Henrique Serratt

The growing interest in Natural Hydrogen Gas (H2) is spurring a new wave of exploration due to its potential as a clean energy source. We investigate the highest concentration of natural  H2 found in Brazil, specifically in the Rio Grande do Sul and Santa Catarina states. Our research identifies free H2 occurrences within the intracratonic Paraná Basin, revealed through formation tests in historic exploratory wells. The H2 concentrations in these tests varied from 0.14% to 8.79%, although associated with non-commercial natural gas volumes (CH4, varying from 87.68% to 98.61%, and He from below detection limit to 1.03%). The He content in the formation tests is inversely proportional to H2 content, suggesting a non-mantellic source. However, He isotope analyses are necessary to determine the relation between these gasses and their source conclusively.  On the other hand, rock alteration, such as biotite hydration did not explain the relation between H2 and natural gas. Although H2 and oil & gas systems can be independent, the probability of the existence of two unrelated systems is statistically more improbable. Due to this, we speculate that the anomaly is related to organic matter maturation, this could explain the natural gas and H2 coexistence in a single system. This model has some issues, as the anomalies are below the levels richer in organic matter, such as coals. However, organic-rich shales exist below the anomaly identified in the well. In addition, this region is known for the existence of reservoir rocks (sandstones with good porosity) and seals (thick basalt layers, sills, and continental flood basalt spills). This study underscores the necessity for comprehensive exploration to realize the economic potential of H2 in Southern Brazil. Our findings lay the groundwork for future research, particularly in understanding the geological conditions conducive to hydrogen accumulation and migration. By highlighting the geological frameworks and potential sources of hydrogen, we aim to contribute to the growing body of knowledge on natural hydrogen systems and support the development of renewable energy resources in South America. The Paraná Basin shows all the elements necessary to host the economic accumulation of natural  H2. For now the southmost of the basin is the best target for hydrogen gas prospecting in Brazil. This research advocates for strategic sampling and detailed geological analysis to harness natural H2 , fostering a sustainable energy future.Serratt, H., - Henrique Serratt (1)(2)(3)Cupertino, J.A., - José Antonio Cupertino (1)Cruz, M.F., - Matheus Fernandez Cruz (1)Teixeira, C.D., - Claudia Domingues Teixeira (1)Oliveira, H.O.S., - Helder Osvaldo Samucuta de Oliveira (1)Lehn, I., - Ilana Lehn (1)Girelli., T.J., - Tiago Jonathan Girelli (1)Rizzi, M.A.M., - Monique Aparecida Marchese Rizzi (1)Augustin A.H. - Adolpho Herbert Augustin (1)Bonato. J.  - Juliano Bonato (1)Chemale Jr, F. - Farid Chemale Junior (1)affiliations :(1) Programa de Pós-Graduação em Geologia, Universidade do Vale dos Sinos, São  Leopoldo, Brazil (2) Instituto de Geociências, Universidade de Brasília, 70910-900, Brasília, DF, Brazil (3) UMR CNRS-IFREMER-CNRS-UBS 6538 Geo-Ocean, IUEM, Université de Bretagne Occidentale, France