Correlation of illite crystallinity and thermal maturity in carboniferous strata of Ouachita Mountains

Conference · Fri Feb 01 04:00:00 EST 1985 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:6002727

Guthrie, J M; Johns, W D; Houseknecht, D W

Carboniferous shales from the Ouachita Mountains have been studied to determine mineralogy and thermal maturities, the latter ascertained by means of vitrinite reflectance and bitumen/organic carbon ratios. The less than 2 ..mu..m fractions of these shales indicate 2 major clay-mineral components, illite and chlorite, and 2 minor varieties, expandable clays and pyrophyllite. Expandable clays are found at low thermal maturities and pyrophyllite at high maturity. Scanning electron micrographs show differences in clay morphology and texture, which are influenced by the degree of thermal maturity. Weaver's sharpness ratio for illite and Kubler's crystallinity index are both significantly related to mean vitrinite reflectance. The log of the sharpness ratio increases while the log of the crystallinity index decreases with increasing mean vitrinite reflectance. These relationships suggest that illite crystallinity is controlled by the same geologic agents that control vitrinite reflectance, namely temperature and time. A plot of vitrinite reflectance and/or crystallinity index versus bitumen/organic carbon ratio shows a maximum analogous to a hydrocarbon window. These statistically significant correlations provide a useful means of estimating the thermal maturity of these strata where they contain insufficient amounts of vitrinite for thermal maturity evaluation.

• Research Organization: Univ. of Missouri, Columbia
• OSTI ID: 6002727
• Report Number(s): CONF-850322-
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 69:2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ARKANSAS
BITUMENS
CLAYS
FEDERAL REGION VI
GEOLOGIC DEPOSITS
ILLITE
MACERALS
MATURATION
MINERAL RESOURCES
NORTH AMERICA
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PETROLEUM DEPOSITS
PHYSICAL PROPERTIES
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SHALES
SOURCE ROCKS
TAR
USA