Multi-scale nonlinear modeling of subsurface energy storage

Abstract

Subsurface geological formations provide giant capacities for large-scale (TWh) storage of renewable energy, once this energy (e.g. from solar and wind power plants) is converted to green gas (e.g. hydrogen and green methane), pressurised or hot fluids. The key aspects of successful development of this technology include estimation of safety and storage capacity for a given formation. Formations are often highly heterogeneous, with complex (nonlinear) transport and material physics. In this work, we present a computational framework for cyclic loading of rock specimens to estimate deformation under nonlinear creep behaviour. Classical creep and relaxation creep are the two methodologies which are modeled to analyse the variation of total strain in the specimen over time. Algebraic multi-scale finite element formulation is then implemented to provide a field-scale relevant computational framework for these nonlinear time-dependent systems. This study indicates that the nonlinear deformation is quite an important aspect of cyclic energy storage in the subsurface formation, and that the proposed multi-scale simulation can provide a field-scale simulation approach to consider this important physics for safety and reliability of the storage projects.