Denver Basin Paleozoic Study

Transcription

1 Denver Basin Paleozoic Study

2 Denver Basin Paleozoic Study Overview GeoDigital Information's Denver Basin Paleozoic Study is designed to enhance both exploration and development efforts that are directed at Paleozoic reservoirs in the Denver Basin. GDI's stratigraphic study in the northern Denver Basin focuses on the relationship between structure and depositional systems in Desmoinesian through Wolfcampian strata. The study area covers more than 51,000 square miles in 1415 townships. Included in the study database are analyses of logs from 373 wells, 27 cores 160 thinsections, and paleontological analyses from seven wells. GDI correlated eleven regional stratigraphic markers throughout the study area. Interval isopachs, lithofacies, and paleogeographic maps were used to develop depositional models and to document the complex depositional history of the area. During the late Paleozoic, cyclic marine incursions resulted from changes in eustatic sea level and variations in local subsidence rates. The major structural feature affecting depositional rates and patterns was the Transcontinental Arch, which bisected the study area. This positive feature separated two subbasins, each with distinct depositional environments and stratigraphic relationships. Along its crest, a mosaic of carbonate facies was deposited in a variety of shallow-marine environments within a barrier/shoal complex. To the north, restricted conditions in the Alliance Basin resulted in resulted in thick evaporites, organic-rich source-potential shales, and dolomites. To the south, more normal marine conditions prevailed in the Sterling Basin, where progradational reservoirpotential carbonate ramp facies interfingered with dolomitic siltstones. A major feature of the GDI study is an internally consistent stratigraphic database. Laterally extensive carbonate and anhydrite beds were correlated over much of the area. These GDI correlations were compared to micropaleontological zonations showing that they have chronostratigraphic significance. The resultant stratigraphic units delineated by the correlations represent timestratigraphic intervals. This permitted the construction of a variety of genetically significant maps. Core descriptions and petrographic analyses were integrated with wireline log data to determine facies and structural relationships. These relationships are presented in a series of subregional depositional models and documented by cross sections, lithofacies maps, and isopach maps. Petrographic analyses, focusing upon diagenetic alterations and their effects on porosity development, are integrated with the stratigraphy, tectonic framework, and depositional models to predict the distribution of potential reservoir facies. Detailed studies of Amazon and Bird fields further illustrate factors controlling hydrocarbon distribution The study components include an extensive summary text and figures, maps and cross sections, core and thinsection descriptions, and stratigraphic data appendices. These components provide the client with a presentation format that is concise and readily useable.

3 Database 373 Study Wells 11 Regional Stratigraphic Markers per Well Correlated 27 Cores Described 7 Paleontological Wells 160 Thinsections Maps Regional Maps (1:500,000) 10 Interval Isopach Maps 1 Structure Map 1 Well Penetration Map Field Maps Interval Isopach Maps Porosity-Feet Maps Structure Maps 8 Regional Stratigraphic Sections Cross Sections Field Studies Amazon, Bird Report Contents TEXT AND FIGURES - An extensively illustrated report includes discussions, figures, and color plates on: Executive Summary, Depositional Setting, Lithofacies, Stratigraphy, Depositional History, Petrography, Field Studies, Synthesis, and Exploration Potential. CORE DESCRIPTIONS - This section contains descriptions of 27 cores. STRATIGRAPHIC DATA - These files contain the stratigraphic data (11 formation tops and stratigraphic markers, and net sandstone values) and isopach values, as well as information on well name, operator, location, API number, completion date, datum, and production status for the 373 study wells. MAPS & CROSS SECTIONS - This section contains 12 regional maps. This includes isopach maps, structure map, and a study well map. 8 regional stratigraphic cross sections are also included.

