X-ray fluorescence analysis of the Bakken and Three Forks Formations and logging applications

Autor: Lance D. Yarbrough, Nicholas B. Lentz, Russell Carr
Rok vydání: 2019
Předmět:
Zdroj: Journal of Petroleum Science and Engineering. 172:764-775
ISSN: 0920-4105
DOI: 10.1016/j.petrol.2018.08.070
Popis: The ability to characterize subsurface lithology downhole is critical for hydrocarbon identification and subsequent production. Well logging methods frequently used in industry are gamma ray, spontaneous potential, and resistivity principles. Few publications have addressed the feasibility of using X-ray fluorescence (XRF) as a logging method. The exploitation of deep shale petroleum systems will demand greater stratigraphic resolution; X-ray fluorescence well logging (XRFWL) may accurately and efficiently identify geochemical signatures in rock samples, which could give information about hydrocarbon bearing strata in both vertical and horizontal drilling applications when depth matching core data to wells is performed. This case study analyzed eight core sections from the lower Bakken and Three Forks Formation of the Williston Basin in North Dakota using X-ray fluorescence. The Charlotte 1-22H core sequence from Continental Resources, Inc. (Continental Resources) was also included to assess the elemental composition of the stratigraphic interval spanning the Lodgepole, Bakken, Pronghorn, and Three Forks Formations. Core sections were exposed to X-ray at 45-keV excitation voltages to provide fluorescence spectra; count rate values were obtained and elemental ratios were calculated to assess the geochemical composition of each stratigraphic interval. From these XRF analyses we created chemostratigraphic logs representing the subsurface lithology of the Williston Basin diagenetic processes in the host unit were then assessed based on elemental ratio quantity. This novel case study of the Bakken and Three Forks Formations in North Dakota may not necessarily be dispositive for identifying other geologic units. Understanding the spatial distribution of lightweight, mid-range, and trace metal elements in the Bakken hydrocarbon system might lead to a better comprehension of what affects the accuracy and precision of typical industry logs. The ability to measure the elemental composition of core samples and drill cuttings precisely and accurately will allow for further insight into how elemental composition changes can be correlated with diagenetic changes of the Bakken Petroleum System. Using a portable XRF (pXRF) brings this analysis method closer to the drilling operations and provides quick turnaround of samples.
Databáze: OpenAIRE
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