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根据D-D反应中子的能谱和角分布数据,建立了中子源模型;根据石灰岩地层标准刻度井群数据,建立了井模型。采用MCNP程序模拟了井中中子和γ射线的输运,得到了不同地层密度和不同源距处NaI探测器中的混合γ射线能谱和非弹γ射线能谱。在混合γ射线能谱2.5～5.0 MeV能区开窗,研究了开窗区混合γ射线相对计数随源距的变化关系,确定源距应选择在30～80 cm范围,给出了密度与混合γ射线计数之间的非线性关系。研究表明,可以利用D-D中子源的混合γ射线能谱来实现n-γ密度测井。
Based on the energy spectrum and angular distribution data of the neutron D-D reaction, a neutron source model is established. Based on the well group calibration data of limestone stratum, a well model is established. The MCNP program was used to simulate the well transport of neutrons and γ-rays, and the mixed γ-ray energy spectra and non-bomb γ-ray energy spectra of NaI detectors at different formation densities and source distances were obtained. In the mixed gamma ray energy spectrum of 2.5-5.0 MeV, the relationship between the relative count of the mixed γ-ray and the source distance in the window area was studied. The source spacing should be selected in the range of 30-80 cm. The relationship between density and mixing Nonlinear relationship between γ-ray counts. Studies have shown that n-γ density logging can be achieved using mixed γ-ray energy spectra from D-D neutron sources.