Numerical simulation of density logging based on X-ray and gamma ray sources

Key words:  X-ray source  gamma ray source  density logging  attenuation coefficient  Monte Carlo method

Abstract:

The attenuation coefficient of photoelectric absorption and Compton scattering for different energy rays with the medium are calculated and analyzed by XCOM.The Monte Carlo method is used to compare the scattering spectrum, the response of density logging, and the precision of X-ray and Cs-137 sources. The results show that because the X-ray energy is lower than that of the 0.662 MeV gamma rays, the X-ray attenuation is faster in the same formation, and this difference is more obvious withincreased density. At the same source-detector distance, the sensitivity to the density of the lower energy X-ray source is higher than that of the Cs-137 source, but is dependent on lithology.Considering the source intensity,when the source-detector distance is 33 cm for the X-ray source and 38 cm for the Cs-137 source, respectively, the counting statistics is equal between the two sources.The sensitivity to the density of the X-ray source is higher than that of the Cs-137 source, and the uncertainty of density measurements of the X-ray source is lower than that of the Cs-137 source, which indicates that the density logging precision of the X-ray source is higher than that of the Cs-137 source. It is concluded that X-ray source can replace gamma ray source for density logging, but further research in instrument design, energy spectrum processing and density calculation is needed.