(546d) High-Resolution Differential Phase-Contrast (DPC) X-Ray Imaging for Multiphase Fluid Flow in Three-Dimensional Porous Media

Maha Yusuf¹, George Herring², Max Yuen², Ching-Wei Chang², Yao-Te Cheng², Lambertus Hesselink^2,3

¹ Department of Chemical Engineering, Stanford University, Stanford, California, 94305

² Department of Electrical Engineering, Stanford University, Stanford, California, 94305

3 Department of Applied Physics, Stanford University, Stanford, California, 94305

Abstract

X-ray imaging is a very valuable technique to investigate the inner structure of bulk samples. Some of the most important applications include medical diagnostics, security screening at airports, and materials science¹. Traditional X-ray imaging uses the differences in X-ray attenuation in different parts of the sample to produce an ‘image contrast’. Therefore, the usefulness of conventional X-ray imaging is limited in materials with small density variations due to poor image contrast. To significantly improve the image contrast, phase-shift of X-rays can be recorded instead of attenuation^2-3. At high energies, X-rays undergo phase shift that are orders of magnitude larger than the attenuation. Thus, detecting phase shifts can be much more sensitive than detecting attenuation. A number of methods have been investigated to detect the phase-shift of X-rays such as interferometric methods, propagation-based methods, and analyzer-based imaging^4-5. However, most of these methods require a coherent X-ray beam/synchrotron radiation for imaging.

Here, we are working on a grating-based differential phase-contrast (DPC) X-ray imaging system that can be used to retrieve quantitative phase information with polychromatic X-ray sources in a laboratory-based setting⁶. DPC differs from traditional X-ray imaging since it provides three outputs (attenuation, phase contrast, dark-field) instead of one, and uniquely identifies unknown materials with improved image contrast based on the material’s absorption, phase, and scattering coefficients. DPC X-ray imaging is a promising non-destructive technique that is particularly useful for the study of fluid interfaces (e.g. fluid flow in porous media) and interfacial aspects with increased image contrast, investigation of multi-phase fluid dynamics in 3-D porous rocks, analysis of real-time mechanisms, and direct pore-scale imaging. These will improve understanding of the fundamental processes in multi-phase fluid flow, thus contributing to enhanced oil recovery.

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