A carbon/oxygen calculation method to improve the response sensitivity of carbon/oxygen logging

IF 1.6 3区工程技术 Q3 CHEMISTRY, INORGANIC & NUCLEAR Applied Radiation and Isotopes Pub Date : 2024-09-04 DOI:10.1016/j.apradiso.2024.111499

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Abstract

Carbon/Oxygen logging is an effective method to perform oil layer recognition and oil saturation calculation, which plays an important role in the evaluation of remaining oil after casing. At present, there are two main methods to calculate the ratio of carbon to oxygen (C/O). Compared with the energy window count method, the element yield method can avoid the influence of background count in the gamma spectrum and calculated carbon/oxygen value has the higher sensitivity and better accuracy, but it is still greatly affected by carbon and oxygen elements in the formation skeleton. Therefore, a new carbon/oxygen calculation method is proposed in this paper to overcome the influence of formation skeleton and improve the response sensitivity of Carbon/Oxygen logging. Based on Monte Carlo method, the inelastic gamma spectrum of pure sandstone and pure limestone skeletons are obtained. Based on spectrum analysis technology, the ratio relationship of carbon, oxygen yield and skeleton mark element (Si, Ca) yield in two skeletons are obtained. Using these ratio relationships, the carbon and oxygen yields from the sandstone and limestone reservoir skeletons are deducted from the total carbon and oxygen yield. A new carbon/oxygen parameter called the residual carbon/oxygen value (C/O)_R is calculated to perform oil-water recognition and a set of oil saturation calculation model suitable for the residual carbon/oxygen value is proposed. The environment application of the residual carbon/oxygen value is also analyzed. The study shows that the residual carbon/oxygen value has higher sensitivity than original carbon/oxygen value in oil layer recognition and has a great accuracy in oil saturation calculation. In environment application aspect, the residual carbon/oxygen value is basically unaffected by formation water salinity and is affected by wellbore fluid and wellbore size obviously. This new carbon/oxygen value calculation method has an important significance to improve the application effect of Carbon/Oxygen logging.

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提高碳/氧测井反应灵敏度的碳/氧计算方法。

碳氧测井是进行油层识别和油饱和度计算的有效方法，在套管后剩余油评价中发挥着重要作用。目前，计算碳氧比（C/O）的方法主要有两种。与能量窗计数法相比，元素产率法可以避免伽马能谱中本底计数的影响，计算出的碳氧值灵敏度更高、精度更好，但受地层骨架中碳氧元素的影响仍然较大。因此，本文提出了一种新的碳/氧计算方法，以克服地层骨架的影响，提高碳/氧测井的响应灵敏度。基于蒙特卡罗方法，得到了纯砂岩和纯石灰岩骨架的非弹性伽马能谱。基于频谱分析技术，得出了两种骨架中碳、氧产率与骨架标志元素（Si、Ca）产率的比值关系。利用这些比例关系，从总碳氧产量中扣除砂岩和石灰岩储层骨架的碳氧产量。计算出一个新的碳/氧参数，称为残余碳/氧值（C/O）R，以进行油水识别，并提出一套适合残余碳/氧值的石油饱和度计算模型。此外，还分析了残余碳氧值在环境中的应用。研究表明，残余碳氧值在油层识别方面比原始碳氧值具有更高的灵敏度，在油饱和度计算方面也有很高的精度。在环境应用方面，残余碳氧值基本不受地层水盐度的影响，受井筒流体和井筒尺寸的影响明显。这种新的碳氧值计算方法对提高碳氧测井的应用效果具有重要意义。

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来源期刊

Applied Radiation and Isotopes 工程技术-核科学技术

CiteScore

3.00

自引率

12.50%

发文量

406

审稿时长

13.5 months

期刊介绍： Applied Radiation and Isotopes provides a high quality medium for the publication of substantial, original and scientific and technological papers on the development and peaceful application of nuclear, radiation and radionuclide techniques in chemistry, physics, biochemistry, biology, medicine, security, engineering and in the earth, planetary and environmental sciences, all including dosimetry. Nuclear techniques are defined in the broadest sense and both experimental and theoretical papers are welcome. They include the development and use of α- and β-particles, X-rays and γ-rays, neutrons and other nuclear particles and radiations from all sources, including radionuclides, synchrotron sources, cyclotrons and reactors and from the natural environment. The journal aims to publish papers with significance to an international audience, containing substantial novelty and scientific impact. The Editors reserve the rights to reject, with or without external review, papers that do not meet these criteria. Papers dealing with radiation processing, i.e., where radiation is used to bring about a biological, chemical or physical change in a material, should be directed to our sister journal Radiation Physics and Chemistry.