The impact of CO₂ storage in fractured shale reservoir on deep fault reactivation

Storing captured CO₂ in fractured shale reservoirs represents an effective approach for carbon neutrality. It involves CO₂ injection into fractured shale reservoirs with fractures dominating storage capacity. However, large injection volumes may induce poroelastic stress change to trigger fault reactivation beyond the pressurized zone. We use dislocation theory to define impacts of poroelastic stress change on deep fault stability. Modelling parameters are set in honor of the typical well configuration of Sichuan Basin. Correspondingly, the influence of CO₂ storage into a single well and a multilateral well system are contrasted. Modelling results identify the poroelastic stress changes decay rapidly with increasing distance. Magnitudes of poroelastic stress changes in both cases are approaching 10⁻³ and 10⁻⁴ MPa at distances of 1 and 2 km, respectively, but a larger value for multilateral well system. Changes in Coulomb failure stress were calculated to assess the fault failure/reactivation potential with values increasing at a shorter distance and for larger fault coefficient of friction. Based on current parameters, CO₂ storage in a multilateral well system is capable of reactivating critically-stressed faults within 750 m. Our modelling results aid in evaluating the seismic potential resulting from CO₂ storage in fractured shale reservoirs in Sichuan Basin and similar sites.