2019 AAPG Annual Convention and Exhibition:

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Optimizing Portable ED-XRF Calibration Routine for Sandstones and Carbonate Reservoirs: Examples from the Delaware Basin and Central Basin Platform


Several aspects of energy-dispersive X-ray fluorescence (ED-XRF) geochemical analysis make it useful to the oil and gas industry, namely the non-destructive nature and rapid acquisition time of each analysis. The speed of the quantitative analysis facilitates the generation of high-resolution data sets, which are particularly important for finely-bedded and heterogeneous packages of rock. These are common characteristics of many unconventional targets. Mudstone-specific XRF calibrations are now widespread but their accuracy as well as their inter-changeability are largely untested. Furthermore, it can be shown that no single set of calibration corrections can accurately quantify the vast spectrum of chemistry found in sedimentary successions. To address this issue for non-mudstone end members, new calibrations have been created that advance the ability to reliably quantify elemental concentrations in 1) sandstones, and 2) dolomite-rich carbonates. The short comings of the “one size fits all” approach to calibration of XRF spectra in varying lithologies will be demonstrated in order to examine the chemical limits at which it becomes advantageous to transition from mudrock to alternative lithology-specific calibrations for sandstones and dolomites. A brief discussion of the underlying reasons that necessitate the transition to lithology-specific calibrations will follow. Examples will be shown from the Delaware Basin and the Central Basin Platform, demonstrating why accuracy is important in order to model mineralogy when using XRF data and how accurate results allow for derivation of meaningful distinctions that increase our understanding of the reservoir and petroleum system.