Presentazioni e Articoli Tecnici

Geological Carbon Storage (GCS) is viewed as a viable option to reduce Carbon Dioxide (CO₂) emissions. In particular, CO₂ injection into deep saline formations (DSF) has been the subject of numerous investigations during the last decade, including pilot and demonstration projects [Reiner 2016; Ringrose et al., 2017]. DSF are attractive because of their vast storage capacity [IPCC 2005], besides storage has been demonstrated in a few sites operating at rates over one megaton per year. However, scaling up at larger scales still requires resolving some technical gaps, particularly in the simulation arena.

The ability to perform reliable simulations is paramount for the success of GCS projects. Modeling and simulation exercises are required along the whole GCS project lifecycle. For instance, simulation results can help to inform or guide site screening assessments, feasibility studies, design of monitoring techniques, support of operations and post-closure stages. However, the occurrence of wide geological variability and multiple temporal scales (typically encountered in GCS projects) requires coupled Multiphysics models.

An important component of GCS projects is risk evaluation, particularly concerning the potential risks which may take place during the injection phase. For example, induced seismicity, fault (re-) activation or CO₂ leakage toward upper layers have been identified as important risks for GCS operations. Recent experience demonstrates that some of these risks may directly be related (and managed) by means of the pressure diffusion from the injection wells [Gonzalez-Nicolas, 2019]. As the CO₂ injection, most probably in liquid or supercritical state, will disturb the initial reservoir equilibrium states (which in general concerns chemical, thermal, hydro-mechanical and other conditions), the dynamic coupling between different phenomena (for instance, multiphase flow, pressure and temperature evolution, reactive component concentration fields and impact of geochemical and thermodynamic equilibrium variations in DSF) should be envisaged and realized for having a reliable numerical analysis [Newell and Ilgen 2019].

This work presents a conceptual model coupling mechanical and hydrodynamic processes that can be encountered under certain situations. Potential routes for CO₂ leakage across an aquifer to adjacent shallow rock layers and the evolution of the spatial distribution of the CO₂ plume are investigated. This conceptual model helps understanding the complex interplay of critical factors affecting the fate of CO₂ injected in DSF.

A 3D fully-coupled model was employed to investigate the dynamics of CO₂ injection, including fault slippage and fluid leakage from the reservoir toward upper formation units. Coupling between multiphase fluid flow and geomechanical deformation was achieved using the Poroelasticity physics. Physical processes occurring in CO₂ sequestration were incorporated into the Subsurface Flow module. Contact modeling features within the Solid Mechanics interface were used for representing the fault behavior. Permeability uncertainty was studied using parametric sweeps. Results indicate that the fault may slip if the fluid pressure injection rises above a critical threshold. The shape of the CO₂ plume can be significantly disturbed by the presence of the fault. This work showcases how Multiphysics simulations could help to gain insights on critical challenges faced by geological carbon storage projects.