Unveiling CCS Potential of the Rio Bonito Formation, Paraná Basin, southern Brazil: The Dawsonite Discovery

Abstract

Dawsonite, a hydrated carbonate, is a key mineral studied for Carbon Capture and Storage (CCS) initiatives. It forms in high pCO₂ environments, enabling gas storage in a solid state within geological reservoirs, thereby helping mitigate greenhouse gas emissions. The Rio Bonito Formation has gained attention as a potential CO₂ reservoir due to its favorable characteristics such as porosity, permeability, depth, thickness, organic matter content, and the presence of an effective sealing layer (Palermo Formation), particularly in the central region of the Paraná Basin. This study reveals the natural occurrence of dawsonite within the Rio Bonito Formation in the southern part of the Paraná Basin, in Rio Grande do Sul State, Brazil. Dawsonite was identified in quartz sandstones through petrographic analysis, indicating its formation during mesodiagenesis, where it crystallized within moldic pores. The presence of dawsonite was further confirmed through scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX) and X-ray diffraction (XRD) techniques. This discovery marks the first documented occurrence of dawsonite within the Rio Bonito Formation. It suggests that under similar conditions, other sections of the Rio Bonito Formation may also include dawsonite, thereby expanding the potential for onshore CCS in the Paraná Basin.