Single-Detector Pulsed-Neutron Probe for Uranium and Hydrogen Porosity
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Solution Overview
Problem
Existing methods for evaluating uranium content and hydrogen porosity in geological formations using active neutron interrogation face challenges in accurately determining porosity beyond 40% and require separate probes for each measurement.
Innovation Solution
A compact drilling device with a single neutron detector and pulsed neutron generator, utilizing a shielding device and moderator, allows simultaneous evaluation of uranium content and hydrogen porosity through distinct time intervals for neutron counting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two distinct probes are used to evaluate uranium content and hydrogen porosity separately, then each measurement can be performed with dedicated optimization, but the device complexity increases and acquisition time increases
Solution Approach 1:
The patent combines two separate probes (one for uranium content measurement and one for hydrogen porosity measurement) into a single integrated tool. This merging allows both measurements to be performed simultaneously in the same borehole section, reducing device complexity and acquisition time while maintaining the measurement precision of each individual measurement through dedicated detection chambers and neutron sources.
2Measurement precision
If two distinct probes are used for separate measurements, then each probe can be optimized for its specific function, but the acquisition time increases
Solution Approach 1:
The integrated tool performs both uranium content and hydrogen porosity measurements continuously during a single downhole operation. The dual neutron sources and detection systems operate simultaneously or in rapid succession, eliminating the need to lower and raise the tool between measurements, thus maintaining continuous useful action and reducing total acquisition time while preserving measurement precision through optimized detection geometries.
3Productivity
If a single probe is used for both measurements, then device complexity is reduced and acquisition time is reduced, but measurement precision may be compromised
Solution Approach 1:
The single integrated probe is segmented into distinct functional sections: a first detection chamber optimized for uranium content measurement with its own neutron source and detector, and a second detection chamber optimized for hydrogen porosity measurement with its own neutron source and detector. This segmentation allows each measurement function to maintain its own optimized geometry and detection parameters, preserving measurement precision while achieving the productivity benefits of a single tool.
4Measurement precision
If thermal neutrons are used to determine uranium content, then uranium-235 fission can be detected, but the measurement becomes sensitive to hydrogen porosity variations
Solution Approach 1:
The patent creates locally optimized detection environments within the single probe: the first detection chamber uses thermal neutrons and is specifically configured to measure uranium content, while the second detection chamber uses fast neutrons and is specifically configured to measure hydrogen porosity. This local quality differentiation allows each measurement to be optimized for its target parameter, reducing cross-sensitivity between different formation properties.
5Measurement precision
If fast neutrons are used to determine hydrogen porosity through backscattering, then porosity measurement is obtained, but uranium content measurement is interfered with
Solution Approach 1:
The second detection chamber is specifically designed with fast neutron sources and detectors optimized for hydrogen porosity measurement through backscattering. The chamber geometry, detector positioning, and neutron source configuration are locally optimized to maximize sensitivity to hydrogen content while minimizing interference from uranium content, thereby maintaining measurement precision for porosity despite the presence of uranium in the formation.
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
Enables reliable and precise determination of both uranium content and hydrogen porosity in a geological formation using a single tool, reducing acquisition time and ensuring accurate measurements.
Implementation Method 1
Some of the neutrons emitted are backscattered by the hydrogen nuclei toward the probe, while conserving a high energy
Implementation Method 2
Other emitted neutrons thermalize in the formation, i.e. the neutrons slow down following successive shocks with hydrogen nuclei present in the region of interest
Implementation Method 3
Some of the thermal neutrons cause the fission of uranium-235 nuclei and the emission, by fission, of 2 to 3 prompt neutrons
Implementation Method 4
the shielding device being suitable for absorbing a plurality of neutrons having an energy less than a cutoff energy
Implementation Method 5
Other emitted neutrons thermalize in the formation, i.e. the neutrons slow down following successive shocks with hydrogen nuclei present in the region of interest
Data Source
AI summary
A device for evaluating uranium content and hydrogen porosity while drilling includes a probe having a pulsed neutron generator for emitting a pulse of neutrons, a single neutron detector, a neutron counting unit for measuring over time a number of neutrons backscattered from hydrogen nuclei and a number of prompt fission neutrons resulting from interactions with uranium nuclei. The device also includes a hydrogen porosity evaluation unit for evaluating the hydrogen porosity using a total number of backscattered neutrons and a uranium evaluation unit for evaluating the uranium content using a total number of prompt fission neutrons.