Potencial de sequestro geológico de CO2 nas rochas basálticas do Sistema Aquífero Serra Geral no estado de São Paulo
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Data
2022-03-17
Autores
Matsui, Thaís Naomi
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Universidade Estadual Paulista (Unesp)
Resumo
O aumento da emissão de gases poluentes, em especial de CO2, proveniente de combustíveis fósseis, tem gerado muita preocupação aos governos de diversos países, incluindo o Brasil. Com isso, a busca por meios de se reduzir as concentrações de CO2 na atmosfera tem aumentado, e uma das formas mais estudadas está relacionada ao sequestro de CO2 em aquíferos basálticos, como o projeto implantado na Islândia, pelo projeto Carbfix. No Brasil, este tema ainda é pouco estudado, especialmente quando se considera a extensão dos derrames basálticos associados ao Sistema Aquífero Serra Geral (SASG). Considerando que os basaltos são rochas ricas em minerais com cátions divalentes, como Ca2+, Mg2+ e Fe2+, os quais são essenciais para a precipitação de minerais carbonáticos, estas rochas podem representar um ótimo ambiente para o armazenamento de CO2. O presente estudo teve como objetivo simular a potencialidade de armazenamento geológico de CO2 em rochas basálticas da Formação Serra Geral no estado de São Paulo, por meio da realização de simulações de modelagem geoquímica. Para tanto, foi utilizado o software Geochemist Workbench, e as simulações realizadas em duas fases: a primeira a fase de injeção de CO2 e, a segunda, a fase de pós-injeção, onde foram observadas as mudanças hidroquímicas das águas e a precipitação de minerais carbonáticos. Estas simulações foram realizadas em cinco amostras representativas de grupos hidroquímicos previamente definidos. Os principais minerais formados após as simulações, foram a calcita e a saponita-Ca. Ao comparar as águas antes e depois das simulações, observou-se que houve um alto consumo dos cátions divalentes para a formação dos minerais secundários. O potencial de sequestro de CO2 no SASG é alto, pois cerca de 98% do CO2 injetado na fase inicial foi completamente consumido para a formação de minerais secundários. Os resultados obtidos neste trabalho, apesar de serem preliminares, podem contribuir para o melhor entendimento da interação água-rocha-CO2 em basaltos.
Increasing emission of polluting gases, especially CO2, derived from fossil fuels, has caused a lot of concern to many countries’ governments, including Brazil. Thereby, the search for means to reduce CO2 concentrations in the atmosphere has increased, and one of the most studied methods is related to carbon sequestration on basaltic aquifers, such as the Carbfix project developed in Iceland. In Brazil, this subject still needs further research, especially taking into consideration the extension of flood basalts associated with the Serra Geral Aquifer System (SGAS). Considering that basalts are rocks rich in divalent cations, such as Ca2+, Mg2+ and Fe2+, which are essential for carbonate minerals precipitation, these rocks can represent a great environment for storing CO2. The current study objective, was to simulate the geological storage potential of CO2 in basaltic rocks of Serra Geral Formation in the state of São Paulo, through geochemical modelling simulations. To do so, simulations were carried out on the software Geochemist Workbench, and divided in two phases: the first, was the CO2 – injection phase, and the second, the post-injection phase, in which hydrochemical changes in water and precipitation of carbonate minerals were monitored. Those simulations were performed on five representative samples from previously defined hydrochemical groups. The main minerals formed after the simulations were calcite and saponite-Ca. When comparing waters from before and after the simulations, a high consumption of the divalent cations was observed, due to the formation of secondary minerals. Carbon sequestration potential in the SGAS is high, as, approximately, 98% of CO2 injected on the first phase was completely consumed through the precipitation of the secondary minerals. The results obtained in this study, though preliminary, can contribute to a better understanding of the water-rock-CO2 interaction in basalts.
Increasing emission of polluting gases, especially CO2, derived from fossil fuels, has caused a lot of concern to many countries’ governments, including Brazil. Thereby, the search for means to reduce CO2 concentrations in the atmosphere has increased, and one of the most studied methods is related to carbon sequestration on basaltic aquifers, such as the Carbfix project developed in Iceland. In Brazil, this subject still needs further research, especially taking into consideration the extension of flood basalts associated with the Serra Geral Aquifer System (SGAS). Considering that basalts are rocks rich in divalent cations, such as Ca2+, Mg2+ and Fe2+, which are essential for carbonate minerals precipitation, these rocks can represent a great environment for storing CO2. The current study objective, was to simulate the geological storage potential of CO2 in basaltic rocks of Serra Geral Formation in the state of São Paulo, through geochemical modelling simulations. To do so, simulations were carried out on the software Geochemist Workbench, and divided in two phases: the first, was the CO2 – injection phase, and the second, the post-injection phase, in which hydrochemical changes in water and precipitation of carbonate minerals were monitored. Those simulations were performed on five representative samples from previously defined hydrochemical groups. The main minerals formed after the simulations were calcite and saponite-Ca. When comparing waters from before and after the simulations, a high consumption of the divalent cations was observed, due to the formation of secondary minerals. Carbon sequestration potential in the SGAS is high, as, approximately, 98% of CO2 injected on the first phase was completely consumed through the precipitation of the secondary minerals. The results obtained in this study, though preliminary, can contribute to a better understanding of the water-rock-CO2 interaction in basalts.
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Palavras-chave
Basalto, Injeção de CO2, Modelagem geoquímica, Pressão de CO2, Basalt, CO2 injection, Geochemical modelling, CO2 pressure