Portable Energy-Dispersive X-Ray Fluorescence Integrates Mineralogy And Chemostratigraphy Into Real-Time Formation Evaluation

Marsala, A.F. (Saudi Aramco) | Loermans, T. (Saudi Aramco) | Shen, S. (Saudi Aramco) | Scheibe, C. (Halliburton) | Zereik, R. (Halliburton)



 Our objective is to unlock the wealth of information contained in drill cuttings in real-time for complementing petrophysical characterization while drilling. The approach is to integrate the direct measurement from drill cuttings with Logging While Drilling (LWD) data to support drilling, geosteering and formation evaluation. In this framework, an accurate mineralogical and lithological characterization of drill cuttings is a key issue. Visual determination for mineralogy via microscopy often substantially varies between analysts, e.g., various mud-logging personnel at the well site and geologists in the office. Further, modern polycrystalline diamond compact (PDC) bits may produce “paste” or “powder,” unsuitable for visual/microscopic determination of mineralogy and lithology rather, than regular drill cuttings. A way to tackle the above challenge is performing a geochemical element analysis, by means of Energy- Dispersive X-Ray Fluorescence (ED-XRF). A reliable, portable ED-XRF instrument, robust enough for rig site employment is routinely used for a well site chemostratigraphy service. The instrument produces accurate elemental data, which can, next to its chemostratigraphic applications, be used for mineral and lithology modeling. A methodology has been developed to convert the elemental analysis into a mineralogical composition of the rock sample that is comparable to measurements from full scale X-Ray Diffraction (XRD) laboratory equipment. An experimental setup was deployed assessing the ability to model the mineralogy from geochemical analyses (well site ED-XRF) of a set of rock samples in a “blind” test (Marsala et al., 2011). The analytical results were compared to results obtained from the same samples through state-of-the-art laboratory EDXRF and wave-length dispersive XRF (WD-XRF) instruments. The geochemical data from the well site and the two lab-based instruments show good agreement. Finally, the modeled mineral compositions from wholerock geochemical data were compared with the mineralogy determined from XRD analyses and showed good agreement.