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Título

POTENTIAL OF THE SOURCE ROCKS IN THE DEEP-WATER POTIGUAR BASIN, BRAZIL, AND ITS RELATION TO OTHER BASINS OF THE EQUATORIAL ATLANTIC

Texto do resumo

The Brazilian Equatorial Margin (BEM) is a petroleum exploration frontier. Knowing the potential of source rocks in the BEM is strategic and necessary for the energy industry. This research aims to assess the potential of the source rocks from the deep-water Potiguar Basin, located in Northeast Brazil, to recognize the quantity, quality, and thermal maturity of the organic matter. TOC, Rock-Eval Pyrolysis, and Vitrinite Reflectance data from five wells granted by the National Petroleum, Natural Gas, and Biofuels Agency were used for such purposes. Proxies of rock samples were calculated and correlated with the three main tectonic phases (rift, post-rift, and drift) and their stratigraphic formations. The dataset was assessed in detail, and the potential to generate oil changes with the basin's evolution was identified. Unlike the literature, the Pescada Fm. is the main source rock of the rift interval. It presents TOC varying between 0.3 and 3.8%, a mixed Type II-III kerogen, and has reached the oil window. On the other hand, the Pendências Fm., the oldest of the rift phase, presents TOC with values between 1.0 and 2.3% and Type III kerogen, which is gas-prone. The post-rift Alagamar Fm. presents the highest potential to generate oil. It presents excellent TOC values varying between 0.1 and 21.1%, type II kerogen which is considered oil-prone and is mature. The formation with the best-generating potential in the drift phase is the Quebradas Fm. It has 0.3 to 16.0% TOC, type II kerogen, which is oil-prone and has reached the oil window in the region around the 1-BRSA-1158-CES (Araraúna) and 1-BRSA-1175-CES (Tango) wells. On the contrary, the Ponta do Mel/Açu Fm. has kerogen type II-III and is considered immature. Finally, the Ubarana Fm. contains type III kerogen and is also regarded as immature. These parameters were essential to evaluate sedimentary rocks acting as source rocks, and they allowed us to disclose the potential of the source rocks according to the tectonostratigraphic phases of the basin. These geochemical characteristics agree with the Cretaceous period, during which excellent conditions for producing and preserving organic matter formed potential source rocks of petroleum in the South American and African equatorial basins. This is mainly related to the kerogen type II from marine anoxic conditions that comprise the chief source rocks of the Tano, Guyana, Suriname, and the Brazilian equatorial basins, including the Potiguar Basin.

Palavras Chave

Petroleum exploration; Brazilian Equatorial Margin; Organic geochemistry; Thermal Maturity