--> Abstract: Evaluating Products and Yields of Green River Oil Shale by Fisher Assay, Rock-Eval, Micro-Scale Sealed Vessel, and Hydrous Pyrolysis, by Michael D. Lewan and Tim E. Ruble; #90078 (2008)

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Evaluating Products and Yields of Green River Oil Shale by Fisher Assay, Rock-Eval, Micro-Scale Sealed Vessel, and Hydrous Pyrolysis

Michael D. Lewan1 and Tim E. Ruble2
1Energy Resources Program, U. S. Geological Survey, Denver, CO
2Humble Geochemical Services, Humble, TX

Although Fisher Assay has been considered the standard for assessing the retorting attributes of oil shale, other pyrolysis methods including Rock-Eval, micro-scale sealed vessel (MSSV), and hydrous pyrolysis have become available. This study uses a sample from the mahogany zone of the Green River Formation in the Uinta Basin to compare products and yields from these four pyrolysis methods. Fisher Assay provides polar-rich oil, spent rock, and condensed water, but does not provide generated gas. Rock-Eval provides a calibrated flame-ionization detector (FID) response to existing (S1) and generated (S2) products that are volatilized in an open-system, but does not provide oil, generated gas, spent rock, or reaction water for characterization. MSSV differentiates products generated in a closed-system into C1, C2-C4, C5-C14 and C15+ fractions using gas chromatography, but does not provide oil, spent rock, or reaction water for characterization. Hydrous pyrolysis provides hydrocarbon-rich oil, generated gas, spent rock, and reaction water. Although this method provides the most complete range of products for characterization, it requires a larger sample and longer run times than the other methods. Based on these results, a hierarchical protocol for determining oil-shale grade is suggested. Initial evaluation of tens to hundreds of meters of potential oil-shale section should use Rock-Eval to divide the section into zones of various grades. Composites representing these zones can be evaluated by MSSV or Fisher Assay to determine zones targeted for retorting. These targeted zones can then be more thoroughly evaluated by hydrous pyrolysis to characterize products for assessing their economic and environmental impact.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas