Pulsed Neutron Generator Radiation Detection Segmentation
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Solution Overview
Problem
Neutron tools used for characterizing earth formations face accuracy issues due to interference from radiation sources other than neutron bombardment, leading to decreased measurement precision in porosity and other property determinations.
Innovation Solution
A pulsed neutron generator and radiation detectors with a crystal structure and coincidence counter are used to emit and detect neutrons, allowing for the exclusion of radiation counts not associated with the formation of interest by tracking neutron trajectories and using a processor to estimate formation properties accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional radiation detectors are used to detect formation radiation, then the measurement process is simple, but measurement accuracy decreases due to interference from radiation sources other than neutron bombardment
Solution Approach 1:
The radiation detection system is segmented into multiple functional components: a neutron generator radiation detector for detecting neutrons and alpha particles, a formation radiation detector for detecting gamma rays from the formation, and a coincidence counter for temporal correlation. This segmentation allows each component to specialize in detecting specific radiation types, improving overall measurement accuracy while maintaining manageable system complexity through modular design.
Solution Approach 2:
The coincidence counter acts as an intermediary between the neutron generator radiation detector and the formation radiation detector. It temporally correlates signals from both detectors, filtering out spurious counts by only accepting formation radiation signals that occur within a defined time interval after neutron pulse emission. This intermediary function eliminates interference from background radiation sources while maintaining measurement accuracy.
2Measurement precision
If all radiation counts are included in the measurement, then the data volume is large, but measurement precision decreases due to irrelevant radiation interference
Solution Approach 1:
The coincidence counter performs preliminary filtering by temporally correlating detected radiation signals with the neutron pulse timing. Only radiation counts occurring within a defined time interval after the neutron pulse are accepted as valid formation radiation measurements. This preliminary action eliminates irrelevant background radiation from the data set before processing, improving measurement precision while reducing the effective quantity of relevant data.
Solution Approach 2:
The system converts the potential harm of background radiation interference into a benefit by using the coincidence counter to identify and exploit the temporal signature of neutron-induced radiation. By focusing only on counts within the specific time window following the neutron pulse, the system transforms the problematic background radiation into a filtering mechanism that actually improves measurement precision by excluding irrelevant signals.
3Reliability
If radiation detectors are placed close to the neutron generator, then detection efficiency is high, but the detectors are exposed to high radiation doses from the neutron generator
Solution Approach 1:
The detection system is spatially segmented into distinct zones: the neutron generator radiation detector is positioned close to the neutron generator for high detection efficiency, while the formation radiation detector is positioned at a distance to minimize radiation dose exposure. The coincidence counter bridges these spatially separated detectors, enabling efficient detection while protecting the formation detector from harmful radiation environments.
Solution Approach 2:
The coincidence counter serves as an intermediary that enables the formation radiation detector to be positioned at a safe distance from the neutron generator. By temporally correlating signals from both detectors, the system maintains detection efficiency without requiring the formation radiation detector to be in the high-radiation environment, thus reducing radiation dose exposure while preserving reliability.
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 measurement accuracy by distinguishing between relevant and irrelevant radiation, resulting in more precise estimates of formation properties such as porosity, with improved signal-to-noise ratio and reliable operation in downhole environments.
Implementation Method 1
The neutron tool bombards the formation with neutrons either continuously from a chemical source or as a pulse from an electronic source. The neutrons interact with the formation to produce radiation that is detected by a gamma-ray detector.
Implementation Method 2
The neutrons interact with the formation to produce radiation that is detected by a gamma-ray detector.
Implementation Method 3
electrons generated in the crystal structure by interaction with the radiation particle emitted by the pulse neutron generator are collected by at least one of the electrically conducting columns
Implementation Method 4
a coincidence counter coupled to the formation radiation detector and to the neutron generator radiation detector and configured to identify formation radiation counts that are detected by the formation radiation detector and are within a defined time interval that starts with detection of an associated radiation particle
Data Source
AI summary
An apparatus for estimating a property of an earth formation includes a pulsed neutron generator configured to emit a pulse of neutrons, a formation radiation detector configured to detect radiation emitted from the formation due to interactions with the pulse of neutrons, and a neutron generator radiation detector having a crystal structure and configured to detect a radiation particle emitted from the pulsed neutron generator and to provide a location within the neutron radiation detector at which the particle was detected. The crystal structure includes a plurality of detection cells, each detection cell having at least two electrically conducting columns with an applied potential difference such that electrons generated in the crystal structure by interaction with the radiation particle are collected by at least one of the electrically conducting columns to provide detection locations. A processor estimates the property using the detected formation radiation and the detection locations.