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密度是储层评价的重要参数.传统的密度测井是测量137Cs同位素放出的伽马射线与地层作用后的剩余伽马射线强度.虽然在密度测量方面已经非常成熟,但是由于同位素源具有放射性危害,使得脉冲中子源密度测井技术应运而生.脉冲中子密度测井使用电控脉冲中子源,中子源发射14MeV的快中子,通过非弹散射和俘获放出伽马射线,伽马射线在伽马源和探测器之间的地层中衰减,据此计算地层密度.脉冲中子密度测井可以计算密度、识别地层骨架,且探测深度大,没有放射性危害,因此越来越受到青睐,商用测井仪器已投入使用.另一方面,因为脉冲中子源密度测井与传统密度测井本质上有所区别,次生伽马源能量不单一、位置不固定,使得该方法的研究也面临着一些新的挑战,需要进一步深入的研究与测试.本文对脉冲中子源密度测井的方法原理、γ场特性、仪器的研究与应用以及未来发展方向进行介绍,以期对我国未来此类仪器的研发与解释方法研究提供一定的借鉴.
Density is an important parameter in reservoir evaluation, which is a measure of the residual gamma ray intensities after γ-ray emission from 137Cs isotopes and stratigraphy.Although density measurements have been well established, due to the radioactive hazard of isotope sources , Making the pulse neutron density logging technology came into being.Pulse neutron density logging using electronically controlled pulsed neutron source, the neutron source emits 14MeV fast neutron, released by non-elastic scattering and capture of gamma rays, gamma The horse ray is attenuated in the formation between the gamma source and the detector, from which the density of the formation is calculated.The pulsed neutron density logging can be used to calculate the density and identify the formation skeleton with a large detection depth and no radioactive hazard, Favored commercial logging tools have been put into use.On the other hand, because the pulse neutron source density logging and traditional density logging are essentially different, the secondary gamma energy is not a single source, the location is not fixed, making the method of The research also faces some new challenges and needs further research and testing.In this paper, the principle of pulse neutron source density logging, the characteristics of γ-field, the research and application of instrumentation And the future development direction are introduced in order to provide a reference for the study of such equipment research and development and interpretation of the future.