Data integration for a geologic model of hydrocarbon microseepage areas in the Tonã Plateau region, North Tucano basin, Brazil

A diversified database was used for investigating the major factors controlling the distribution of hydrocarbon microseepage in the region of the Tona Plateau, North Tucano sedimentary basin, Brazil. Visual analysis of this database suggested the existence of spatial relationships between anomalous geochemical soil gas data with rift faults, lithologic contact, and groundwater discharge areas. As a result, a geologic model was proposed. According to this model, rift faults constitute the primary pathways for the upward migration of gaseous hydrocarbons from a deep-seated source rock in the depocenter of the basin. Cherty limestone layers in the Tona Plateau act as a seal to prevent the escape of the hydrocarbons to the surface. As a result, hydrocarbon microseepage occurs preferentially in the contact zone of the cherty limestones of the Tona Sequence with porous sandstones of the Marizal Formation, mainly in areas of groundwater discharge. The importance of these three patterns for controlling the near-s...