Programmed pyrolysis of organic matter from thermally altered Cretaceous black shales
Organic-rich Cretaceous black shales from the Cape Verde Rise in the eastern Atlantic were penetrated by hot diabase sills during the Miocene. Programmed pyrolysis and pyrolysis-gas chromatography of organic matter from core samples taken at various distances from a major sill were used to show: the type of kerogen, its relative level of thermal maturity, the fraction of pyrolyzable organic compounds which are free, and the compositions of the bitumen and kerogen. The dominant factor affecting these sediments appears to be thermal maturity rather than differences in the quality of the organic matter. Systematic changes in the pyrolyzate resulted from thermal cracking of volatile organics from the oil-prone Type II kerogen. Generation of these products caused progressive aromatization of the residual kerogen closer to the sill. These conclusions are supported by changes in kerogen elemental compositions, quantity of bitumen extract, and vitrinite reflectance. Although the major sill is 15 m (about 50 ft) thick, solvent extraction and pyrolysis results show that hydrocarbon generation was restricted to within about 10 m (about 33 ft) of the shale/sill contacts. At equal distances, the maximum temperature reached by the shales was higher above than below the sill. The reflectance of vitrinite responds more rapidly than bitumen composition to high temperatures imposed over a short time.
- Research Organization:
- Chevron Oil Field Research, La Habra, CA
- OSTI ID:
- 6289425
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 67:11
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ATLANTIC OCEAN
OIL SHALE DEPOSITS
BLACK SHALES
MATURATION
PYROLYSIS
AROMATIZATION
BITUMENS
CHEMICAL COMPOSITION
CRETACEOUS PERIOD
GAS CHROMATOGRAPHY
KEROGEN
MATERIALS
ORGANIC MATTER
REFLECTIVITY
TERTIARY PERIOD
VOLATILE MATTER
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CENOZOIC ERA
CHATTANOOGA FORMATION
CHEMICAL REACTIONS
CHROMATOGRAPHY
DECOMPOSITION
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
MATTER
MESOZOIC ERA
MINERAL RESOURCES
OIL SHALES
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
RESOURCES
SEAS
SEPARATION PROCESSES
SURFACE PROPERTIES
SURFACE WATERS
TAR
THERMOCHEMICAL PROCESSES
040201* - Oil Shales & Tar Sands- Site Geology- (-1989)