Depositional Environment and Reservoir Characterization of the Paleocene Fort Union Formation, Washakie Basin, Southwest Wyoming, U.S.A
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DEPOSITIONAL ENVIRONMENT AND RESERVOIR CHARACTERIZATION OF THE PALEOCENE FORT UNION FORMATION, WASHAKIE BASIN, SOUTHWEST WYOMING, U.S.A. by Matthew John Bircher A thesis submitted to the Faculty and 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: ____________________ Matthew J. Bircher Signed: ____________________ Dr. John B. Curtis Thesis Advisor Golden, Colorado Date ___________________ Signed: ____________________ Dr. Paul Santi Professor and Head Department of Geology and Geological Engineering ii ABSTRACT Recent horizontal wells in the Washakie Basin of Southwestern Wyoming have targeted liquids-rich fluvial sandstones within the Paleocene China Butte Member of the Fort Union Formation. Deposition was in alternating meandering and braided fluvial successions which created complex reservoir compartmentalization and depositional heterogeneity. Liquid-rich hydrocarbons migrated from deeper source rocks or were generated from in situ interbedded coals. Four slabbed cores were described to determine relationships between facies, wireline log data, and quantitative core data. Generally, cross-stratified and coarser-grained active channel fill facies correspond to higher quality reservoir. Minor or abandoned channel fill facies are generally finer-grained, clay and shale rich, and produce lower quality reservoirs. Locally, abrupt contacts between channel sands indicate uninterrupted channel migration and deposition. Floodplain deposits are abundant and comprised of mudrocks, carbonaceous shales, and coals. Floodplain facies overlie levee deposits, and are subsequently overlain by younger channel fill deposits associated with channel migration. In some stratigraphic intervals, amalgamated sands with sparse interfluve sediments are associated with periods of lower-sinuosity, or braided fluvial deposition. X-ray diffraction, scanning electron microscopy, and thin section petrography analyses were performed on all reservoir facies. In decreasing quantities, detrital grains consist of quartz and feldspar grains, with chert, metamorphic, and argillaceous rock fragments. Reservoir sandstones are well-consolidated, moderately sorted, medium to coarse-grained, subfeldspathic to feldspathic litharenites, sub-litharenites, and litharenites. Metamorphic, iii plutonic, and sedimentary grains and rock fragments indicate variable clastic sources most likely originating from the Uinta and Wind River Mountains. Fort Union sands were most certainly deposited by alternating cycles of high-sinuosity meandering and braided stream processes. Channel, channel margin, and floodplain facies are identified in wireline logs and cores, and are typical of high-sinuosity fluvial deposition. Pervasive coal deposition indicates prolonged hiatus between established and confined fluvial channels. Local carbonaceous shales are composed of Type III organic matter and source primarily gas within the system. Evidence for in-place liquid-hydrocarbons are Type II kerogen and fluorescence in coals. Deeper Type II source rocks in the Cretaceous Almond and Lewis Formations may also be volumetrically contributing liquid hydrocarbons to the system via fractures and fault systems. iv TABLE OF CONTENTS ABSTRACT……………………………………………………………………………………...iii LIST OF FIGURES……………………………………………………………………………...xii LIST OF TABLES………………………………………………………………………………………xviii ACKNOWLEDGMENTS………………………………………………………………………………..xix CHAPTER 1 INTRODUCTION…………………………………………………………………………...1 1.1 Purpose and Scope……………………………………………………………………………………...5 1.2 Regional Geological Setting……………………………………………………………………………5 1.3 Location of Study Area………………………………………………………………………………...7 1.4 Research Objectives……………………………………………………………………………………7 1.5 Data Set and Methods…………………………………………………………………………………..7 1.6 Previous Research and Analogue Depositional Model………………………………………………...9 1.6.1 USGS Lower Tertiary Correlations and Nomenclature……………………………….......9 1.6.2 Jonah Field Cretaceous Lance Deposition……………………………………………….10 1.6.3 Big Horn Basin Fort Union Deposition………………………………………………….10 1.6.4 Sand Wash Basin Fort Union Deposition………………………………………………..10 1.6.4.1 Lithofacies………………………………………………………………………13 1.6.4.2 Sand Wash Basin Depositional Trends………………………………………….14 1.6.4.3 Depositional Environment………………………………………………………14 1.6.4.4 Powder Wash Field……………………………………………………………...15 1.7 Fort Union Production History…………………………………………………………………..........15 1.7.1 Washakie Basin…………………………………………………………………………..16 1.7.2 Sand Wash Basin…………………………………………………………………….......17 v 1.8 Summary………………………………………………………………………………………............17 CHAPTER 2 GENERAL WASHAKIE BASIN FORT UNION FORMATION