Pore-Scale Visualization of Methane Hydrate-Bearing Sediments With Micro-CT

Abstract

X-ray computed tomography (CT) has become a critical technique in the study of porous media. It has attracted growing attention for analyzing hydrate-bearing sediment, but this has been done using surrogates (Xe/Kr) only due to difficulties in distinguishing methane hydrate from water. This study presents the successful imaging of methane hydrate coexisting with pore liquid, gas, and sediments. We used potassium iodide (KI) solutions and in-line propagation-based phase-contrast CT analysis of X-ray attenuation and diffraction to distinguish the four materials. Thus, consideration for CT-related X-ray physics was necessary to optimize KI concentrations, improve material separation with X-ray propagation, and properly interpret artifacts within the images. The images clearly show methane hydrate in the pore space of sand (~250 μm) coexisting with KI solution and gas. Following this, X-ray CT can now be used to visualize pore habits of natural methane hydrate in sediment cores.