BLACKFEET RESERVATION ? List of Topics
BACKGROUND � Overview of Reservation � Production Overview
GEOLOGIC OVERVIEW � Geologic History � Summary of Play Types
CONVENTIONAL PLAY TYPES � Play 1 - Fracture/Folded Anticline Mississippian Carbonate � Play 2 - Jurassic/Cretaceous Sandstone Play � Play 3 - Devonian/Mississippian Carbonate Play � Play 4 - Montana Disturbed Belt - Imbricate Thrust
UNCONVENTIONAL / HYPOTHETICAL PLAY TYPES � Play Types 5,6,7 - Bakken, Cambrian Sandstone, and Biogenic Gas Plays
REFERENCES three provinces, only the Sweetgrass Arch has received more than a very limited OVERVIEW Petroleum Exploration and Development amount of exploration. BLACKFEET INDIAN RESERVATION � The first commercial oil discovery in Montana was made in the spring of � The Disturbed/Overthrust Belt is a zone of northerly, closely-spaced, sub Blackfeet Nation 1903 in the Swift Current Valley, just west of the Reservation in what is now parallel thrust faults and folds with some known normal faults. The large scale Glacier National Park (Darrow, 1955). This discovery was made by a prospector structural dislocation of these sub-parallel thrust faults may result in older named Sand D. Somes who was looking for copper ore in the Swift Current reservoir rocks overlying younger source rocks, or in the fracturing of source TRIBAL HEADQUARTERS:� Browning, Montana Valley, now covered by the water of present day Sherburne Lake near Many rocks to create a reservoir. This geologic province extends from the Brooks GEOLOGIC SETTING:� � Southern Alberta Basin Glaciers Lodge (Douma, 1953). His interest in oil developed in 1902 when he Range in Alaska southward to Central America. In Alberta, Canada this belt found pools of oil when cleaning out his workings after blasting. This early contains a number of large fields including Pincher Creek and Waterton Lakes. General Setting production came from a depth of 500'. By 1906, twelve wells had been drilled, There is limited production of oil and gas from the Disturbed Belt portion of the � The Blackfeet Reservation is located in northwestern Montana and includes six of which produced oil (Darrow, 1955). The best oil well, completed during Reservation near East Glacier. The primary reservoir rocks in this region would most of Glacier County. On the north it borders the Canadian Province of the spring of 1906, had an initial production of 60 barrels of oil per day. be the Mississippian carbonates - limestones and dolomites - which are Alberta. On the west it shares a border with Glacier National Park. The Badger Although production from this oil field was short lived, it marked the beginning productive to the south of the Reservation at the Blackleaf Canyon Field. Other Two Medicine portion of the Lewis and Clark National Forest borders on the of the petroleum industry in Montana. potential reservoirs would include the sands of the Cretaceous and the carbonates southwest. Other natural boundaries include Birch and Cut Bank Creeks. � Just off the Reservation’s eastern edge, along the west flank of the of the Devonian. Elevations vary from a low of 3400' in the southeast to a high of over 9000' at Sweetgrass Arch, random drilling led to the discovery of gas in 1926 and of oil in � The Foreland Basin is represented by a relatively undeformed wedge of Chief Mountain on the northwest boundary. 1929 (Chickering, 1958; Del Monte, 1958). By the early 1930’s, development Mesozoic and Paleozoic rocks that vary in thickness from approximately 5,000' � Major railroads and highways serving the Reservation include Burlington drilling had extended the known limits of this field onto the reservation. on the east to 14,000' on the west. Although the Cretaceous, Jurassic, and the Northern Railroad’s main east/west line. This is paralleled by U.S. Highway #2, � The Cut Bank Field, which extends from Townships 31 to 36 North, in Mississippian portions of the geological section have a high potential for oil and and is bisected by U.S. Highway #89 at Browning, the administrative center for Ranges 5 and 6 West, produced 164,499,336 barrels of oil through December gas production, the Devonian should also be considered as having significant the Reservation. Great Falls, Montana, an air traffic center, is approximately 125 1992 (Montana Oil and Gas Conservation Division, 1993), with annual undiscovered hydrocarbon potential. It is this Foreland Basin broad shelf that, miles to the southeast, and Calgary, Alberta, Canada is approximately 210 miles production of oil still over 740,000 barrels, and nearly 3 million cubic feet of gas. during the Devonian, was the site of the deposition of reef-type rocks and to the north. Approximately 25 percent of the Cut Bank Field area lies within the Reservation. sediments that have shown production to the north in the Alberta Basin. When production began to decline in the mid 1940’s