Real-time Mineralogy, Lithology, and Chemostratigraphy While Drilling using Portable Energy-Dispersive X-ray Fluorescence

Abstract

AbstractOur objective is to obtain — while drilling, in real time — a complete petrophysical characterization from drill cuttings and the return mud-stream. Currently such rock and fluid direct characterization is achievable only, with significant time delay and at a considerable cost, from measurements on cores. The approach is to integrate the direct measurements on cuttings with the Logging While Drilling (LWD) practices and tools, to support drilling, geosteering and formation evaluation.In this framework, it is key to accurately characterize drilling cuttings from a mineralogical and lithological point of view. This characterization can be achieved performing an elemental analysis, by means of Energy-Dispersive X-ray Fluorescence (ED-XRF), in real time, with a portable instrument capable for use at the rig-site, integrated inside the mud logging operations.The portable X-ray Fluorescence (XRF), coupled with a methodology that enables to convert the elementary analysis into a mineralogical composition, produces a characterization comparable to what can be obtained by full scale X-ray Diffraction (XRD) laboratory equipment. An experimental set up was deployed, to assess the ability to model the mineralogy from geochemically analyses of a set of rock samples.After portable ED-XRF geochemical analyses, further lab-based analyses were carried out on the same samples: laboratory Wavelength-Dispersive XRF (WD-XRF) and ED-XRF in state of the art facilities. The geochemical data from the portable ED-XRF were compared to the lab-based XRF results (both WD-XRF and ED-XRF) and showed good agreement, particularly between the two ED-XRF instruments. As a final result, the modeled mineralogy from geochemical whole-rock data showed good agreement with the mineralogy determined from XRD analyses. Finally, a first field geochemical monitoring, by portable ED-XRF while drilling, was then successfully executed in Saudi Arabia.