In this study, we developed a three-dimensional numerical simulator that can simultaneously calculate the compositional fluid flow behavior and the geomechanical behavior around the CO2 injection reservoir to accurately predict CCS performances including induced seismicity effects. In this simulator, the functions to simulate the phase behavior/equilibrium and fluid flow in a multicomponent system were formulated using the Equation of State (EOS), which were verified by comparing the simulation results with analytical solutions and with the calculation results by a commercial simulator. On the other hand, the functions to simulate geomechanical behavior assumed that the elastic deformation and were validated with 1D and 2D analytical solutions.
Since faults play a key role in induced seismicity, we also incorporated the functions to deal with various types of faults into the above simulator. That is, the three types of fluid flow can be considered depending on the features of faults: (1) fluid flow along a fault, (2) fluid flow across a fault with non-neighboring connection, and (3) no flow along/across a fault due to sealing capability of a fault.
Finally, we constructed the simple 3D model of a hypothetical CCS site with a fault having the above features. We then conducted case studies with various parameters and clarified the conditions that caused the induced seismicity by injecting CO2 into the underground.