Browsing by Subject "XRF"
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Item Paleoenvrironmental Controls on Diagenesis of Organich-Rich Shales in the Eagle Ford Group(2014-08-27) Kruse, KendraCarbonate precipitation can be either promoted or inhibited by microbial processes in different redox zones. It is therefore possible for basin redox evolution to indirectly control early carbonate diagenesis and modify reservoir properties of corresponding shale units. The goals of this study were to analyze geochemical characteristics of the Late Cretaceous Eagle Ford Group in McMullen County, Texas to test the hypotheses that (1) the redox state of the water column controlled carbonate cement abundance and (2) carbonate cement lowered organic matter content by volumetric dilution. An x-ray analytical microscope was used to map elemental compositions of fresh core samples within the Eagle Ford Group. Resultant maps were used to characterize carbonate cements and to estimate the redox state of the overlying water column during deposition, as indicated by the relative abundances of the trace metals Mo, V, and Cr. Results indicate that cementation occurred early relative to compaction. Ti Kal normalized Mo Kal and CaKal fluorescence intensities are positively correlated throughout the unit, suggesting that carbonate cementation was related to the redox state. Total organic carbon is negatively correlated in the upper Lower Eagle Ford with (Ca Kal)/(Ti Kal) fluorescence ratio, consistent with volumetric dilution of organic matter by diagenetic cementation prior to compaction. In contrast, there is no significant correlation between total organic carbon and carbonate content in the more organic-rich Lower Eagle Ford.Item XRF elemental and mineralogical analysis of core sample and well cuttings in granite wash area of Wheeler County, Texas(2014-12) Aguilar, Gabriel; Fisher, W. L. (William Lawrence), 1932-; Rowe, HarryX-Ray Fluorescence (XRF) technology is used in the oil and gas industry to supplement traditionally-acquired well data and to assess mineralogical variability in a non-destructive manner. The application and usefulness of this technology permits many smaller oil and gas companies to spend limited research funds on other areas besides expensive and labor-intensive NMR/SEM/XRD testing. This paper demonstrates XRF technology used for a mineralogical study of the Granite Wash area in Wheeler County, Texas. The Granite Wash is 160 miles long and 30 miles wide and is located in Western Oklahoma and the Texas panhandle and is Pennsylvanian (Morrowan) in age. The most productive stratigraphy in this region comes primarily from several detrital washes derived from the Wichita-Amarillo Uplift (Railroad Commission of Texas). The geologic characteristics of this region range from coarse conglomerates to sandstone, shale, and turbidite sequences and this is reflected in the complexity and heterogeneity of the reservoirs. The XRF datum are correlated to CoreLab analyses of spectral gamma ray and radioactive elements, confirming the interpretation of the composition of sandstones and organic markers in the subsurface. The heavy and radioactive elements are also helpful in assisting the geologic interpretation to indicate possible maximum flooding surfaces and source rocks containing hydrocarbons. This study also confirms the presence of chlorite and carbonate cements which can have significant effects on porosity and permeability and can lead to and more accurate reservoir characterization of future oil and gas wells. The data from the XRF instrument is also able to support the user in interpreting and recognizing drilling muds that have infiltrated formations and altered the chemical composition of the formation rocks. Plots of pyrite versus clay content define trends across the different wells and can help build the subsurface geologic understanding. Finally, the similarities in the readouts of the XRF data are compared with BakerHughes’ Rockview nuclear magnetic resonance test to confirm elemental composition and the use of this instrument in assessing the mineralogy and lithology of future oil and natural gas reservoirs.