自然伽玛能谱测井仪是探测从地层发射出的不同能量的自然伽玛射线。地层中所含元素的种类和数量取决于地层是怎么沉积的以及沉积后发生的变化。Th、U和K是仪器记录的能谱的主要成分。根据能谱记录,可以计算出这三种元素各自在地层中的含量。计算得到的元素含量与下列因素有关:沉积环境,新生变形和成岩过程,粘土类型和含量。为了提高测量这些变量的精度,采用一种基于自然伽玛能谱分析原理和统计概算理论的复杂数据处理方法。使用CSU计算机测井系统在现场进行实时滤波处理,可以进一步减小Th、U和K的统计误差。于是,在解释之前,涉及自然放射性测量值的大部分统计误差就已经被消除了。在测井和滤波处理之后,可在现场作出初步解释。通过分析自然伽玛能谱测井资料,可以确定地层中最可能存在的放射性物质的性质和数量。特别是,这可以改善泥质指示,并可在现场更精确估算粘土的百分含量。对于复杂岩性,不能立即辨明放射性矿物混合物的确切性质。但是可以提出有关放射性矿物的种类和含量的假设,并综合应用自然伽玛能谱测井及其他测井资料在计算中心进行研究,以便作出定量解释和更准确地判别岩性。自然伽玛能谱测井的附加用途包括地层对比、识别岩相、再现沉积环境、圈定储集层边缘,以及作为识别火成岩、确定渗透率和生产能力的辅助资料。总之,从自然伽玛能谱测井的原理已经了解到,用它可以取得更多有关地层和储集层性质的资料。 Natural gamma ray logging tools are natural gamma rays that detect different energies emitted from the formation. The type and amount of elements contained in the formation depend on how the formation was deposited and what changed after the deposition. Th, U and K are the main components of the energy spectrum recorded by the instrument. According to energy spectrum records, we can calculate the content of these three elements in the formation. The calculated elemental content is related to the following factors: sedimentary environment, deformation and diagenesis, clay type and content. In order to improve the accuracy of measuring these variables, a complex data processing method based on the principle of natural gamma spectroscopy and statistical estimates theory is used. The use of CSU computer logging system in the field of real-time filtering, can further reduce the Th, U and K statistical errors. As a result, most of the statistical errors involved in natural radiometric measurements have been eliminated prior to interpretation. After logging and filtering, a preliminary explanation can be made in the field. By analyzing natural gamma ray log data, the nature and amount of the most likely radioactive material in the formation can be determined. In particular, this can improve mud quality and provide a more accurate estimate of the clay content in the field. For complex lithologies, the exact nature of the radioactive mineral mixture can not be discerned immediately. However, assumptions about the type and content of radioactive minerals can be made and integrated with gamma ray spectroscopy and other logging data in computational centers for quantitative interpretation and more accurate lithology identification. Additional uses for gamma-ray logging include stratum contrast, identification of lithofacies, reconstitution of depositional environments, delineation of reservoir margins, and ancillary data identifying igneous rocks, determining permeability and productivity. In summary, it has been learned from the principle of gamma ray spectrometry logging that it can be used to obtain more information on the properties of formations and reservoirs.