Natural gas hydrate investigations by synchrotron radiation X‐ray cryo‐tomographic microscopy (SRXCTM)

Abstract

We report the 3D microstructure analyses of natural gas hydrates sampled from Gulf of Mexico. The samples were characterized by synchrotron radiation X‐ray cryo‐tomographic microscopy (SRXCTM) using the ‘TOMCAT’ beam line at the Swiss Light Source (SLS). The SRXCTM demonstrates its applicability to unlock some microscopic features of the marine hydrates, in particular of crystallite size and grain boundary network. The gas hydrate domains are surrounded by a network of pores of typically a few micrometers, which are largely due to decomposition. Out of the SRXCTM data, the porosity, total volume of the voids, the void surface area and number of the total gas‐filled voids have been calculated. The results reveal the capability of SRXCTM to access the 3D microstructure which is of fundamental importance to model the petrophysical properties of natural gas hydrates.

A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

“…Schneebeli and Sokratov, 2004;Heggli et al, 2011) and polar firn (Freitag et al, 2004) at 5-40 µm resolution. It has furthermore been claimed that brine networks have been imaged in sea ice by XMT (Obbard et al, 2009) and in natural marine ice-gas-hydrate mixtures (Murshed et al, 2008), which would make XMT a promising method to investigate the distribution of brine in porous snow samples. Yet, using XMT is difficult when liquid is present, due to the small difference in absorption of liquid solutions and of solid ice.…”

“…Yet, using XMT is difficult when liquid is present, due to the small difference in absorption of liquid solutions and of solid ice. Hence it seems likely that the liquid features documented by Obbard et al (2009) and Murshed et al (2008) are to a certain degree sea salts that have precipitated at their imaging temperature of 263 K. A contrast agent may be added to enhance the brine-ice absorption contrast when studying saline ice grown in the laboratory (Golden et al, 2007), although laboratory ice may differ from natural sea ice. In future studies the problems with the ice-brine contrast may be overcome by means of phase-contrast-based XMT (McDonald et al, 2011) enabling the observation of brine and void air simultaneously.…”

X-ray computed microtomography of sea ice – comment on "A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow" by Bartels-Rausch et al. (2014)

“…In it, they state that "using XMT is difficult when liquid is present, due to the small difference in absorption of liquid solutions and of solid ice. Hence it seems likely that the liquid features documented by Obbard et al (2009) and Murshed et al (2008) are to a certain degree sea salts that have precipitated at their imaging temperature of 263 K". This is misleading.…”

3-D imaging and quantification of graupel porosity by synchrotron-based micro-tomography

“…A special setup was therefore specifically developed for ice particle analysis (Miedaner et al, 2007;Murshed et al, 2008). The sample holder was custom-made of a polyamide cup that can be closed air-tight with a polyamide cap which in turn bears a metal tip (Fig.…”