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Impact of Mineral Spatial Distribution on CO2 Dissolution Rates in Multimineral Carbonate Rocks.

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Title: Impact of Mineral Spatial Distribution on CO2 Dissolution Rates in Multimineral Carbonate Rocks.
Authors: Adedipe, Olatunbosun A.1 (AUTHOR) o.adedipe23@imperial.ac.uk, Al‐Khulaifi, Yousef1 (AUTHOR), Foroughi, Sajjad1 (AUTHOR), Lin, Qingyang1 (AUTHOR), Blunt, Martin J.1 (AUTHOR), Bijeljic, Branko1 (AUTHOR)
Source: Water Resources Research. May2026, Vol. 62 Issue 5, p1-30. 30p.
Subjects: Carbon sequestration, Reactive flow, X-ray computed microtomography, Carbonate rocks, Mass transfer, Chemical processes
Abstract: Understanding the reactive dissolution of carbonate rocks in CO2 ${\text{CO}}_{2}$‐rich brine environments is critical for optimizing carbon capture and storage (CCS). This study integrates flow experiments with high‐resolution micro‐CT imaging and pore‐scale simulation to analyze the interplay between physical and chemical heterogeneity during reactive transport. By examining two carbonate samples comprised principally of dolomite and calcite with anhydrite also present, we quantify how the initial distribution of minerals and permeability variations influence flow patterns, dissolution dynamics, and the increase in permeability. The results show that reaction rates decrease with increasing flow heterogeneity due to enhanced mass transfer limitations. Furthermore, the proximity of minerals to fast‐flow channels impacts their effective reaction rates and alters their hierarchy, highlighting the interplay between transport processes, mineral spatial distribution and mineral dissolution. Both samples displayed dissolution patterns with localized channel widening and formation. The study provides key insights into mineral‐specific reaction behavior and flow‐dependent dissolution patterns, further evaluating a detailed framework for improving predictive models of subsurface CO2 ${\text{CO}}_{2}$ storage. Plain Language Summary: Storing CO2 ${\text{CO}}_{2}$ deep underground is one of the main strategies to reduce greenhouse gas emissions but predicting how rocks will react when exposed to CO2 ${\text{CO}}_{2}$‐rich fluids is still a challenge, especially for multimineral systems. We investigate how carbonate rocks composed of three different minerals dissolve when CO2 ${\text{CO}}_{2}$‐rich water flows through them. Using high‐resolution 3D X‐ray imaging and computer simulations, we studied two carbonate samples containing dolomite and calcite, with some anhydrite. We find that the initial spatial arrangement of the minerals and the distribution of flow speeds within the pore space strongly affect dissolution. We highlight the role of the time‐dependent coupling of transport with reaction by quantifying evolving velocity distributions and mineral proximity to fast flow channels from the images. Minerals closer to fast‐flowing channels dissolve faster, resulting in either emergence of new dominant channels or widening the existing ones. These mechanisms lead to different dissolution patterns and are quantified through the hierarchy of mineral reaction rates. The effective reaction rates measured are orders of magnitude lower than the batch reaction rates due to mass transfer limitations. Overall, these new insights can help improve models for design of safe CO2 ${\text{CO}}_{2}$ storage in multimineral carbonates. Key Points: The coupling of transport with reaction is quantified by evolving velocity distributions and mineral proximity to fast flow channels from the micro‐CT imagesMinerals near fast channels dissolve faster altering reaction rate hierarchy, either forming dominant channels or widening existing channelsMineral reaction rates are orders of magnitude lower than the batch rates and the single‐mineral system rates due to additional mass transfer limitations [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Understanding the reactive dissolution of carbonate rocks in CO2 ${\text{CO}}_{2}$‐rich brine environments is critical for optimizing carbon capture and storage (CCS). This study integrates flow experiments with high‐resolution micro‐CT imaging and pore‐scale simulation to analyze the interplay between physical and chemical heterogeneity during reactive transport. By examining two carbonate samples comprised principally of dolomite and calcite with anhydrite also present, we quantify how the initial distribution of minerals and permeability variations influence flow patterns, dissolution dynamics, and the increase in permeability. The results show that reaction rates decrease with increasing flow heterogeneity due to enhanced mass transfer limitations. Furthermore, the proximity of minerals to fast‐flow channels impacts their effective reaction rates and alters their hierarchy, highlighting the interplay between transport processes, mineral spatial distribution and mineral dissolution. Both samples displayed dissolution patterns with localized channel widening and formation. The study provides key insights into mineral‐specific reaction behavior and flow‐dependent dissolution patterns, further evaluating a detailed framework for improving predictive models of subsurface CO2 ${\text{CO}}_{2}$ storage. Plain Language Summary: Storing CO2 ${\text{CO}}_{2}$ deep underground is one of the main strategies to reduce greenhouse gas emissions but predicting how rocks will react when exposed to CO2 ${\text{CO}}_{2}$‐rich fluids is still a challenge, especially for multimineral systems. We investigate how carbonate rocks composed of three different minerals dissolve when CO2 ${\text{CO}}_{2}$‐rich water flows through them. Using high‐resolution 3D X‐ray imaging and computer simulations, we studied two carbonate samples containing dolomite and calcite, with some anhydrite. We find that the initial spatial arrangement of the minerals and the distribution of flow speeds within the pore space strongly affect dissolution. We highlight the role of the time‐dependent coupling of transport with reaction by quantifying evolving velocity distributions and mineral proximity to fast flow channels from the images. Minerals closer to fast‐flowing channels dissolve faster, resulting in either emergence of new dominant channels or widening the existing ones. These mechanisms lead to different dissolution patterns and are quantified through the hierarchy of mineral reaction rates. The effective reaction rates measured are orders of magnitude lower than the batch reaction rates due to mass transfer limitations. Overall, these new insights can help improve models for design of safe CO2 ${\text{CO}}_{2}$ storage in multimineral carbonates. Key Points: The coupling of transport with reaction is quantified by evolving velocity distributions and mineral proximity to fast flow channels from the micro‐CT imagesMinerals near fast channels dissolve faster altering reaction rate hierarchy, either forming dominant channels or widening existing channelsMineral reaction rates are orders of magnitude lower than the batch rates and the single‐mineral system rates due to additional mass transfer limitations [ABSTRACT FROM AUTHOR]
ISSN:00431397
DOI:10.1029/2025WR042362