4 Denver Basin Paleozoic Study CON- VERSE NIOBRARA Study Boundary T 30 N R 70 W SIOUX R 5 E T 7 S FALL RIVER SOUTH DAKOTA NEBRASKA DAWES SHANNON SHERIDAN BENNETT R 35 W T 40 N CHERRY PLATTE GOSHEN BOX BUTTE Scottsbluff GRANT SCOTTS BLUFF BANNER MORRILL GARDEN ARTHUR LARAMIE Cheyenne KIMBALL WYOMING COLORADO CHEYENNE DEUEL NEBRASKA SEDGWICK LOGAN KEITH PERKINS WELD PHILLIPS CHASE MORGAN DUNDY T 5 S R 70 W Denver ADAMS ARAPAHOE WASHINGTON YUMA KANSAS CHEYENNE R 35 W T 5 S 0 N 40 ELBERT LINCOLN KIT CARSON SHERMAN MILES

5 Denver Basin Paleozoic Study Study Table of Contents

6 DENVER BASIN LATE PALEOZOIC STUDY TABLE OF CONTENTS Table of Contents i List of Maps and Cross Sections.. v List of Figures.. vi List of Tables xii Acknowledgements. xiv Executive Summary Executive Summary E-1 Introduction. E-2 Tectonic Setting. E-3 Stratigraphy and Depositional History.... E-3 Depositional Models E-4 Lithofacies and Petrography E-4 Exploration Potential. E-5 Report Format E-5 Chapter 1 Introduction General Stratigraphy Scope Procedures Study Well Selection. 1-4 Cores Petrography Paleontology Stratigraphic Picks 1-4 Lithologic Determinations 1-5 Computer Data Base 1-5 Regional Cross Sections Regional Maps Chapter 2 Tectonic Setting and Paleogeography. 2-1 Depositional Setting Basin Configuration Basement Tectonics i

7 Major Structural Elements Transcontinental Arch Chadron-Cambridge Arch Complex Las Animas Arch - Yuma High Hartville Uplift Ancestral Rocky Mountains. 2-5 Sea-Level Fluctuations. 2-6 Paleoclimate Paleoceanography. 2-7 Chapter 3 Stratigraphy Stratigraphic Picks Atokan Series Desmoinesian Series Missourian Series. 3-3 Virgilian Series Admire Group 3-4 Council Grove Group Chase Group Paleontology Cross Sections Chapter 4 Depositional History Lithofacies Distribution Pre-Desmoinesian Depositional History Early Desmoinesian Depositional History Late Desmoinesian Depositional History Early Missourian Depositional History Late Missourian Depositional History Early Virgilian Depositional History Late Virgilian Depositional History Admire Depositional History Early Council Grove Depositional Histroy Late Council Grove Depositional History Chase Depositional History. 4-6 Chapter 5 Lithofacies Black Laminated Shale. 5-3 Burrowed Mudstone Skeletal Wackestone 5-5 Skeletal Packstone 5-6 ii

8 Phylloid Algal Wackestone/Packstone Non-Skeletal Packstone/Grainstone Stromatolitic Boundstone Mottled to Homogeneous Finely Crystalline Dolomite Laminated to Bedded Finely Crystalline Dolomite Dark Laminated Microcrystalline Dolomite 5-12 Anhydrite Breccia Shale/Claystone Siltstone Sandstone Chapter 6 Depositional Models Early Desmoinesian Depositional Model Barrier/Shoal Complex Depositional Model Modern Analogs 6-4 Composite Shoals and Barriers Pennsylvanian Backramp Depositional Model Modern Analog Wolfcampian Backramp Depositional Model. 6-8 Analogs Ramp Models High Stillstand Ramp Depositional Model. 6-9 Low Stillstand Ramp Depositional Model. 6-9 Chapter 7 Petrography Lower Desmoinesian Rocks. 7-3 Lithology. 7-3 Porosity Diagenesis Upper Desmoinesian And Missourian Rocks 7-6 Lithology. 7-6 Porosity Diagenesis Missourian Rocks of Southwestern Nebraska Lithology Porosity Diagenesis Virgilian Rocks Lithology Porosity Diagenesis iii

9 Admire and Lower Council Grove Rocks Lithology Porosity Diagenesis Upper Council Grove Rocks Lithology Porosity Diagenesis Chase Rocks Lithology Porosity Diagenesis Chapter 8 Detailed Study of Amazon and Bird Fields. 8-1 Location and Field Discovery Geological Setting Productive Virgilian Facies Porosity Diagenesis. 8-5 Structural Controls on Reservoir Formation Reservoir Parameters Summary. 8-7 Chapter 9 Exploration Potential and Recommendations Lower Desmoinesian Exploration Potential Upper Desmoinesian and Lower Missourian Exploration Potential Upper Missourian Exploration Potential. 9-5 Virgilian Exploration Potential Admire Exploration Potential 9-7 Council Grove Exploration Potential Chase Exploration Potential. 9-9 Bibliography Bibliography. B-1 Appendix A Appendix B Appendix C Appendix D Stratigraphic Data Core Descriptions Thin Section Descriptions Paleontological Data iv

