Effects of thermal maturation on steroid hydrocarbons as determined by hydrous pyrolysis of phosphoria retort shale
Hydrous pyrolysis experiments on the Phosphoria Retort Shale generate bitumen extracts and expelled oils that have steroid hydrocarbons with m/z 217-, 231-, and 253-mass chromatographic distributions that are similar to those of bitumens and crude oils in the natural system. These experiments agree with the natural observations that diasteroid hydrocarbons increase relative to their regular counterparts with increasing thermal stress, while their C/sub 27/ through C/sub 29/ proportionally shows a slight enrichment in C/sub 27/. Relative concentrations of 20S to 20R configurations of 24-ethyl-14..cap alpha.., 17..cap alpha..-cholestane show the expected increase with increasing thermal stress in to the early part of the primary oil generation stage, but thereafter decrease with increasing thermal stress. If this reversal is found in high maturity sections of the natural system, the utility of this transformation as a maturity index be limited. Triaromatic- to monoaromatic-steroid hydrocarbon concentrations increase with increasing thermal stress as observed in the natural system. Preferred migration of monoaromatic steroid hydrocarbons from bitumen extracts to expelled oils places considerable doubt on currently employed kinetic models for this aromatization reaction. As in the natural system, the experiments show relative concentrations of low-molecular weight- to high-molecular weight-triaromatic steroid hydrocarbons to increase with increasing thermal stress. Assuming a first-order reaction rate, the apparent activation energy and pre-exponential factor for this apparent side-chain cleavage reaction are 175.59 kJ mol/sup -1/ and 2.82 x 10/sup 13/ hr/sup -1/, respectively. These kinetic parameters are geologically reasonable and are similar to those for the overall generation of expelled oil.
- Research Organization:
- Amoco Production Co. Research Center, Tulsa, OK
- OSTI ID:
- 7148452
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 50:9; ISSN GCACA
- Country of Publication:
- United States
- Language:
- English
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040500* -- Oil Shales & Tar Sands-- Properties & Composition
58 GEOSCIENCES
580400 -- Geochemistry-- (-1989)
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
DECOMPOSITION
ENERGY SOURCES
FOSSIL FUELS
FUELS
MATERIALS
MATURATION
OIL SHALES
ORGANIC COMPOUNDS
PYROLYSIS
SOURCE ROCKS
STEROIDS
TEMPERATURE EFFECTS
THERMOCHEMICAL PROCESSES