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Laboratory Experiments to Understand CO2 Reactivity

Complementary techniques offer unique advantages

  • The infrared spectroscopic titration system allows measurements of water concentrations dissolved in scCO2, detection of adsorbed water films on mineral surfaces, and characterization of both crystalline and amorphous products.
  • The AFM provides atomic scale images and structural information in real time, from which reaction rates can be derived.
  • MAS NMR is highly quantitative, can detect both crystalline and amorphous products, is capable of experiments with long reaction times, and has a niche for silicate characterization.
  • XRD gives definitive mineral identification and quantification for crystalline solids, provides structural data, and has high measurement turnover.

Laboratory experiments are being conducted at PNNL to discover and demonstrate general truths about subsurface conditions relative to geologic carbon storage. Experimental results are filling gaps in the current knowledge and leading to the development of an associated suite of tools for application in research and the field. Researchers are gaining a better understanding of caprock-greenhouse gas reactions, acquiring much-needed thermodynamics and kinetics data about wet supercritical carbon dioxide (scCO2)-mineral interactions, and leveraging EMSL capabilities to develop one-of-a-kind instrumentation to observe reactions in situ at scCO2 pressures and temperatures to understand reservoir and caprock properties. EMSL, the Environmental Molecular Sciences Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at PNNL.

Novel high-pressure in situ probes developed under PNNL’s Carbon Sequestration Initiative are unmatched internationally. Their development involves an infrared spectroscopic titration system, a hyperbaric atomic force microscope (AFM), a magic angle sample spinning nuclear magnetic resonance (MAS NMR) spectroscopy capability, and a x-ray diffraction (XRD) system. Together, these capabilities form a powerful toolkit for studying wet supercritical carbon dioxide (scCO2)-mineral reactions in situ. PNNL’s strategy is to integrate results from these techniques, while capitalizing on their advantages.

Study of Wet scCO2-Mineral Reactions

Research at PNNL has focused on in situ investigations of the reactions of variably wet-scCO2 with a range of geologically relevant materials, including 1) water partitioning and clay expansion in the scCO2-H2O-montmorillonite system, and 2) mineral carbonation in the scCO2-H2O-forsterite system.

Water Partitioning and Clay Expansion in the ScCO2-H2O-Montmorillonite System [+ expand/ - collapse]

Mineral Carbonation in the scCO2-H2O-Forsterite System [+ expand/ - collapse]

The results of these studies provide important insights into clay hydration and metal silicate carbonation mechanisms in low water scCO2environments. They also constrain thermodynamic models and molecular dynamic simulations used to predict volume changes in high clay content caprocks and mineral trapping extents in basaltic host rocks.

Geological Carbon Storage Research at PNNL

Energy and Environment Directorate