Dual-Function Radiation Detectors for Accurate Borehole Sigma Measurement
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Solution Overview
Problem
Current pulsed neutron logging tools can only detect either thermal neutrons or gamma rays, limiting their ability to accurately measure borehole and formation sigma, and fail to comprehensively correct for environmental effects such as wellbore size and salinity, leading to incomplete and imperfect measurement results in various field situations.
Innovation Solution
The use of multiple dual-function radiation detectors capable of distinguishing between neutron and gamma rays using pulse shape discrimination techniques, allowing for simultaneous measurement of thermal neutron time-decay signals and capture gamma ray time-decay signals to obtain accurate borehole and formation sigma values, while also compensating for environmental effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple single-function detectors (neutron or gamma ray) are used to measure borehole and formation sigma, then measurement coverage is improved, but device complexity and number of detectors increase
Solution Approach 1:
The patent applies pulse shape discrimination technology to enable detectors to distinguish between neutron and gamma ray signals, allowing a single detector to perform both neutron detection and gamma ray detection functions. This multi-functional capability resolves the contradiction by maintaining comprehensive measurement coverage while reducing the total number of detectors required.
Solution Approach 2:
The patent merges the detection functions for neutrons and gamma rays into a single detector system using pulse shape discrimination. By combining what were previously separate single-function detectors into a unified multi-functional detector, the system reduces device complexity while preserving the ability to measure both borehole and formation sigma accurately.
2Measurement precision
If environmental corrections for wellbore size, casing size, and cement thickness are applied, then measurement accuracy in various field situations is improved, but computational complexity increases
Solution Approach 1:
The patent performs environmental corrections for wellbore size, casing size, and cement thickness simultaneously with the primary sigma measurements rather than as separate subsequent steps. By incorporating these corrections into the measurement process itself, the system achieves high measurement accuracy while managing computational complexity through integrated processing.
Solution Approach 2:
The pulse shape discrimination technology enables the detector system to collect multiple types of data (neutron and gamma ray signals) that are then used for both primary measurements and environmental corrections. This multi-functional data collection approach supports comprehensive corrections without proportionally increasing computational complexity.
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 enables more accurate and comprehensive measurement of borehole and formation sigma, reducing the number of detectors required and improving measurement precision by simultaneously detecting both neutrons and gamma rays, thereby enhancing the accuracy of hydrocarbon reservoir characterization.
Implementation Method 1
multiple dual-function radiation detectors of neutrons and gamma rays that can be priorly distinguished using pulse shape discrimination techniques
Implementation Method 2
water and hydrocarbons will slow down (thermalize) the neutrons
Implementation Method 3
neutrons will scatter inelastically from some elements resulting in the emission of gamma rays
Implementation Method 4
certain elements will capture the neutrons either right away or after they slow down, emitting gamma rays and reducing neutron flux
Implementation Method 5
measuring the decline of the thermal neutron population in said formations within a fixed period
Data Source
AI summary
A method for wireline or logging-while-drilling systems that uses pulsed neutron sources coupled to multiple dual-function radiation detectors of neutrons and gamma rays, as well as a non-transitory computer readable memory device that can distinguish using pulse shape discrimination techniques the neutrons from the gamma rays in order to measure thermal neutron time-decay signals and thermal neutron capture gamma ray time-decay signals that are later further process using the non-transitory computer readable memory device to obtain a borehole sigma and formation sigma that are not affected by near-wellbore environments.