due to the pressure decline Production from the Devonian section also occurs in the Kevin-Sunburst area of Mineral Ownership and Leasing of the solution gas drive (Chickering, 1958), secondary recovery operations were the Sweetgrass Arch. Although highly productive of oil and gas in Canada, � The Blackfeet Reservation contains 1,525,712 acres, with the mineral estates initiated. The secondary recovery methods used were chiefly waterfloods, which exploration for the Devonian on the Reservation has been insignificant. divided as follows. Approximately 41.8% of the minerals is tribally owned. resulted in an increase of production by the early 1950’s. The Montana Oil and � The Sweetgrass Arch portion of the Reservation contains most of the existing Another 31.3% is owned by allottees, and the remaining 26.9% is owned by fee Gas Annual Review for 1992 lists 11 secondary recovery projects in the Cut production. This production occurs in the clastic sediments of the Cretaceous owners. Bank Field. All of these are listed as waterfloods, with six of them listed as and Jurassic sections, and in the carbonates of the Mississippian. � A Mineral Assessment Program is currently operating under a three-year plan being idle. Oil and/or gas production is found in the following formations within � In contrast to the structurally complex Disturbed/Overthrust Belt, the to evaluate and further define the oil and gas potential of the Reservation. This the Cut Bank field area: Blackleaf, Bow Island, Dakota, Kootenai (Moulton, Sweetgrass Arch structure is controlled by the generally westward dipping flank program also assists the Tribe in the evaluation of new leasing, operating and Lander, Sunburst, and Cut Bank sands), and the Madison Group. So far, of the Sweetgrass Arch. The largest producing field, the Cut Bank Field, is the joint venture agreements. New leases, other mineral exploration, and secondary recovery operations have been limited to the Cut Bank sands, Lander result of a stratigraphic trap in the Kootenai Formation. Some localized development agreements are designed in accordance with the 1982 Indian sand and the Madison Formation. structural irregularities occurred along the west flank of the Sweetgrass Arch. Mineral Development Act, and the rules and regulations contained in 25 CFR. � Other oil and/or gas fields on or near the Reservation include Big Rock, Reagan Field is developed on one of these localized structural irregularities. Of Companies are welcome to negotiate with the Blackfeet Tribal Business Council Blackfoot Shallow Gas, Bradley, Little Rock, Blackfoot, East Glacier, Landslide the three geological provinces, only the Sweetgrass Arch has received more than for any type of lease or joint venture agreement which will satisfy both parties. Butte, and Reagan. Inactive or abandoned fields include Two Medicine Creek, limited exploration. However, even in this highly productive area of the and Blackfoot East. Cumulative production from these fields through 1992 is Sweetgrass Arch the full potential of the geologic section has not been Seismic Data 11,381,868 barrels of oil (Montana Oil and Gas Conservation Division, 1992 adequately tested. � Seismic data from past seismic surveys are available from several seismic Annual Review). Two of these fields, Blackfoot and Reagan, have active brokerage firms. The Tribe has purchased seismic data for some portions of the secondary waterfloods. Annual gas production plus associated gas produced CANADA Reservation and are in the process of reprocessing the data using technology of from these fields for 1992 was approximately 815,000 mcf. MONTANA today. Information on conducting new seismic operations can be obtained from � Only limited exploration and development drilling has taken place within the BLACKFEET Eureka Glacier the BIA or the Blackfeet Tribe. Reservation boundaries during the past ten years. The most recent drilling 15 � Most of the leases and other types of agreements currently in effect on the activity involves the use of horizontally drilled wells, by Unocal, in the Cut Bank 89 Toole 83 Reservation are in areas now under production. This leaves a large portion of the Airport Unit. The use of horizontal wells in conjunction with secondary recovery West Glacier Browning Shelby Reservation’s minerals available for leasing. methods should result in a higher percentage of the original oil in place being Whitefish East 2 Glacier recovered. 2 Liberty Kalispell Park Contact: Pondera Conrad Flathead Geology 87 � � Gary MadMan The Blackfeet Indian Reservation occupies a portion of the southern Alberta � FLATHEAD Choteau Ft. Benton � � Director, Minerals Department Basin. Tectonically, the area can be divided into three provinces: the Pelson Teton 287 � � Blackfeet Nation Disturbed/Overthrust Belt on the west, the Foreland Basin in the central portion, 93 89 Great Falls � � P.O. Box 639 and the Sweetgrass Arch on the east. The stratigraphy of the Reservation is 15 Cascade � � Browning, MT 59417 generally characterized by the clastic section of the Cretaceous-Jurassic and the Ravalli Bowmans Corner � Superior carbonates of the Mississippian-Devonian. On the Reservation, production exists Lewis � � TEL: (406) 338-5020 in formations within the Cretaceous, Jurassic, and the Mississippian. Of these and Wolf Creek Missoula Clark
