Investigation of Mineral Transformations in Wet Supercritical CO2 by Electron Microscopy

Journal Article · Mon Oct 10 04:00:00 EDT 2011 · Microscopy and Microanalysis, 17(Suppl S2):1928-1929

DOI:https://doi.org/10.1017/S1431927611010518· OSTI ID:1074331

Arey, Bruce W; Kovarik, Libor; Wang, Zheming; Felmy, Andrew R

The capture and storage of carbon dioxide and other greenhouse gases in deep geologic formations represents one of the most promising options for mitigating the impacts of greenhouse gases on global warming. In this regard, mineral-fluid interactions are of prime importance since such reactions can result in the long term sequestration of CO2 by trapping in mineral phases. Recently it has been recognized that interactions with neat to water-saturated non-aqueous fluids are of prime importance in understanding mineralization reactions since the introduced CO2 is likely to contain water initially or soon after injection and the supercritical CO2 (scCO2) is less dense than the aqueous phase which can result in a buoyant scCO2 plume contacting the isolating caprock. As a result, unraveling the molecular/microscopic mechanisms of mineral transformation in neat to water saturated scCO2 has taken on an added important. In this study, we are examining the interfacial reactions of the olivine mineral forsterite (Mg2SiO4) over a range of water contents up to and including complete water saturation in scCO2. The surface precipitates that form on the reacted forsterite grains are extremely fragile and difficult to experimentally characterize. In order to address this issue we have developed experimental protocols for preparing and imaging electron-transparent samples from fragile structures. These electron-transparent samples are then examined using a combination of STEM/EDX, FIB-TEM, and helium ion microscope (HIM) imaging (Figures 1-3). This combination of capabilities has provided unique insight into the geochemical processes that occur on scCO2 reacted mineral surfaces. The experimental procedures and protocols that have been developed also have useful applications for examining fragile structures on a wide variety of materials. This research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research located at Pacific Northwest National Laboratory.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1074331
• Report Number(s): PNNL-SA-81736; 39937; KP1704020
• Journal Information: Microscopy and Microanalysis, 17(Suppl S2):1928-1929, Journal Name: Microscopy and Microanalysis, 17(Suppl S2):1928-1929
• Country of Publication: United States
• Language: English

Related Subjects

CO2
Electron
Environmental Molecular Sciences Laboratory
Investigation
Microscopy
Mineral
Supercritical
Transformations
Wet