ABSTRACT Geochemical Controls on Production in the Barnett Shale, Fort Worth Basin Jana L. Klentzman, M.S. Thesis Chairperson: Steve Dworkin, Ph.D. The Newark East field (Barnett Shale) in the Fort Worth Basin, Texas currently has the largest daily production of any gas field in Texas. Major controls on production in the basin include: the quantity and character of organic matter, the thermal maturity history, and the mineralogy of the Barnett Shale. This study uses Rock Eval to investigate the quantity and character of the organic matter and general thermal maturity, vitrinite reflectance, δ¹³C of produced methane and methane abundance to evaluate thermal maturity in more detail, and x-ray diffraction (XRD) to determine mineralogy. Based on these analyses, it is apparent that the best production from the Barnett Shale is typically found in maturation areas from 1.65 to 2.10%Ro with high organic carbon content, high quartz content, low calcite content and low dolomite content. Geochemical Controls on Production in the Barnett Shale, Fort Worth Basin by Jana L. Klentzman, B.S. A Thesis Approved by the Department of Geology ___________________________________ Steven G. Driese, Ph.D., Chairperson Submitted to the Graduate Faculty of Baylor University in Partial Fulfillment of the Requirements for the Degree of Master of Science Approved by the Thesis Committee ___________________________________ Stephen I. Dworkin, Ph.D., Chairperson ___________________________________ Stacy C. Atchley, Ph.D. ___________________________________ C. Kevin Chambliss, Ph.D. Accepted by the Graduate School August 2009 ___________________________________ J. Larry Lyon, Ph.D., Dean Page bearing signatures is kept on file in the Graduate School. Copyright © 2009 Jana L. Klentzman All rights reserved TABLE OF CONTENTS List of Figures vi Acknowledgments x Chapter One 1 Introduction 1 Geologic Setting and Stratigraphy 2 Methods 7 Organic Matter Abundance and Character 10 Vitrinite Reflectance 14 δ¹³C of Produced Methane 15 Mineralogy 15 Map Building 21 Chapter Two 22 Organic Carbon Content of the Barnett Shale 22 Results 22 Distribution of TOC in the Barnett Shale zones 23 Spatial Distribution of TOC 23 Barnett Shale zone 1 27 Barnett Shale zone 2 27 Barnett Shale zone 3 27 Barnett Shale zone 4 27 Barnett Shale zone 5 27 Barnett Shale zone 6 28 Barnett Shale zone 7 28 Barnett Shale zone 8 28 Discussion 28 iii Chapter Three 30 Thermal Maturity of the Barnett Shale 30 Results and Discussion 30 Hydrogen Index 30 Barnett Shale zone 1 31 Barnett Shale zone 2 31 Barnett Shale zones 3 through 7 34 Barnett Shale zone 8 34 Vitrinite Reflectance 34 δ¹³C of Produced Methane 43 Thermal Maturity of the Basin 49 Thermal Maturity Controls on Production 55 Anomalies Found in Production and the Thermal Maturity 61 Chapter Four 69 Mineralogy 69 Results 70 Mineralogical Controls on Production 70 Mineralogy of the Barnett Shale Zones 72 Barnett Shale zone 1 80 Barnett Shale zone 2 80 Barnett Shale zone 3 80 Barnett Shale zone 4 80 Barnett Shale zone 5 80 Barnett Shale zone 6 81 Barnett Shale zone 7 81 Barnett Shale zone 8 81 Discussion 81 Chapter Five 85 iv Conclusions 85 Appendices 86 Appendix A: Mineral Standard Data 88 Appendix B: Rock Eval Data 96 Appendix C: Vitrinite Reflectance Data 103 Appendix D: Produced Methane Gas Isotope Data 108 Appendix E: Mineral Abundance Data 116 References 125 v LIST OF FIGURES 1. Fort Worth Basin map 3 2. Generalized stratigraphic column of the Fort Worth Basin 5 3. Barnett burial history maps 8 4. Barnett Shale type log 9 5. Rock Eval diagram 12 6. XRD pattern type 16 7. XRD calibration curves 18 8. XRD calibration curves 19 9. Kaolinite XRD calibration curve 20 10. Total Organic Carbon Box and Whisker Plots 24 11. TOC content maps 25 12. TOC content maps 26 13. Hydrogen Index maps 32 14. Hydrogen Index maps 33 15. Vitrinite reflectance values verses present day depth 36 16. Vitrinite reflectance verses estimated maximum burial depth graph 37 17. Vitrinite reflectance verses depth with maturity profiles 39 18. Maturity regimes map 40 vi 19. Produced δ¹³CCH4 versus depth 45 20. Proxy vitrinite reflectance versus δ¹³CCH4 47 21. Expanded maturity regimes map 48 22. Proxy vitrinite reflectance Barnett Shale thermal maturity map 50 23. Published Barnett Shale thermal maturity map 51 24. Thermal maturity comparison map 52 25. Daily average of the first month of production versus vitrinite reflectance 57 26. Regime area comparison of hydrocarbon production 58 27. Median average daily production verses median proxy vitrinite reflectance 59 28. Cumulative oil production verses calculated vitrinite reflectance 62 29. Thermal maturity map showing areas of anomalous production 63 30. Methane abundance verses proxy vitrinite reflectance 64 31. Quartz abundance versus production 70 32. Calcite and dolomite abundance verses production 70 33. Mineral abundance stacked bar chart 72 34. Quartz abundance box and whisker plots 