Exploration plays of the Potiguar Basin in deep and ultra-deep water, Brazilian Equatorial Margin

Abstract

Following the discoveries on West Africa conjugated margin since 2007 (Jubilee, Tweneboa, Venus, Mercury, and other fields) and in the Guiana-Suriname Basin since 2011 (Zaedyus field and Liza Complex/Exxon's Stabroek block), the Potiguar Basin deep/ultra-deep waters represents one of the most important exploratory frontier basins, like others on the Brazilian Equatorial Margin. Aiming to apply similar plays of these discoveries, was performed a 2D seismic interpretation supported by well data in deep/ultra-deep waters of the Potiguar Basin. Thus, based on the seismic horizons corresponding to the main tectono-sedimentary events, five chronostratigraphic intervals were interpreted: U1, U2, U3, U4, and U5. Moreover, there were interpreted three petroleum systems: Pendência-Pescada (!), Alagamar–Alagamar (!) and Quebradas-Ubarana (.). Pendência Formation source rocks are late Berriasian-early Barremian lacustrine shales. Alagamar Formation source rocks are Aptian-Albian evaporitic marine shales and marls of the Galinhos Member and Ponta do Tubarão Beds. Quebradas Formation source rocks are Cenomanian-Turonian deep water marine shales. Among these source rocks, the best is Galinhos Member/Ponta do Tubarão Beds, reaching up to 21% TOC, Type I, II, and III kerogens, excellent petroleum potential for oil/gas generation, and with thermal maturity at the studied area. Quebradas Formation, which is correlated to Cenomanian-Turonian source rocks of the West Africa Equatorial Margin and Guyana-Suriname basins, reaches up 6% TOC, Type I/II kerogen, very good to excellent petroleum potential for oil generation, and adequate thermal maturity at the studied area. Three plays were interpreted: Strike-slip, Anticlinal, and Late Cretaceous Turbidites, whose water-depth varies from 1,500 m to 1,900 m. Considering the sea bottom as a datum, reservoir rocks (fluvio-deltaic and turbidites sandstones) are about 3,050 m to 5,800 m, and source rocks nearly 3,500 m to 6,500 m. Seal rocks could be Late Cretaceous marine shales. Traps are mainly stratigraphic (pinch-out). Migration pathways are mainly lateral (Late Cretaceous Turbidites play) or also vertical through transtensive faults (Strike-slip and Anticlinal plays). The oil window top estimated depth based on well geochemical profiles is about 2,600 m below the sea bottom. Besides that, studies in West Africa Equatorial Margin basins state the oil window top occurs approximately at 2700 m below the sea bottom. Therefore, all the source rocks to the three interpreted plays are below the oil and/or gas window top. In such a way, the studied area in deep/ultradeep waters of PB has great exploration potential for both oil and/or gas.