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Título

HYDROCARBON EXPLORATORY POTENTIAL IN THE PARÁ-MARANHÃO BASIN: ASSESSMENT OF THE TRAVOSAS FORMATION AS A SOURCE ROCK

Texto do resumo

The Pará-Maranhão Basin, situated on Brazilian Equatorial Margin, spans approximately 92,890 km², adjacent to the Foz do Amazonas Basin to the NW and the Barreirinhas Basin to the SW. The Pará-Maranhão Basin contains potentially hydrocarbon source rocks, being the main one the Travosas Formation composed of transgressive shales dating from Cenomanian and Middle Campanian. This study develops an evolutionary model for specific petroleum systems and examines the relationship between source rocks and basin domains, with a focus on the Travosas Formation, using geochemical data analysis, it aims to determine the potential for oil exploration in that basin. Data from two wells provided by the National Agency of Petroleum, Natural Gas and Biofuels (ANP) were used in this study. Both wells contain a complete set of data, including total organic carbon (TOC), insoluble residue (IR), and Rock-Eval pyrolysis. The well 1-BRSA-906-PAS drilled in 2011 in deeper waters in the basin’s west part reaching only the Travosas Formation with 58 samples available and well 1-MAS-16-MA from 1983 in shallower waters and located in the central portion of the basin also detecting the Travosas Formation with of 34 samples. Regarding 1-BRSA-906-PAS, in the Travosas Formation the TOC content ranges from 0.21 to 0.9%, falling within the classification of low to moderate levels for hydrocarbon generation. Values of S2, which represents the amount of hydrocarbons generated from kerogen during the pyrolysis, range from 0.3 to 1.24, indicating a low hydrocarbon source potential. The Hydrogen Index (HI) varies from 49.93 to 160.62, suggesting presence of type III kerogen favorable to gas generation. The Van Krevelen diagram classify the kerogen as mostly type III with some sample being classified like type IV. Tmax values range from 311 to 458°C, with 24 samples above 435°C and 11 samples below this temperature. These values indicate that the organic matter can be considered mature for oil generation, but some samples with very low S2 values may have affected the Tmax reading. In well 1-MAS-16-MA the Travosas Formation presents TOC ranging from 0.36 to 0.91, indicating a poor to fair level of organic richness. The S2 varies from 0.94 to 1.69, indicating a poor hydrocarbon source potential. However, the values of the HI range from 123.68 to 201.19, making it possible to infer that the depositional paleoenvironment varied between oxic and dysoxic. and that the kerogen type III suggest a potential for gas exploration. Van Krevelen diagram shows that the organic matter it's mostly type III, and the Tmax values (432 to 435°C) suggest immaturity for hydrocarbon generation. Overall, both wells present relatively modest organic richness and hydrocarbon generation potential, the HI values suggest promising prospects for gas generation in deep waters where thermal maturity should be greater. This information provides guidance for future oil exploration efforts in the Pará-Maranhão Basin.

Palavras Chave

Brazilian Equatorial Margin; Pará-Maranhão Basin; Travosas Formation; Cenomanian; Rock-Eval pyrolysis