10 Production map LIST OF MAPS AND CROSS SECTIONS Maps (1:500,000) Isopach maps Interval from the top of the Atokan to the Precambrian granite Lower Desmoinesian interval isopach Upper Desmoinesian interval isopach Lower Missourian interval isopach Upper Missourian interval isopach Lower Virgilian interval isopach Upper Virgilian interval isopach Admire Group interval isopach Lower Council Grove interval isopach Upper Council Grove interval isopach Chase Group interval isopach Dip Sections A-A' B-B' B'-B" C-C' Cross Sections Strike Sections W-W' X-X' Y-Y' Z-Z' Amazon/ Bird fields F- F' v

11 LIST OF FIGURES Chapter 1 - Introduction 1.1 Study well distribution 1.2 Stratigraphic nomenclature 1.3 General depositional model showing relationship to regional tectonics 1.4 Distribution of cored wells 1.5 Distribution of thin sections 1.6 Distribution of paleontological control 1.7 Type log with RPI picks and mapped stratigraphic units 1.8 Representative lithologies in cored interval compared to geophysical log response 1.9 Regional cross sections Chapter 2 - Tectonic Setting and Paleogeography 2.1 Structure map on the base of the Red Shale Marker 2.2 Late Paleozioc structural elements 2.3 General depositional model 2.4 Precambrian shear zones 2.5 Early Paleozoic tectonic framework 2.6 Fault block relationships 2.7 Structural elements affecting Late Paleozoic deposition 2.8 Lower Desmoinesian isopach map 2.9 Upper Desmoinesian isopach map 2.10 Lower Missourian isopach map 2.11 Wolfcampian isopach map 2.12 Schematic of subsidence rates of basement blocks on arch 2.13 Structural uplifts associated with the Ancestral Rocky Mountains 2.14 Variations in cyclic sequences, Alliance Basin 2.15 Variations in cyclic sequences, Sterling Basin 2.16 Position of Pennsylvanian and Permian paleoequators i

12 Chapter 3 - Stratigraphy 3.1 Regional variation in lower Missourian lithofacies 3.2 Regional variation in lower Council Grove lithofacies 3.3 Type log of GDI picks and stratigraphic intervals 3.4 Confidence level for Pennsylvanian picks 3.5 Confidence level for Wolfcampian picks 3.6 Response variations of Pennsylvanian picks 3.7 Response variations of Wolfcampian picks 3.8 Diagnostic Late Paleozoic endothyrids and fusulinids 3.9 Comparison of paleontological zonation with GDI intervals 3.10 Schematic cross section W-W' 3.11 Schematic cross section B-B' 3.12 Schematic cross section C-C' 3.13 Schematic cross section A-A' 3.14 Schematic cross section B'-B" 3.15 Schematic cross section X-X' 3.16 Schematic cross section Y-Y' 3.17 Schematic cross section Z-Z' Chapter 4 - Depositional History 4.1 Stratigraphic distribution of described cores 4.2 Interval isopach from Precambrian granite to top of Atokan 4.3 Lower Desmoinesian isopach map 4.4 Lower Desmoinesian lithofacies map 4.5 Upper Desmoinesian isopach map 4.6 Upper Desmoinesian lithofacies map 4.7 Lower Missourian isopach map 4.8 Lower Missourian lithofacies map 4.9 Upper Missourian isopach map 4.10 Upper Missourian lithofacies map 4.11 Lower Virgilian isopach map vii

