Electronic Neutron Source Porosity Conversion via Density Correlation
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Solution Overview
Problem
In hydrocarbon exploration, existing neutron porosity tools using chemical sources are less desirable due to radiation concerns and scarcity, while electronic source tools provide less commonly used epithermal hydrogen index measurements that differ significantly from traditional thermal neutron porosity, necessitating a method to convert measurements between different neutron tools.
Innovation Solution
A method to convert slowing-down length and countrate ratios from electronic neutron source tools to equivalent measurements from chemical source tools using correlation functions dependent on formation bulk density and thermal neutron capture cross section, allowing derivation of thermal neutron porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chemical neutron sources are used, then thermal neutron porosity measurements can be obtained, but radiation safety concerns and source scarcity worsen
Solution Approach 1:
The patent changes the neutron energy parameter from thermal to epithermal range, allowing electronic sources to replace chemical sources while maintaining porosity measurement capability through conversion algorithms
Solution Approach 2:
The patent creates a computational copy of thermal neutron porosity measurements by converting epithermal neutron data through correlation functions, eliminating the need for actual thermal neutron sources
2Object-affected harmful factors
If electronic neutron sources are used, then radiation safety improves, but measurement type changes to epithermal hydrogen index
Solution Approach 1:
The patent introduces correlation functions as intermediaries that translate epithermal neutron measurements into equivalent thermal neutron porosity values, bridging the gap between different measurement types
Solution Approach 2:
The patent transforms the measurement parameter from epithermal hydrogen index to thermal neutron porosity through mathematical conversion, allowing electronic sources to provide traditional measurement outputs
3Adaptability or versatility
If epithermal neutron measurements are taken, then electronic source compatibility improves, but direct thermal neutron porosity measurement capability deteriorates
Solution Approach 1:
The patent makes the measurement system universal by enabling electronic sources to perform both epithermal hydrogen index measurements and converted thermal neutron porosity measurements through software algorithms
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 conversion of epithermal neutron measurements to thermal neutron porosity, reducing reliance on chemical sources and enhancing safety and environmental sustainability by allowing electronic source tools to provide traditional thermal neutron porosity measurements.
Implementation Method 1
These high-energy neutrons interact with nuclei in the formation and become slowed mainly by elastic scattering to near thermal energies
Implementation Method 2
The slowing-down process is dominated by hydrogen
Implementation Method 3
At thermal energies, the neutrons diffuse through the material until they undergo thermal capture
Implementation Method 4
Capture is dominated by hydrogen and other thermal neutron absorbers
Implementation Method 5
When 2D and 3T collide, they react to produce high-energy neutrons (about 14 MeV)
Data Source
AI summary
A method for determining at least one formation property calculated from neutron measurements acquired with a downhole tool includes emitting neutrons from a source in the tool into the formation, detecting neutrons with at least one detector in the downhole tool, calculating a first slowing-down length (L1) based on the detected neutrons, and deriving a second slowing-down length (L2) based on the first slowing-down length (L1). Further steps include deriving a correlation function for relating slowing-down lengths from a first tool to slowing-down lengths associated with a different source, wherein the correlation function depends on formation properties such as bulk density; and applying the correlation function to the slowing-down length of the first tool to derive the slowing-down length of the second tool. A method for determining a thermal neutron formation porosity based on a slowing-down length from epithermal neutron measurements from an electronic neutron source includes converting the slowing-down length into a computed neutron slowing-down length from thermal neutron measurements from a chemical neutron source, wherein the converting uses a correlation function that depends on formation bulk density; deriving a thermal neutron countrate ratio based on the computed neutron slowing-down length, wherein the deriving uses a function that depends on the formation bulk density and formation sigma; and computing the thermal neutron formation porosity from the thermal neutron countrate ratio.