Blackfeet Reservation index topics Montana �OVERVIEW map A L B E R T A Blackfoot Field Border/Red Coulee Reagan Darling EARLY EXPLORATION ON THE G L A C I E R BLACKFEET RESERVATION PRODUCING HORIZON LEGEND 37 S = Source Rock 11 10 9 8 7 6 5 Approximate WESTERN & COLOR WILLISTON POWDER RIVER WESTERN WYOMING � Oil and gas was discovered in Montana in the late 19th CODE NORTHERN ERA BASIN BASIN 36 SOUTHERN MONTANA
SERIES MONTANA SYSTEM Sharp century as oil seeps, in what is now Glacier National Park. The White River 35 first Montana well in this area was drilled in October of 1901, and Green River D I S T U R B E D Wind River achieved a depth of 1450 feet in 1902. Gas was flared from a Wasatch G Cutbank Wasatch L A C I "sand unit" at a depth of 720 feet. TERTIARY 34 E R CENOZOIC Fort Union Fort Union Fort Union Surface Fort Union 750 Kevin-Sunburst � Swift Current Valley was the scene of the first commercial oil N A T I O N A L East Lance Lance Hell Creek production in 1902. Early copper prospectors, among them Sand Teckla 33 Fox Hills Fox Hills Judith River S 0 1000 Mesaverde -1000 250 500 Clagget -250 D. Soomes, is credited with the discovery of oil seeps during Judith River Teapot Mesaverde Browning 2250 Cody Eagle -500 mining operations. By 1906, the field had six producing wells. Eagle Parkman Telegraph Creek 1750 UPPER Sussex Shannon Folds -750 Niobrara Limit Niobrara East Glacier 2000 With the establishment of Glacier National Park in 1910, oil Shannon Niobrara Greenhorn Greenhorn Niobrara Frontier Frontier Frontier 31 exploration was suspended. Two Medicine � Early exploration on the Sweetgrass Arch, to the east of the Dakota Group Mowry Mowry Blackleaf Underlain Muddy Bow Island P A R K CRETACEOUS Muddy Kootenai reservation culminated in gas and oil discoveries in the late Bear River 30 Dakota Cat Creek of Dakota LOWER Moulton 1920's. January 1931, heralded the discovery of Cutbank Field, Fall River Explanation Cloverly Sunburst S which is one of the largest in the Rocky Mountains. Twenty Lakota Cut Bank 29 Oil and Gas from Lewis Gannet P O 1250 DisturbedN percent of this "giant" field is within the reservation boundaries. Morrison Cretaceous Greenhorn by D E R Morrison Morrison Morrison OVERTHRUST FAULT Ellis Group Ellis Group Oil or Gas from Cretaceous 1500 � Exploration during the late 1920's led to the discoveries in the Sundance Sundance Swift Swift Gypsy Basin Highview Canyon Springs Kootenai Thrust Mississippian Madison with Pondera Field. Other discoveries Reirdon Stump-Preuss Reirdon Overthrust JURASSIC Piper Gypsum Spring Sawtooth Oil or Gas from Madison Teton County throughout the 1930's and 40's led to both Cretaceous and Twin Creek D Nesson U M E S O Z I C Nugget Reservation Boundary Belt Madison production. The 1950's saw a flurry of activity in the Chugwater Chugwater Montana disturbed belt which led to the discoveries of East Ankareh Structure on Top of Colorado Shale Blackleaf Thaynes Pondera Woodside Glacier/Two Medicine and Blackleaf Canyon. In 1980, Williams TRIASSIC Spearfish Spearfish Thrust Fault Fault Canyon 1000 Exploration and Milestone Petroleum tested the "A" Thrust Sheet Dinwoody D Normal Fault Faults 2500 U 2000 at Blackleaf Canyon and discovered gas with rates as high as 5.1 2250 Minnekahta High angle Reverse Fault MMcfd. Goose Egg Phosphoria
Opeche
Anticline PERMIAN Park City North Syncline Minnelusa Weber Figure BF-2.1. General structure map of reservation and surrounding region. Amsden Minnelusa Tensleep Amsden NEARBY FIELDS Amsden 1956 Blackfoot - 1.6 MMBO, 3.0 MMcf, 8 wells oil, 7 wells gas Tyler Darwin Tyler 1958 Graben Coulee - 2.4 MMBO, 63 wells oil PENNSYLVANIAN Big Snowy Group Big Snowy Group Heath 1958 Red Creek - 6.5 MMBO, 1.2 MMcf, 18 wells oil Heath GENERAL PRODUCTION INFORMATION Otter Madison Otter Kibbey Madison Kibbey 1954 Darling - 70,000 BO (Abn'd) Madison Group Madison Group Mission Canyon Sun River S 1929 Border - 497,000 BO, 346,000 Mcf, 1 well oil, 1 well gas Charles Charles U.S.G.S Geologic Province: � North Central Montana Mission Canyon Lodgepole
MISSISSIPPIAN Mission Canyon 1929 OId Border - 798,450 BO, 7 wells oil Lodgepole Englewood Lodgepole Tectonic Province: � � Sweetgrass Arch, Foreland Basin, 1954 Gypsy Basin - 504,783 BO, 3.1 MMcf, 4 wells total Bakken Three Forks Jefferson Jefferson Three Forks 1976 Highview - 101,477 BO, 741,600 Mcf, 7 wells total Nisku � � � � � Montana Disturbed Belt Nisku S 1958, 1980 Blackfeet Canyon- 33,748 BO, 7.0 MMcf, (Abn'd) Duperow Souris River Darby Duperow DEVONIAN Other small fields with no current production Dawson Bay Souris River Overall Production:� � 440 MMBO and 1.1 TCFG Winnipegosis from U.S.G.S. Play Production Province PLAY TYPES ENCOUNTERED Interlake Interlake
