Triassic Doig Formation Sand Bodies in the Peace River Area of Western Canada
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TRIASSIC DOIG FORMATION SAND BODIES IN THE PEACE RIVER AREA OF WESTERN CANADA : DEPOSITIONAL AND STRUCTURAL MODELS, AND THE IMPACT OF DIAGENESIS ON RESERVOIR PROPERTIES by RICHARD GORDON HARRIS B.Eng. (Hons.), Queen's University, 1990, 1997 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Earth and Ocean Sciences We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA February 2000 '••>;. © Richard Gordon Harris, 2000 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT Middle Triassic Doig reservoirs in the Fireweed, Buick Creek, Cache Creek and West Stoddart fields (94-A-13 to Twp.86, Rge.18) of northeastern British Columbia consist of deltaic and shoreline sands encased in shelf and offshore mudstones and siltstones. The reservoirs comprise a series of northwest and northeast trending elongate sand bodies that lie along a south-southeast depositional trend analogous to the position of the original Doig shoreline. Sediments of the Doig Formation are divisible into two facies associations and ten lithofacies representing deposition in shelf to offshore, and deltaic and inter-deltaic environments. Hydrocarbon producing intervals consist of clean, very fine to fine grained, sub-lithic to quartz arenites, inter-bedded sandstones and bioclastic detritus, and disseminated bioclasts. Effective porosity is primarily inter-granular in the sandstone facies with significant moldic and intra-granular porosity developed in the coquina facies at the West Stoddart and Cache Creek fields. Average porosities range from 6.5 - 9.5% for sandstone lithofacies and 4.9 - 8.6% for coquina lithofacies. Pore occluding cements are mainly calcite in the northwest part of the reservoir trend to dolomite and anhydrite in the southeast. The sedimentology and facies architecture of recent discoveries at Cache Creek and West Stoddart contrast with those identified in previous studies of Doig reservoirs at Buick Creek in northeastern British Columbia and Sinclair in west central Alberta. A three-dimensional facies model of the Doig Formation at the Cache Creek, West Stoddart and Fireweed fields depicts sandstone deposition in a deltaic environment as distributary channel fills and slumped delta front deposits. Data for the Buick Creek field ii confirms and extends the incised shoreface model to include fluvial or tidal channels deposited laterally continuous in the same systems tract as the shoreface sands. Sand bodies for all four fields were deposited contemporaneously as the Doig shoreline prograded over mudstones and siltstones of the Doig shelf. Seismic and well data reveal tectonic control on the position and orientation of the Doig reservoir trend. Syn- sedimentary growth faults control the location and geometry of thick sand bodies along the reservoir trend in the Fireweed area. Diagenetic controls along the reservoir trend include the precipitation of calcite in the near surface and shallow burial realm, fracturing of cemented horizons prior to extensive burial and dissolution of cements and framework grains in three distinct episodes. Multiple dissolution phases created moldic, vuggy and inter-granular secondary porosity. Reservoir quality and production from Doig Formation sand bodies in the Peace River area of Western Canada are significantly impacted by the preservation of inter-granular porosity and fracturing related to the distribution of early calcite cements. The early calcite cements were sourced from bioclastic debris and calcareous mudstones distributed during sand body deposition. The formation of open fractures during early diagenesis enhanced both the secondary pore network and the permeability of the West Stoddart and Cache Creek Doig pools. Sand bodies with only minor interstitial calcite have extensive porosity loss by compaction and precipitation of authigenic quartz. A fairway for Doig sand body exploration is constrained by production and core analysis data, structural and depositional models, thermal maturity data and diagenesis. iii TABLE OF CONTENTS Abstract ii Table of Contents iv List of Figures viii List of Tables x Acknowledgements xi CHAPTER 1 - INTRODUCTION 1.1. - Introduction 1 1.4. - Structure of Thesis 2 1.5. - References Cited 3 CHAPTER 2 - DEPOSITIONAL AND STRUCTURAL MODELS FOR DOIG FORMATION SAND BODIES IN THE PEACE RIVER AREA OF NORTHEASTERN BRITISH COLUMBIA 2.1. - Abstract 4 2.2. - Introduction 5 2.3. - Geologic Setting 6 2.4. - Lithostratigraphy and Sand Body Geometry 10 2.4.1. - Facies and Facies Associations 12 2.4.2. - Cross-sections and Facies Architecture 14 2.4.2.1. - West Stoddart and Cache Creek 14 2.4.2.2. - Fireweed 16 2.4.2.3. - Buick Creek.... 