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Understanding Geologic Carbon Sequestration through Multi-Scale Imaging

byZEISS Microscopy 22 April 2025 5 min read

Introduction

Understanding Geologic Carbon Sequestration through Multi-Scale Imaging

As the world grapples with the challenges of climate change, innovative solutions are essential for reducing carbon emissions. One promising approach is geologic carbon sequestration, a process that involves storing carbon dioxide (CO₂) in deep geological formations for a long time, helping to reduce the amount of CO₂ in the atmosphere and its impact on the environment.

CO₂ is collected from sources like power plants and factories before it can be released into the air. The captured CO₂ is then transported, usually through pipelines, to a storage site. At the storage site, it is injected deep underground into rock formations. These formations have spaces (pores) that can hold the CO₂, preventing it from contributing to atmospheric pollution.

Stijn Dilissen | University of Hasselt — From left to right: Samantha Mariano, Zhuofan Shi, Md. Fahim Salek, Abdullah Al Nahian, Riana Rivera

Studying the Interactions Between CO₂ and Geological Formations

Dr. Lauren Beckingham is an Associate Department Chair and the W. Allen and Martha Reed Associate Professor in the Department of Civil & Environmental Engineering at Auburn University, Alabama, USA. She leads a research group dedicated to investigating the geochemical reactions in subsurface energy systems – with the ultimate goal of decarbonizing energy production.

Trapping and Storing Carbon Dioxide

Geologic carbon sequestration involves the injection of CO₂ into deep geological formations for permanent storage. Once injected, the CO₂ interacts with formation brine and mineralogy, which plays a crucial role in trapping the gas effectively.

When CO₂ dissolves into brine, it lowers the pH, creating conditions that favor the dissolution of certain formation minerals. As these minerals dissolve, ions are released into the solution, potentially leading to the precipitation of carbonate minerals that incorporate the injected CO₂. This process, known as mineral trapping, provides a secure and permanent means of CO₂ storage.

However, not all mineral phases are reactive under CO₂ storage conditions, and the rate of these reactions can vary significantly. Dr. Beckingham's group focuses on understanding the potential reactivity of minerals in storage formations and the rate, extent, and timescale of these reactions to predict their impact on CO₂ storage and trapping.

We use multi-scale imaging to assess the mineralogy of potential storage formations and the potential CO₂-brine-mineral interactions.

Dr. Lauren Beckingham Associate Professor in Civil & Environmental Engineering at Auburn University, USA

Wormhole development in a limestone sample exposed to CO2 acidified brine — _{Wormhole development in a limestone sample exposed to CO₂ acidified brine}

Elevating CO₂ Storage Security Through Multi-Scale Imaging

Multi-scale imaging is a powerful approach that contributes to the understanding of CO₂ sequestration processes, particularly in assessing long-term storage security. Dr. Beckingham emphasizes the importance of accurately predicting the reactive evolution of geological formations, as changes in mineral properties can significantly impact storage capacity and injectivity.

Mineral dissolution and precipitation reactions that occur after CO₂ injection can change the properties of the formation, including porosity and permeability, which affect storage capacity and injectivity. Accurately predicting the reactive evolution of the formation is critical to assessing the fate and effects of the injected CO₂ and the viability of a potential storage site.

Using 2D scanning electron microscopy imaging, the team creates mineral maps that show the distribution of minerals relative to each other and to the pore space. This information is critical for understanding the mineral phases that may interact with reactive fluids. Finally, they combine this with 3D X-ray CT imaging of the pore structure to better understand flow and transport through the formation.

Despite the advancements in imaging technology, studying the interactions between fluids and porous materials at different scales presents challenges. Natural systems are inherently complex, with heterogeneity occurring across a wide range of scales, from nanometers to kilometers.

Characterization of Multi-Scale Pore Structure of Possible CO2 Storage Formations

Segmented pore regions in two carbonate samples being considered for carbon storage where the various colors reflect different connected pore regions.

As different imaging approaches provide different information about these highly complex natural systems, it is challenging to gain a complete picture of the formation that captures all heterogeneities.

Dr. Lauren Beckingham Associate Professor in Civil & Environmental Engineering at Auburn University, USA

3D Characterization of Distribution of Carbonate Precipitation in Porous Media

3D X-ray microCT image of 3D printed pore structure with calcite precipitation (left). Segmented image showing 3D printed pore structure in yellow, pores in green, and calcite precipitates in red (second from left).

Right two images depict distribution of calcite precipitation throughout the 3D printed core sample.

From left to right: Nora Lopez River, Otis Williams, Dejene Legesse Driba, Lauren Beckingham

Future Enhancements in CO₂ Storage Through Improved Imaging

Advancing imaging techniques to reliably identify minerals in 3D X-ray CT scans will significantly improve our understanding of reactive interfaces and the evolving 3D pore structure in CO₂ storage systems. In the realm of reactive transport modeling, developing more effective methods for upscaling is crucial to enhance simulations at the field scale. While mineral dissolution and precipitation reactions occur at the pore scale, simulating an entire field at this level is impractical. Therefore, we depend on upscaled relationships to accurately represent the rate and impact of these reactions.

Geologic carbon sequestration is the process of storing carbon dioxide (CO₂) in deep geological formations to reduce its presence in the atmosphere. This method is crucial for mitigating climate change by preventing CO₂ emissions from sources like power plants and factories from contributing to global warming.
After injection, CO₂ interacts with the brine and minerals within the geological formations. This interaction can lead to changes in the chemical environment, such as a decrease in pH, which may cause certain minerals to dissolve and release ions. These ions can then form new carbonate minerals, effectively trapping the CO₂ and providing a secure and permanent storage solution.
Multi-scale imaging techniques, such as 2D scanning electron microscopy and 3D X-ray CT imaging, are essential for understanding the distribution of minerals and the pore structure in CO₂ storage formations. These advanced imaging methods help researchers predict how mineral properties evolve over time, which is critical for assessing the long-term security and effectiveness of CO₂ storage sites.