科研之友
微信
新浪微博
Facebook
分享链接
摘要
Pulsed-neutron gamma density (NGD) logging, as an emerging density measurement technology, is of significance for radioprotection and technological development of logging-while-drilling (LWD). Compared to the gamma-gamma density (GGD), the NGD technique has the advantages of environment, safety and health. However, due to the lack of theory, the quantitative relationship between the inelastic gamma field distribution and formation parameters has not been resolved so far. The current data-processing methods are mainly based on the empirical formulas obtained by experiment and simulation methods. In order to quantitatively clarify the logging mechanism and theoretically develop a new density algorithm, the coupled idea is introduced to NGD logging. Based on the theories of fast-neutron scattering and gamma attenuation, the fast neutron-gamma coupled field theory is put forward to describe the distribution of inelastic gamma field. The inelastic gamma field distribution is characterized by the inelastic scattering cross section, fast-neutron scattering free path and formation density, and the influence of the formation parameters on the field distribution is quantified and a new density algorithm is derived from the coupled theory. The new density algorithm can avoid the complex correction of hydrogen index and simplify the process of density measurement. In addition, the coupled field theory and the new density algorithm are verified by Monte Carlo simulation. The research not only clarifies the NGD mechanism but also provides theoretical guidance for NGD logging.
- 出版日期2017-8
- 单位中国石油大学（北京）; 南京航空航天大学
