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Reservoir and Source Potential of Eocene Microbialites, Green River Formation, USA

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Reservoir and Source Potential of Eocene Microbialites, Green River Formation, USA Reservoir and Source Potential of Eocene Microbialites, Green River Formation, USA by Copyright © 2015 Nicholas Cestari Submitted to the Department of Geology and the Faculty of the Graduate School of the University of Kansas in partial fulfillment of the requirements for the degree of Master of Science. Advisory Committee: Alison Olcott Marshall, Chair Craig P. Marshall Eugene C. Rankey Date Defended: 12/2/2015 The Thesis Committee for Nicholas Cestari certifies that this is the approved version of the following thesis: Reservoir and Source Potential of Eocene Microbialites, Green River Formation, USA ___________________________________ Alison Olcott Marshall, Ph.D., Chairperson Date Approved: 12/2/2015 ii ABSTRACT In recent years, large petroleum discoveries within the lacustrine microbialite facies of pre-salt systems of offshore Brazil, Angola, and Gabon have increased interest in the potential of microbial carbonates as reservoir rocks. Whereas a multitude of studies have been conducted on microbialites and the associated lacustrine facies separately, there is still little known regarding whether there are definitive dissimilarities between the geochemical footprints of microbialites and associated lithofacies within a system. To explore this unknown, organic geochemistry was evaluated with the aim of comparing the microbialite facies (stromatolites and thrombolites) with the associated lacustrine carbonates (dolomitic marlstone, ooid grainstone, peloidal packstone and wackestone) to test if there are dissimilarities in regard to reservoir and source potential. Specifically, the goal is to understand the petroleum significance of lacustrine microbialites deposited in various lake conditions. Total Organic Carbon (TOC) and extractable organic material were analyzed for microbialite and associated lacustrine lithofacies in the Green River Formation of Colorado and Utah. The samples were from three cores: two from Piceance Basin (Nielsen 17-1 and Colorado Core 01A) and one from Uinta Basin (1 Coyote Wash). Additional hand samples collected from an outcrop at Douglas Pass, Colorado, represent shallow lake-margin deposits. The lake of the Piceance Creek Basin was a hydrologically closed, hypersaline lake characterized by deposition of organic rich microbialites, and dolomitic marlstones. In contrast, the Uinta Basin lake was a hydrologically open lake characterized by accumulation of organically lean microbialites, siltstone, mudstone, ooid grainstone, and iii peloidal packstone and wackestone. Gas chromatography/mass spectroscopy (GC/MS) analysis yielded biomarker distributions distinct between the lacustrine microbialite facies and the associated lithofacies. The abundance of biomarkers associated with hydrocarbon potential is 10 to 100x greater in the microbialites than in the associated lacustrine carbonate lithofacies. Understanding the geochemical footprints of lacustrine microbialites and how they differ from associated carbonates as a function of depositional environment is crucial in identifying prospects in similar ancient reservoir systems. iv Acknowledgements I would like to thank the University of Kansas for the opportunity to complete my Masters degree. However, if it weren’t for Alison Olcott Marshall I would never have had this opportunity to grow in my scientific background. I truly appreciate everything that she has sacrificed to make sure I completed everything to the best of my ability and in a timely manner. Alison was a great mentor to me throughout the whole process never letting me get discouraged and always causing me to reach farther in my brain for an answer. I have learned so much and gained valuable expertise that will help better my future in oil and gas. My committee members Craig Marshall and Gene Rankey provided valuable feedback that helped me reach my goal. I was challenged in ways that bettered me as a student and person throughout this journey. I couldn’t have done it without the help of the USGS Core Research Center in Denver Colorado with sampling core for my research. Dr. Rick Sarg was of great assistance with guiding me to the outcrop of Douglas Pass so that I was able to do field work and collect my samples for analysis. I want to also extend a great deal of gratitude to the fellow graduate students in my lab Brenden Keel and Ted Morehouse who were a source of constant support and relief. I couldn’t have done this without the constant encouragement coming from my family that truly got me through some of my toughest days. I owe a great deal to all of those who supported, and guided me throughout this learning process. v TABLE OF CONTENTS ABSTRACT .............................................................................................................................................. iii Acknowledgements .............................................................................................................................. v 1.1 Introduction .................................................................................................................................... 1 1.2 Geologic Background ................................................................................................................... 3 1.2.1 Study Area and Stratigraphy .................................................................................................. 6 1.3 Lake Evolution ............................................................................................................................... 9 1.4 Microbial Carbonates ................................................................................................................. 12 1.5 Biomarkers ................................................................................................................................... 15 1.6 Source Potential .......................................................................................................................... 19 CHAPTER TWO: Sample Collection and Methods .................................................................... 20 2.1 Field Sampling Site ................................................................................................................................ 20 2.2 Sample Collection ........................................................................................................................ 22 2.3 Sample Preparation ................................................................................................................... 23 2.3.1 Organic Material Extraction ................................................................................................. 24 2.3.2 GC/MS Methods and Analysis .............................................................................................. 25 2.4 TOC analysis .................................................................................................................................. 26 CHAPTER THREE: Results ................................................................................................................ 27 3.1 Outcrop and Core descriptions ............................................................................................... 27 3.2 TOC Analysis ................................................................................................................................. 34 3.3 Biomarkers ................................................................................................................................... 36 3.3.1 N-alkanes and Isoprenoids ............................................................................................................. 36 3.3.2 Hopanes ................................................................................................................................................. 41 3.3.3 Steranes ................................................................................................................................................. 42 3.3.4 Polycyclic aromatic hydrocarbons (PAHs) ................................................................................ 43 CHAPTER FOUR: Discussion ........................................................................................................... 45 4.1 Analysis of Extractable Organic Matter ............................................................................... 45 4.1.1 N-alkane parameters ........................................................................................................................ 45 4.1.2 Sterane Parameters ........................................................................................................................... 53 4.1.3 Sterane/Hopane parameter ........................................................................................................... 57 4.2 Pr/Ph ............................................................................................................................................... 60 4.3 Pr/n-C17 and Ph/n-C18 ................................................................................................................ 61 4.4 Depositional Model .................................................................................................................... 64 4.5 TOC and Source Rock Properties ........................................................................................... 66 4.6 Reservoir and Source Potential .............................................................................................. 69 vi CHAPTER FIVE: Conclusion ............................................................................................................
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