Poroelastic model in a vertically sealed gas storage: a case study from cyclic injection/production in a carbonate aquifer

Abstract

Summary Natural gas can be temporarily stored in a variety of underground facilities, such as depleted gas and oil fields, natural aquifers, and caverns in salt rocks. Being extensively monitored during operations, these systems provide a favorable opportunity to investigate how pressure varies in time and space and possibly induces/triggers earthquakes on nearby faults. Elaborate and detailed numerical modeling techniques are often applied to study gas reservoirs. Here we show the possibilities and discuss the limitations of a flexible and easily formulated tool that can be straightforwardly applied to simulate temporal pore-pressure variations and study the relation with recorded microseismic events. We use the software POEL (POroELastic diffusion and deformation) which computes the poroelastic response to fluid injection/extraction in a horizontally layered poroelastic structure. We further develop its application to address the presence of vertical impermeable faults bounding the reservoir and of multiple injection/extraction sources. Exploiting available information on the reservoir geometry and physical parameters, and records of injection/extraction rates for a gas reservoir in southern Europe, we perform an extensive parametric study considering different model configurations. Comparing modeled spatiotemporal pore-pressure variations with in situ measurements, we show that the inclusion of vertical impermeable faults provides an improvement in reproducing the observations and results in pore-pressure accumulation near the faults and in a variation of the temporal pore-pressure diffusion pattern. To study the relation between gas storage activity and recorded local microseismicity, we applied different seismicity models based on the estimated pore-pressure distribution. This analysis helps to understand the spatial distribution of seismicity and its temporal modulation. The results show that the observed microseismicity could be partly linked to the storage activity, but the contribution of tectonic background seismicity cannot be excluded.

Comprehensive review of geomechanics of underground hydrogen storage in depleted reservoirs and salt caverns

“…The injection and production of energy-rich green fluids into underground reservoirs are influenced by the cyclical nature of demand and supply of renewable energy [55,56]. Consequently, the reservoir's pore pressure and temperature will cyclically vary, leading to potential hazards during and after operations, such as reduced strength, subsidence, or uplift [57], compromised well integrity [48], chronic H 2 leakage, reduced caprock sealing capability, and induced seismicity from fault reactivation [58,59]. The use of salt caverns for storage may also result in unintended consequences, including excessive cavern convergence (loss of storage volume) [60], roof collapse [61], fluid leakage [62], and other events [63].…”

Simulation of the inelastic deformation of porous reservoirs under cyclic loading relevant for underground hydrogen storage

“…Additionally, the impact of inelastic deformation in a field-scale relevant test case is studied. It is worth mentioning that an important consequence of altering the subsurface stress is the subsidence/uplift; specially if the site is close to populated urban areas 74 – 76 . In this study, as a relevant test case, the Dutch Bergermeer gas field is also investigated in detail to quantify the associated uplift over a few years of cyclic loading.…”