74 35. Calcite and dolomite abundance box and whisker plots 74 36. Quartz abundance maps 75 37. Quartz abundance maps 76 38. Calcite and dolomite abundance maps 77 39. Calcite and dolomite abundance maps 78 vii LIST OF TABLES 1. Rock Eval pyrolysis and their descriptions 11 2. Kerogen types and their descriptions 13 3. The relative standard deviation for each mineral 20 4. Vitrinite reflectance production information 56 5. Mineralogy of the Barnett Shale Zones 73 Appendices 85 Appendix A: Mineral Standard Data 86 Table A1: Standard Sample JS-1 86 Table A2: Standard Sample JS-2 86 Table A3: Standard Sample JS-3 87 Table A4: Standard Sample JS-4 87 Table A5: Standard Sample JS-5 88 Table A6: Standard Sample JS-6 88 Table A7: Standard Sample JS-7 89 Table A8: Standard Sample JS-8 89 Table A9: Standard Sample JS-9 90 Table A10: Standard Sample JS-10 90 Table A11: Standard Sample JS-11 91 Table A12: Standard Sample JS-12 91 Table A13: Standard Sample JS-13 92 Table A14: Standard Sample JS-14 92 Table A15: Standard Sample JS-15 93 Table A16: 100% Mineral Peak Heights 93 Appendix B: Rock Eval Data 94 Table B1: Rock Eval Data 94 Appendix C: Vitrinite Reflectance Data 102 viii Table C1: Vitrinite reflectance data 102 Appendix D: Produced Methane Gas Isotope Data 107 Table D1: Produced Methane Gas Isotope Data 107 Appendix E: Mineral Abundance Data 116 Table E1: Barnett Shale Zone 1 Mineral Composition 116 Table E2: Barnett Shale Zone 2 Mineral Composition 117 Table E3: Barnett Shale Zone 3 Mineral Composition 118 Table E4: Barnett Shale Zone 4 Mineral Composition 119 Table E5: Barnett Shale Zone 5 Mineral Composition 120 Table E6: Barnett Shale Zone 6 Mineral Composition 121 Table E7: Barnett Shale Zone 7 Mineral Composition 122 Table E8: Barnett Shale Zone 8 Mineral Composition 123 ix ACKNOWLEDGMENTS This study was sponsored by EnCana Corporation and greatly benefited from the use of Baylor Universities XRD Laboratory and the Applied Petroleum Studies Laboratory. I want to thank Dr. Dworkin for providing me the incredible opportunity to complete my masters education at Baylor as one of his students and also Josh Talbert without whom the project would not have been possible. I also want to thank Josh Talbert, Dr. Mark Tobey and Natalie Givens of EnCana Corporation for their teachings and guidance throughout the course of this project. I owe so much of this to my family whose encouragement and financial and emotional support made this process much more enjoyable. x CHAPTER ONE Introduction The Fort Worth Basin of north-central Texas (Figure 1A) has been producing hydrocarbons since the early 1900s. Within the Fort Worth Basin, the Barnett Shale was recognized as the source rock for overlying Ordovician to Permian conventional reservoirs (Ball and Perry, 2006; Pollastro et al., 2007) prior to the 1980’s. After the successful application of water fractures (a combination of water, friction reducer, bactericide, scale inhibitor, and low sand concentration) and the discovery that true gas in place is nearly four times what was previously believed, the Barnett Shale became a major target for unconventional natural gas production (Bowker, 2007). An unconventional, continuous petroleum system is defined as an accumulation of hydrocarbons found in low-permeability rocks that depend on fracture permeability, either natural or as a result of completion practices, for production. Unconventional reservoirs contain large amounts of hydrocarbons but have low gas recovery factors (Schmoker, 1995 in Jarvie et al., 2007). Unconventional shale gas has become an important resource for many countries and accounted for more than 14% of produced gas in the United States by the end of 2004 (Energy Information Administration, 2006 in Jarvie et al., 2007). The estimated total mean volume of undiscovered recoverable 1 gas within the Fort Worth Basin is about 26 tcf in two Barnett Shale gas assessment units (Pollastro et al., 2004 and 2007). This study focuses on petrologic and geochemical aspects of the Barnett Shale and how they influence production. Specifically the abundance and character of organic matter (measured using Rock Eval), the thermal maturity history (derived from Hydrogen Index, vitrinite reflectance data, δ¹³C of produced methane data and methane abundance data), and the mineralogy (quantified using x-ray diffraction) are used to investigate controls on production. The major objectives of this study are to: 1) locate areas of high total organic carbon, 2) build a thermal maturity map of the basin, 3) find the optimal maturity range for hydrocarbon production, 4) map the distribution of mineral abundance within the basin that influence production and 5) determine the geographic area(s) of optimal exploration potential. Geologic Setting and Stratigraphy During the Paleozoic Ouachita orogeny, Barnett Shale strata were deposited in a narrow inland seaway on the leading southern edge of the Oklahoma aulacogen Figure 1A).