaining the benefits of statistical fitting while eliminating its harmful effects.
Solution Approach 2:
The patent converts the harmful statistical fluctuations that produce negative yields into a beneficial correction mechanism. By accumulating these negative yields and using them to adjust subsequent estimates, the system transforms the noise and unphysical results into valuable information that improves overall measurement accuracy and eliminates the very problem they originally caused.
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
The method effectively identifies zero yield regions and reduces positive yield bias by correcting elemental yields, ensuring accurate elemental concentration estimation.
Implementation Method 1
Induced gamma ray spectroscopy measurements may be used to estimate elemental concentrations of the formation from characteristic energy levels of gamma rays emitted by nuclei that have been activated by neutron bombardment
Implementation Method 2
gamma rays emitted by nuclei that have been activated by neutron bombardment
Implementation Method 3
a gamma ray detector deployed in a logging tool body
Data Source
AI summary
A method for correcting elemental yields obtained from gamma ray spectra includes acquiring a plurality of elemental yields corresponding to a plurality of time intervals; summing one of the plurality of elemental yields with an accumulated negative yield to compute a corrected yield; setting the accumulated negative yield to a minimum of zero and the computed corrected yield; resetting the corrected yield to a maximum of zero and the computed corrected yield; and repeating the summing, the setting, and the resetting, for each of the acquired plurality of elemental yields to compute a corresponding plurality of corrected elemental yields.