� � � SILURIAN No. of Fields:� � � 170 discovered fields Conventional Stonewall � 1) Fractured/Folded Anticline Mississippian Carbonate Play (2807) Big Horn Big Horn Red River
� � � � � 58 greater than 1 MMBO or 6 BCFG P A L E O Z O I C � 2) Jurassic-Cretaceous Sandstone Play (2808) Stony Mountain Red River � 3) Mississippian/Devonian Carbonate Play (2805) Winnipeg � 4) Montana Disturbed Belt-Imbricate Thrust Play (2701) ORDOVICIAN Fields Within Reservation Boundaries - (1995 Cummulative Production) Winnipeg Unconventional or Hypothetical Gallatin Emerson � 5) Fractured Bakken (2804) Deadwood Deadwood Gros Ventre � 1941 Reagan� � � � 9.3 MMBO, 15 MMcfd, 54 wells Flathead Flathead CAMBRIAN � 1955 Two Medicine� � � 9.3 MMBO, 15 MMcf, 54 wells � 6) Cambrian Sands (2802) � 7) Shallow Biogenic Gas (2810, 2811, 2812) Figure BF-2.2. Producing Horizon Legend (after Geomap Executive Reference � 1926, 1929 Cutbank � � � 167.3 MMBO, 317 MMcf Map,1983). � � (est. 20% within boundary)� � 447 wells oil, 235 wells gas
Blackfeet Reservation OVERVIEW index topics Montana Oil & Gas Production PAGE 2 of 13 map Figure BF-3.1. Present day structural Alberta Shelf CANADA 98 97 uplifts and basins, Fort Peck 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 99 Reservation and location of regional A Longitude Values (In Degrees) A' Hogeland Bowdoin Blackfeet Reservation East Dome UNITED STATES cross-section A-A' (modified after West BF Sweetgrass Arch Bearpaw Basin Uplift Peterson 1987). 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 Poplar 6000 Poplar FaultDome A Hinsdale Fault FP A'
Nesson Little Anticline Judith Rocky Mtns 5000 Mtns Blood NORTH Syncline Creek FORT Early Tertiary Intrusions Big Weldon-Brockton FaultCedar Creek BERTHOLD DAKOTA Bearpaw Uplift Little Snowy Anticline Belt Mtns Cat Creek Fault 4000 Mtns MONTANA Wheatland Summatra Williston Basin Little Rocky Mountains Syncline Porcupine Willow Creek Fault 3000 Dome Miles City Poplar Dome Crazy Bull Arch Mountains Mountains Basin STANDING 2000 Upper Cretaceous Lake Basin Fault ROCK Basin Rocks Nye-Bolwer Fault Powder Beartooth Mtns Tertiary Rocks Pryor 1000 Niobrara and Eagle Fort Union and Golden Valley Mtns. River
Yellowstone BIGHORN MTN 0 0 Bighorn Basin Snake Black SOUTH OVERTHRUST Absaroka River DAKOTA Upper Cretaceous Mtns Basin WYOMING Hills - 1000 Rocks - 1000 Elevation (in Feet) Lower Cretaceous Rocks Lower Cretaceous Owl Niobrara and Eagle Creek Laramie Uplift Mowry Kootenai Mtns Casper - 2000 - 2000 Wind RiverWind Mtns Arch Mtns. River
BELT Jurassic Rocks Basin Fault Choctaw Arch - 3000 IDAHO Casper Mtn - 3000 Sweetwater Jurassic Laramie Rocks Green Uplift Mississippian Rocks Hartville - 4000 Mtns Triassic Rocks - 4000 River Hanna Red Laramie NEBRASKA Basin - 5000 Desert Basin Basin Alliance Permian Rocks - 5000 Rock Devonian Rocks Medicine Basin Cambrian Rocks Springs Basin Uplift Bow Mtns Sands and Shales Sierra - 6000 UTAH - 6000 PreCambrian Rocks Uinta Mtns. Washake Madre Pennsylvanian Basin COLORADO Cambrian Rocks Rocks - 7000 Sweetgrass Arch Sands and Shales - 7000 Rocky Mountain Trench Mississippian Rocks EXPLANATION Overthrust Belt PRESENT DAY - 8000 - 8000 Anticline Bakken Shale Precambrian Basement Uplifts STRUCTURAL FEATURES - 9000 Syncline Rocky Mountain Region - 9000 Other Uplifts or Basins Devonian - 10,000 Rocks Cenozoic Volcanic Fields Faults Generalized X-Section A-A' - 10,000 Prairie Salt
A A' - 11,000 Present Day Structure Reservations Cross-Section Silurian Rocks - 11,000 Line of Section along 48 degrees of latitude with Cambrian Rocks Ordovician - 12,000 selected points every 1 degree of longitude. Sands and Shales Rocks - 12,000 Regional Geology longitude intervals. Datum : Sea Level Scale : 1 deg = about 50 miles The Blackfeet Reservation lies within three distinct geologic provinces, the - 13,000 Nesson � The western end of the section, near the Blackfeet Reservation is dominated Anticline - 13,000 Montana Disturbed Belt to the west, the Foreland Basin in the center, and the by high relief (greater than 5000 feet). The Cretaceous and older Paleozoic Williston Basin Sweetgrass Arch to the east (see tectonic map and structure cross-section A-A'). section is about 11,000 feet thick. Major basement uplifts, such as the Figure BF-3.2. Generalized cross-section A-A', present day structure. The Mesozoic section, composed of Cretaceous and Jurassic rocks is Sweetgrass Arch and Bearpaw Uplift, influenced sedimentation throughout predominatly sand and shale. The Paleozoic section is Mississippian and geologic