Modelagem matemática do armazenamento geológico de CO2 em aquíferos salinos profundos

Abstract

Most of the forecast scenarios on climate change reveal a significant increase of greenhouse gases emissions in the absence of mitigation actions. Notwithstanding, even with the existence of mitigation actions to limit the 2°C increase in global temperature, the primary power supply will be 40% based in fossil fuels until the mid of the century. Carbon Capture and Storage (CCS) is the only technology able to achieve significant emissions reductions based on the use of fossil fuels. One of the main questions is if this technique is safe and which are the environmental impacts that are directly related to the public acceptance of this technology. The main way to answer to this is through the mathematical modelling of the CO2 flow in the storage site. It is presented a broad literature review about geological storage of CO2 focused on storage in saline aquifers and the physical and chemical processes involved. It is presented a complete description of the mathematical modelling representing this system and the thermodynamic submodels applied to the modelling performed in the reviewed work. It was concluded that one of the most important mechanisms of trapping of the CO2 to the success of the storage is the residual (or capillary) trapping, because it happens in a moderate time scale (hundreds to thousands of years) and because it influences the other trapping mechanisms). Based on this, it was developed a mathematical model that allowed to evaluate this mechanism, taking into consideration the capillary pressure effects and relative permeability hysteresis. It is recognized the other trapping mechanisms of CO2, not considered in the model presented, are as much important as the residual trapping with the view to understand the fate of the injected CO2, and need to be taken into account.