PETROLEUM POTENTIAL OF THE GRANEROS-GREENHORN PETROLEUM SYSTEM: GREATER WATTENBERG AREA, DENVER BASIN, COLORADO by Craig Kaiser i A thesis submitted to the Faculty and the Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Science (Geology). Golden, Colorado Date 4"4- /a Craig Kaiser Signed: Dr. Stephen Thesis Advisor Golden, Colorado signed: i,4'\ B. &Ldc{, ta4 doue oute 4-2-12 Dr. John Curtis Thesis Co-Advisor Dr. John Flfmphrey Geology and Geological Engineering ABSTRACT Interest in unconventional petroleum potential of the Late Cretaceous Greenhorn and Graneros formations has drastically increased due to success of many producers in the stratigraphically higher, but mineralogically similar Niobrara Formation. Previous Greenhorn and Graneros research has mainly focused on depositional cyclicity and stratigraphic controls rather than describing hydrocarbon potential within these two intervals. The focus of this study is to examine petroleum potential of these two organic- rich formations within the greater Wattenberg area of the Denver Basin. The two formations represent regional transgression in the Cretaceous Western Interior Seaway where large amounts of organic-rich calcareous sediment were deposited throughout much of the North American Mid-Continent. The ratio of carbonate to siliciclastic sedimentation increased as the transgression took place and water depths deepened, resulting in the lower Graneros Formation predominantly consisting of shales and marls and the higher Greenhorn Formation mainly consisting of marls and chalks. Geochemical analysis of organic-rich shales and marls within the two source units (Graneros Formation and Hartland Member of the Greenhorn Formation) indicate that significant amounts of hydrocarbons have been generated within the study area. Several unconventional chalk reservoirs of the Greenhorn Formation (Lincoln and Bridge Creek members) have been influenced by this generation resulting in hydrocarbon accumulations. iii Data from log-derived total organic carbon (TOC), Type I shows from formation drill stem tests (DTS’s), geochemical analyses, and geological characterization of the units with the study interval, together indicate that source rock maturation and hydrocarbon accumulation has taken place within the Greenhorn and Graneros formations in the study area. The Lincoln Member of the Greenhorn Formation is considered to have the highest petroleum potential to yield hydrocarbons within the study interval. Numerous Type I shows within this unit proves that accumulations exist. Low- angle shear fractures provide well bore deliverability as well as a migration pathway between source and reservoir rock, and geochemical analyses show the presence of both oil and gas in the study area. Current horizontal drilling and multi-stage hydraulic stimulation technologies allow the Lincoln Member of the Greenhorn Formation to be a viable and likely reservoir target in and around the greater Wattenberg area. iv Table of Contents ABSTRACT ....................................................................................................................... iii LIST OF FIGURES .......................................................................................................... vii ACKNOWLEDGMENTS ............................................................................................... xiv CHAPTER 1 INTRODUCTION ....................................................................................... 1 1.1 Objectives and Purpose ........................................................................................ 3 1.2 Study Area ............................................................................................................ 3 1.3 Research and Methods ......................................................................................... 7 1.3.1 Digital Wireline Logs ................................................................................... 7 1.3.2 Outcrop ....................................................................................................... 13 1.3.3 Core ............................................................................................................. 16 1.3.4 Cuttings ....................................................................................................... 17 1.4 Industry Activity ................................................................................................ 18 CHAPTER 2 GEOLOGIC BACKGROUND .................................................................. 21 2.1 Regional Setting and Structure ........................................................................... 21 2.2 Stratigraphy ........................................................................................................ 23 2.2.1 Graneros ...................................................................................................... 24 2.2.2 Greenhorn ................................................................................................... 27 Chapter 3 RESULTS........................................................................................................ 35 3.1 Graneros ............................................................................................................. 35 3.1.1 Mapping ............................................................................................................ 35 3.1.2 Core ............................................................................................................. 40 3.1.3 Cuttings ....................................................................................................... 40 3.2 Greenhorn ........................................................................................................... 43 3.2.1 Mapping ...................................................................................................... 44 3.2.2 Outcrop ....................................................................................................... 54 3.2.3 Core ............................................................................................................. 60 3.2.4 Cuttings ....................................................................................................... 81 3.2.5 Drill Stem Tests/Historical Data ................................................................. 84 CHAPTER 4 INTERPRETATIONS ............................................................................... 90 v CHAPTER 5 SUMMARY AND CONCLUSIONS ...................................................... 102 CHAPTER 6 FUTURE WORK .................................................................................... 105 REFERENCES CITED ................................................................................................... 107 APPENDIX A: OUTCROP ANALYSIS ...................................................................... 113 APPENDIX B: CORE ANALYSIS................................................................................ 117 APPENDIX C: CUTTING ANALYSIS ........................................................................ 120 APPENDIX D: LINCOLN MEMBER DST RESULTS ................................................ 127 CD/DVD ................................................................................................................ POCKET vi LIST OF FIGURES Figure 1.1 Stratigraphic column of productive Cretaceous intervals within the Greater Wattenberg Area. The Greenhorn and Graneros formations lie directly between two currently productive systems. The focus of the study is to provide evidence of the petroleum potential for Greenhorn and Graneros formations. Typical depths throughout the study area are noted to the right of each formation (modified from Sonnenberg, 2011)......................................................................... 2 Figure 1.2 (a) Map showing the regional location of the study area (red outline). The GWA is located in the west-central part of the Denver Basin (orange dashed line), and includes several urban areas (yellow polygons) along the Colorado Front Range. (b) Map showing the local boundaries of the study area. City boundaries are shown in yellow polygons................................................................................. 4 Figure 1.3 Map of residual magnetic intensity and vitrinite reflectance data (white text next to well symbols) within the study area (red outline and shading). Faults can be seen trending in a northeast direction (modified from Weimer, 1996; Higley and Gautier, 1988; Higley et al., 2003). .................................................................. 6 Figure 1.4 Map of the GWA (red outline) which show location of Aristocrat Angus 12-8 core (Sec.8, T3N, R65W; blue circle), locations of well cuttings (blue triangles), Lykins Gulch outcrop (purple square), and well-control locations (wells). City boundaries (yellow) and interstate highway (black)s are also shown..................... 8 Figure 1.5 Log of Aristocrat Angus 12-8 (Sec.8 T3N R65W) with Δ Log RDensity shaded in light red. The log-derived TOC curve calculated from the Passey equations is shown with measured TOC values from the Aristocrat Angus 12-8 core and show a good relationship with calculated and measured values within source rock intervals (Graneros Formation and Hartland Member of the Greenhorn Formation)............................................................................................................. 10 Figure 1.6 Map of