A method for determining density based on gamma ray and fast neutron detection using a Cs2LiYCl6 detector in neutron-gamma density logging. (December 2018)

• Record Type: Journal Article
• Authors: Zhang, Quanying; Zhang, Feng; Gardner, Robin P.; Yan, Huizhong; Wu, Guoli; Tian, Lili; Chen, Qian; Ti, Yongzhou
• Is Part Of: Applied radiation and isotopes. Volume 142(2018:Dec.)
• Page Start: 77
• Page End: 84
• Publication Date: 2018-12
• Subjects: Pulsed neutron-gamma density -- CLYC detector -- Monte Carlo simulation -- Fast neutron -- Inelastic gamma; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2018.09.011
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: With the increasing demand for radioisotope-free operations, pulsed neutron-gamma density (NGD) has become increasingly important for logging-while-drilling (LWD) development. However, current NGD tools, adopting the multiple-detector array design, are not conducive to the simplification of instrument design and measurement system. To break obstacles, based on the fast neutron-gamma coupled theory, a new density measurement method was proposed. Further, combined with the neutron-gamma simultaneous detection characteristics of the Cs2 LiYCl6 (CLYC) detector, an NGD measurement system consisting of a D-T source and one CLYC detector was used. Results show that the new method is capable of determining formation density using a single CLYC detector, which can not only avoid complex instrument systems but also improve density sensitivity. Moreover, the applicability of the new density method was well verified by Monte Carlo simulation. Additionally, the method was successfully applied in a simulated well, and density results are in good agreement with the benchmarked formations. The research provides theoretical guidance for NGD instrument design. Highlights: A new NGD measurement system with a D-T source and one CLYC detector is proposed neutron gamma density logging. The neutron and gamma information can be recorded with a single CYLC detector, which can simplify the tool structure. The new method cannot only avoid multiply detectors array and complex systems, but also improve the density sensitivity.