Project Summary: Geologic storage of carbon dioxide (CO2)−a main cause of climate change−into deep saline aquifers is a promising strategy to mitigate global atmospheric CO2 levels. Despite comprehensive studies on CO2 storage, a majority of the previous studies have overlooked the presence of dissolved methane (CH4) gases and solid precipitation that normally occurs during CO2 injection. When CO2 is injected into CH4- saturated aquifers, the dissolved CH4 species affects geochemical reactions of CO2 with resident fluid and rocks. It is crucial to correctly understand these geochemical processes as they impact the geologic CO2 sequestration process and therefore global environmental sustainability. In addition, quantitative analysis of CH4 production, a byproduct of the CO2 dissolution, needs to be investigated since CH4 is considered a substantial energy source. Furthermore, understanding of solid precipitations due to dry-out at the CO2- brine interface is also important to achieve successful CO2 sequestration. The decrease in porosity and permeability due to the solid precipitations causes a decline in long-term storage capacity, an increase in injection cost, and a much higher injection pressure, possibly inducing artificial earthquakes. Despite its importance, the issue of solid precipitation has been essentially neglected in many previous studies.
In this project, microfluidic sensing technologies will be employed to understand the coupled interfacial phenomena, CO2 dissolution-CH4 exsolution-salt precipitation, and the corresponding development of multiphase domains under reservoir conditions. The gas-liquid-solid interfacial interactions and reactive processes will be investigated using one-dimensional (1D) and 2D microfluidic models. All experimental results will be validated by advanced simulation methods. The outcomes of the proposed research including identification of CO2-CH4 exchanges and their diffusion rates, gas-fluid interactions, and associated solid precipitation in porous media will serve as a fundamental roadmap for successful geological disposal of energy byproducts, thus contributing to future environmentally sustainable CO2 sequestration projects.