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Speculative Petroleum Previous HitSystemsNext Hit of the Southern Pelotas Basin, Offshore Uruguay

Abstract

At present commercial oil accumulations in the Pelotas Basin have not been identified (as opposed to the other basins of the Brazilian Atlantic margin), nor the current geological knowledge allows to identify proven petroleum Previous HitsystemsNext Hit. In spite of that, this basin continues to be underexplored with a total of only 18 exploratory wells drilled in an area of more than 330,000 km2, all of them located in its Brazilian portion. This study focused in the Uruguayan portion of the basin that has not been drilled yet. 2D and 3D seismic data acquired in this area reveal a promising hydrocarbon potential allowing the identification of stratigraphic plays that have analogies with accumulations discovered in other basins of both sides of the Atlantic not affected by halokinetic deformation (as in French Guiana and Ghana). The main purpose of this study is to evaluate the hydrocarbon potential of the southern part of the Pelotas Basin, defining the speculative petroleum Previous HitsystemsNext Hit (based on geophysical data). Sequence stratigraphy concepts were used as the main methodology to interpret the depositional sequences from 2D seismic sections of the Uruguayan portion of the Pelotas Basin and available well data. It is possible to identify a syneclise stage that preserves Permian geological units of a prerift Previous HitphaseNext Hit corresponding to the Paleozoic intracratonic Paraná Basin; an Early Cretaceous continental synrift Previous HitphaseNext Hit constituted by the volcanic-sedimentary infill of halfgrabens and SDRs; and a Cretaceous to Cenozoic postrift Previous HitphaseNext Hit represented by a sedimentary stacking associated to successive transgressions and regressions of the Previous HitseaNext Hit Previous HitlevelNext Hit. The sequence analyses allowed interpreting the system Previous HittractsNext Hit and identifying the distribution of the main elements of the potential petroleum Previous HitsystemsNext Hit. The source rocks of the speculative petroleum Previous HitsystemsNext Hit proposed in this study for the Uruguayan portion of the Pelotas Basin are represented by a Permian restricted marine source rock of the prerift Previous HitphaseNext Hit, and two marine source rocks of the postrift Previous HitphaseNext Hit of Aptian-Albian (OAE 1) and Cenomanian-Turonian (OAE 2) ages. The main reservoirs proposed are continental sandstones of the synrift Previous HitphaseNext Hit and Cretaceous and Cenozoic turbidites from the postrift Previous HitphaseNext Hit. The main regional seals are related to the postrift Previous HitphaseTop, represented by shales of the Aptian-Albian, Cenomanian-Turonian and Paleocene marine transgressions.