Geological carbon dioxide storage can be used to reduce carbon dioxide emissions only if the carbon dioxide remains in deep geological formations for thousands of years. Unfortunately free-phase carbon dioxide in sedimentary basins is less dense than the formation water and therefore leakage of carbon dioxide from these storage reservoirs back to the surface is a major concern. Over time, however, carbon dioxide dissolves into formation waters and increases the water density. Dissolved carbon dioxide will then sink to deeper parts of the sedimentary basins and it is very unlikely to surface again. The faster carbon dioxide dissolves the sooner it is stored safely. This project will evaluate the dissolution of CO2 on two scales: (1) The geological and geochemical record of a large natural carbon dioxide reservoir called Bravo Dome in New Mexico will be used estimate how fast carbon dioxide has dissolved on the geologic timescale and how tight the natural CO2 trap has been; (2) This study will also build scaled laboratory models for the transport of the dissolved carbon dioxide that determine the overall rate of carbon dioxide dissolution. The spatial structure of the dissolved carbon dioxide currents will be imaged with x-ray tomography. The experiments will be used to calibrate a dynamic model that can then be used to model laboratory observations and to interpret the observed field data to constrain the dissolution and sequestration rates for CO2 over long time.
This project brings together fluid mechanics, geology, and geochemistry and will provide a first estimate of carbon dioxide dissolution rates in the field, to inform the debate about the long-term safety of geological carbon dioxide storage. The experimental study will address several fundamental questions about the migration of solutes due to density differences that have implications for a broad set of questions for salt-water intrusion to geothermal energy. The models that will be developed will capture the essential physics of these processes. The development of such models is key to enable uncertainty quantification in geological CO2 storage.
