Abstract The Barracuda and Roncador giant oil fields, located in the Campos Basin, southeastern Brazil, represent two of the most important worldwide discoveries in the last decade, containing estimated reserves of almost 4 billion BOE accumulated in siliciclastic turbidites. Both fields are located in deep and ultradeep waters, with water depth extending from 600 to 2100 m. The Barracuda field was discovered in April 1989 by the 4-RJS-381 well in a water depth of 980 m. It covers an area of about 157 km 2 , in water depths ranging between 600 and 1200 m. It produces from Tertiary turbidite reservoirs. Seismic attribute analysis discriminates oil-saturated Paleocene, Eocene, and Oligocene sandstones encased in shale and marls, mainly in stratigraphic traps. This giant oil field contains in-place volumes of 2.7 billion bbl, and the total reserves achieved 659 million bbl (for Oligocene reservoirs) and 580 million bbl (for Eocene reservoirs). The Barracuda field is under development along with the Caratinga field because of their geographic proximity. The development strategy foresees an ongoing pilot system (concluded in October 2002) and a definitive one (being implemented). The pilot system started production in 1997 through a floating production, storage, and offloading (FPSO)-type stationary production unit. Production by means of the definitive system is expected to start in the second semester of 2004 and comprises 20 production and 14 injection wells. The loading, processing, and offloading of the oil and gas from the field will be through an FPSO unit with processing capacity of 150,000 BOPD and 4.8 million m 3 /day of gas. The peak production is expected in 2006. The Roncador field, discovered in October 1996 by the 1-RJS-436A wildcat, is in water depths ranging from 1500 to 2100 m. This giant field contains large volumes of hydrocarbons (9.2 billion bbl of oil in place and total reserves of 2.6 billion BOE) accumulated in Upper Cretaceous (Maastrichtian) turbidite reservoirs. The discovery well found total net pay of 153 m of Maastrichtian reservoirs divided into five main zones, separated by interbedded shales. Only the uppermost reservoir zone shows a seismic amplitude anomaly that can be detected on seismic profiles. The other four reservoirs do not show acoustic impedance contrasts with the interbedded shales, and thus they have no amplitude anomalies. During the appraisal activities, different types of oil (18 - 31.5 ° API) and a high reservoir complexity were verified. The external geometry is defined to the north and east by dipping and to the south and west directions by pinch-out. The trap is a combined structural and stratigraphic trap. The field is cut by some major faults to form three main blocks: an upthrown southwestern block, an upthrown northern block, and a downthrown southeastern block. Because of the size of the field and large volumes of hydrocarbon production, development of the Roncador field is envisaged to occur in four modules. Production peak will reach 500,000 BOP D in 2011. Production module I is being implemented to produce oil from the northern and eastern blocks, including 21 subsea production and 7 subsea water injection wells. Module II will develop the western block [heavy oil); two production units are planned (one deep-draft caisson vessel [SPAR] and one floating production, storage, and offloading [FPSO] unit). Peak production is expected to reach 180,000 BOP D from 31 wells in 2 yr.

Abstract Name: Riachuelo and Continguiba carbonate systems, Sergipe basin Authors: Eduardo A. M. Koutsoukos, Nivaldo Destro, Nilo C. de Azambuja Filho, and Adali Ricardo Spadini Location: From 9° to 11 ° 30' south latitude and 35° 30' to 37° west longitude, Sergipe, northeastern Brazil Geologic time interval: Middle Cretaceous, late Aptian–early Coniacian (Epicheloniceras sp-Diadochoceras sp.–Eodouvilleiceras sp. zone to the Solgerites armatus–Prionocycloceras lenti zone) Tectonic-sedimentary setting: Formed by a series of half-grabens with a regional dip averaging 10–15° to the southeast, resulting from normal faults arranged in a northeast-southwest direction Basin type: Atlantic-type passive marginal basin Paleoclimate: Dominantly dry, semi-arid, tropical Platform types: Mixed carbonate–siliciclastic system (late Aptian-Albian Riachuelo Fm.) and carbonate ramp system (Cenomanian–early Coniacian Cotinguiba Fm.) Platform geometry: Riachuelo carbonate system: average thickness of 500 m, but locally attains a maximum of 1700 m; about 20 km wide and 115 km long onshore. Cotinguiba carbonate system: thickness ranging from 200 m to over 1000 m locally in the onshore part; about 5–10 km wide and 200 km long onshore. Facies and fossils: Riachuelo Fm: oncolitic–oolitic–bioclastic packstone–grainstone; fine-grained limestone, marlstone, and shale; conglomerate, sandstone, and siltstone. Ammonites, planktonic and benthonic foraminifera, ostracods, radiolarians, algae, bivalves, brachipods, gastropods, serpulids, crustaceans, corals, echinoderms, and fishes. Cotinguiba Fm: rhythmic fine-grained carbonate mudstone, marlstone, shale, and wackestone breccia. Ammonites, nautiloids, planktonic and benthonic foraminifera, ostracods, radiolarians, diatoms, calcispheres, siliceous sponge spicules, bivalves, brachipods, gastropods, serpulids, crustaceans, cirripeds, corals, bryozoans, echinoderms, fishes, and reptiles. Systems tracts: lagoonal, neritic, upper bathyal, basin Stacking patterns: Not determined