13 4.12 Lower Virgilian lithofacies map 4.13 Upper Virgilian isopach map 4.14 Upper Virgilian lithofacies map 4.15 Admire Group isopach map 4.16 Admire Group lithofacies map 4.17 Lower Council Grove isopach map 4.18 Lower Council Grove lithofacies map 4.19 Upper Council Grove (Wolfcamp dolomite) isopach map 4.20 Upper Council Grove (Wolfcamp dolomite) lithofacies map 4.21 Chase Group isopach map 4.22 Chase Group lithofacies map Chapter 5 - Lithofacies 5.1 Facies 1; Black laminated shale 5.2 Facies 2a; Burrowed mudstone 5.3 Facies 2b; Skeletal wackestone 5.4 Facies 2c; Skeletal packstone 5.5 Facies 3; Phylloid algal wackestone/packstone 5.6 Facies 4; Non-skeletal packstone/grainstone 5.7 Facies 5; Stramatolitic boundstone 5.8 Facies 6; Mottled to homogeneous finely-crystalline dolomite 5.9 Fades 7; Laminated to bedded finely-crystalline dolomite 5.10 Fades 8; Dark laminated microcrystalline dolomite 5.11 Facies AN; Anhydrite 5.12 Facies B; Breccia 5.13 Facies Sh; Shale/Claystone 5.14 Facies SLTS; Siltstone 5.15 Facies SS; Sandstone viii

14 Chapter 6 - Depositional Models 6.1 General depositional model showing wave energy zones 6.2 Early Desmoinesian depositional model 6.3 Early Desmoinesian lithofacies distribution 6.4 Early Desmoinesian representative cores 6.5 Typical log responses for early Desmoinesian model 6.6 Grain-rich progradational barrier 6.7 Progradational grainstone shoreface/beach facies 6.8 Log response and lithic variations in grain-rich shoreface sequence 6.9 A spectrum of Texas Gulf Coast barrier islands 6.10 Barrier/shoal depositonal model 6.11 Transgressive barrier facies relationships 6.12 Modern Trucial Coast carbonate barrier islands 6.13 Evolution of Trucial Coast barrier islands 6.14 Component lithofacies of barrier/shoal model 6.15 Representative cores of barrier/shoal model 6.16 Characteristic log responses of barrier/shoal model 6.17 Composite barrier/shoal sequences (See Figs and 8.14) 6.18 Pennsylvanian backramp depositional model 6.19 Modern coastal environments south of Corpus Christi, Texas 6.20 Facies relationships in Baffin and Alazan bays, Texas 6.21 Component lithofacies of Pennsylvanian backramp model 6.22 Representative cores of Pennsylvanian backramp model 6.23 Characteristic log responses of Pennsylvanian backramp model 6.24 Wolfcampian backramp model 6.25 Cross section Wolfcampian backramp evaporitic basin 6.26 Component lithofacies of Wolfcampian backramp model 6.27 Representative cores of Wolfcampian backramp model 6.28 Characteristic log responses of Wolfcampian backramp model 6.29 Areal distribution of Trucial Coast sabkha deposits 6.30 Trucial Coast sabkha facies relationships 6.31 Bristol Dry Lake facies relationships 6.32 Jurrasic Ferry Lake anhydrites ix

15 6.33 Depositional model for Texas Panhandle Permian evaporites 6.34 Comparison of carbonate- and clastic-dominated evaporitic basins 6.35 Interpretation of Kansas City cyclothems 6.36 High stillstand ramp model 6.37 Low stillstand ramp model 6.38 Component facies distribution for high stillstand ramp model 6.39 Representative cores of high stillstand ramp model 6.40 Characteristic log responses of ramp models 6.41 Component facies distribution for low stillstand ramp model 6.42 Representative cores of low stillstand ramp model Figure 7 - Petrography 7.1 Lower Desmoinesian photomicrographs 7.2 Upper Desmoinesian and Missourian photomicrographs 7.3 Southwestern Nebraska Missourian photomicrographs 7.4 Virgilian photomicrographs 7.5 Porosity in Virgilian rocks 7.6 Admire and lower Council Grove photomicrographs 7.7 Upper Council Grove photomicrographs 7.8 Chase photomicrographs Chapter 8 - Detailed Study of Amazon and Bird Fields 8.1 Amazon/Bird field type log 8.2 General depositional model 8.3 Photomicrographs of reservoir facies 8.4 Virgilian reservoir facies, Amazon Field 8.5 Admire lithofacies 8.6 Virgilian and Admire lithofacies adjacent to Amazon field 8.7 Map of Cretaceous J Sand structure 8.8 Map of structure on base of Red Shale Marker x

