Product evolution during rapid pyrolysis of Green River Formation oil shale

doi:10.1016/0016-2361(87)90054-8

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Volume 66, Issue 9, September 1987, Pages 1176-1184

https://doi.org/10.1016/0016-2361(87)90054-8 Get rights and content

Abstract

The devolatilization of rich (209 cm³ kg⁻¹), rapidly heated (1000 K s⁻¹) Green River Formation, Colorado, oil shale has been studied at temperatures from ≈ 600 to 1100K, under helium (170 kPa) and vacuum. Oil yields decrease with increasing pressure at temperatures above the 800–900 K range. This is attributed to an increased probability of condensed phase cracking reactions involving oil precursors with increased pressure. The fact that escape of the oil from shale particles is vaporization-rate limited is supported by a comparison of the molecular weights of oil collected outside the particle and that left within the particle. The measured nature of particle porosity is consistent with the view that external gas pressure can affect vaporization rates within pores. Elemental and infrared characterization of different molecular weight fractions of oil are presented.

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Although artificial maturation of hydrocarbon source rocks by laboratory pyrolysis is far from representing natural maturation, it is a useful tool to investigate the process. In this study, we used routine open system pyrolysis for powder samples and Restricted System anhydrous Pyrolysis (RSP) for cm-sized Silurian shale source rock fragments to artificially mature the samples to different end-temperatures in the presence of a flowing carrier gas. Maturation experiments on rock fragments enable the simulation of physical barriers for the generated hydrocarbons that need to be overcome before expulsion from the source rock can occur. Based on the artificial maturation results in this study, oil expulsion efficiency from the Silurian shale source rock was 46% at the early oil generation stage and increased to 74% at approximately the peak oil generation stage.
Furthermore, we have compared artificial maturation results from powder-form and fragment-form samples with natural-maturation series and found that artificial maturation of fragment-form samples sufficiently resembles natural maturation of the Silurian shales. It is therefore possible to simulate the early, middle and peak oil generation stages of natural maturation and expulsion efficiencies. This implies that, lab-based oil expulsion efficiencies from increasing maturity and hydrocarbon generation can be incorporated into the basin modeling.
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^∗: Present address: ICI Polyurethanes, West Deptford, NJ, USA.

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Main paperProduct evolution during rapid pyrolysis of Green River Formation oil shale

Abstract

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Lawrence Livermore National Laboratory, Report UCRL-52619

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Am. Chem. Soc. Div. Fuel Chem. Preprints

Am. Chem. Soc. Div. Fuel Chem. Preprints

Am. Chem. Soc. Div. Fuel Chem. Preprints

In Situ

Main paper
Product evolution during rapid pyrolysis of Green River Formation oil shale