Study on the impact of pair production interaction on D-T controllable neutron density logging. (May 2016)

• Record Type: Journal Article
• Authors: Yu, Huawei; Zhang, Li; Hou, Boran
• Is Part Of: Applied radiation and isotopes. Volume 111(2016:May)
• Page Start: 104
• Page End: 109
• Publication Date: 2016-05
• Subjects: Density logging -- Induced gamma source -- D-T controllable neutron source -- Compton scattering -- Pair production; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2016.01.030
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: This paper considers the effect of pair production on the precision of D-T controllable neutron source density logging. Firstly, the principle of the traditional density logging and pulsed neutron density logging are analyzed and then gamma ray cross sections as a function of energy for various minerals are compared. In addition, the advantageous areas of Compton scattering and pair production interactions on high-energy gamma ray pulse height spectrum and the errors of a controllable source density measurement are studied using a Monte Carlo simulation method. The results indicate that density logging mainly utilizes the Compton scattering of gamma rays, while the attenuation of neutron induced gamma rays and the precision of neutron gamma density measurements are affected by pair production interactions, particularly in the gamma rays with energy higher than 2 MeV. By selecting 0.2−2 MeV energy range and performing proper lithology correction, the effect of pair production can be eliminated effectively and the density measurement error can be rendered close to the precision of chemical source density logging. Highlights: The effect of pair productions on D-T neutron gamma density logging is validated. The inelastic gamma spectrum above 2 MeV is sensitive to pair production. Mass attenuation coefficient due to pair production varies with lithology. The measurement precision can be effectively improved through lithology correction.