A review of CO2-injection projects in the Brazilian Pre-Salt — Storage capacity and geomechanical constraints

This review describes the main geological and geomechanical aspects of CO₂-injection projects in the Brazilian Pre-Salt reservoirs, focusing on the storage potential and geomechanical aspects of CO₂ injection. The Pre-Salt reservoirs in the Santos Basin offer favorable conditions for CCS due to their geological characteristics and existing infrastructure. The thick evaporite caprock, primarily composed of halite, acts as an efficient seal against CO₂ migration. The ${\text{CO}}_2$-injection in the Pre-Salt has been active since 2010, with significant amounts of CO₂ already stored in the reservoirs. The volumetric assessment estimates the static storage capacity of the Pre-Salt reservoirs to be over 3.3 Gt of CO₂, considering only the four fields currently undergoing injection. Geomechanical constraints, including the maximum injection pressure and caprock integrity, are crucial considerations for safe CCS operations. The high stress regime and the hydrostatic state of the caprock minimize the risk of fracturing during injection. Furthermore, dynamic storage capacity calculations indicate the feasibility of injecting CO₂ into Pre-Salt reservoirs. This review provides insights into the current state and future prospects of CO₂-injection projects in the Brazilian Pre-Salt, contributing to the development of sustainable carbon mitigation strategies in the region.