Abstract
Hydrocarbon discoveries in Equatorial Brazil, Equatorial Africa and
French Guiana-Suriname-Guyana have recently confirmed their importance
as new exploration frontiers. The Mundati sub-basin, located on the
Brazilian Equatorial Margin, comprises four producing fields in shallow
waters: Xareu, Atum, Espada e Curima. In order to understand the
structural and seismic-stratigraphic frameworks of an oil-producing
region in Equatorial Brazil, this work addresses the 3D geometry and
spatial distribution of main faults in the Curima and Espada fields. The
occurrence of hydrocarbons in the Mundati sub-basin is compared with
fields in other parts of the Brazilian Equatorial Margin and Equatorial
Africa. Data from 12 wells and a 3D post-stack time-migrated
multichannel seismic volume are used to define nine (9)
seismic-stratigraphic units: the syn-rift Mundati Formation (Units 1, 2,
3 and 4); the transitional Paracuru Formation (Unit 5); and the drift
Ubarana (Uruburetama and Itapage Members, Units 6 and 7), Tibau and
Guamare Formations (Units 8 and 9). The study area is dominated by NW-SE
planar normal faults, basinward-dipping, that form multiple
half-grabens, and tilted blocks with small anticlines and synclines
genetically related to a transtensional system. Three types of plays are
recognised in the Mundati sub-basins: structural, combined
(structural-stratigraphic) and stratigraphic (turbiditic). In the
eastern part of the study area, where the basement is shallow, no oil
was found. Conversely, oil was discovered in an anticlinal trap formed
over a hanging-wall block analogous to fields on the Cote D'Ivoire-Ghana
transform margin. This work shows that combined traps on footwall blocks
are successful plays near the shelf break of the Mundati sub-basin, in
similarity with the Espoir and Baobab fields in Ivory Coast.
Furthermore, turbiditic reservoirs in drift units are analogous to the
Stabroek block in Guyana and prospects in the Gulf of Guinea. The
structural and petroleum-play analyses in this work are therefore
crucial to understand the multiple geological processes leading to the
trapping of hydrocarbons in the larger Equatorial Atlantic Ocean.
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