Potential for permanent CO2 sequestration in depleted volcanic reservoirs in the offshore Campos Basin, Brazil

Abstract

The pre-salt oil and gas production in Brazil faces a significant challenge due to the high CO₂ content in these reservoirs. Approximately 600,000 t of CO₂ are reinjected monthly in the reservoirs, but the increased production of CO₂ will demand alternatives for sequestration. Experiments and pilot projects have demonstrated the viability of CO₂ sequestration through the mineralization method in basaltic rocks. Here, we present a study aimed at demonstrating the feasibility of using the volcanic rocks of the Cabiúnas Formation, located at the base of the pre-salt section in shallow waters of the Campos Basin, for CCS projects. We used legacy data to determine the regional characteristics and porosity distribution of the volcanic sequence to assess the feasibility of geological sequestration in this region. Our estimates demonstrated that the Cabiúnas flood basalts have a good to excellent storage capacity. The modeling of a 31km² hypothetical reservoir with a thickness of 300 m in the upper part of the sequence above the Badejo Field revealed a storage estimate of 16–47 Mt. The technical aspects discussed in this study provide valuable insights that can help with the development of future CCS projects in the volcanic rocks of this petroleum province.