Effects Of Porosity And Mineral Composition On Cement Alteration During Geological Carbon Sequestration

Open Access
Author:
Brunet, Jean-patrick Leopold
Graduate Program:
Energy and Mineral Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 04, 2012
Committee Members:
  • Dr Li Li, Thesis Advisor
Keywords:
  • Carbon capture and storage
  • carbon sequestration
  • wellbore cement
  • carbon dioxide reaction
Abstract:
With increasing concentrations of greenhouse gases such as CO2, it is likely that major climate change will occur by the end of the century if abatement measures are not implemented. Carbon capture and storage (CSS) is considered a promising strategy for carbon mitigation. However, there is the potential that sequestrated CO2 will leak from underground geological formations. Assessment of this risk is one of the major challenges for CSS and is critical to ensuring the success of sequestration and the safety of the human population and environment. After injection, CO2 can dissolve into in situ brine to increasing its acidity. Acidified brine can react with wellbore cement, potentially changing its composition and transport properties. In this work, we develop a reactive transport model based on experimental observations to understand and predict the property evolution of cement in direct contact with CO2-saturated brine under diffusion-controlled conditions. This works also quantified the role of initial cement properties such as initial portlandite content and porosity in the alteration process. Results show alteration as initially fast before slowing down at later time. It appears that the initial portlandite content to porosity (defined here as φ) ratio is a key parameter in determining the evolution of cement properties. Portlandite rich cement, for which φ values are large, results in a localized reactive diffusive front characterized by calcite precipitation. This leads to a significant porosity reduction, which eventually clogs the pore preventing further acid penetration. However at the cement brine interface severe degradation will occurs. This will insure a preferential path through the degraded zone. The developed reactive transport model provides a valuable tool to link cement-CO2 reactions with wellbore cement behavior, and can facilitate risk assessment associated with geological CO2 sequestration.