<p>The application of a controllable neutron source for measuring formation porosity in the advancement of nuclear logging has garnered increased attention. The existing porosity algorithm, which is based on the thermal neutron counting ratio, exhibits lower sensitivity in high-porosity regions. To enhance the sensitivity, the effects of elastic and inelastic scattering, which influence the slowing-down of fast neutrons, were theoretically analyzed, and a slowing-down model of fast neutrons was created. Based on this model, a density correction porosity algorithm was proposed based on the relationship between density, thermal neutron counting ratio, and porosity. Finally, the super multifunctional calculation program for nuclear design and safety evaluation (TopMC/SuperMC) was used to create a simulation model for porosity logging, and its applicability was examined. The results demonstrated that the relative error between the calculated and actual porosities was less than <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1654_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">$1\%$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>%</mo> </mrow> </math></EquationSource> </InlineEquation>, and the influence of deviation in the density measurement was less than <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1654_Article_IEq2.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">$2\%$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>2</mn> <mo>%</mo> </mrow> </math></EquationSource> </InlineEquation>. Therefore, the proposed density correction algorithm based on the slowing-down model of fast neutrons can effectively improve the sensitivity in the high-porosity region. This study is expected to serve as a reference for the application of neutron porosity measurements with D–T neutron sources.</p>

Study of the elastic scattering effects of a slowing-down model on D–T neutron porosity logging

期刊论文
发表日期：

2025年3月20日

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Shao-Heng Zhou,
Ying-Long Tao,
Bo Chang,
Li-Juan Hao,
Jie-Qiong Jiang,
Ya-Zhou Li,
Fang Wang,
Quan Gan

摘要

The application of a controllable neutron source for measuring formation porosity in the advancement of nuclear logging has garnered increased attention. The existing porosity algorithm, which is based on the thermal neutron counting ratio, exhibits lower sensitivity in high-porosity regions. To enhance the sensitivity, the effects of elastic and inelastic scattering, which influence the slowing-down of fast neutrons, were theoretically analyzed, and a slowing-down model of fast neutrons was created. Based on this model, a density correction porosity algorithm was proposed based on the relationship between density, thermal neutron counting ratio, and porosity. Finally, the super multifunctional calculation program for nuclear design and safety evaluation (TopMC/SuperMC) was used to create a simulation model for porosity logging, and its applicability was examined. The results demonstrated that the relative error between the calculated and actual porosities was less than $1\%$ $1 %$ , and the influence of deviation in the density measurement was less than $2\%$ $2 %$ . Therefore, the proposed density correction algorithm based on the slowing-down model of fast neutrons can effectively improve the sensitivity in the high-porosity region. This study is expected to serve as a reference for the application of neutron porosity measurements with D–T neutron sources.