Muddy Sandstone

Northern Powder River Basinof the

Depositional systemsof the Lower Cretaceous

Muddy Sandstone of the Northern Powder River Basin Overview

GeoDigital Information's study of the Muddy Sandstone of the Northern Powder River Basin examines the stratigraphy, sedimentology, petrography, and oil and gas potential of the Muddy Sandstone in the northern part of the Powder River Basin. This area covers approximately 231 townships and more than 8,300 square miles. The study, representing six man-years of geologic research, provides the explorationist with a chronostratigraphic framework for the lower Cretaceous Thermopolis, Muddy, Shell Creek, and Mowry formations. Also included in the study is a sedimentologic and reservoir characterization analysis of valley-fill deposits.

LOWER CRETACEOUS STATIGRAPHIC FRAMEWORK - The Lower Cretaceous stratigraphy of the Powder River Basin consists of, in ascending order, the Cloverly and Lakota formations, Thermopolis Shale, Muddy Sandstone, Shell Creek Shale, and Mowry Shale. Seventeen formation tops or bentonite marker beds including seven members of the Muddy Sandstone were correlated and mapped throughout the study area. Regional cross sections tie stratigraphic intervals throughout the study area of the Powder River Basin.

Although rarely greater than 100 feet thick throughout most of eastern and central Wyoming, GDI subdivided the Muddy Sandstone into seven mappable, chronostratigraphic members, which are bounded by bentonite beds or unconformities. This chronostratigraphic methodology facilitated mapping of time-bounded lithofacies sequences and reconstruction of paleogeography through time. Of greatest importance was the recognition and mapping of a complex paleovalley system and marine shoreline trends within the northern part of the Powder River Basin.

Exploration interest in the northern portion Powder River Basin was generated by numerous discoveries. The play consists of fluvial/estuarine valley-fill deposits. GDI's analysis of the stratigraphy, sedimentology, and petrographic characteristics is designed to assist exploration and production geologists in understanding the complex stratigraphic relationships, fluvial/estuarine valley-fill geometries, diagenetic history, and hydrocarbon production within the trend. The study discusses the potential for other valley-fill and marine shoreline trends throughout the northern part of the Powder River Basin.

Database

3,092 - Study Wells

7,637 - Wells with Shows, Core Footages, Production

17 - Regional Stratigraphic Markers Correlated

164 - Cores Described

215 - Thinsections

58 - Outcrops Measured

545 - DST Samples Examined - Horner Plots

Maps

Regional Maps (1:250,000) (1:96,000)

Isopach Maps

Net Sandstone Map

Structure Map

Study well Map

Field Maps (1:24,000)

Isopach Maps

Net Sandstone Maps

Structure maps

Cross Sections

5 - Regional Stratigraphic Sections 22 - Field Cross Sections

Field Studies

Ute-Olmstead, Amos Draw-Elk Draw, Collums-Morse, Store-Oedekoven-Carson, Kitty

Report Contents

TEXT AND FIGURES - An extensively illustrated report includes discussions, figures, and color plates on: Executive Summary, History of Study, Depositional Facies, Stratigraphy, Petrography, Depositional Setting, Modern Analogs, Field Studies, Hydrodynamics, Synthesis, and Exploration Potential.

CORE AND OUTCROP DESCRIPTIONS -This appendix contains descriptions of 164 cores from the study area. It also contains descriptions of 58 outcrop localities along the margins of the Powder River Basin.

STRATIGRAPHIC DATA - This file contains the stratigraphic data (17 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 3092 study wells.

MAPS AND CROSS SECTIONS - This appendix contains regional maps and field study maps. This includes isopach maps, structure maps, net sandstone maps, and a study well map. Also included are 27 Regional and Field cross sections.

CROOK

WESTON

CAMPBELL

JOHNSON

WYO

MIN

G

SO

UTH

D

AKO

TA

Gillette

Muddy Sandstonesof the Northern Powder River Basin

MONTANA

POWDERRIVER CARTER

SHERIDAN

BIG HORN

ROSEBUD

Sheridan

Buffalo

MILES

240 N

Study Boundary

R 40 ET6S

R 59 ET6S

R 67 WR 82 W

T50N

T50N

StudyTable of Contents

Muddy Sandstones

Powder River Basinof the Northern

TABLE OF CONTENTS

Page

Preface Table of Contents ……………………………………………………….. ii List of Maps ………………………………………………………………. vi

List of Cross Sections ………………………………………………….. viii Acknowledgements …………………………………………………….. ix

Executive Summary

Executive Summary …………………………………………………….………... E-1

Chapter 1 Introduction ………………………………………………………………………. 1-2 General Stratigraphy ………………………………………….………… 1-2 Scope .……………………………………………………………………. 1-3 Procedures ………………………………………………………………. 1-3

