The Paleozoic Parnaíba Basin has proven to be one of the most successful onshore gas basins in Brazil. Since 2010, seven gas fields have been declared as commercial. Conventional gas accumulations occur in the Devonian Cabeças Formation sandstone, Upper Devonian/Lower Carboniferous heterolitic sandstones of the Longá Formation, Carboniferous Poti Formation arkosic-sandstones and in the Upper Carboniferous Piauí Formation sandstones. The stacked geometry of an extensive Mesozoic igneous complex is responsible for the creation of several four-way structures and compartmentalization of both source rock and reservoirs. The dolerite sills intrude the organic-rich intervals of the Devonian Pimenteiras shale, triggering maturity and hydrocarbon generation, thus creating an atypical igneous–sedimentary petroleum system. Major seismic concerns are the complexity of imaging subigneous plays, the large areal extent of the basin, strong velocity heterogeneity and the difficulty of imaging high-angle or vertical sealing structures, critical to prospect success. The recognition and understanding of this atypical igneous–sedimentary petroleum system could be used to unlock the potential of analogue basins worldwide and also to expand the exploration successful cases in the Parnaíba Basin itself.

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