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Monte Carlo Study on Gas Pressure Response of He-3 Tube in Neutron Porosity Logging

TIAN Li-li;ZHANG Feng;WANG Xin-guang;LIU Jun-tao   

  1. School of Geosciences, China University of Petroleum, Qingdao 266580, China
  • Online:2016-05-20 Published:2016-06-03

中子孔隙度测井探测器气压响应数值模拟

田立立;张锋;王新光;刘军涛   

  1. 中国石油大学(华东)地球科学与技术学院,山东 青岛266580

Abstract:

Thermal neutrons are detected by (n,p) reaction of Helium-3 tube in the compensated neutron logging. The helium gas pressure in the counting area influences neutron detection efficiency greatly, and then it is an important parameter for neutron porosity measurement accuracy. The variation law of counting rates of a near detector and a far one with helium gas pressure under different formation condition was simulated by Monte Carlo method. The results showed that with the increasing of helium pressure the counting rate of these detectors increased firstly and then leveled off. In addition, the neutron counting rate ratio and porosity sensitivity increased slightly, the porosity measurement error decreased exponentially, which improved the measurement accuracy. These research results can provide technical support for selecting the type of Helium-3 detector in developing neutron porosity logging.

Key words: Helium-3 tube, counting area gas pressure, neutron, Monte Carlo simulation

摘要:

在补偿中子孔隙度测井中He-3管利用(n,p)反应来探测热中子,管内灵敏区所充氦气气压对中子探测效率影响较大,决定中子孔隙度测量精度。利用蒙特卡罗方法模拟研究不同地层条件下远、近探测器计数率随He-3气压的变化规律。计算结果显示,随着He-3气压增大,近、远探测器计数先增大再趋于平缓,计数比值略有增大,孔隙度灵敏度增加,孔隙度测量误差呈幂指数减小,提高了测量精度。研究结果可为仪器研制过程中选择He-3管提供技术支持。

关键词: He-3管, 灵敏区气压, 中子, 蒙特卡罗模拟