Muddy-Penetrating Wells ……………………………………… 1-3 Study Wells ……………………………………………………... 1-4 Measured Outcrop Sections ………………………………….. 1-4 Cores ……………………………………………………………. 1-4 Petrography …………………………………………………….. 1-4 Computer Database …………………………………………… 1-5 Downhole Picks ………………………………………………… 1-5 Muddy Member Picks ………………………………………….. 1-5 Field Studies ……………………………………………………. 1-6 Regional Maps …………………………………………………. 1-6 Regional Cross Sections ……………………………………… 1-7

Chapter 2 History of Study - Previous Investigations ……………………………………. 2-2 Nomenclature …………………………………………………………… 2-3 Evolution of Environmental Interpretations …………………………... 2-6

Chapter 3 Depositional Facies and Facies Sequences ………………………….……… 3-2 Open-Marine Facies ……………………………………………………. 3-2 Open-Marine Shale ……………………………………………. 3-3 Transition Zone ………………………………………………… 3-4 Shoreface………………………………………………………… 3-5 Moderate-Wave-Energy Shoreface …………………. 3-5

ii

Depositional Facies and Facies Sequences (continued) Lower Shoreface ……………………………… 3-5 Middle Shoreface ……………………………... 3-6 Upper Shoreface ……………………………… 3-7 Low Wave-Energy Shoreface ………………………… 3-8

Estuarine Facies ………………………………………………………… 3-8 Bayfloor Muds …………………………………………………… 3-9 Fringing Sandstone …………………………………………….. 3-10 Swamps and Marshes ………………………………………… . 3-11 Tidal Channels ………………………………………………….. 3-11 Fluvial Facies ……………………………………………………………. 3-12 Channel Deposits ………………………………………………. 3-12 Flood-Basin Deposits ………………………………………….. 3-14 Unconformities ………………………………………………………….. 3-14 Skull Creek Unconformity ……………………………………... 3-14 Rozet Unconformity ……………………………………………. 3-16 Criteria Facilitating Recognition of Rozet Unconformity ………………………….……. 3-16 Color Change and Kaolinization …………….. 3-16 Log Response to Kaolinized Horizon ………. 3-17 Siderite Concretions …………………. 3-17 Deep Penetration by Roots …………. 3-17 Relationships Between the Two Muddy Unconformities …………………………….. 3-18

Chapter 4 Stratigraphy of Muddy Members ……………………………………………….. 4-2 Rozet Member …………………………………………………………… 4-3 Lower and Upper Recluse Members ………………………………….. 4-7 Cyclone Member ………………………………………………………… 4-9 Ute Member ……………………………………………………………… 4-11 Springen Ranch Member ………………………………………………. 4-13

Chapter 5 Petrography ………………………………………………………………………… 5.1 Procedures ………………………………………………………………… 5.1 General Description of the Subsurface Sandstones ………………….. 5.9 Authigenic Constituents …………………………………………. 5.15 General Description of Outcrop Samples ………………………………. 5.52

Diagenetic History of the Muddy Formation ………………………… 5-xx Previous Petrographic Studies …………………………………………… 5.61 Lithological Variations in the Muddy Formations ………………………. 5.62 Variation in Porosity in the Muddy Formation ………………………….. 5.66 Effects of Authigenic Minerals on Geophysical-Log Response ………………………………………….. 5.76

iii

Chapter 6 Depositional Setting ……………………………………………………………… 6.1 Tectonic Setting …………………………………………………………. 6.1 Sea Level ………………………………………………………………… 6.7 Hydrographic Regime …………………………………………………… 6.11 Waves and Currents ……………………………………………. 6.11 Tidal Range ……………………………………………………… 6.14 Salinities …………………………………………………………. 6.15

Chapter 7 Modern Analogs ………………………………………………………………….. 7.1 Port Lavaca Area, Texas ……………………………………………….. 7.1 Modern-Ancient Comparisons …………………………………………. 7.12

Chapter 8 Studies of Selected Oil and Gas Fields ………………………………………… 8.1 Collums-Morse Area ……………………………………………………… 8.2 Rozet Member ……………………………………………………. 8.3 Ute Member……………………………………………………….. 8.3 Trapping Mechanisms …………………………………………… 8.5 Oedekoven-Store Area …………………………………………………… 8.8 Lower and Upper Recluse Members …………………………… 8.9 Cyclone Members ………………………………………………… 8.9 Trapping Mechanisms …………………………………………… 8.12 Ute-Olmstead Area ……………………………………………………….. 8.15 Rozet Member ……………………………………………………. 8.16 Ute Member ………………………………………………………. 8.17 Trapping Mechanisms …………………………………………… 8.17 Amos-Draw - Elk Draw Area ………………………………..…………… 8.19 Rozet Member ……………………………………………………. 8.22 Trapping Mechanisms …………………………………………… 8.24 Kitty Field Area ……………………………………………………………. 8.25 Rozet Member ……………………………………………………. 8.26 Upper Recluse Member …………………………………………. 8.27 Cylcone Member …………………………………………………. 8.27 Ute Member……………………………………………………….. 8.30 Trapping Mechanisms …………………………………………… 8.33

