Dynamic 3D imaging of gas hydrate kinetics using synchrotron computed tomography

¹ Department of Civil and Environmental Engineering, 325 John Tickle Building, University of Tennessee, 37996 Knoxville, TN, USA
² Department of Civil and Architectural Engineering, Qatar University, P.O Box 2713 Doha Qatar
³ School of Civil Engineering, Chungbuk National University, Cheongju‑si, 28644, Chungbuk, Korea

^* Corresponding author: alshibli@utk.edu

Abstract

The availability of natural gas hydrates and the continuing increase in energy demand, motivated researchers to consider gas hydrates as a future source of energy. Fundamental understanding of hydrate dissociation kinetics is essential to improve techniques of gas production from natural hydrates reservoirs. During hydrate dissociation, bonds between water (host molecules) and gas (guest molecules) break and free gas is released. This paper investigates the evolution of hydrate surface area, pore habit, and tortuosity using in-situ imaging of Xenon (Xe) hydrate formation and dissociation in porous media with dynamic three-dimensional synchrotron microcomputed tomography (SMT). Xe hydrate was formed inside a high- pressure, low-temperature cell and then dissociated by thermal stimulation. During formation and dissociation, full 3D SMT scans were acquired continuously and reconstructed into 3D volume images. Each scan took only 45 seconds to complete, and a total of 60 scans were acquired. Hydrate volume and surface area evolution were directly measured from the SMT scans. At low hydrate saturation, the predominant pore habit was surface coating, while the predominant pore habit at high hydrate saturation was pore filling. A second-degree polynomial can be used to predict variation of tortuosity with hydrate saturation with an R² value of 0.997.