Cryogenic vitrification and 3D serial sectioning using high resolution cryo‐FIB SEM technology for brine‐filled grain boundaries in halite: first results

Abstract

The structure of brine films in grain boundaries of halite has been the subject of much controversy over the past 20 years; although a number of innovative methods have been developed to study these structures, much is still unknown and fundamental information is missing. In this study, we investigated different methods of plungefreezing to vitrify the brine fill of grain boundaries for natural salt polycrystal. This was followed by a preliminary study of the 3D morphology of a vitrified grain boundary in a natural rock salt sample with a focused ion beam (FIB) excavation system. We have shown that brine-filled grain boundaries in rock salt can be efficiently well frozen when dimensions are less than about 1 mm. Coupled with an ion beam tool, cryo-SEM allows 3D observation of the well-frozen grain boundaries in large volumes and high resolution. Initial results of brine-filled natural halite grain boundaries show non-faceted crystal-brine interfaces and unexpectedly low dihedral angles at room temperature and pressure.

Three-dimensional pore networks and transport properties of a shale gas formation determined from focused ion beam serial imaging

“…Typically, three dimensional imaging of these tiny pore systems have been inaccessible via microCT and/or optical methods due to resolution issues. SEM and TEM imaging methods can resolve useful two-dimensional information for mudstone pore sizes down to nanometre (nm) sizes (Desbois et al, 2008(Desbois et al, , 2009Loucks et al, 2009). In conjunction with successive FIB milling of nanometre-scale surfaces (Yao, 2007), image stacks are obtained that can be used to reconstruct three dimensional digital pore and mineral structures (Heath et al, 2011).…”

Imaging pore space in tight gas sandstone reservoir: insights from broad ion beam cross-sectioning

“…Thus, the combination of Ar-BIB and SEM facilities provides an efficient method to get a direct access to porosity and allowing its detailed understanding. It offers the basis for a fundamental understanding of pore geometry, fluid flow, and, in combination with cryogenic techniques ( [3], [4]) should be able to offer insight into the geometry and wetting characteristics of in-situ fluid phases in sandstone reservoirs. For industry purposes this approach should yield to an optimized frac planning to reduce possible formation damages and therefore skin effects.…”

“…Consequently, image analysis and structural-geometrical interpretation has been of limited confidence ( [1], [2]). The recent development of Argon ion source milling tools which allow producing polished cross-sections of exceptionally high quality offer now a new technical milestone of surface preparation suitable for high resolution porosity SEM imaging at nano-scale ( [3], [4], [5], [6]). …”

Investigation of Microstructures in Naturally and Experimentally Deformed Reference Clay Rocks Using Innovative Methods in Scanning Electron Microscopy

“…At first order, this approach allows up-scaling by estimating the porosity as measured by MIP. The combination of cryogenic techniques with ion-beam milling preparation (Desbois et al, 2008(Desbois et al, , 2009 allows study of the distribution of pore fluids in preserved clay-rich samples at a scale below a few tens of nanometers. The characterization of the pore network in a given volume is done by means of the FIB-SEM method to access to pore throats and try to establish correlation (Hemes et al, 2015) between volumetric measurements (FIB-SEM) using 2D porosity analysis (BIB-SEM) and bulk porosity measurement (e.g.…”

“…BIB and FIB) has improved microstructural investigations in fine-grained geomaterials, providing unprecedented clarity of microstructures at below the micrometer scale (Loucks et al, 2009;Curtis et al, 2010;Desbois et al, 2009Desbois et al, , 2011bHeath et al, 2011;Hemes et al, 2013Hemes et al, , 2015Houben et al, 2013Houben et al, , 2014aHouben et al, , 2014bKeller et al, 2011Keller et al, , 2013aKeller et al, , 2013bKlaver et al, 2012Klaver et al, , 2015aKlaver et al, , 2015b. Cryogenic methods combined with FIB, BIB, and SEM has delivered, for the first time, direct imaging of pores filled with original pore fluids (Desbois et al, 2008(Desbois et al, , 2009. Injection of Wood's metal (WM), as an analog of MIP, but solid at room temperature, combined with BIB has been developed to visualize effective porosity decorated with WM at a given pore-throat entry pressure (Abell et al, 1999;Hildenbrand and Urai, 2003;Lloyd et al, 2009;Klaver et al, 2015b).…”