SEQUENCE STRATIGRAPHY, DEPOSITIONAL HISTORY, AND HYDROCARBON POTENTIAL OF THE MANCOS SHALE, UINTA BASIN, UTAH by Andrew Donald McCauley A thesis submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of Master of Science in Geology Department of Geology and Geophysics The University of Utah December 2013 Copyright © Andrew Donald McCauley 2013 All Rights Reserved The University of Utah Graduate School STATEMENT OF THESIS APPROVAL The thesis of _________________ Andrew Donald McCauley has been approved by the following supervisory committee members: Lauren P. Birgenheier , Chair 8/28/13 Date Approved Cari Johnson , Member 9/10/13 Date Approved Robert Ressetar , Member 8/28/13 Date Approved and by ____________________ John M. Bartley____________________ , Chair/Dean of the Department/College/School o f _____________Geology and Geophysics____________ and by David B. Kieda, Dean of The Graduate School. ABSTRACT The Mancos Shale, an organic-lean marine mudstone dominated by detrital quartz and clay, was deposited into the Upper Cretaceous Western Interior Seaway. It is a proven source rock with potential as a target for hydrocarbon production from horizontal drilling and hydraulic fracturing, but prospective reservoir target intervals from its 4,000 ft (1220 m) thickness must be identified and characterized. The distribution of lithofacies throughout the Mancos has not previously been studied in detail, so this formation remains undifferentiated and the relationship with paleodepositional up- and downdip strata undefined. Previous core-based analysis has provided a depositional and sequence stratigraphic framework for predicting the distribution of lithofacies in the Mancos. However, a unified, basin-wide facies and sequence stratigraphic correlation which tests existing outcrop and core-based models is lacking. 157 wireline logs were chronostratigraphically correlated across the basin to build a regional subsurface map and cross sections that highlight stacking patterns, regional facies relationships, stratal architecture, and sequence stratigraphy within a depositional framework. A sequence stratigraphic model is established for the Mancos Shale, which incorporates seminal outcrop-based models from strata of central Utah, Mancos core, and stacking patterns identified from wireline log data. The Mancos thickens to the north and west, matching regional trends of tectonically driven subsidence, the most significant control on accommodation. The Mancos Shale consists of 29 4th order T-R cycles, which can be stacked to form four 3rd order cycles and a single 2nd order cycle. Whereas the stacking patterns of 2nd and 3rd order cycles are consistent across the basin, suggesting allocyclic control, 4th order cycles are more variable, influenced by both allocyclic and autocyclic controls. Deposition of the Mancos evolved from a low gradient ramp, to a deeper water basin, which was then infilled by basin-floor fans. Two organic-rich facies associations, each corresponding to transgressive and early highstand sequence sets, heterolithic facies of the Juana Lopez and lowermost Blue Gate (FA1) and sediment starved shelf deposits of the Lower Blue Gate (FA2) offer the most prospective intervals for unconventional hydrocarbon production. Preliminary petrophysical analysis and basin modeling corroborate this analysis. iv TABLE OF CONTENTS ABSTRACT............................................................................................................................ iii LIST OF FIGURES.............................................................................................................. vii ACKNOWLEDGEMENTS.................................................................................................. ix Chapter 1 TRANSGRESSIVE-REGRESSIVE CYCLES IN THE MANCOS SHALE, UINTA BASIN, U TAH................................................................................................... 1 Abstract.....................................................................................................................................1 Introduction.............................................................................................................................. 3 Geologic Background.............................................................................................................6 Dataset.....................................................................................................................................14 Methods and Approach.........................................................................................................18 Results.....................................................................................................................................23 Discussion.............................................................................................................................. 33 Conclusions............................................................................................................................ 44 2 DEPOSITIONAL SEQUENCE STRATIGRAPHY AND HYDROCARBON POTENTIAL OF THE MANCOS SHALE, UINTA BASIN, UTAH ................... 47 Abstract...................................................................................................................................47 Introduction............................................................................................................................ 49 Geologic Background...........................................................................................................53 Dataset.....................................................................................................................................56 Methods and Approach.........................................................................................................60 Results.....................................................................................................................................63 Discussion.............................................................................................................................. 81 Conclusions.......................................................................................................................... 112 Appendices A WELL DATABASE.................................................................................................... 116 B REVISED LOWER MANCOS STRATIGRAPHY................................................143 REFERENCES................................................................................................................... 146 vi LIST OF FIGURES 1. Foreland basin schematic (modified from DeCelles and Giles, 1996)..................... 7 2. Paleogeographic map of western North America (modified from Blakey, 2013) ... 9 3. Generalized regional stratigraphy of the Western Interior Basin (modified from Kauffman, 1977)............................................................................................................ 10 4. Generalized lithostratigraphy of the Mancos Shale, Uinta Basin, U T.....................12 5. Basin-wide data distribution map with T-R cross section traces............................. 15 6. Gamma ray log and core analysis correlation.............................................................20 7. West-east T-R cycle cross section from southeastern Uinta Basin, U T ................. 24 8. West-east T-R cycle cross section from northeastern Uinta Basin, U T ................. 26 9. North-south T-R cycle cross section from eastern Uinta Basin, U T .......................28 10. Stacking pattern summary of Mancos Shale T-R cycles.......................................... 29 11. Relative sea level curve of Mancos Shale....................................................................36 12. Comparison of Upper Cretaceous records of sea level change and Mancos Shale Relative sea level (calibrated with Gradstein et al., 2012)............................. 38 13. Sevier foreland backstripping analysis and subsidence history (modified from Pang and Nummedal, 1995).......................................................................................... 42 14. Basin-wide data distribution map with regional cross section traces......................57 15. Type log, Mancos Shale.................................................................................................64 16. Outcrop photos from exposures of the Mancos Shale in the Uinta Basin..............67 17. Exposure of Mancos B, Prairie Canyon, C O ..............................................................69 18. Isopach Maps, Mancos Shale and Lower Blue Gate Member of the M ancos........70 19. Isopach Maps, Mancos B Member of the Mancos Shale.......................................... 72 20. West-east regional cross section of Mancos Shale facies variability and Sequence stratigraphic correlation................................................................................74 21. North-south regional cross section of Mancos Shale facies variability and sequence stratigraphic correlation.................................................................................75 22. Lower Mancos correlation cross section detail...........................................................78 23. Schematic illustration of FA1, FA2 and Mancos B deposition............................... 83 24. Paleogeographic maps of the study area during Mancos deposition.......................85 25. SEM images of Blue Gate Member facies association