Geomechanical simulation of energy storage in salt formations

Abstract

A promising option for storing large-scale quantities of green gases (e.g., hydrogen) is in subsurface rock salt caverns. The mechanical performance of salt caverns utilized for long-term subsurface energy storage plays a significant role in long-term stability and serviceability. However, rock salt undergoes non-linear creep deformation due to long-term loading caused by subsurface storage. Salt caverns have complex geometries and the geological domain surrounding salt caverns has a vast amount of material heterogeneity. To safely store gases in caverns, a thorough analysis of the geological domain becomes crucial. To date, few studies have attempted to analyze the influence of geometrical and material heterogeneity on the state of stress in salt caverns subjected to long-term loading. In this work, we present a rigorous and systematic modeling study to quantify the impact of heterogeneity on the deformation of salt caverns and quantify the state of stress around the caverns. A 2D finite element simulator was developed to consistently account for the non-linear creep deformation and also to model tertiary creep. The computational scheme was benchmarked with the already existing experimental study. The impact of cyclic loading on the cavern was studied considering maximum and minimum pressure that depends on lithostatic pressure. The influence of geometric heterogeneity such as irregularly-shaped caverns and material heterogeneity, which involves different elastic and creep properties of the different materials in the geological domain, is rigorously studied and quantified. Moreover, multi-cavern simulations are conducted to investigate the influence of a cavern on the adjacent caverns. An elaborate sensitivity analysis of parameters involved with creep and damage constitutive laws is performed to understand the influence of creep and damage on deformation and stress evolution around the salt cavern configurations. The simulator developed in this work is publicly available at https://gitlab.tudelft.nl/ADMIRE_Public/Salt_Cavern.

Subsurface carbon dioxide and hydrogen storage for a sustainable energy future

“…Injectivity loss due to salt precipitation is a well-studied phenomenon for CO2 storage (Miri and Hellevang, 2016), while for UHS there is still uncertainty around analogous evaporative processes. The intermittency of injection and withdrawal cycles on shorter time-frames, compared to monotone storage of CO2, raises additional challenges for wellbore integrity and rock plastic deformation under cyclic loading (Carroll et al, 2016;Kumar et al, 2021). In addition, fault integrity could be a greater risk with increased cycling frequency and loads, as observed in petroleum applications (Kaldi et al, 2013).…”

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

“…Salt rocks may contain small amounts of water that enable pressure solution creep [240]. H 2 percolation through salt grains can suppress pressure solution creep by causing water desiccation [266]. However, this is more likely to occur in the near-wall region, where pressure solution creep is not a dominant deformation mechanism.…”

“…Some researchers thus develop constitutive models to account for specific processes rather than complete models. A well-known example is the (Norton) power-law model for dislocation creep [239], which takes temperature effects into account via the Arrhenius law, and it has been extensively applied [266,247]. A specific model for pressure solution creep has also been proposed in [240], which is formulated similarly to Norton's creep law, but with a linear dependency on stress and inversely proportional influence of the grain size.…”

Compositional variation of the Zechstein Group in the Norwegian North sea: Implications for underground storage in salt caverns

“…However, halite usually occurs as layered evaporitic sequences (LES) containing beds of different composition and mechanical properties such as different evaporites, carbonate, clastic and volcanic rocks (Raith et al, 2015; Rowan et al, 2019; Strozyk, 2017; Warren, 2006). The proportion of these components control the sealing properties, the contamination of the stored fluid and the final geometry of the salt cavern (Cyran, 2020; Gillhaus & Horvath, 2008; Hemme & Van Berk, 2017; Kumar et al, 2021; Looff, 2017; Portarapillo & Di Benedetto, 2021). The presence of ductile and low‐viscosity K‐Mg salts can be highly problematic during the drilling process, leading to project delays or well abandonment (Strozyk, 2017).…”