Geology and major oil plays, Coastal Margin basins, Brazil
Six major tectonic-depositional sequences, reflecting rift and passive margin evolution, variously characterize the filling of Brazilian coastal margin basins: (1) Late Jurassic prerift, (2) Early Cretaceous tectonic rift, (3) Early Cretaceous quiescent stage (evaporitic or calcilutitic), (4) middle Cretaceous platform/deltaic progradational and deep marine retrogradation, and (6) Tertiary main passive margin progradation. Habitat of oil discovered to date meets two regional geologic conditions: (1) in tectonic rifts known to have basin core of starved, lacustrine shales, and (2) in basins which developed a quiescent phase during the transition from tectonic rift to passive margin. Two major plays characterize the central core rifts, including (I) underlying prerift sediments in fault contact with the central core, and (II) sublacustrine fans overlying the central core. These plays, typified in the Reconcavo basin, constitute about half the recoverable oil found to date. Exploration implications of the established plays are: (1) source is from tectonic or quiescent stage fill (Aptian or older); (2) structural integrity of the quiescent stage seals is critical to oil migration; and (3) tectonic rifts are productive when a core of deep lacustrine shales was developed.
- Research Organization:
- PETROBRAS, Rio de Janeiro, Brazil
- OSTI ID:
- 6528011
- Report Number(s):
- CONF-8405216-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 68:4; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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