Abstract
One of the challenges of the present century is to limit the greenhouse gas emissions for the mitigation of climate change which is possible for example by a transitional technology, CO2 geological storage. Clay minerals are considered to be responsible for the low permeability and sealing capacity of caprocks sealing off stored CO2. However, their reactions are not well understood for complex simulations. This work aims to create a kinetic geochemical model of Na-montmorillonite standard SWy-2 supported by solution and mineral composition results from batch experiments. Such experimentally validated numerical models are scarce. Four 70-hours experiments have been carried out at atmospheric conditions, and with CO2 supercritical phase at 100 bar and 80 °C. Solution samples have been taken during and after experiments and their compositions were measured by ICP-OES. The treated solid phase has been analyzed by XRD and ATR-FTIR and compared to in-parallel measured references (dried SWy-2). Kinetic geochemical modelling of the experimental conditions has been performed by software PHREEQC. Experiments and models show fast reactions under the studied conditions and increased reactivity in presence of scCO2. Solution composition results cannot be described by the change of the uncertain reactive surface area of mineral phases. By considering the clay standard’s cation exchange capacity divided proportionally among interlayer cations of Na-montmorillonite, the measured variation can be described on an order of magnitude level. It is furthermore indicated that not only the interlayer cations take part in this process but a minor proportion of other, structural ions as well, differently in the reference and scCO2 environments.
Highlights
It is beyond doubt that human activity influences the climate system and that mitigating climate change requires reduction of greenhouse gas emissions [1]
3 Results and discussion 3.1 Experimental results 3.1.1 Measured "on-the-go" solution composition changes During batch experiments, solution compositions sensitively changed due to standard-fluid interaction already starting at atmospheric conditions
4 Conclusions Batch experiments and kinetic geochemical models of this study primarily aimed to simulate the behavior of a selected clay mineral in CO2 geological storage caprocks
Summary
It is beyond doubt that human activity influences the climate system and that mitigating climate change requires reduction of greenhouse gas emissions [1]. The Paris Agreement [2] aims to keep global temperature rise well below 2 °C and pursue efforts for a 1.5 °C limit. This "low-stabilization" scenario can only be reached by applying low, and net negative emission technologies [3]. In the near-term, the only approach capable of making a major contribution to these seems to be the transitional technology of Carbon Capture and
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