time. Devonian in age and is mainly carbonates. The Cambrian section is mainly � The eastern side of the cross-section is dominated by the Williston Basin, a composed of coarse-grained clastics. stabel cratonic depocenter which has more than 15,000 feet of sediments. The � Proven hydrocarbon production (see correlation chart and type log), is mainly Fort Berthold Reservation is located near the depocenter and is within close from Lower Cretaceous Blackleaf and Kootenai sandstones, although some proximity to Nesson Anticline, a major oil producing structure. production is from Upper Cretaceous Greenhorn. Oil and gas is also produced Between these two tectonic provinces lie the Fort Peck and the Fort Belknap from Jurassic age Swift and Sawtooth sands. Paleozoic production is from the Reservations, Fort Peck is on the western flank of the Williston Basin and is Madison Sun River Dolomite and the Devonian Nisku. dominated by Poplar Dome, a Laramide age structure, while Fort Belknap is between Bowdoin Dome and Bearpaw Uplift. Geologic History � A paleo cross-section attempts to show what the subsurface geolgy may have A generalized structural cross-section (see cross-section A-A', Figure BF-3.2) looked like within that time interval. For the sake of space, only the particular summarizes present day tectonic provinces and older paleostructure. The cross- interval is shown; no rocks older than it are illustrated. The rock units above the section uses rock thickness values from each of the geologic periods. The section interval have not yet been deposited; the top of the section is the datum. The runs along the 48 degree latitude line and values were selected at one degree datum is flat, representing the paleo ground surface. Introduction Blackfeet Reservation index topics Montana Regional Geologic Overview PAGE 3 of 13 map Longitude Values (in degrees) West A A' East Blackfeet Reservation
114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 0 Cambrian Rocks PreCambrian Rocks Cambrian Rocks Sands and Shales 1000 Sands and Shales Sweetgrass Arch
2000 Bearpaw Uplift PreCambrian Rocks Blackfeet Poplar Dome Williston Basin 3000 4 2 Rocky Mountain Trench Little Rocky Mountains 6 0 4000 Generalized X-Section A-A' 10 2 Overthrust Belt A Ft. Belknap 12 Ft. Peck 0 Cambrian and Older Rocks 15 A' 5000 Line of section along 48 degrees latitude with Ft. Thickness of Sediment (feet) selected points every 1 degree of longitude. Berthold 0 6000 Datum: Base of Ordovician 10 10
Figure BF-4.1. Generalized time slice cross-section of Cambrian paleo-topography along line of section A-A". 4 NORTH 8 15 DAKOTA Standing Rock 12 SOUTH DAKOTA 6 10 8 8 2 0 Cambrian Geologic History 10 MONTANA � Precambrian age supracrustal sedimentary rocks (Superbelt) are buried in the 10 WYOMING western part of the reservation and extend into Glacier National Park. These rocks are estimated to be from 900 to 1400 million years old. EXPLANATION � During Cambrian time, a major seaway existed in western Montana and Cambrian and older rocks 12 eastern Idaho (see cross-section A-A' Figure BF-4.1 and map of the Cambrian). exposed at land surface This seaway gradually transgressed from west to east across eastern Montana and the Dakotas. The major source of coarse-grained clastics was to the east (from Sandstone Facies Shale, Sandstone and Minor the Sioux Arch) and graded into shales and limestones to the west. Thickness of Limestone Facies 0 the Cambrian varies from over 2000 feet at the reservation to less than 100 feet Green Shale Facies thick at the eastern edge of the Williston Basin. Oil Field, Cambrian NEBRASKA � Between these two tectonic provinces lie the Fort Peck and the Fort Belknap Reservoir Reservations. Fork Peck is on the western flank of the Williston Basin and is 12 = 1200' thickness dominated by Poplar Dome, a Laramide age structure, while Fort Belknap lies between Bowdoin Dome and the Bearpaw Uplift. Figure BF-4.2. Thickness of Deadwood and equivalent rocks. Blackfeet Reservation, location of analog fields and location of regional cross-section A-A' (modified after Peterson, 1987). � To better illustrate the geologic history of the region, which has been influenced by all of these tectonic provinces, a series of paleo cross-sections are shown. Each section summarizes a particular time interval; Cambrian and older rocks, Ordovician to Triassic and Cretaceous to Jurassic. Since Tertiary sediments are present only in the Williston Basin, no paleostructure section is shown. � A paleo cross-section attempts to show what the subsurface geology may have looked like within that time interval. For the sake of space, on the particular interval is shown; no rocks older than it are illustrated. The rock units above the interval have not yet been deposited; the top of the section is the datum. The datum is flat, representing the paleo ground surface.
