GEOLOGIC RESERVOIR CHARACTERIZATION OF THE CODELL SANDSTONE: CENTRAL WATTENBERG FIELD, COLORADO by John Stamer 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 ______________ Signed: _____________________________ John Stamer Signed: _____________________________ Dr. Stephen A. Sonnenberg Thesis Advisor Golden, Colorado Date ______________ Signed: _____________________________ Dr. Paul Santi Professor and Department Head Department of Geology And Geological Engineering ii ABSTRACT Colorado’s Wattenberg Field is a giant natural gas and oil field. Since its discovery in the 1970’s, the field ranks as the seventh largest domestic natural gas field in the United States, with cumulative production according to IHS 210 MMBo and 4.03 Tcf. The Codell serves as an important and highly productive reservoir in the area. The Late Turonian Codell Sandstone Member of the Carlile Shale is a zone which has produced almost exclusively from the Wattenberg Field since production from the formation began in 1981 with little to no success elsewhere in the basin until recent years. With advancements in multi-stage hydraulic fracturing and horizontal drilling there has been renewed interest in the development and continued exploration of the Codell Sandstone. This study is meant to focus on the geologic reservoir characterization of the Codell Sandstone in Wattenberg Field, and understand the future potential for the Codell play that remains untapped. The Codell Sandstone within Wattenberg Field is the low porosity (4-12%), low permeability (<0.1 mD) member of the Carlile Shale Formation. The sandstone was deposited on a shallow marine shelf below normal fair-weather storm wave base under low energy conditions. The Codell is the upper member of the Carlile Formation and unconformably overlies the lower Carlile Shales or the Greenhorn Marlstones and is unconformably overlain by the Fort Hays Member of the Niobrara Formation. Within the study area the Greenhorn and Niobrara Formations are considered to be the main source beds for the Codell hydrocarbon accumulations. Throughout Wattenberg Field the Codell Sandstone contains three distinct facies. The first of which is highly bioturbated and thick (7-15 ft), and is found at the very top and very bottom parts of the sandstone and encapsulates the other two facies. Facies #2 is thinner (1-10 ft) containing clay laminae with sand-filled burrows, and is found in the middle part of the Codell. iii The third facies, facies 3, is the most distinct of the three with low angle (hummocks) cross- stratification. In total the three facies of the Codell are on average 10 to 30 ft thick. High clay content, sometimes exceeding 25%, within the Codell Sandstone lead to the low permeability and low resistivity observed. Within the study area the Codell is classified as a “tight” oil and gas sand, with a dual porosity system. Hydrocarbon entrapment in the Codell Sandstone is due to a combination of low permeability, stratigraphic compartmentalization, structural compartmentalization, and clay smearing in faults. This makes the Codell play a combination play, with areas of continuous accumulation along with some areas of discontinuous accumulations. High temperature and pressure anomalies, as well, coincide with increased production rates within the Central Wattenberg Field. The future of the play will see increased horizontal drilling on closer spacing, and more precisely designed hydraulic fracture stimulations with multiple stages. In the long run there will be lower drilling and completion costs, which will make the play as profitable as possible. The culmination of this entire study can be a basis for future exploration around the world. Identifying tight, bioturbated, shelf-deposited sandstones and using the conclusion drawn from this study to aid in their economic success. iv TABLE OF CONTENTS ABSTRACT……………………………………………………………………………...............iii LIST OF FIGURES...………………………………………………………………...…………viii LIST OF TABLES……………………………………………………………………................xvi ACKNOWLEDGMENTS...…………………………………………………………................xvii CHAPTER 1 INTRODUCTION...………………………….………………………………….…1 1.1 Study Objectives……………………………………………………………………....6 1.2 Study Area…………………………………………………………………………….6 1.3 Methods and Purpose………………………………………………………………….8 CHAPTER 2 BACKGROUND GEOLOGY...…….………………………….…………………11 2.1 Geologic Overview…………………………………………………………………..11 2.2 Tectonics……………………………………………………………………………..17 2.3 Sedimentation………………………………………………………………………..20 CHAPTER 3 CORES.…………….……………………………………………………………..23 3.1 Facies Description……………………………………………………..