Dados da Submissão

Título

Geochemical characterization of the hydrocarbon generation potential of the Upanema and Galinhos Members of the Alagamar Formation, Potiguar Basin, Brazil.

Texto do resumo

The Potiguar Basin, located on the Brazilian Equatorial Margin, covers an area of 222,100 km² and is bounded by basement rocks to the south, east, and west, extending northward to the 2,000 m isobath. It has significant petroleum potential onshore and limited potential in shallow offshore waters. However, there is still limited knowledge of the potential in the deep and ultra-deep offshore regions, which represent a new exploratory frontier. The recent discovery of oil fields in deep waters in this basin suggests significant potential for future discoveries, especially considering the region's geology. This study investigates the Upanema and Galinhos Members of the Alagamar Formation in two deep and ultra-deep water wells. Data from 142 samples provided by the National Agency of Petroleum, Natural Gas, and Biofuels (ANP) were used. Hydrocarbon generation potential and maturity were assessed through parameters such as Total Organic Carbon (TOC) content and Rock-Eval Pyrolysis data: Hydrocarbon Generation Potential (S2), Hydrogen Index (HI), Tmax (Maximum Temperature), S1/TOC ratio, Production Index (PI), and Vitrinite Reflectance (%Ro). In the Upanema Member, TOC values reach 4.99% and S2 values of 13 mg HC/g rock, indicating good potential for oil generation. In well 1-CES-0121-CE, in deep waters, the Upanema Member shows a highly enriched organic matter interval, with TOC of 18% and S2 of 164.41 mg HC/g rock, indicating excellent hydrocarbon generation potential. The Galinhos Member has TOC and S2 values of 34 mg HC/g rock. In well 1-BRSA-1205-RNS, in ultra-deep waters, the shales of the Upanema Member have TOC values of 21.10% and S2 of up to 33.53 mg HC/g rock, indicating excellent generation potential. In the shales of the Galinhos Member, TOC values are higher, reaching up to 21.10% and S2 of up to 186 mg HC/g rock, suggesting greater generation potential, especially at the top of the Member (Ponta do Tubarão Layer - CPT). HI values show a predominance of Type II kerogen in the Upanema Member, while in the Galinhos Member, at the CPT the kerogen is Type I, while in the rest of the formation the kerogen is Type II, suggesting oil/gas generation potential from marine organic matter. Tmax values suggest higher maturity in the Upanema Member, with an average of 440°C (oil generation window) and immaturity in the Galinhos Member (431°C). S1/TOC and PI indexes, presented in both Members, reveal low maturity. Ro% in the wells studied indicated that in the Upanema Member, the samples are within the oil and gas generation window, while in the Galinhos Member, there is a range between immaturity and the beginning of maturity. The results suggest that the Upanema Member, in the analyzed wells, has very good oil/gas generation potential, with Type II organic matter, and mature samples (generation window). The Galinhos Member has excellent potential for oil/gas generation, both at the top of the Alagamar Formation and in the CPT. The Galinhos Member presents Type I kerogen (CPT) and Type II with thermally immature samples. This study is preliminary and proposes additional investigations, such as organic petrography, palynofacies, seismic profile studies, and computational modeling, aiming for a more comprehensive understanding of the petroleum potential in deep waters in the Potiguar Basin.

Palavras Chave

Geochemical Characterization; Parnaíba Basin; Source Rock; Rock-Eval pyrolysis; Thermal Maturity.