Potential value of spectral gamma ray logging and data analysis to environmental applications of hydrofacies analysis and mass flux estimation

PreviousNext You have accessSymposium on the Application of Geophysics to Engineering and Environmental Problems 2021Potential value of spectral gamma ray logging and data analysis to environmental applications of hydrofacies analysis and mass flux estimationAuthors: Gregory ByerGregory ByerArcadis U.S., Inc.Search for more papers by this authorhttps://doi.org/10.4133/sageep.33-028 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract Spectral Gamma Ray (SGR) logging in sedimentary sequences can provide significantly greater information about geologic conditions than natural gamma ray logs. Although a number of naturally occurring gamma ray emitters exist in nature, three elements generally contribute the majority of natural gamma rays that are logged. Because of its ability to quantify a broad spectrum of gamma ray energies, SGR logging can yield estimates of the three most dominant naturally occurring radioisotopes which include potassium (K) via potassium-40, thorium (Th) via thorium-232, and uranium (U) via uranium-238. Of these, potassium is the most abundant in sedimentary rocks, but thorium and uranium are present in small quantities. The petroleum industrial has benefited from the information provided by SGR logging utilizing the concentrations of K, U and Th, and there are a number of useful relationships that have been found associated with data obtained from SGR logging. For example, evidence of the maturity of sediments by the types of clay minerals and other mineral phases present can be derived from the ratio of thorium to potassium (Th/K). There are a number of inferences that can be made. Immature sediments containing feldspars and micas will have a relatively high concentration of K and a low Th/K ratio. Conversely, a high Th/K ratio can be indicative of a 1) high concentration of heavy, thorium bearing minerals associated with high energy channel deposits at an erosional unconformity or 2) existence of clay minerals low in potassium content such as kaolinite and chlorite. Low Th/U ratios can be indicative of black organic-rich shales. In addition, under oxidizing conditions uranium is mobile, whereas thorium is stable. In a oxidation-reduction zone created by subaerial exposure of sediments, redistribution of uranium downward into the reduced soils will yield a relatively high Th/U ratio at the uppermost limit of the paleosol, followed by a reversal to a low Th/U ratio within the reduced zone where mobilized uranium is concentrated. Additionally, potassium will also be leached from the oxidized zone and a high Th/K ratio can also be expected. Traditionally, plots of Th/K and Th/U have been made to tease out the various relationships noted above. However, a more powerful tool for the examination of SGR data is available via the Briggs Color Cubing (BCC) method. Sullivan and Song (2017) presented this method of blending potassium, uranium and thorium concentrations derived from SGR data processing as a powerful method for creating continuous, depth-based plots which extend the information yielded by SGR analysis in a way cross-plots and ternary diagrams cannot. This method of analysis is increasingly being used in the oil and gas industry to improve stratigraphic analysis and correlation. However, it is not commonplace in environmental applications, and with the growing use of sequence stratigraphy and hydrofacies analysis to determine contaminant mass flux, the use of the BCC method applied to SGR data offers the opportunity to add a level of unique information about the depositional environment of sediments. Examples of this type of analysis in an alluvial setting, created using WellCAD 5.2, show the potential value of this approach to environmental applications. Keywords: environmental, facies, logging, shale, sedimentPermalink: https://doi.org/10.4133/sageep.33-028FiguresReferencesRelatedDetails Symposium on the Application of Geophysics to Engineering and Environmental Problems 2021ISSN (online):1554-8015Copyright: 2021 Pages: 349 publication data© 2021 Published in electronic format with permission by the Society of Exploration Geophysicists and Environment and Engineering Geophysical SocietyPublisher:Environmental & Engineering Geophysical Society HistoryPublished: 11 Jun 2021 CITATION INFORMATION Gregory Byer, (2021), "Potential value of spectral gamma ray logging and data analysis to environmental applications of hydrofacies analysis and mass flux estimation," Symposium on the Application of Geophysics to Engineering and Environmental Problems Proceedings : 62-62. https://doi.org/10.4133/sageep.33-028 Plain-Language Summary KeywordsenvironmentalfaciesloggingshalesedimentPDF DownloadLoading ...