Chapter 9 Hydrodynamics ………………………………………………………………….… 9.1 Scope………………………………………………………………………. 9.1 Procedures ………………………………………………………………… 9.2 Computer Database ……………………………………………... 9.2 Horner Plots ……………………………………………………… 9.2 Elimination of Data ………………………………………………. 9.6

iv

Hydrodynamics (continued) Hydrodynamic Characteristics of the Muddy Sandstone ……………. 9.6 Fluid Pressures ………………………………………………….. 9.7 Delta P Map ……………………………………………………… 9.30 Synopsis ………………………………………………………………….. 9.32 Additional References Cited ……………………………………………. 9.34

Chapter 10 Synthesis …………………………………………………………………………… 10.1 Muddy Depositional History ……………………………………………... 10.1 Skull Creek Regression and Unconformity …………………… 10.1 Evidence of Movement of Basement Faults in Early Muddy Time ……………………………………………. 10.4 Pre-Rozet Transgression ……………………………………….. 10.6 Rozet Member …………………………………………………… 10.9 Rozet Unconformity …………………………………….. 10.10 Basement Structures and Shape of the Recluse Valley ……………………………………………….. 10.11 Post-Rozet Transgression ……………………………………… 10.15 Lower Recluse Member ……………………………….. 10.15 Upper Recluse Member ………………………………… 10.15 Cyclone and Ute Members …………………………….. 10.16 Springen Ranch Member ………………………………. 10.17 Shell Creek-Mowry Transgression ……………………. 10.17 Types of Muddy Stratigraphic/Diagenetic Traps ……………………… 10.20 Strandplain Sandstones ………………………………………… 10.20 Barrier-Strandplain Sandstones ………………………. 10.21 Tidal Channel Sandstones ……………………………………… 10.21 Bayhead Delta Sandstones …………………………………….. 10.22 Fluvial-Channel Sandstones ……………………………………. 10.22 Applications in Oil and Gas Exploration ………………………………... 10.23 Rozet Member ……………………………………………………. 10.23 Lower and Upper Recluse Members …………………………… 10.24 Cyclone Member …………………………………………………. 10.27 Ute Member ………………………………………………………. 10.30 Springen Ranch Member ………………………………………... 10.30

Bibliography

Bibliography ………………………………………………………………………… B1

v

LIST OF MAPS

Regional Maps-1:96,000

Penetration Map (1-4) Structure Top of Shell Creek Shale (1-4) Total Muddy Isopach (1-4) Interval Isopach of Dakota Silt 1 to Top of Skull Creek Shale (1-4) Interval Isopach of Rozet Unconformity to Top of Muddy (1-4) Rozet Member Isopach (1-4) Rozet Member Gross Sandstone Isopach (1-4) Rozet Member Net Porous Sandstone Isopach (1-4) Upper and Lower Recluse Member Isopach (1-4) Upper and Lower Recluse Member Gross Sandstone Isopach (1-4) Upper and Lower Recluse Member Net Porous Sandstone Isopach (1-4) Cyclone Member Isopach (1-4) Cyclone Member Gross Sandstone Isopach (1-4) Cyclone Member Net Porous Sandstone Isopach (1-4) Ute Member Isopach (1-4) Ute Member Gross Sandstone Isopach (1-4) Ute Member Net Porous Sandstone Isopach (1-4) Springen Ranch Member Isopach (1-4) Springen Ranch Member Gross Sandstone Isopach (1-4) Springen Ranch Member Net Porous Sandstone Isopach (1-4)

1:250,000

Total Shell Creek Shale Isopach Total Mowry Shale Isopach Interval Isopach of Dakota Silt 1 to Skull Creek Unconformity

Field Maps - 1:24,000

Amos Draw Field Area--Structure Top of Muddy Amos Draw Field Area--Rozet Member Isopach Amos Draw Field Area--Rozet Member Gross Sandstone Isopach Amos Draw Field Area--Rozet Member Net Porous Sandstone Isopach Collums-Morse/Oedekoven-Store Field Areas--Structure Top of Muddy Collums-Morse/Oedekoven-Store Field Areas--Rozet Member Isopach Collums-Morse/Oedekoven-Store Field Areas--Rozet Member Gross

