Inelastic Background Correction for Pulsed-Neutron Instruments
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Solution Overview
Problem
Current neutron logging instruments face interference from background gamma rays generated by the instrument itself, particularly from fast neutrons, which complicates the analysis of gamma ray spectra from neutron inelastic scattering, as no material effectively absorbs these fast neutrons.
Innovation Solution
A method is developed to correct data collected by neutron emitting instruments by obtaining characterization data that includes inelastic background information and subtracting this from the gross data signal to produce a corrected signal, effectively creating a 'virtual inelastic shield' to remove interfering background radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a neutron source is used to activate sub-surface materials for neutron inelastic scattering measurements, then additional gamma-ray emissions are generated for data collection, but background gamma rays from the instrument itself interfere with the measurement accuracy
Solution Approach 1:
The patent extracts and removes the background gamma ray signal from the total measured signal through mathematical processing. The background spectrum obtained in air is subtracted from the gross signal to isolate the formation signal, effectively taking out the harmful background component from the measurement.
Solution Approach 2:
The patent introduces an intermediary measurement process where the instrument first characterizes its own background signal in air, then uses this intermediate background spectrum as a reference to correct the actual formation measurements. This intermediary step enables separation of instrument background from formation signal.
2Object-affected harmful factors
If boron material is applied to the instrument housing to absorb thermal neutrons and reduce capture gamma ray background, then capture gamma ray interference is reduced, but no material exists to absorb fast neutrons causing inelastic scattering background
Solution Approach 1:
The patent converts the harmful inelastic background gamma rays into a useful characterization tool. By measuring the background spectrum in air, the instrument characterizes its own inelastic background, which is then subtracted from formation measurements. The harmful background becomes a source of correction information.
Solution Approach 2:
The patent changes the measurement parameter from attempting to physically block fast neutrons (which has no effective material) to measuring and characterizing the inelastic background spectrum in air. This parameter change from physical shielding to spectral characterization enables correction of the inelastic background.
3Quantity of substance
If the instrument measures gross data signal including background radiation, then complete signal is captured, but the interfering background radiation must be removed to achieve accurate subsurface material measurements
Solution Approach 1:
The patent segments the total gamma ray signal into two distinct components: the background signal (measured in air) and the formation signal (measured in subsurface). This segmentation allows separate characterization and subsequent mathematical separation of the two signal sources through spectrum subtraction.
Solution Approach 2:
The patent performs preliminary measurement of the background spectrum in air before or during formation measurements. This preliminary action captures the instrument's background characteristics, which are then used to correct the formation signals, preventing background interference from obscuring the formation information.
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 allows for accurate measurement of subsurface materials by removing the interfering background radiation, resulting in a corrected data signal that is relatively free from instrument-generated noise, enhancing the analysis of both inelastic and capture gamma ray spectra.
Implementation Method 1
The neutrons interact with the nuclei, which may emit characteristic gamma rays, for the most part through one of two processes, neutron inelastic scattering, and neutron capture.
Implementation Method 2
The gamma radiation detector may be used to estimate the energy of each gamma ray entering the detector. The gamma ray energy levels may be used to create gamma ray energy spectra.
Implementation Method 3
Although background gamma rays resulting from neutron capture can be reduced by applying a material, such as boron, to the outside of the housing of the instrument to prevent outside thermal neutron interacting with tool materials
Data Source
AI summary
A method for correcting data collected with a neutron emitting instrument, includes: obtaining characterization data for the instrument, the characterization data including inelastic background data of the instrument; and correcting the collected data according to the characterization data. A computer program product and an instrument are provided.