--> Abstract: New Maturity Indicators Based on the Spectral Fluorescence of Alginite and Bitumen, Monterey Formation, California, by C-I. Lee, M. C. Kennicutt, II, and H. B. Lo; #91004 (1991)

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New Maturity Indicators Based on the Spectral Fluorescence of Alginite and Bitumen, Monterey Formation, California

LEE, CHUNG-I, and MAHLON C. KENNICUTT, II, Texas A&M University, College Station, TX, and H. B. LO, Exxon Production Research Company, Houston, TX

Conventional assessment of maturation level in the Monterey has been problematic, since sporinite and vitrinite are rare or absent. Organic matter is largely alginite and amorphous material, and reliable vitrinite reflectance [R(0)%] and Thermal Alteration Index (TAI) are difficult to obtain. Large amounts of bitumen often imbedded in the highly fractured Monterey shales cause a suppression of T(max) and low values of S(1)/S(1) + S(2). It is often difficult to determine whether bitumen is indigenous or migrated from other more mature strata.

Spectral fluorescence measurements of alginite and bitumen have proved useful in assessing the maturity of the Monterey. A maturity scale based on red/green quotient [Q(v)] measured as the fluorescence of alginite B when excited by violet-light has been developed and applied to the Monterey. Alginite B is common in the Monterey, and accurate fluorescent measurements can be readily obtained given the highly fluorescent character of alginite B. A total scanning fluorescence technique was used to develop a maturity scale based on bitumen aromatic content and composition. The maturity parameter [R(1)] developed in this study uses the intensity of fluorescence emitted at 360 nm ratioed to that at 320 nm when the solvent-dissolved bitumen is excited at the 270 nm. These parameters allow for the evaluation of the thermal maturity of algal organic matter and bitumen from the Monterey with R(0)% < 1. Indigenous bitumen is also indicated by a comparison of maturity based on Q(v) (the solid phase) and bitumen maturity (the liquid phase) based on R(1).

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)