STRATIGRAPHY……18 2.1 Methodology……………………………………………………………………………………..........18 2.2 Keystone Stratigraphy…………………………………………………………………………….......18 2.2.1 Tertiary China Butte Member………………………………………………………........18 2.2.2 Cretaceous Red Rim Member……………………………………………………………21 2.3 Summary…………………………………………………………………………………………........21 CHAPTER 3 FORT UNION FORMATION CORE DESCRIPTIONS AND FACIES DEFINITIONS...25 3.1 Methodology……………………………………………………………………………………..........25 3.2 Facies Analysis and Core Descriptions………………………………………………………….........26 3.2.1 Samson Resources Barricade #33-12…………………………………………………….26 3.2.1.1 Facies A – Siltstone and Very Fine-Grained Sandstone ………………………..26 3.2.1.2 Facies B – Sandstone Very Fine-Grained ………………………………………26 3.2.1.3 Facies C – Mudstone………………………………………………….................26 3.2.1.4 Facies D – Coal………………………………………………………………….29 3.2.1.5 Facies E – Carbonaceous Shale…………………………………………………29 3.2.1.6 Facies F – Sandstone Medium-Grained ………………………………………...29 3.2.1.7 Facies G – Sandstone Medium-Grained and Cross-Stratified ………………….29 3.2.1.8 Facies H – Sandstone Medium-Grained.………………………………………..35 3.2.2 Samson Resources Endurance #44-29 Core #1………………………………………….35 3.2.2.1 Facies 1A – Silt-Mudstone……………………………………….......................35 3.2.2.2 Facies 1B – Carbonaceous Shale………………………………………………..35 3.2.2.3 Facies 1C – Sandstone Fine-Grained and Burrow Mottled ………………….....35 3.2.2.4 Facies 1D – Mudstone………………………………………………..................40 vi 3.2.2.5 Facies 1E – Sandstone Lower Medium-Grained ……………………………….40 3.2.2.6 Facies 1F – Sandstone Fine-Grained …………………………………………...40 3.2.2.7 Facies 1G – Sandstone Medium-Grained and Cross-Stratified ………………...40 3.2.2.8 Facies 1H – Sandstone Coarse-Grained …………………………………….......40 3.2.2.9 Facies 1I – Sandstone Medium-Grained Cross-Stratified....……………………40 3.2.2.10 Facies 1J – Sandstone Fine-Grained.…………………………………………....46 3.2.2.11 Facies 1K – Sandstone Medium-Grained With Contorted Bedding ……………46 3.2.2.12 Facies 1L – Silt-Mudstone……………………………………............................46 3.2.3 Samson Resources Endurance #44-29 Core #2………………………………………….46 3.2.3.1 Facies 2A – Mudstone………………………………………………..................46 3.2.3.2 Facies 2B – Silt-Mudstone……………………………………............................46 3.2.3.3 Facies 2C – Mudstone………………………………………………..................53 3.2.3.4 Facies 2D – Carbonaceous Shale………………………………………………..53 3.2.3.5 Facies 2E – Siltstone………………………………………………….................53 3.2.3.6 Facies 2F – Sandstone Medium-Grained ……………………………………….53 3.2.4 Samson Resources Endurance #44-29 Core #3………………………………………….53 3.2.4.1 Facies 3A – Mudstone………………………………………………..................53 3.2.4.2 Facies 3B – Sandstone Very Fine-Grained …………………………………......59 3.2.4.3 Facies 3C –Siltstone………………………………………..................................59 3.2.4.4 Facies 3D – Sandstone Fine-Grained and Cross-Stratified.………………….....59 3.2.4.5 Facies 3E – Carbonaceous Shale……………………………………..................59 3.2.4.6 Facies 3F – Sandstone Medium-Grained Laminated...........…………………….59 3.2.4.7 Facies 3G – Sandstone Medium-Grained and Cross-Stratified ………………...59 3.3 Facies Associations……………………………………………………………………………….......65 3.3.1 Active Fluvial Channel Fill………………………………………………………………65 3.3.2 Abandoned Channel Fill…………………………………………………………………65 vii 3.3.3 Channel Margin………………………………………………………………………….70 3.3.3.1 Levee…………………………………………………………………………….70 3.3.3.2 Crevasse Splay…………………………………………………………………..70 3.3.4 Floodplain Deposits……………………………………………………………………...72 3.3.4.1 Mud Rock……………………………………………………………………….72 3.3.4.2 Carbonaceous Shale……………………………………………………………..72 3.3.4.3 Coal……………………………………………………………………………...74 3.4 Relationships in Facies, Measured Core Data, and Open-hole Log Data…………….........................74 3.5 Depositional Environment……………………………………………………………….....................77 3.6 Summary…………………………………………………………………………………………........77 CHAPTER 4 FORT UNION FORMATION FACIES PETROGRAPHY AND MINERALOGY............79 4.1 X-Ray Diffraction (XRD) Analysis……………………………………………………………...........79 4.2 XRD Results……………………………………………………………………………………..........79 4.2.1 Barricade #33-12………………………………………………………………………....79 4.2.2 Endurance #44-29………………………………………………………………………..79 4.2.3 Barricade #21-11…………………………………………………………………............81 4.3 Scanning Electron Microscope (SEM) Analysis………………………………………………….......81 4.4 SEM Results……………………………………………………………………………………..........81 4.4.1 Barricade #33-12………………………………………………………………………....81 4.5 Petrographic Methods…………………………………………………………………………............81 4.6 Petrographic Descriptions……………………………………………………………………….........83 4.6.1 Facies H………………………………………………………………………………….83 4.6.2 Facies G………………………………………………………………………………….84 4.6.3 Facies F…………………………………………………………………………………..84 4.6.4 Facies 1K………………………………………………………………………………...85 viii 4.6.5 Facies 1J……………………………………………………………………………….....85