Dados da Submissão

Título

Serra Geral Group Carbon Storage Potential by Mineral Sequestration: Experimental and Geochemical Modeling

Texto do resumo

Geological CO2 storage has become a central topic in addressing the challenges of climate change. Our research investigates the potential of the Serra Geral Group (SGG) for CO2 storage, focusing on its capacity to act as both a seal and a reservoir. Utilizing a combination of experiments and geochemical modeling, we explore the ability of these volcanic rocks to capture CO2 through mineral interactions. The first step we considered in the experiments was the effects of pH on the volcanic rock dissolution process. We simulated CO2-H2O-mafic volcanic rock interactions using a batch-mode hydrodynamic reactor. The experiments were conducted under pressure conditions of 100, 150, and 200 bar at a temperature of 100°C with a reaction time of 168 hours. These reaction conditions ensure (physicochemically) that CO2 is reacting in the supercritical state. This process begins with the dissolution of CO2 in water, leading to the formation of carbonic acid. As carbonic acid is generated, it alters the pH of the water within the reactor, increasing its reactivity. This increased reactivity causes hydrogen ions (H+) in the solution to interact with the volcanic rock and dissolve the primary minerals present in the matrix, releasing cations such as calcium (Ca2+), magnesium (Mg2+), and iron (Fe2+) into the solution. These initial steps play a crucial role in creating the geochemical environment necessary for forming carbonate species ((CaMgFe)CO3), aiming for the mineral trapping of CO2. An important aspect of SGG magmatism is the heterogeneity of rock composition. To evaluate the effects of pH (dissolution process efficacy) and the CO2 capture potential in different lithologies, we collected and analyzed 20 different rock samples from the Rio Grande do Sul and Santa Catarina states. Pre- and post-experiment analyses, including pH measurements, ICP-OES (liquid solution), and X-ray diffraction (mineral phases), were performed to assess compositional and mineralogical changes resulting from CO2-H2O-mafic rock interactions. pH measurements revealed that the CO2 dissolved in the reactions produced carbonic acid, causing a drop in the hydrogen ion concentration of the remaining solution in the reactor from approximately 6 (before the reaction) to a slightly acidic range of 5.5–4.70 (after the reaction). The results obtained from these experiments were used as input data for developing geochemical models, incorporating variables such as partial pressure of CO2, temperature, and reaction time. These models predict the reactive behavior of H+ (as a function of the reaction pH) as well as the formation of calcite, dolomite, and siderite, driven by an increase in mineral saturation indices and a decrease in the concentrations of Mg2+, Ca2+, and Fe2+. The study concludes that the interaction of supercritical CO2 with mafic rocks under high-pressure and high-temperature conditions effectively sequesters carbon in mineral form. Although it cannot replace empirical experimentation, geochemical modeling has proven invaluable for bridging the gap between laboratory findings, field observations, and the long-term dynamics of the CO2-H2O-mafic rock system. Integrating geochemical modeling with the petrographic characteristics of these rocks provides a comprehensive data set that enhances our understanding of CO2-H2O-mafic rock interactions, paving the way for more efficient sequestration strategies in volcanic rocks.

Palavras Chave

Carbon Capture and Store; Paraná Basin; Supercritical CO2; Energy Transition