GEOLOGY OVERVIEW Blackfeet Reservation index topics Montana Geologic History PAGE 4 of 13 map BLACKFEET and carbonate units including the Prairie Salt sequence in the Williston. The inland seaway. This seaway covered most of eastern Montana, and the great WEST A RESERVATION Longitude Values (in Degrees) A' EAST Prairie's western edge was dissolved away during late Devonian time, and plains from Texas to the Arctic Circle. Extensive chalk (Niobrara Formation) 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 caused the formation of several hydrocarbon traps. Deposition of marine shales was deposited in the Williston southeast into South Dakota, Nebraska and 0 Triassic Rocks and limestones continued throughout Devonian time, culminating with the Colorado. Pennsylvanian Rocks Bakken Shale Permian Rocks � By the end of the Upper Cretaceous, mountain building began in western 1000 Bakken Shale. The Bakken, and it's Alberta equivalent, the Exshaw, is a black, Montana with increasing volcanic activity and thrust faulting. Fluvial deposition Devonian Rocks organic-rich shale, which is thought to be the main source rock for the Madison 2000 Mississippian Rocks oil throughout the region. Devonian rocks including the Bakken are about 700 increased due to uplift and erosion and resulted in the deposition of nearshore Bearpaw Uplift feet thick at the reservation. The Bakken/Exshaw varies from 10 feet thick to and continental sands (Eagle/Judith River/Foxhills). Cretaceous units are 3000 PreCambrian Rocks Sweetgrass Arch Cambrian Rocks Bakken Shale more than 50 feet thick in this area (Figure BF-5.2). abundant on the reservation. Estimated thickness of Cretaceous rocks is greater Sands and Shales � By Mississippian time, the Williston Basin to the west was continually than 7200 feet. Rocky Mountain Trench 4000 Ordovician Rocks depositing limestones and evaporites in a shallow, marine shelf environment. Overthrust Belt Little Rocky Mountains Prairie Salt Most of the producing reservoirs in the Williston Basin area are from these Tertiary and Younger 5000 Generalized Cross-Section A-A' cyclic marine shales, limestone/dolomite porosity zones and evaporite seal � Tertiary time saw the erosion of older Cretaceous rocks and is characterized Poplar Dome Triassic through Ordovician Silurian Rocks sequences. Eventually, the Charles Salt would cover the entire basin and part of by fluvial deposition. Swamps existed in Paleocene and Eocene time in the 6000 Line of cross section along 48 degrees eastern and central Montana. By late Mississippian time, deposition was mainly central Williston, which formed coal deposits at the end of the Eocene. Western Cambrian Rocks latitude with selected points every 1 Sands and Shales shales and mudstones confined to the central Williston and the Big Snowy Montana apparently had no Tertiary deposition while central and eastern degree of longitude 7000 Montana had deposition of some continental sediments.
Thickness of Sediment (in ft) trough in Central Montana. DATUM: Base of Jurassic - Permian missing Ordovician Rocks � A smaller depocenter of Mississippian rocks existed west of the Sweetgrass � Quaternary time was a period of major continental ice sheets extending into 8000 Arch and Bearpaw uplift which were positive features in Mississippian time. North Dakota and Montana. Alpine glaciers existed in Montana's western
Williston Basin Total thickness of Mississippian rocks within Reservation boundaries is about mountains. Extensive glacial lakes were present along the ancestral Missouri River and its tributaries. Figure BF-5.1. Generalized cross-section A-A', line of section along 48 degrees of latitude with selected points 1500 feet. every 1 degree of longitude (after C.W. O'Melveny, 1996). � A major unconformity at the end of Mississippian time led to widespread erosion and karstification. Pennsylvanian sediments are confined to the center of the Williston and in central Montana south of the reservation. Tyler sands and Ordovician to Triassic Rocks shales are present in the Williston. No Pennsylvanian rocks occur west of � From late Cambrian through most of the Paleozoic, the Williston Basin on the east side of the longitude 106 degrees along the line of section. cross-section was the dominant receiver of sediments (see cross-section A-A', Figure BF-5.1). The � Permian deposits are confined to the central Williston and are predominantly Williston is a major, stable, cratonic basin, and is characterized by shallow, marine sediments. sand/shale and evaporite sequences. A major unconformity at the end of Ordovician and Silurian rocks were deposited in a tidal flat, cyclic carbonate and evaporite sequence. Permian time has removed any evidence of these rocks west of longitude 104 At the end of Silurian time, a regional unconformity extended across the Williston and to the west. degrees. Triassic rocks are confined to the center of the Williston and are not There are no Ordovician or Silurian rocks within the reservation boundaries. present on the Blackfeet Reservation. � Devonian rocks are widespread across the area.The Devonian is characterized by cyclic evaporite Jurassic to Cretaceous Rocks o o o 2 3 110 100 4 4 0 105 � In Jurassic time, the Williston was still the major 3 3 4 3 2 1 Blackfeet 25 5 50 75 50 100 25 depocenter for clastic and marine/evaporite sediments. The Blackfeet Ft. Belknap 25 Ft. Peck o western edge of the cross-section shows that the Jurassic was Reservation 48 Ft. 3Belknap 4.5 A A 0 Ft. Peck 50 A' fairly thin, implying that the Sweetgrass Arch and Bearpaw 0 Ft. Berthold 0 Uplift were still positive features (see cross-section A-A', 3 A' 75 4 Ft. 0 Figure BF-5.1). Fluvial sands from the eroding highlands Berthold 0 0 0 25 1 0 Approximate limit of the filled paleovalleys cut in the exposed Mississippian rocks. Bakken Formation 3 0 Thickness of Jurassic rocks is estimated to be about 500 feet 0 2 0 NORTH DAKOTA 46 o thick. 