A Methodology for Geological Hazard Assessment in Temporary Storage Facilities

The main risks and hazards related to fluid storage in subsurface are associated with reservoir rocks deformation, pore pressure change and/or change in stress around faults (depending on their properties and orientations): a change in pore pressure due to injection or extraction of fluid from a well, may change the stress acting on a nearby fault; this change in stress may induce slip or movement along that fault creating a seismic event. Compaction or dilation of reservoir volume induce stress changes inside the reservoir and the surrounding caprock, also generating ground movements: subsidence and uplift,, in consequences of fluid withdrawing or fluid injection in reservoir, are related to reservoir performances, geological setting and reservoir/caprock mechanical properties. Despite an increased understanding of the basic causes of their hazards, these kinds of energy projects will retain a certain level of risk for inducing seismic events, manufacture integrity, and ground movements. For assessing geological hazards associated to subsurface temporary storage, we develop a 3-step, quite fast and easy procedure; starting from a real reservoir, converted to temporary storage facility, we quantify 1) reservoir deformations, 2) induced stress changes and 3) areas in the caprock which are more affected by stress changes distribution.