Photon Sensor with Scintillator Discrimination for Borehole Density Logging
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Solution Overview
Problem
Existing systems for measuring fluid density in oil and gas wells using radio-isotope sources pose health and safety concerns, and the use of separate output-monitor detectors is impractical due to space constraints in borehole environments.
Innovation Solution
A photon sensor and fluid-density logging tool utilizing multiple scintillators with distinct scintillation-light-time characteristics, coupled to a common photodetector and pulse-shape discriminator, which enhances sensitivity to specific radiation paths and allows for the differentiation of signals based on the scintillator origin, enabling accurate measurement of fluid density without the need for separate output-monitor detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radio-isotope sources are used for measuring fluid density, then measurement capability is achieved, but health and safety concerns arise for personnel and security of radio-isotopes
Solution Approach 1:
The patent replaces long-lived radio-isotope sources with short-lived x-ray photons generated by an x-ray tube. The x-ray source can be turned on and off as needed, eliminating the persistent safety hazards of radio-isotopes while maintaining the ability to perform density measurements. The x-ray tube provides a controlled, non-persistent radiation source that resolves the health and safety concerns.
2Measurement precision
If separate output-monitor detectors are added to monitor tube output, then measurement accuracy is improved, but space constraints in borehole environments make this impractical
Solution Approach 1:
The patent combines the measurement detector and output-monitor detector functions into a single integrated detector assembly. The same detector that measures fluid density also monitors x-ray tube output by detecting photons that travel through known-density reference materials. This merging eliminates the need for separate monitoring detectors, resolving the space constraint problem while maintaining measurement accuracy.
Solution Approach 2:
The detector assembly is designed to perform multiple functions: measuring fluid density through the borehole fluid path and simultaneously monitoring tube output through reference material paths. This multi-functional design allows one detector to replace what would traditionally require separate detectors, accommodating the limited space in borehole environments.
3Measurement precision
If multiple scintillators with distinct characteristics are used to differentiate radiation paths, then sensitivity to specific paths is enhanced, but device complexity increases
Solution Approach 1:
The patent uses multiple scintillators with different light decay time constants positioned at specific locations within the detector assembly. Each scintillator has optimized characteristics for detecting photons from specific paths (e.g., through reference materials versus through borehole fluid). This local differentiation of scintillator properties enables path-specific sensitivity while maintaining a relatively compact and manageable device structure.
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 solution effectively measures fluid density in boreholes by distinguishing between different radiation paths and enhancing sensitivity, providing accurate density measurements while addressing health and safety concerns and space constraints.
Implementation Method 1
at least two scintillators (e.g., YSO, CaF2), each having scintillation-light-time characteristics distinguishable from scintillation-light-time characteristics of the other scintillators
Implementation Method 2
These scintillators are each coupled to a common photodetector (e.g., photomultiplier tube)
Implementation Method 3
shielding configured to enhance the sensitivity of the scintillators to photons travelling along certain paths as compared to photons traveling other paths
Data Source
AI summary
Technology for estimating the density of a material is disclosed. A radiation sensor includes at least two radiation detectors each configured to produce electronic signals having a characteristic time parameter, a pulse-shape discriminator to distinguish amongst the detector signals using the characteristic time parameters, and radiation shielding that is configured to provide different radiation paths to the detectors wherein the different radiation paths include at least some different material. A method includes providing at least two detectors and two radiation paths through a radiation shield, measuring the intensity of radiation at each of the detectors, and combining the measures of intensity to estimate a density of a material found in greater amounts in one radiation path than in the other radiation path.