Subsurface reservoirs are used for various applications that are part of the energy transition towards zero-carbon energy sources. They can serve as a direct source of energy(geothermal production), cyclic energy storage required by renewable energy production technologies (sun and wind) and sequestration of “energy waste” (carbon dioxide sequestration). Making optimal use of subsurface reservoirs is a great challenge for both academia and society. In this research project, we are going to develop a numerical framework capable of modelling and optimizing energy transition applications relevant to subsurface reservoirs. The developed software will allow for accurate prediction of the effects of the subsurface use and assessment of techno-economical risks (e.g., induced seismicity) for applications relevant to the energy transition. The results of this project can be directly used for more efficient energy production, risk assessment in energy transition applications and various legislativeinitiatives.