5 5 5 NORTH � Early Cretaceous time saw the development of the Thrust DAKOTA Standing Rock SOUTH DAKOTA 34 6 Standing 1 0 sheets in western Utah and eastern Idaho. The Sevier 2 SOUTH 1 DAKOTA Rock MONTANA Orogenic event created a major mountain front which formed 0 MONTANA 4 WYOMING 5 an asymmetrical basin with the long axis at the present WYOMING 3 1 5 2 o Idaho-Montana border. Sediment from the western highlands 1 EXPLANATION 44 6 were continually deposited at the foot of the mountain front. 0 0 Mississippian or EXPLANATION 6.5 older rocks exposed Deposits were mainly composed of Mississippian and older at land surface rocks, with some Cretaceous aged volcanic rocks. This Pre-Cretaceous rocks 0 25 Thickness in feet of exposed at land surface 0 6 3 1 Bakken Formation material was carried by rivers and deposited eastward into the 1 4 5 NEBRASKA 2 3 Cretaceous seaway (Lower Cretaceous, Kootenai formation). Tertiary rocks present 42 Deposition continued, becoming more marine (Mowry shale, NEBRASKA 0 Blackleaf sandstone). Gas field (Cretaceous reservoir) 0 � By Upper Cretaceous time, volcanic activity increased. Figure BF-5.2. Map showing thickness of Bakken Rocks, facies, location of analog fields, Blackfeet Reservation and location of regional cross-section A-A' (modified after Peterson, 1987). Fluvial deposits continued to carry sediments to the eastern Figure BF-5.3. Map showing general distribution of Cretaceous and Tertiary rocks, Blackfeet Reservation and location of regional cross-section A-A'. Blackfeet Reservation GEOLOGY OVERVIEW index topics Montana Geologic History PAGE 5 of 13 map PLAY TYPES - Explanation WEST Schematic Diagram of Play Types on Blackfeet Reservation EAST
1. Folded and Fractured Mississippian Carbonates (2807) 2. Jurassic / Cretaceous Sands (2808) 7 3. Mississippian / Duperow (2805) Eagle 4. Imbricate Trust Sheets (2701) Judith River 7 Upper Cretaceous 5. Fractured Bakken (2804) 6. Cambrian Sands (2802) Blackleaf 7. Shallow Biogenic Gas (2811, 2812) Lower Cretaceous 2
Cutbank Sandstone Chalk Sunburst 4 Lower Cretaceous Shale Limestone Jurassic Swift 2 Jurassic 1 Ellis Mississippian Shales, sands, Dolomite 5 Bakken Shale and siltstones 3 Gas Igneous / Mississippian 4 Metamorphics 1 Oil Sandstone Duperow Lenses Madison 5 3 Sun River Devonian Cambrian Thrust Unconformity 6 Faults Disturbed Belt Sweetgrass Arch
No Scale - Drawing is approximate width of Blackfeet Reservation
Figure BF-6.1. Schematic diagram of play types Blackfeet Reservation
Total Production Reservation: Blackfeet ( by province-1996) North-Central Montana Disturbed Belt Undiscovered resources and numbers of fields are Geologic Province: North Central Montana, Sweetgrass Arch, Montana Disturbed Belt � Oil: 440 MMBO for Province-wide plays. No attempt has been made Province Area: North Central Montana (62,500 sq. miles), Thrust Belt (41,400 sq. miles) � Gas: 1.1 TCFG 6 BCFG to estimate number of undiscovered fields within the Reservation Area: 2385 sq. miles (1,525,712 acres) � NGL: 192 MBNGL 33,000 BNGL Fort Berthold Reservation
USGS Play Type Description of Play Oil or Gas Known Accumulations Undiscovered Resource (MMBOE) Play Probability Drilling depths Favorable factors Unfavorable factors Designation Field Size (> 1 MMBOE) min, median, mean (chance of success) Fractured, folded 2807 folded structures, porosity Both 49.32 MMBO Median: 9 MMBO (9 fields @ 1MMBO) 1 1,000-6700 ft 1) confirmed play 1) lack of well control anticlines in controlled by matrix or 21,506 MMCFG Field Size (>1 MMBOE) not estimated 2) structure detected on seismic 2) rough topography Mississippian fractures. 585 MBNGL 1 MMBO(min) 3 MMBO(median) 1.2 MMBO(max) 3) source / reservoir rocks exists 3) porosity may vary (numbers include No. of undiscovered fields (> 1 MMBOE) 4) thermally mature Carbonates Mississippian 3 (min) 9 (median) 17 (max) 9.4 (mean) and Devonian Play) 1
Jurassic, Cretaceous Median: 30 MMBO (15 fields @ 2 MMBO) 2808 stratigraphic traps; discontinuos Both 134 MMBO 1 1,000-4,000 ft 1) confirmed play 1) lack of well control Field Size (>1 MMBOE) sandstones sands, updip pinchouts. Fluvial 318 BCFG not estimated 2) source / reservoir rock exists 2) seismic may not detect 2 MMBO(min) 20 MMBO(median) 5.3 MMBO(max) and nearshore sandstones. 9 MMBNGL 3) thermally mature strat traps (most from Cutbank) No. of undiscovered fields (> 1 MMBOE) 4) shallow drilling targets 3) porosity may vary 2 6 (min) 15 (median) 28 (max) 15.8 (mean) 5) probably many fields
Mississippian and Median: 48 MMBO (12 fields @ 4 MMBO) 2805 1) Jurassic / Mississippian Both (see numbers from Miss.) 1 1300-7000 ft 1) confirmed play 1) deeper drilling depths Field Size (>1 MMBOE) Devonian carbonates unconformity traps not estimated 2) source / reservoir rocks exist 2) Devonian contains nitrogen 3 MMBO(min) 21 MMBO(median) 4.8 MMBO(max) 2) Devonian Structural Traps 3) thermally mature gas No. of undiscovered fields (> 1 MMBOE) 4) structure detected on seismic 3) porosity unknown for Devonian 3 3 (min) 12 (median) 21 (max) 12 (mean) rocks
Table BF-6.1. Play summary chart.
