Depositional environment, diagenetic history, and reservoir geology of the Santiago member sandstones of the Pojuca Formation (Lower Cretaceous) in the Aracas oil field, Reconcavo basin, Brazil

Thesis/Dissertation · Thu Jan 01 00:00:00 EST 1987

OSTI ID:5968776

Couto dos Anjos, S M

Core analysis, sand isolith maps, shape of SP curves, and comparison with recent depositional models defined crevasse mouth bar, distal bar, bay fill, and transitional (distal bar/bay) environments. The best potential reservoirs occur in crevasse mouth bar deposits. Ten microfacies were defined, namely, two wackes, six arenites which are the most frequent in all sandstone bodies (S-1 to S-5), and two carbonates. The diagenetic evolution of the various microfacies of the Santiago sandstone is very similar and comprises: destruction of primary porosity by compaction and burial cementation; development of secondary porosity by leaching of cements; decrease in secondary porosity by late cementation and compaction; and preservation of secondary porosity due to oil migration which halted further diagenetic evolution. Framework grains, cements, and porosity in the S-2, S-3, and S-4 reservoirs display different distribution patterns. Framework grains display patterns similar to those of depositional environment whereas cements and porosity patterns reflect predominantly diagenetic processes. They show closed geometry indicating the effect of a dome-like structure of compaction origin which probably controlled the circulation of pore fluids. Highest values of porosity occur in the least cemented areas with exception of the matrix-rich interval (S-4) where the reverse values of porosity and cement are not observed. The distribution pattern of permeability is complex, and does not follow that of porosity. It does not seem to be directly related to any observable variation in framework grains or cements.

• Research Organization: Illinois Univ., Urbana (USA)
• OSTI ID: 5968776
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
BRAZIL
PETROLEUM DEPOSITS
DIAGENESIS
GEOLOGIC HISTORY
GEOLOGY
COMPACTING
CRETACEOUS PERIOD
DEPOSITION
ENVIRONMENTAL TRANSPORT
PERMEABILITY
PETROLEUM
POROSITY
RESERVOIR ROCK
SANDSTONES
STRATIGRAPHY
DEVELOPING COUNTRIES
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
LATIN AMERICA
MASS TRANSFER
MESOZOIC ERA
MINERAL RESOURCES
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SOUTH AMERICA
020200* - Petroleum- Reserves
Geology
& Exploration