Studying the physics of carbon dioxide storage at microscopic scale with simulations and experiments

Abstract

Carbon dioxide storage into underground geological formations is a promising route to reduce atmospheric CO2 concentrations and limit climate change. Geological sequestration involves the injection of carbon laden solutions directly into the pore space of subsurface rock formations, such as saline aquifers and abandoned oil reservoirs. More scientific research is still needed to understand how the pore structure and mineral properties of the rock matrix influence the extent to which pressurized fluids can be injected, permeate and form stable carbonate minerals within the pore network. Accelerated discovery of low-cost materials and scalable processes through AI-driven design and cloud-based computational simulations can help identify injection processes and additives capable of enhancing CO2 sequestration. 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 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 and inform the simulation, we developed a Si/SiO2 lab-on-chip platform for studying the flow and chemistry of carbon dioxide on well-defined geometries at the microscale. In this work, we report the progress in the development of microscopy and spectroscopy techniques that can be applied on-chip to monitor the flow of CO2-laden fluids in constricted geometries. We perform flow experiments on the microfluidic chip and monitor the fluid dynamics in real time using optical microscopy and particle tracing techniques to extract physical properties of the fluid, such as flow speed. This allows to validate the fluid flow in pore network models that provide insight into the percolation of the fluid in real sandstone rock samples. In parallel, we demonstrate how correlative Raman-AFM microspectroscopy and other optical microscopy techniques can be employed to estimate rates of CO2 mineralization and mineral dissolution that will allow us to build and calibrate computational models that consider the joint effects of infiltration and mineralization of CO2 at the pore scale.