Sandstone Isopach Collums-Morse/Oedekoven-Store Field Areas--Rozet Member Net

Porous Sandstone Isopach

vi

Field Maps - 1:24,000 (continued) Collums-Morse/Oedekoven-Store Field Areas--Upper and Lower Recluse Member Isopach Collums-Morse/Oedekoven-Store Field Areas--Upper and Lower Recluse Member Gross Sandstone Isopach Collums-Morse/Oedekoven-Store Field Areas--Upper and Lower Recluse Member Net Porous Sandstone Isopach Collums-Morse/Oedekoven-Store Field Areas--Cyclone Member Isopach Collums-Morse/Oedekoven-Store Field Areas--Cyclone Member Gross Sandstone Isopach Collums-Morse/Oedekoven-Store Field Areas--Cyclone Member Net Porous Sandstone Isopach Collums-Morse/Oedekoven-Store Field Areas--Ute Member Isopach Collums-Morse/Oedekoven-Store Field Areas--Ute Member Gross Sandstone Isopach Collums-Morse/Oedekoven-Store Field Areas--Ute Member Net Porous Sandstone Isopach Kitty Field Area--Structure Top of Muddy (North and South) Kitty Field Area--Rozet Member Isopach (North and South) Kitty Field Area--Upper Recluse Member Isopach (North and South) Kitty Field Area--Upper Recluse Member Gross Sandstone Isopach (North and South) Kitty Field Area--Upper Recluse Member Net Porous Sandstone Isopach (North and South) Kitty Field Area--Cyclone Member Isopach (North and South) Kitty Field Area--Cyclone Member Gross Sandstone Isopach (North and South) Kitty Field Area--Cyclone Member Net Porous Sandstone (North and South) Kitty Field Area--Ute Member Isopach (North and South) Kitty Field Area--Ute Member Gross Sandstone Isopach (North and Soutb) Kitty Field Area--Ute Member Net Porous Sandstone (North and South) Ute Field Area--Structure Top of Muddy Ute Field Area--Rozet Member Isopach Ute Field Area--Rozet Member Gross Sandstone Isopach Ute Field Area--Rozet Member Net Porous Sandstone Isopach Ute Field Area--Ute Member Isopach Ute Field Area--Ute Member Gross Sandstone Isopach Ute Field Area--Ute Member Net Porous Sandstone Isopach

vii

LIST OF CROSS SECTIONS

Regional

BFJM DEFGH CEI IJK AGKL

Field

Amos Draw D'E'H'L'P' Amos Draw G'H'I' Amos Draw B'C'G'Q' Amos Draw A'C'E'F' Amos Draw J'L'M'N' Amos Draw K'M'0'

Collums-Morse A'C'E' Collums-Morse B'C'D'

Kitty A'C'E'G'H'J'K' Kitty D'E'S'T' Kitty F'G'Q'R' Kitty M'J'N' Kitty L'0'H'Q'S'U'V'X' Kitty A'X` Kitty B'C'U'V'W' Kitty I'0'P'

Oedekoven-Store A'E'F'G'H'I'J'K'L' Oedekoven-Store B'F'E'M' Oedekoven-Store C'H'G'N' Oedekoven-Store D'K'J'I'0'

Ute A'C'E' Ute B'C'D'

viii

Selected Figuresfrom the Study

Muddy Sandstones

Powder River Basinof the Northern

Return to Text

Figure 1.7. Representative log showing the stratigraphic picks made in this study. Picks and associated stratigraphic information, including gross-sandstone and net-porous-sandstone thicknesses, are presented in Appendix 3 Muddy Study Wells-Stratigraphic Picks. The methodologies used in determining thicknesses of gross and net porous sandstone are also described there.

Figure 3.3. Map view, cross section, and vertical sequence of a modern prograding barrier island environment and associated facies, Galveston Island (modified from Bernard and others, 1970).

Return to Text Page 3-3 Return to Text Page 3-5 Return to Text Page 6-5

Return to Text

Figure 3.52. Beds of carbonaceous shale and coal are common in both bay-fill and flood-basin deposits. The carbonaceous shale pictured here occurs within bay-fill muds of the Ute Member at Scoggin Draw (NW NE sec. 11, T 57 N, R 63 W) locally and can be traced for several miles along the outcrops.

Return to Text

Figure 3.86. Core of the Rozet Member in Elk Draw Fed. C 5-6, NW SW sec. 6, T 51 N, R 75 W, 9970-9955 feet, showing upward change in color from dark gray to light gray and tan. This color change is typical of shoreface sandstone of the Rozet and is the result of weathering beneath the younger Muddy unconformity. Top of core is at upper left, bottom at lower right. The core has been rearranged in the boxes so as to run continuously from top to bottom of the photo. The black shale at the top of the core represents the basal beds of the Ute Member. The basal, unconformable contact between the Rozet Member and the Skull Creek Shale was not cut in this core.

Example of a Core Description

Example of a Measured Outcrop Section