The Parnaíba cratonic basin: resource system
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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Cratonic Basin Formation: A Case Study of the Parnaíba Basin of Brazil
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Cratonic basins are large, distinctive features of the continental crust. They are preferentially developed on thick continental lithosphere, are typically sub-circular in shape and subside over periods of hundreds of millions of years. They are also endowed with significant resources. However, in spite of their location in continental interiors and often well-known geology, the subsidence driving mechanism and tectonic setting of these basins remains controversial.
This volume presents both lithospheric and basin scale datasets acquired specifically to interrogate the tectonic process of cratonic basin formation. Focused on the Silurian to Triassic Parnaíba cratonic basin of Brazil, the papers discuss the results of a multidisciplinary basin analysis project comprising new geophysical, geological and geochemical data. This unique dataset enables the characterization of the lithospheric crust and mantle beneath the Parnaíba Basin, constrains the detailed evolution of the basin itself, and enables comparisons with cratonic basins globally. Several convergent themes emerge providing new and powerful constraints for models of the driving mechanisms of these enigmatic basins.