Single Gamma Detector Gas Saturation Analysis
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Solution Overview
Problem
Accurately determining gas saturation in underground formations using neutron-gamma tools is challenging, especially when the salinity of the water is unknown, as existing methods require complex detection and analysis from multiple detectors.
Innovation Solution
A system and method utilizing a single gamma detector to determine gas saturation by analyzing the ratio of inelastic count rate to modified capture count rate, where the chlorine response is removed from the capture count rate, allowing for accurate gas saturation indication even without knowing the water salinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple detectors are used to determine gas saturation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the chlorine response component from the capture count rate data, isolating the signal related to gas saturation from the interfering chlorine signal. This allows accurate gas saturation determination using a single gamma detector by eliminating the harmful interference rather than requiring multiple detectors to separate the signals.
Solution Approach 2:
The patent transforms the capture count rate by removing the chlorine response component, changing the parameter from raw count rate to modified count rate. This parameter transformation enables the single detector to provide gas saturation information that would otherwise require multiple detectors to obtain simultaneously.
2Measurement precision
If chlorine response is not removed from capture count rate, then measurement precision deteriorates, but device complexity remains low
Solution Approach 1:
The patent converts the harmful chlorine interference into a useful signal by measuring the chlorine response and then subtracting it from the total capture count rate. The previously harmful chlorine signal becomes a correction term that, when removed, reveals the underlying gas saturation information hidden within the mixed signal.
3Measurement precision
If water salinity is unknown, then measurement precision deteriorates, but ease of operation is improved
Solution Approach 1:
The system performs self-calibration by using the single gamma detector to measure both the chlorine response and the gas saturation signal. The method automatically determines the chlorine component from the capture count rate and subtracts it, enabling the system to adapt to unknown salinity conditions without requiring external calibration data or prior knowledge of water composition.
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 accurate determination of gas saturation using a single gamma detector, simplifying the detection process and providing reliable results across varying formation conditions, including different salinity levels and lithologies.
Implementation Method 1
obtaining an inelastic count rate and a capture count rate of a gamma detector
Implementation Method 2
obtaining an inelastic count rate and a capture count rate of a gamma detector
Data Source
AI summary
Determining a value indicative of gas saturation of a formation. At least some of the illustrative embodiments are methods including: obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth; removing at least a portion of the chlorine response from the capture count rate, thereby creating a modified capture count rate; calculating a ratio of an inelastic count rate to the modified capture count rate for the particular borehole depth; determining a value indicative of gas saturation based on the ratio; and producing a plot of the value indicative of gas saturation as a function of borehole depth for a formation that the borehole at least partially penetrates.