New Study Unveils Key Mechanisms in Geological CO₂ Storage

Researchers from Imperial College London and Petroliam Nasional Berhad (PETRONAS) have uncovered critical insights into the complex processes involved in storing CO₂ in sandstone formations. Published in Engineering, their study addresses gaps in understanding multiphase reactive flow—a pivotal factor in making geological CO₂ storage a viable solution for reducing greenhouse gas emissions.

The team conducted experiments on sandstone samples using advanced techniques like in situ X-ray imaging and scanning electron microscopy (SEM). Their results revealed two major findings:

1. Reduced Permeability: Both CO₂ relative permeability and absolute permeability decreased significantly during multiphase flow, even when the brine was pre-equilibrated with CO₂. This decline, caused by chemical reactions, could impact CO₂ injectivity and storage capacity in real-world applications.
2. Altered Pore Structures: The study observed shrinking pore and throat sizes, reduced connectivity, and increased irregularity in pore shapes. These changes, visualized through imaging, were linked to mineral dissolution (e.g., feldspar and calcite) and precipitation (e.g., transformation of feldspar to kaolinite).

This research is the first to provide a comprehensive analysis of multiphase reactive flow in sandstone CO₂ storage. By identifying the mechanisms behind permeability and pore structure changes, the study offers a foundation for optimizing storage strategies. For instance, tailored approaches may be needed for mineralogically complex formations to mitigate adverse reactions.

The researchers recommend developing quantitative models to better predict how permeability, petrophysical properties, and geochemical reactions interact. Such models could enhance the efficiency and safety of CO₂ storage in diverse geological settings.

This groundbreaking work advances our understanding of geological CO₂ storage, bringing us closer to practical solutions for combating climate change. With further research, these insights could pave the way for more effective and sustainable carbon capture technologies.