Modeling Gaseous CO₂ Flow Behavior in Layered Basalts: Dimensional Analysis and Aquifer Response

Area of Science:

• Earth Sciences
• Environmental Engineering
• Geology

Background:

• Geologic carbon sequestration (GCS) is crucial for climate change mitigation.
• Potential leakage of stored carbon dioxide (CO2) poses risks to underground drinking water sources and sequestration efficacy.
• Understanding the multiphase flow behavior of gaseous CO2 is essential for assessing leakage risks.

Purpose of the Study:

• To model a hypothetical gaseous CO2 leak from a well integrity failure in a GCS operation.
• To analyze the factors influencing CO2 migration in the subsurface.
• To quantify potential CO2 release volumes and understand pressure dynamics during leakage.

Main Methods:

• Numerical simulation of a gaseous CO2 leak scenario at the Hellisheiði (CarbFix2) GCS site.
• Analysis of CO2 plume migration influenced by formation stratigraphy, permeability, and retention properties.
• Dimensional analysis to compare buoyant, viscous, and capillary forces.

Main Results:

• Gaseous CO2 migration is primarily controlled by geological formations and retention properties, with minimal impact from groundwater hydraulic gradients.
• Potential atmospheric release of 18.3% and 30.6% of injected CO2 over 3 days in different scenarios.
• Significant aquifer pressure buildups observed, exacerbated by less conductive layers.
• Buoyant and viscous forces found to be comparable within gaseous plumes over time.

Conclusions:

• Subsurface CO2 leakage is complex, influenced by multiple forces including pressure gradients, buoyancy, viscosity, and capillary effects.
• Accurate prediction of CO2 flow behavior requires considering all relevant forces; neglecting any can lead to flawed interpretations and operational decisions.
• This study highlights the importance of robust well integrity and comprehensive modeling for safe GCS operations.