Diagenetic evolution of Cretaceous-Tertiary turbidite reservoirs, Campos Basin, Brazil

Journal Article · Mon May 01 00:00:00 EDT 1989 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6377992

Moraes, M A.S.

Three sandstone turbidite sequences of the Campos basin (offshore, state of Rio de Janeiro, Brazil) were petrologically studied: (1) the Albian-Cenomanian Namorado Sandstone on the Macae Formation, (2) the Upper Cretaceous Carapebus Member of the Campos Formation, and (3) the Eocene Carapebus Member of the Campos Formation. The sequences represent deep marine deposits consisting mostly of massive sandstones rather than classical turbidites, indicating sand-rich submarine fans were the main depositional system of these sequences. The framework composition of the sandstones averages for quartz, feldspar, and lithics are Q/sub 60/F/sub 40/L/sub tr/ for the Cretaceous rocks and Q/sub 71/F/sub 29/L/sub tr/ for the Eocene rocks, plotting granitic rock fragments at the feldspar pole. The main diagenetic phases that affected the sandstones studied were (1) development of a clay matrix due to compaction of rip-up mud clasts, (2) partial replacement of the matrix by opal, (3) precipitation of small pyrite framboids, (4) widespread direct precipitation or replacement of different materials by calcite, (5) intense generation of secondary porosity, (6) localized kaolinite development, (7) minor precipitation of quartz and feldspar overgrowths, (8) development of dolomite, ferroan dolomite, and ankerite, and (9) replacement of different materials with minor direct precipitation of late pyrite. Geologic and geochemical evidence lets them infer the main processes that controlled diagenetic transformations and mass transfer within the sequence studied. The principal source of carbonate cements was pressure solution of the underlying Macae Formation. Most of the diagenetic evolution of the sandstones was apparently controlled by the relative balance between the activity of CO/sub 2/ and carboxylic acid species in the formation waters, both related to organic matter transformations within adjacent marine shales.

• Research Organization: Cidade Universitaria, Rio de Janeiro (Brazil)
• OSTI ID: 6377992
• Journal Information: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Vol. 73:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
BRAZIL
PETROLEUM DEPOSITS
RESERVOIR ROCK
DIAGENESIS
CRETACEOUS PERIOD
EOCENE EPOCH
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MINERALOGY
SEDIMENTARY BASINS
CENOZOIC ERA
DEVELOPING COUNTRIES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
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RESOURCES
SOUTH AMERICA
TERTIARY PERIOD
020200* - Petroleum- Reserves
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& Exploration