Local diffusion coefficient measurements in shale using dynamic micro-computed tomography. (1st November 2017)

• Record Type: Journal Article
• Authors: Zhang, Yulai; Mostaghimi, Peyman; Fogden, Andrew; Middleton, Jill; Sheppard, Adrian; Armstrong, Ryan T.
• Is Part Of: Fuel. Volume 207(2017)
• Page Start: 312
• Page End: 322
• Publication Date: 2017-11-01
• Subjects: Micro-CT -- Shale -- Local diffusion coefficients -- Dynamic imaging; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2017.06.050
• Languages: English
• ISSNs: 0016-2361

Abstract

Abstract: Diffusion is an important mass transport mechanism in ultra-low permeability shale matrix and thus, characterization of shale diffusivity is of practical necessity for shale gas developments. We present a novel method for measuring bulk and local diffusion coefficients of shale core-plugs using dynamic X-ray micro-computed tomography (micro-CT). Liquid diffusion experiments are conducted on a centimeter-scale shale core and a series of time-sequenced 3D micro-CT images are acquired through dynamic imaging. Local diffusion coefficients are measured numerically from the micro-CT data using a new mathematical method that allows us to evaluate the heterogeneity of shale diffusivity at the sub-core scale. The variation of local diffusion coefficients is quantified using the Dykstra Parsons method, which provides a means to quantify core-scale heterogeneity in shale samples. Although the micro-CT image data may be influenced by noise, the presented technique provides reasonable results and our validation studies provide fundamental design parameters for measuring diffusivity values from dynamic micro-CT experiments. In addition the presented method can be applied to other porous materials where diffusion occurs.