Well-log signatures of alluvial-lacustrine reservoirs and source rocks, Lagoa-Feia Formations, Lower Cretaceous, Campos Basin, offshore Brazil
The Campos basin is situated in offshore southeastern Brazil. The Lagoa Feia is the basal formation in the stratigraphic sequence of the basin, and was deposited during rifting in an evolving complex of lakes of different sizes and chemical characteristics, overlying and closely associated with rift volcanism. The stratigraphic sequence is dominated by lacustrine limestones and shales (some of them organic-rich), and volcaniclastic conglomerates deposited on alluvial fans. The sequence is capped by marine evaporites. In the Lagoa Feia Formation, complex lithologies make reservoirs and source rocks unsuitable for conventional well-log interpretation. To solve this problem, cores were studied and the observed characteristics related to log responses. The results have been extended through the entire basin for other wells where those facies were not cored. The reservoir facies in the Lagoa Feia Formation are restricted to levels of pure pelecypod shells (''coquinas''). Resistivity, sonic, neutron, density, and gamma-ray logs were used in this work to show how petrophysical properties are derived for the unconventional reservoirs existing in this formation. The same suite of logs was used to develop methods to define geochemical characteristics where source rock data are sparse in the organic-rich lacustrine shales of the Lagoa Feia Formation. These shales are the main source rocks for all the oil discovered to date in the Campos basin.
- OSTI ID:
- 6805666
- Report Number(s):
- CONF-880301-
- Resource Relation:
- Conference: Annual meeting of the American Association of Petroleum Geologists, Houston, TX, USA, 20 Mar 1988
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BRAZIL
PETROLEUM DEPOSITS
GEOPHYSICS
RESERVOIR ROCK
WELL LOGGING
ALLUVIAL DEPOSITS
CRETACEOUS PERIOD
EVAPORITES
LIMESTONE
LITHOLOGY
OFFSHORE SITES
PERMEABILITY
POROSITY
SEDIMENTARY BASINS
SHALES
SOURCE ROCKS
STRATIGRAPHY
CARBONATE ROCKS
DEVELOPING COUNTRIES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
LATIN AMERICA
MESOZOIC ERA
MINERAL RESOURCES
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SOUTH AMERICA
020200* - Petroleum- Reserves
Geology
& Exploration