16 8.9 Interval isopach from Precambrian granite to Red Shale Marker 8.10 Interval isopach from Red Shale Marker to Minnekahta Limestone 8.11 Amazon/Bird cross section 8.12 Isopach of Niobrara Formation 8.13 Facies-to-log comparison, Christensen well 8.14 Facies-to-log comparison, Deaver well Chapter 9 - Exploration Recommendations 9.1 Lower Desmoinesian exploration potential 9.2 Upper Desmoinesian and lower Missourian exploration potential 9.3 Upper Missourian exploration potential 9.4 Virgilian exploration potential 9.5 Admire Group exploration potential 9.6 Upper Council Grove exploration potential 9.7 Chase Group exploration potential xi

17 LIST OF TABLES Chapter 1 - Introduction Table 1.1. Significant 1986 Paleozoic discoveries, northern Denver Basin Table 1.2. List of cored wells Chapter 5 - Lithofacies Table 5.1. List of lithofacies Table 5.2. Facies 1: black laminated shale Table 5.3. Facies 2a: burrowed mudstone Table 5.4. Facies 2b: skeletal wackestone Table 5.5. Facies 2c: skeletal packstone Table 5.6. Facies 3: phylloid algal wackestone/packstone Table 5.7. Fades 4: non-skeletal packstone/grainstone Table 5.8. Facies 5: stromatolitic boundstone Table 5.9. Facies 6: finely-crystalline dolomite (dolomudstone) Table Facies 7: laminated finely-crystalline dolomite Table Facies 8: dark laminated microcrystalline dolomite Table Facies AN: anhydrite Table Facies B: breccia Table Facies SH: shale/claystone, and Facies SLTS: siltstone Table Facies SS: sandstone Chapter 8 - Detailed Study of Amazon and Bird Fields Table 8.1. Producing wells in the Amazon/Bird areas Table 8.2. Thin section data from the Christensen well Table 8.3. Amazon and Bird fields reservoir summaries Chapter 9 - Exploration Potential Table 9.1. Lower Desmoinesian exploration potential Table 9.2. Upper Desmoinesian and lower Missourian exploration potential xii

18 Table 9.3. Upper Missourian exploration potential Table 9.4. Virgilian exploration potential Table 9.5. Admire exploration potential Table 9.6. Council Grove exploration potential Table 9.7. Chase exploration potential xiii

19 Denver Basin Paleozoic Study Selected Figures from the Study

20 Figure E.2. Type log with stratigraphic picks and mapped intervals. Return to Text

21 Figure Schematic of the relationship of basement block movements to depositional framework. A) Pennsylvanian framework included a broad Transcontinental Arch with a poorly defined flexure along its southern margin. B) Wolfcampian framework was modified by a southward shift and greater prominence of this flexure zone. The backramp became more extensive and the barrier/shoal complex shifted to the south. Greater subsidence rates south of the study area increased the prominence of the ramp which was best developed south of the study area. Return to Text

22 Figure 1.2 Correlation chart comparing stratigraphic nomenclature in the northern Denver Basin and adjacent areas. Nomenclature used in this study is shaded. Return to Text

23 C. #1 Hansen, 4,344 ft. Partly dolomitized peloidal (and skeletal) packstone to grainstone with well-developed moldic porosity. Some intergranular porosity is also present. The cement is dominantly coarse equant calcite (here stained pink), but coarse dolomite (white, unstained) has replaced some grains and also fills some molds. These textures are indicative of relatively stagnant water during diagenesis (incomplete cementation) and near equilibrium conditions in the diagenetic fluid (few nucleation sites allow only a few large crystals to form), probably deep in the subsurface. D. #34-13 Foster Brothers, 4,382 ft. Stylolite truncating a brachiopod in a skeletal wackestone with fusulinids, pellets, and a variety of other grains (not visible here). Preservation of primary intragranular porosity within the fusulinid indicates that the diagenetic fluids were relatively stagnant and that the rock was never exposed to extensive freshwater diagenesis, possibly because of its downdip position on the depositional ramp. Figure 7.3 (cont) Photomicrographs of Missourian lithofacies in southwestern Nebraska. Thin section core depths are recorded. Return to Page 7-9 Return to Page 7-10

24 Example of a Core Description