Reliable assessment of the long-term effects of hydrocarbon production from sandstone reservoirs, on induced subsidence and seismicity, requires an understanding of the processes that lead to associated reservoir compaction. The compaction is typically small (strain < 1%) and often considered to be purely elastic, but in reality is partly permanent and possibly even time-dependent. This means compaction may continue even after production stops. Empirical models are often used to evaluate future reservoir compaction, however the reliability of such extrapolation in time is questionable without underpinning in terms of the governing processes. We develop a simplified microphysical model with a variable microstructure (i.e., unit cells with varying grain packings), aimed at capturing the deformation mechanisms observed in triaxial compression experiments on clay-bearing Bleurswiller sandstone (porosity 21%). The mechanisms include rate-independent consolidation of intergranular clay films, rate-dependent intergranular slip along the clay films and stress corrosion cracking of quartz/clastic grains. Our model predicts mechanical behaviour consistent with the main features and trends observed in the experimental data. Stresses and strains are localized in unit cells with relatively low and high grain contact inclination, respectively, over the full range of deviatoric loading. Sensitivity analysis showed that quartz/clastic grain shape (aspect ratio) is an important factor determining the modelled mechanical behaviour. The present model provides mechanistic underpinning for existing geomechanical models accounting for rate-dependent deformation relevant to hydrocarbon production-induced subsidence and seismicity, at field conditions and timescales. ... Read more

Fluid extraction from sandstone reservoirs leads to reservoir compaction, potentially inducing surface subsidence and seismicity, as observed in the Groningen Gas Field, Netherlands. Such compaction is partly elastic, but can additionally be caused by instantaneous plastic and rate/time-dependent processes, such as subcritical crack growth, meaning that compaction may continue even if production is stopped. Despite the need to evaluate the impact of post-abandonment reservoir behavior (>10–100 years), few mechanism-based, rate/time-dependent compaction laws exist. Compaction due to grain breakage, either via critical or subcritical crack growth, is driven by tensile stresses acting on surface and volume flaws. We performed high-resolution 3D linear elastic finite element method simulations on simplified grain assemblies to investigate the effect of stress–strain boundary conditions, porosity and mineralogical variations on grain-scale stress fields. Our simulations showed tensile stress concentrations at grain contact edges and on pore walls, which increased in magnitude with increasing aggregate porosity and local porosity variation. The fraction of surface area with tensile stresses sufficient to extend flaws with a size up to 30μm showed a clear correlation with compactive yield envelopes for the Groningen reservoir sandstone. This suggests that compactive failure is related to the probability of pre-existing surface flaws, falling in a pore surface region where the Griffith criterion is satisfied. A preliminary, time-independent failure probability model, using the observed tensile stress distribution, qualitatively predicts a non-linear increase in grain cracking during deviatoric loading, and suggests a new route to predict sandstone compaction through brittle grain failure. ... Read more

Achieving climate neutrality requires rapid scale-up of CO2 storage to gigatonne scale. Storage clusters—multiple injection sites sharing regional aquifers—offer economic benefits but introduce new challenges in subsurface pressure management. Elevated reservoir pressures can lead to fault slip and leakage, generating environmental and operational risks that span beyond individual license areas. Current site-focused workflows are insufficient for characterizing such cross-boundary effects.

This work introduces the research activities and key ideas of the international research project MuPSI which develops an integrated, multiscale screening and simulation approach to assess geomechanical risks in storage clusters. We present results of a new screening workflow that enables rapid evaluation of pressure interference and fault activation risk across regional aquifers. This is coupled with high-resolution modeling of fault response and new software to bridge region-, project-, and fault-scales. A new highly efficient approach for pressure-stress coupling offers greater software flexibility in geomechanical assessment of individual projects.

The approach is demonstrated using North Sea case studies, including the Horda Platform (Norway) and East Mey (UK). Outputs will support operators and regulators in improving investment decisions, permitting, and cross-license coordination. MuPSI also delivers stakeholder training and knowledge-transfer tools to accelerate adoption of robust, risk-informed storage cluster design. ... Read more

Hydrocarbon production from sandstone reservoirs causes elastic and inelastic reservoir compaction, potentially leading to surface subsidence and even seismicity, such as observed in the Groningen gas field, Netherlands. Inelastic compaction can partly be instantaneous, though rate-/time-dependent processes may play a role on the longer term. Therefore, compaction may continue even if production is stopped. To reliably evaluate the impact of post-abandonment behaviour, mechanism-based rate-/time-dependent compaction laws are needed. We performed triaxial compression experiments on Slochteren sandstone (reservoir of the Groningen field) samples, with porosity ϕ= 14.6–18.9%, to investigate the effect of strain rate (rates of 10-6-10-8s-1) under conventional triaxial and uniaxial strain (i.e. zero-lateral strain) boundary conditions. Under triaxial conditions, lowering of stress–strain curves was observed with decreasing strain rate at all differential stresses, the effect being enhanced at higher temperature and pore fluid pH. By contrast, strain rate had limited effect on axial stress vs. strain behaviour under uniaxial strain conditions, though decreasing strain rate, as well as increasing fluid pH, resulted in a smaller increase in confining pressure required to maintain a zero-displacement lateral boundary condition. The mechanical data, complemented by microstructural analysis, suggest that subcritical cracking, coupled with grain rearrangement, was the dominant mechanism causing inelastic deformation under triaxial and uniaxial strain conditions. Our results suggest that the amount of reservoir compaction will be limited after production stops. However, time-dependent deformation will lead to changes in the in-situ state of stress, which should be included in models assessing reservoir compaction and induced seismicity in the Groningen field. ... Read more