Numerical simulation and analysis of the characteristics of spatial distribution of induced γ-ray source used for D-D source density measurement

Abstract

Abstract D-D source has a promising prospect of application in the field of controllable source density logging. However, the spatial distribution of a D-D ‘induced γ-ray source’ varies significantly and such a source is more susceptible to the influence of various formation factors, resulting in relatively low accuracy of density measurement. This study researched the spatial distribution of an induced γ-ray source. First, the principle of D-D controllable source density measurement was analyzed. Second, the generation process of a D-D induced γ-ray source and the spatial distribution under different formation conditions were simulated and studied. Finally, the associated influential factors were summarized. The results indicate that the spatial position and intensity of the induced γ-ray source were susceptible to the influence of various formation factors, such as HI, lithology and salinity. Among these factors, HI had greatest impact on the spatial position of induced γ-ray source and, particularly, when formation HI varied within the range of 0–0.1, the spatial positions of capture γ-rays changed significantly. In addition, as HI increased, the intensity of γ-rays also increased gradually. Formation lithology and salinity had a greater impact on the intensity of induced γ-rays than on the spatial distribution of these γ-rays. For formations of different lithologies, as the types and contents of main elements were different, the intensity of capture γ-rays also varied. This research provides the basic data for correcting the effects on a D-D induced γ-ray source and establishing a method of density measurement using a D-D controllable source.