Coupled Geomechanical‐Flow Assessment of CO₂ Leakage through Heterogeneous Caprock during CCS

Abstract

The viability of carbon capture sequestration (CCS) is dependent on the secure storage of CO2 in subsurface geologic formations. Geomechanical failure of caprock is one of the main reasons of CO2 leakage from the storage formations. Through comprehensive assessment on the petrophysical and geomechanical heterogeneities of caprock, it is possible to predict the risk of unexpected caprock failure. To describe the fracture reactivation, the modified Barton–Bandis model is applied. In order to generate hydro-geomechanically heterogeneous fields, the negative correlation between porosity and Young’s modulus/Poisson’s ratio is applied. In comparison with the homogeneous model, effects of heterogeneity are examined in terms of vertical deformation and the amount of leaked CO2. To compare the effects of heterogeneity, heterogeneous models for both geomechanical and petrophysical properties in coupled simulation are designed. After 10-year injection with petrophysically heterogeneous and geomechanically homogeneous caprock, CO2 leakage is larger than that of the homogeneous model. In contrast, heterogeneity of geomechanical properties is shown to mitigate additional escape of CO2. Vertical displacement of every heterogeneous model is larger than homogeneous model. The model with compressive tectonic stress shows much more stable trapping with heterogeneous caprock, but there is possibility of rapid leakage after homogeneous caprock failure.

A CCUS Optimisation for a Greener Tomorrow Using a Proxy Model Driven Numerical Simulation

“…5 Moreover, fluid leakage channels over caprocks may be provided by faults and pre-existing fracture systems. 4 Furthermore, after a highrate CO 2 injection, the reservoir pressure rises, which frequently causes induced stresses greater than the sum of the least primary effective stress and tensile strength. These stresses might reactivate preexisting fractures or cause new ones to form.…”

Effects of Anisotropy and CO2 Wettability on CO2 Storage Capacity in Sandstone

“…The geological sequestration of CO 2 (GSC; i.e., storage of captured and pressurized CO 2 in deep saline rock formation covered by the impermeable cap rock) is not only a potential alternative and reliable solution to mitigate climate change [4][5][6][7] but has also been applied to increase hydrocarbon production in enhanced oil recovery [8,9] and geothermal extraction [10,11]. However, the use of GCS needs to be further examined as it is associated with potential risk of CO 2 leakage, i.e., a discontinuity in the rock structure, deteriorated well integrity, and long-term seismicity [7,[12][13][14][15]. Therefore, the accurate estimation of CO 2 storage capacity is crucial for the long-term security of a successful and effective sequestration strategy.…”