准直孔对三探测器法密度测井精度影响的MC模拟研究

MC simulation of the collimation effects on measurement precision of high-resolution logging

本文应用MonteCarlo数值模拟方法,计算了窗形、楔形γ源准直孔和窗形、楔形、槽形探测器准直孔以及开口角度对探测器计数率和地层灵敏度的影响。结果表明,γ源的准直孔形状和开口角度对测量精度的影响远大于探测器准直孔形状和开口角度;γ源和探测器的准直孔形状和开口角度对计数率的影响远大于对地层灵敏度的影响;45°楔形γ源准直孔、0°窗形长源距探测器准直孔、5°-15°的窗形中源距探测器准直孔和0°窗形短源距探测器准直孔会提高高分辨率密度测井的测量精度。

In this paper, the MCNP code is used to calculate responses to detector counting rate and formation sensitivity in oil-well logging with different opening shapes and angles of the y-ray source aperture and detector collimator. The results show that the opening shape and angle of the source aperture affect the measurement precision far more than the opening shape and angle of the detector collimator, and the influences are greater than that of the formation sensitivity. A logging system that is equipped with a y-ray source having a cuniform aperture of 45° opening angle, and a window aperture of 0° opening angle for a long-spacing detector or a short-spacing detector, and 5°-15° opening angle for a middle-spacing detector, will improve the measurement precision.