Micro X-ray fluorescence reveals pore space details and spatially-resolved porosity of rock-based microfluidic devices

Characterization of microscopic details of the fabric of mudstones and shales (i.e., structure and composition) is important to understand their storage and transport properties. Current characterization methods struggle to probe reliably multiple scales of interest (e.g., pore and fracture) and measure properties at the finest resolution under representative in situ conditions. Micro X-ray fluorescence (& mu;XRF) is a high-performance imaging technique that produces elemental images at sub-10 & mu;m spatial resolution and could offer insight into a diversity of shale properties, such as mineral composition, porosity, and in situ pressure gradients. This study designed and carried out a porosity mapping protocol using model and real-rock microfluidic devices and contrast fluids. Etched silicon micromodels with real-rock pore network patterns served as ideal models to establish a proof of concept. Measurements were performed on a novel & mu;XRF microscope not powered by synchrotron radiation. We registered the & mu;XRF datasets with the binary rock masks used for micromodel fabrication and applied segmentation algorithms to compare porosities. We assessed expected advantages and limitations through a sensitivity analysis and beam study. & mu;XRF is an important new imaging technique for microfluidic applications.

Automated summary

Characterizing the microscopic details of mudstones and shales is crucial for understanding their storage and transport properties. However, current methods struggle to accurately probe multiple scales and measure properties at the finest resolution under in situ conditions. The study introduces micro X-ray fluorescence (μXRF) as a high-performance imaging technique that can offer insights into various shale properties. By designing and implementing a porosity mapping protocol, the study demonstrates the potential advantages of μXRF for microfluidic applications.