Dynamic Pore-scale Reservoir-condition Imaging of Reaction in Carbonates Using Synchrotron Fast Tomography

Area of Science:

• Geochemistry and Petroleum Engineering
• Carbon Capture, Utilization, and Storage (CCUS)

Background:

• Underground storage permanence for carbon capture and storage (CCS) is critical.
• CO2 injection into carbonate reservoirs risks dissolving geologic seals, leading to leakage.
• Dissolution processes under reservoir conditions remain poorly understood.

Purpose of the Study:

• To investigate the pore-scale dissolution of limestone by CO2-saturated brine.
• To observe and predict the nature and rate of dissolution at reservoir conditions.
• To assess the impact of dissolution on porosity and permeability over time.

Main Methods:

• Utilized synchrotron fast tomography (Diamond Lightsource Pink Beam) for time-resolved imaging.
• Dynamically imaged limestone dissolution in the presence of CO2-saturated brine at reservoir conditions.
• Acquired 100 scans at 6.1 µm resolution over 2 hours; analyzed porosity and permeability via image analysis and network extraction.

Main Results:

• Observed uniform increase in porosity along the sample length.
• Measured a decrease in the rate of porosity and permeability increase over time.
• Provided dynamic, pore-scale insights into CO2-limestone interactions.

Conclusions:

• Synchrotron fast tomography enables effective visualization of dynamic dissolution processes.
• Dissolution rates slow down over time, influencing long-term storage security.
• Findings are crucial for predicting and ensuring the permanence of underground CO2 storage.