Thermal and solubility effects on fault leakage during geologic carbon storage: Fid-Bau Portal

Thermal and solubility effects on fault leakage during geologic carbon storage

Meguerdijian, Saro / Pawar, Rajesh J. / Harp, Dylan R. / Jha, Birendra

Highlights • Solubility is important for estimating free-phase CO $_{2}$ fault-leakage rates. • Thermal stresses can have the same order of magnitude as pressure-induced stresses when phase change is present in the fault. • Thermal stresses during phase change tend to be largest at the top of the fault while overpressures tend to be largest near the bottom of the fault. • Thermal stresses can be sufficient to cause fault reactivation if phase change is present.

Abstract Geologic carbon storage (GCS) is a promising method for reducing anthropogenic CO $_{2}$ emissions to the atmosphere. To safely deploy GCS in the field, it is necessary to assess risks and the effect of uncertainty on safe storage. The effect of uncertainty can be quantified using batches of simulations, but the high computational costs of high-resolution simulations necessitate use of reduced-order models (ROMs). Previous work involves ROMs for quantifying the risk of different potential leakage paths from storage reservoirs to shallow formations. However, previous studies on development of fault-leakage ROMs have limited numbers of uncertain parameters and do not explicitly examine impacts of CO $_{2}$ solubility and thermal stresses on fault reactivation, which can generate high-permeability pathways and compromise CO $_{2}$ storage. In this study, we analyze an ensemble of simulations considering CO $_{2}$ leakage from a storage reservoir to a shallow aquifer through a fault while varying a number of uncertain parameters related to thermo-hydro-mechanical properties and CO $_{2}$ injection. We show the effects of solubility on: free-phase CO $_{2}$ -leakage rates, brine-leakage rates, and poroelastic fault destabilization. We find that CO $_{2}$ solubility is more important for estimating free-phase CO $_{2}$ -leakage rates compared to brine-leakage rates or poroelastic fault destabilization. We also find that thermal stresses and overpressures have different spatial distributions within the fault, indicating that the spatial variability of overpressures due to variation in flow parameters does not necessarily make the spatial variability of thermal stresses negligible. We suggest the use of the CO $_{2}$ phase-change path as a variable in future fault-leakage ROMs.