QUANTIFICATION OF HETEROGENEITY WITHIN THE TUSCALOOSA MARINE SHALE BASED ON X-RAY FLUORESCENCE ANALYSES OF CUTTINGS FROM HORIZONTALLY DRILLED WELLS IN LITTLE SILVER CREEK FIELD, TANGIPAHOA PARISH, LOUISIANA

The Upper Cretaceous Tuscaloosa Marine Shale (TMS) is an oil-producing play in central Louisiana and southwest Mississippi located at depths between 3,000 and 6,000 m. The TMS is considered an important hydrocarbon reservoir with potential reserves of 7 billion barrels of oil. X-ray fluorescence (XRF) is a rapid, nondestructive method that can be used to analyze cuttings while drilling to improve geosteering within a pay zone. The objective of this research is to test this approach by spatially evaluating geophysical properties and chemostratigraphy of the TMS and characterizing elemental changes along well paths for two completed wells (B-NEZ 43H 001 and B-NEZ 43H 002). Geophysical properties analyzed in this study are from wire-line log data, including resistivity and total gamma ray logs. XRF is used to analyze 175 available well cutting samples from the TMS to measure elemental abundances, which correlate directly to geochemical properties. The geophysical results are used to improve the investigation of the formations in the vertical portion, while XRF results are used to make horizontal chemostratigraphic profiles using major elements and trace elements. Mineralogical analysis is obtained from oxides calculated based on elemental oxide conversions from the XRF data. Based on principal component analysis and mineralogical analysis, chemical changes define the six interbeds in B-NEZ 43H 001 and the five zones in B-NEZ 43H 002. The interbeds are defined due to their relative differences in chemical composition from the main formation. The results have the potential to evaluate the homogeneity of the formation where the target wells were drilled and provide geochemical information for the TMS for future research.