……………..24 3.2 PetroQuest State B-41-36……………………………………………………………31 3.3 Dome Petroleum Franks #1-13……………………………………………………....35 3.4 Brooks Harrington #2-30…………………………………………………………….41 3.5 Discussion……………………………………………………………………………47 CHAPTER 4 PETROGRAPHIC ANALYSIS..……………….………………………...............48 4.1 PetroQuest State B-41-36……………………………………………………………49 4.2 Dome Petroleum Franks #1-13………………………………………………………54 4.3 Brooks Harrington #2-30…………………………………………………………….63 v 4.4 Discussion……………………………………………………………………………66 CHAPTER 5 PORE ANALYSIS…………………….………………………………………….68 5.1 FESEM Description………………………………………………………………….68 5.2 MICP Analysis……………………………………………………………………….78 CHAPTER 6 SUBSURFACE MAPPING.……….……………………………………………..85 6.1 Introduction and Methods……………………………………………………………85 6.2 Codell Structure and Isopach………………………………………………...............86 6.3 Resistivity and Porosity……………………………………………………...............91 6.4 Pressure and Temperature……………………………………………………………94 6.5 Pay Isopach…………………………………………………………………………..97 CHAPTER 7 OIL AND GAS PRODUCTION AND ECONOMICS..…….……………………98 7.1 Reservoir……………………………………………………………………………..98 7.2 Source………………………………………………………………………………102 7.3 Migration and Impedance…………………………………………………………..108 7.4 Production…………………………………………………………………………..111 7.4.1 Wattenberg Field………………………………………………………….111 7.4.2 Codell Sandstone, Central Wattenberg Field……………………………..115 7.5 Completion………………………………………………………………………….120 7.5.1 Historical Industry Standard Techniques…………………………………120 7.5.2 Hydraulic Re-Fracture Stimulation……………………………………….125 7.6 Horizontal versus Vertical Wells…………………………………………………...127 7.6.1 Production………………………………………………………………...128 7.6.2 Economics………………………………………………………………...131 vi 7.7 Discussion…………………………………………………………………………..135 CHAPTER 8 CONCLUSIONS..……………………………………………………………….137 CHAPTER 9 RECOMMENDATION FOR FUTURE WORK.……………………………….141 REFRENCES CITED..…………………………………………………....…………………....143 vii LIST OF FIGURES Figure 1-1: Modified from Sonnenberg (2015). Stratigraphic column for the Denver Basin. Depths in feet on the right, and source rock along with reservoirs labeled on the left. .......2 Figure 1-2: Modified from Encana (2011). Wells drilled in a section. 32 acre spacing led to 5 wells per quarter section for a total of 20 wells per section. On the right Rule 318A showing 20 acre spacing leading to 8 wells per quarter section for a total of 32 wells producing form the same formation per section. .................................................................3 Figure 1-3: Map displaying all Codell wells that have been drilled in the Wattenberg Field. Wattenberg Field outlined and labeled in red. Major cities are outlined and labeled. ........4 Figure 1-4: Daily production rates for the Wattenberg Field from 1970 until present. Oil rates on the left are colored in green while gas rates on the right are colored in red. Information comes from IHS Enerdeq. ....................................................................................................5 Figure 1-5: Location map showing the outline of the Wattenberg Field labeled and outlined in red and Central Wattenberg Field in blue. Cities are outlined and labeled. ........................7 Figure 1-6: Map displaying names and locations of the three cores used in this thesis. Codell producing wells are displayed along with the outline of the CWF, and the city of Greeley, CO ........................................................................................................................................7 Figure 2-1: Probable distribution of land and sea in North America during late Cretaceous time showing where the epeiric seaway divided Notrth America. The Wattenberg Field is located in the west central portion of the seaway (modified from Gill & Cobban, 1973).12 Figure 2-2: Structural cross section across the Wattenberg Field. Showing gently dipping structure from East to West until a steep uplift due to the Laramide Orogeny. The approximate top of the oil window is shown, with the Codell within the mature hydrocarbon generation zonein the Wattenberg Field. (Modified from Sonnenberg, 2015).13 Figure 2-3: Distribution of the Codell Sandstone. The three different types are shown within the Denver Basin. The “Codell Play” is essentially the outline of the Wattenberg Field. (Modified from Weimer & Sonnenberg, 1983) .................................................................15 Figure 2-4: Greater Wattenberg Area outlined, showing the Wattenberg thermal anomaly and its position relative to the Colorado Mineral Belt. Major wrench faults and other fault systems are also shown. (Modified from Birmingham , 2006)..........................................16 Figure 2-5: From Panigoro (1988) after Schedl and Wiltschko (1984). The relationship between tectonic events and the facies distribution is shown in the Idaho