2014 NGWA Groundwater Summit

May 04 - 07, 2014

2014 NGWREF Darcy Lecture — Optimizing Capillary Trapping as a Carbon Dioxide Mitigation Strategy: Pore-Scale Findings in Support of Larger-Scale Implementation

Discover how x-ray microtomography is being studied for possible use as a technique to optimize capillary trapping of carbon dioxide in this presentation. Capillary trapping is a mechanism supporting carbon capture and storage (CCS), which is being considered as a mitigation strategy for emissions from concentrated sources such as coal-fired power plants. CCS relies on geologic sequestration of captured carbon dioxide. Of concern in this process is the leakage of carbon dioxide back to the atmosphere, either acute or slower longterm escape, as well as related acidification of groundwater resources along the migration path. Initial work using x-ray microtomography has focused on proxy fluid-based systems and experiments carried out at ambient conditions. As the interfacial tension, viscosity, and carbon dioxide injection (as well as subsequent brine flood injection) rates are varied, trends have been observed with the type of porous medium (unconsolidated vs. consolidated), varying wetting and nonwetting phase viscosity, and flow rates. The latter in particular has been investigated for its effect on morphology and connectivity of the trapped nonwetting phase (i.e., the supercritical carbon dioxide). Results so far indicate that carbon dioxide injection can be manipulated to facilitate optimal trapping of residual carbon dioxide, both in terms of amount and with respect to size/ connectivity characteristics that may favorably support subsequent trapping reactions (e.g., dissolution and mineral formation).