19 iv 2.5. - Depositional Setting 21 2.5.1. - Interpretation of Fades and Fades Assodations 21 2.5.2. - Depositional Models for Sand Bodies Comprising the Fireweed, Cache Creek, West Stoddart and Buick Creek Pools 25 2.5.3. - Alternative Depositional Environments 31 2.5.3.1. - Tidal Inlets/Barrier Islands 31 2.5.3.2. - Shelf Sheet Sands Incised by Tidal/Storm Channels 31 2.6. - Structural Controls on Reservoir Distribution 32 2.6.1. - Regional Considerations 32 2.6.2. - Deposition of Doig Sands at Structurally Controlled Slope Breaks 35 2.6.3. - Structural Features form Log Data 35 2.6.4. - Syn-Sedimentary Growth Faulting 38 2.7. - Summary and Conclusions 40 2.8. - References Cited 42 CHAPTER 3 - DIAGENESIS, RESERVOIR QUALITY AND PRODUCTION TRENDS OF DOIG FORMATION SAND BODIES IN THE PEACE RIVER AREA OF WESTERN CANADA 3.1. - Abstract 46 3.2. - Introduction 47 3.3. - Lithology and Depositional Setting 49 3.4. - Database 52 3.5. - Petrology of Doig Sandstones 54 3.5.1. - Sandstone Composition 54 V 3.5.2. - Coquina Composition 55 3.5.3. - Diagenesis 55 3.5.3.1. - Calcite Cement 57 3.5.3.2. - Quartz 57 3.5.3.3. - Apatite 59 3.5.3.4. - Dolomite 59 3.5.3.5. - Anhydrite 59 3.6. - Paragenesis 61 3.6.1. - Early Calcite 61 3.6.2. - Fracturing and Microfaulting 63 3.6.3. - Formation of MoldicA/uggy Porosity 65 3.6.4. - Compaction 65 3.6.5. - Replacement of Quartz by Carbonate 65 3.6.6. - Precipitation of Ferroan Calcite 66 3.6.7. - Carbonate Dissolution - Secondary Porosity 66 3.6.8. - Dolomite Precipitation 67 3.6.9. - Hydrocarbon Migration 67 3.6.10. - Geochemical Considerations 67 3.7. - Reservoir Quality 68 3.7.1. - Trend of Porosity and Permeability with Depths 70 3.7.2. - Bioclastic Facies and Calcite Cement Distribution 72 3.7.3. - Distribution of Secondary Porosity 72 3.8. - Production Trends 75 3.9. - Discussion 79 3.10. - Constraints on Exploration 82 vi 3.11. - Conclusions 85 3.12. - References Cited 86 CHAPTER 4 - CONCLUSIONS 89 APPENDIX A - CORE IDENTIFICATION AND LOCATION 92 APPENDIX B - CORE DESCRIPTIONS 94 APPENDIX C - CATALOGUE OF THIN SECTION 186 APPENDIX D - CORE ANALYSIS DATA 190 vii LIST OF FIGURES Figure 2.1. Map illustrating Doig penetrations within pools of the study area and cross-section locations 7 Figure 2.2. Stratigraphic framework for the study area 9 Figure 2.3. Facies associations within the Doig Formation at West Stoddart and Buick Creek 13 Figure 2.4. Section A-A' through West Stoddart field oriented parallel to depositional dip 15 Figure 2.5. Section B-B' through Fireweed, Cache Creek and West Stoddart fields, oriented perpendicular to depositional dip 15 Figure 2.6. Section C-C through Buick Creek field oriented perpendicular to depositional dip 17 Figure 2.7. Total Doig sand isopach within the study area 17 Figure 2.8. Core photographs of Facies 1a, 1c, 2a and 2b 18 Figure 2.9. Core photographs of Facies 2c, 2e and 2f 18 Figure 2.10. Sedimentary features in core photographs of the sandstone and bioclastic lithofacies 24 Figure 2.11. Sedimentological model for the Doig Formation at West Stoddart, Cache Creek and Fireweed fields, northeastern British Columbia 26 Figure 2.12. Dipmeter log through interpreted channel sandstones of the Cache Creek field 29 Figure 2.13. Structural elements intersecting the regional Doig sand trend 33 Figure 2.14. Structure contour map of the top of the Doig Formation upper phosphatic marker 34 Figure 2.15. Doig Formation isopach within the study area 36 Figure 2.16. Stratigraphic Section D-D' located in Fig 7 37 Figure 2.17. 3D seismic line showing middle Triassic growth fault at down-dip edge of the Fireweed delta complex 39 viii Figure 3.1. Location map of the study area showing the reservoir trend 48 Figure 3.2. Stratigraphic framework for the study area 50 Figure 3.3. Total Doig sand isopach within the study area 53 Figure 3.4. Core photographs of calcite cements in Doig Formation sandstone 56 Figure 3.5. Photomicrographs and SEM images of diagenetic phases in Doig Formation sandstones 58 Figure 3.6. Photomicrographs and core images of diagenetic features within Doig Formations sandstones 60 Figure 3.7. Generalized paragenetic sequence and porosity evolution of Doig Formation sand bodies 62 Figure 3.8. Fracture styles in Doig Formation sandstones..... 64 Figure 3.9. Core image and photomicrograph of compaction features 64 Figure 3.10. Graphs of core analysis data versus true vertical depth for various Doig pools 71 Figure 3.11.