title: Study on the impact of pair production interaction on D-T controllable neutron density logging.
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 2MeV. By selecting 0.2-2MeV 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.
authors.affiliation: College of Geo-Resources and Information, China University of Petroleum, Qingdao, Shandong, 266580, China.
authors.forename: Huawei
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Resources and Civil Engineering, Shandong University of Science and Technology, Tai'an, Shandong, 271019, China. Electronic address: lilyofchina@sina.com.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: College of Geo-Resources and Information, China University of Petroleum, Qingdao, Shandong, 266580, China.
authors.forename: Boran
authors.initials: B
authors.lastname: Hou
keywords: Compton scattering; D-T controllable neutron source; Density logging; Induced gamma source; Pair production