Petroleum migration and mixing in the Potiguar basin, Brazil

Journal Article · Tue Dec 01 00:00:00 EST 1992 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:6847606

Trindade, L A.F.; Santos Neto, E V ^[1]; Brassell, S C ^[2]

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1. Cidade Universitaria, Rio de Janeiro (Brazil)
2. Stanford Univ., CA (United States)

Regional studies of petroleum samples from both offshore and onshore reservoirs of the Potiguar basin, Brazil, reveal compositional differences, with discernible landward trends, attributable to oil mixing. These chemical discrepancies can be related to a combination of source rocks, maturity, and migration history. The source rocks are classified in two groups based on their geochemical and molecular characteristics: (1) Neocomian and Aptian lacustrine freshwater shales, and (2) Aptian marine evaporitic shales and marls. Both lie in an offshore structural low. The geochemically contrasting oils derived from these source beds migrated updip, constrained by a monoclinal structure, through Aptian carrier beds to thermally immature strata. Evaluation of compositional heterogeneities in the oils and an investigation of migration effects on their compositions reveal trends related to the amount of mixing which, in turn, reflects the timing of both oil generation and migration, and the direction of migration. The more migrated oils contain greater contributions from freshwater sources, whereas the less migrated oils display more pronounced contributions from the younger and shallower hypersaline source beds. Biomarker maturity parameters indicate that the most migrated oils are less mature, consistent with their early generation from the deeper lacustrine freshwater source beds and migration to fill the shallower reservoirs first. 16 figs., 2 tabs.

• DOE Contract Number: FG05-87ER75377
• OSTI ID: 6847606
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 76:12; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
BRAZIL
PETROLEUM DEPOSITS
PETROLEUM
CHEMICAL COMPOSITION
ENVIRONMENTAL TRANSPORT
PETROLEUM GEOLOGY
CORRELATIONS
FRESH WATER
GEOCHEMISTRY
MASS TRANSFER
MIXTURES
SALINITY
VARIATIONS
CHEMISTRY
DEVELOPING COUNTRIES
DISPERSIONS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC DEPOSITS
GEOLOGY
HYDROGEN COMPOUNDS
LATIN AMERICA
MINERAL RESOURCES
OXYGEN COMPOUNDS
RESOURCES
SOUTH AMERICA
WATER
020200* - Petroleum- Reserves
Geology
& Exploration
023000 - Petroleum- Properties & Composition