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AAPG Bulletin

Abstract

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AAPG Bulletin, V. 85, No. 8 (August 2001), P. 1333-1371.

Copyright ©2001. The American Association of Petroleum Geologists. All rights reserved.

New insights on the Green River petroleum system in the Uinta basin from hydrous pyrolysis experiments

Tim E. Ruble,1 M. D. Lewan,2 R. P. Philp3

1CSIRO Division of Petroleum Resources, Box 136, North Ryde, NSW, 1670, Australia; email: [email protected]
2U.S. Geological Survey, Box 25046, MS 977, Denver, Colorado, 80225; email: [email protected]
3University of Oklahoma, School of Geology and Geophysics, 100 E. Boyd Street, Norman, Oklahoma, 73019; email: [email protected]

AUTHORS

Tim Ruble is a research scientist at CSIRO Petroleum in Sydney, Australia, and is currently undertaking organic geochemical studies on kinetics of hydrocarbon generation, hydrocarbon-bearing fluid inclusions, and lacustrine petroleum systems. He received a B.S. degree from Truman State University (1987) and an M.S. degree from the University of Oklahoma (1990). He obtained his Ph.D. from the University of Oklahoma (1996) for research into the mechanisms of oil generation in the Uinta basin, Utah. During the course of his studies, he was employed as an intern with Mobil Oil both in their research labs (1990) and in an exploration unit (1991). In 1995, he was employed with the U.S. Geological Survey in Denver, Colorado, and participated in a geochemical study of the Dnieper-Donets basin, Ukraine. In 1996 he joined CSIRO and has been actively involved in a variety of research and contract projects using the analysis of hydrocarbons trapped within fluid inclusions.

Michael D. Lewan is an organic geochemist and petroleum geologist for the Central Energy Team of the U.S. Geological Survey. He has 13 years' experience with Amoco Production Co. as a research scientist in their Tulsa Research Center and 3 years experience with Shell Oil Co. as an exploration geologist in their New Orleans Offshore E&P Office. He has pioneered the development of hydrous pyrolysis in simulating natural petroleum formation, which has been used to evaluate expulsion, kinetic parameters, and quality of petroleum formed from various source rocks containing different types of organic matter. He is the recipient of the Organic Geochemistry Division of the Geochemical Society 1985 Best Paper Award and the AAPG 1991 George C. Matson Memorial Award for Best Paper and was an AAPG 1992 Distinguished Lecturer. He has a Ph.D. from the University of Cincinnati and an M.S. degree from Michigan Technology University.

R. Paul Philp is currently professor of petroleum and environmental geochemistry in the School of Geology and Geophysics at the University of Oklahoma. He received his Ph.D. from the University of Sydney, Australia, and more recently received his D.Sc. degree from the same university. His current research interests are focused on petroleum, environmental, and forensic geochemistry, with an emphasis on molecular and isotopic characterization of oils, gases, rock extracts, and contaminants for the purposes of source determination; characterization of depositional environments, maturity, and biodegradation; and correlation. He has published more than 240 articles in national and international journals and has lectured extensively on various aspects of geochemistry around the world.

ACKNOWLEDGMENTS

Financial support for this research was provided in part by the U.S. Geological Survey Volunteers for Science program (M. D. Lewan and Janet K. Pitman) and by a research assistantship sponsored by Phillips Petroleum. We gratefully acknowledge the assistance of Jon Allen, Donald E. Anders, Brian J. Cardott, Jerry L. Clayton, Ted A. Daws, Thomas D. Fouch, Dick Gibson, Daniel M. Jarvie, J. David King, Martin Koopmans, Paul G. Lillis, S. Mark Monk, Vito F. Nuccio, James G. Palacas, Mark J. Pawlewicz, Eleanora I. Robbins, Charles N. Threlkeld, and Augusta Warden. We also thank Kevin Bohacs, Ken Peters, Neil Sherwood, and Jerry J. Sweeney for the significant time they spent reviewing this manuscript and for their very helpful suggestions.

ABSTRACT

The Tertiary Green River petroleum system in the Uinta basin generated about 500 million bbl of recoverable, high pour-point, paraffinic crude oil from lacustrine source rocks. A prolific complex of marginal and open-lacustrine source rocks, dominated by carbonate oil shales containing up to 60 wt. % type I kerogen, occur within distinct stratigraphic units in the basin. Petroleum generation is interpreted to originate from source pods in the basal Green River Formation buried to depths greater than 3000 m along the steeply dipping northern margin of the basin. Producing fields in the Altamont-Bluebell trend have elevated pore-fluid pressures approaching 80% of lithostatic pressure and are completed in strata where open fractures provide permeability. Active hydrocarbon generation is one explanation for the origin of the overpressured reservoirs.

In this study, experiments were undertaken to examine the mechanisms of hydrocarbon generation and accumulation in the Uinta basin. We combined analyses of representative source rocks from the entire Green River stratigraphic section with detailed laboratory simulation experiments using both open- and closed-system pyrolysis. This information provides new insights on lacustrine source rock lithofacies, gas-oil-source rock correlations, hydrocarbon generation kinetics, and basin modeling. The results show that the basal Green River Formation contains a unique type I source facies responsible for generation of paraffinic crude oils. The classic type I oil shales in the upper Green River Formation correlate well with low-maturity aromatic-asphaltic samples. We determined kinetic parameters for the source rocks and used them to develop basin models for hydrocarbon generation. The models show that hydrous pyrolysis kinetic parameters are more consistent with the natural data in terms of predicted timing and extent of oil generation as compared to models using Rock-Eval kinetics.

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