Advanced optical on-chip analysis of fluid flow for applications in carbon dioxide trapping

Carbon dioxide capture and storage into underground geological formations is a promising route to reduce emissions into the atmosphere and limit global warming. Geo-sequestration involves the injection of carbon laden solutions directly into the pore space in sedimentary rocks, saline formations, or abandoned oil fields. More scientific research is still needed to understand how the pore structure and material properties of the rock matrix influence the extent to which pressurized fluids can be injected and permeate the pore network. Our research focuses on studying the fundamental mechanics of pore infiltration at micro- and nanoscopic scales to develop a comprehensive model of carbon dioxide sequestration within geological pore networks. We are using single and two-phase flow simulations of fluid injection into the rock pore space, modeled as a network of capillaries representing the geometry extracted from high-resolution X-ray microtomography of suitable rocks. To experimentally validate the simulation results, we have developed a Si/SiO2 lab-on-chip platform for testing porosity models on well-defined geometries at the microscale. The single and multiphase flow measurements performed on the microfluidic chip are monitored with optical microscopy in real time. In this contribution, we will report the progress in our research and development of optical imaging techniques applied to the microfluidic chip. Specifically, we demonstrate how advanced image analysis can be used to extract information about the flow properties. The image analysis results are critical for calibrating high-accuracy flow simulation models for pore scale injection and mineralization of carbon dioxide. The rock-on-chip platform is used also to measure chemical and physical processes governing the carbonate precipitation step of CO2 mineralization. The reaction of CO2 in the microfluidic channels can be detected through crystal formation over time. Fluorescence microscopy and Raman-spectroscopy is used to monitor carbonate precipitation rates directly on chip, to map minerals and track reaction kinetics under different conditions.