Ceará Basin: tectono-sedimentary evolution and oil habitat

Abstract

The origin of the Ceará Basin is linked lo the drifting of the African and South American continents. Its Tectono-sedimentary evolution began in the Early Aptian with the deposition of fluvial and lacustrine continental sediments during a rift phase and continued with f1uvial, deltaic, and lacustrine sedimentation in a transitioned phase, ending with a phase of thermal subsidence during which dextral transcurrent motion and the tilting of the basin constituted the most significant tectonic events. This test phase was characterized by major transgressive and regressive cycles, when the sediments of the Ponte do Mel, Ubarana, Guamaré, and Tibau formations were deposited. Systematic basin exploration has made it possible lo individualize several different plays, the most noteworthy being the turbidite, which includes the Espada field; the rotational, which includes the Xaréu field; and the combination, which includes the Atum and Curimã fields. The best reservoirs consist of deltaic sandstones from the transitional phase, which are interlaid with the best source rocks and produce in lhe Xaréu, Alum, and Curímã fields. Due to the inadequacy of geochem1cal data on other sub-basins, the most promising chances for exploratory success are concentrated in the Mundaú area, and the greatest volumes of oil lo be discovered are related lo deep-waler turbidites. The present paper proposes the terms 'Mundaú Formation', 'Paracuru Formation, 'Xaréu Sandstone', and 'Atum Sandstone' for future formalization.