Rb-Sr and K-Ar dating of clay diagenesis in Jurassic sandstone oil reservoir, North Sea
Rb-Sr and K-Ar isotopic determinations were combined with scanning electron microscopy (SEM) observations and x-ray diffractometry (XRD) controls to date the diagenetic formation of clay minerals from oil-bearing sandstones of the Middle Jurassic Brent Sandstone in the North Sea. The separated clay fractions often contain detrital components, especially K-feldspars, which are reduced to sizes smaller than 0.4 ..mu..m either by intense in-situ alteration or by destructive sample preparation. Direct Rb-Sr and K-Ar isotopic dating of diagenetic illite therefore was not possible. Isotopic data obtained on mixtures of detrital and newly formed components showed, however, that illite formed about 40 to 45 Ma. This value also was obtained directly on clay fractions separated by a gentle method of disaggregation. Illitization is related to emplacement of hydrocarbons and associated waters into the formation. Aqueous and hydrocarbon fluids simultaneously trapped in quartz-overgrowth inclusions indicate late silicification contemporaneous with this fluid migration. Minimum trapping temperatures of at least 110/sup 0/C for these fluid inclusions are too high for the present burial depth. Hot fluids are assumed to have originated in deep source rocks beneath the Brent reservoirs and migrated upward during the middle Eocene. 7 figures, 3 tables.
- Research Organization:
- Centre de Sedimentologie et Geochemie de la Surface, Strasbourg (France)
- OSTI ID:
- 6594766
- Journal Information:
- AAPG Bull.; (United States), Journal Name: AAPG Bull.; (United States) Vol. 71:12; ISSN AABUD
- Country of Publication:
- United States
- Language:
- English
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K/Ar dating of illite in understanding fault-related diagenesis
K/Ar dating of illite in understanding fault-related diagenesis
Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
ARGON ISOTOPES
ATLANTIC OCEAN
CLAYS
DIAGENESIS
ELECTRON MICROSCOPY
FELDSPARS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC TRAPS
ISOTOPES
JURASSIC PERIOD
MESOZOIC ERA
MICROSCOPY
MINERAL RESOURCES
MINERALS
NORTH SEA
PETROLEUM DEPOSITS
POTASSIUM ISOTOPES
RESERVOIR ROCK
RESOURCES
ROCKS
RUBIDIUM ISOTOPES
SANDSTONES
SCANNING ELECTRON MICROSCOPY
SEAS
SEDIMENTARY ROCKS
STRONTIUM ISOTOPES
SURFACE WATERS