Binary diagrams using compositional and isotopic data from the São Francisco Basin wells. (a) Correlation between the concentration of H₂ and its isotopic ratio; (b) Correlation between the H₂ isotopic ratio of ethane versus the helium concentration of the gases. The wells A and B are located inside the study area and their data come from Prinzhofer’s private dataset and are not discussed in this article, as they do not correspond to the public data provided by the Brazilian institutions. They were added to the figure solely to better illustrate the H₂ consumption.