Blackfeet Reservation index topics North Dakota Play Types PAGE 6 of 13 map Total Production Reservation: Blackfeet ( by province-1996) North Central Montana Disturbed belt Undiscovered resources and numbers of fields are Geologic Province: North Central Montana, Sweetgrass Arch, Montana Disturbed Belt � Oil: 440 MMBO for Province-wide plays. No attempt has been made Province Area: North Central Montana (62,500 sq. miles), Thrust Belt (41,400 sq. miles) � Gas: 1.1 TCFG 6 BCFG to estimate number of undiscovered fields within the Reservation Area: 2385 sq. miles (1,525,712 acres) � NGL: 192 MBNGL 33,000 BNGL Fort Berthold Reservation
USGS Play Type Description of Play Oil or Gas Known Accumulations Undiscovered Resource (MMBOE) Play Probability Drilling depths Favorable factors Unfavorable factors Designation Field Size (> 1 MMBOE) min, median, mean (chance of success) Montana Disturbed Belt; Median: 900 BCFG (10 fields @ 90 BCFG) 2701 Thrusted units forming shallow Mainly gas No total available from 0.5 3000-19,000 ft. 1) confirmed play 1) small accumulations to date Field Size (>1 MMBOE) and deep anticlines United States Geological not estimated 2) source / reservoir rocks exists 2) seismic intensive Imbricate Thrust Sheets 90 BCFG(median) 366.2 BCFG(max) Society 3) thermally mature 3) maybe thermally over mature No. of Undiscovered Fields (>1 MMBOE) 4) structure detected on seismic (some Nitrogen Gas) 4 5 (min) 10 (median) 115 (max) 5 (mean)
Fractured Bakken 2804 Bakken / Exshaw shale Oil Not applicable Not estimated 0.25 5,000-10,000 ft. 1) Bakken exists 1) no existing production within high organic content, thermally 18,000 BO / sp. mi. 47,520 BO / sq. mi. 0.2 2) thermally mature province mature; fractured reservoir 5328 sq. mi. untested 3) structures and flexures exist 2) source rock unknown 3) thermal maturity unknown 5 4) lack of deep well control
Median: 2 MMBO (2 fields @ 1 MMBO) Cambrian Sands 2802 Coarse sands trapped as Both Not applicable 0.5 1,700-7000 ft. 1) reservoir rock exists 1) no exciting production within pinchouts or on deeper Field Size (>1 MMBOE) not estimated 2) structures exist province structures 1 MMBO (min) 5 MMBO(median) 1.3 MMBO(max) 3) structure detected on seismic 2) source rock unknown No. of Undiscovered fields (> 1 MMBOE) 3) thermal maturity unknown 6 1 (min) 2 (median) 4 (max) 1.1 (mean) 4) lack of deep well control
Shallow Biogenic Gas Median: 280 BCFG (14 fields @ 20 BCFG) 2811 Accumulation in Upper Cretaceous Biogenic Gas 504,000 MMCFG Field Size (>1 MMBOE) 1 700-3000 ft. 1) source rock / self source 1) size of accumulation unknown 2812 units; Eagle, Judith River, from numerous fields in 20 BCFG(median) 27.4 BCFG (max) 0.50-0.70 2) reservoir rock exists 2) porosity decreases with depth Niobrara province 3) shallowing drilling depths 3) exposed to atmosphere No. of Undiscovered fields (> 1 MMBOE) 4) occasional gas shows possible leakage 5 (min) 14 (median) 26 (max) 14 (mean) 7 4) tracking mechanism
Table BF-7.1. Play summary chart. Conventional play type
Unconventional/Hypothetical play type
index Blackfeet Reservation PAGE 7 of 13 topics Montana Play Types map PLAY TYPE 1 EAST-WEST CROSS SECTION Fracture / Folded Anticline Mississippian REAGAN FIELD Carbonate Play Mont. Power Mont. Power Mont. Power Mont. Power UNION Tribal 355 No. 7 Tribal 355 No. 5 Tribal 355 No. 21 Tribal 355 No. 1 Tribal 19-4 No. 13 CONE M. Elev. 4017' Elev. 4054' Elev. 4067' Elev. 4106' Elev. 4108' CANADA 4 +3000 General Characteristics - This play consists of folded or fractured Madison 3 2 USA 2200 FLOWREE M.
Top Colorado limestones or dolomites. Reservoir rock consists of either (1) sub-tidal carbonate +400 BLACKLEAF "A" SAND +2900 beds with enhanced porosity zones due to dolomitization or (2) paleokarst BOW ISLAND SAND PROD. BOW ISLAND CRETACEOUS SAND porosity that developed during post-Mississippian erosion. Source rock along the 2400 +2800
+200 Sweetgrass Arch is thought to be the black, organic rich Bakken /Exchaw shale,
+175 +150 or marine Lodgepole limestone. WELLS USED FOR Top Blackleaf CROSS-SECTION +2000 UPPER CUT BANK � Source rocks on the Arch are considered mature, while those in the Montana +350 +375 +400 +325 3500 LOWER CUT BANK CRET. RIERDON disturbed Belt are overmature. Typical traps are folded Madison rocks, with +1900 CAMBRIAN TEST enhanced fracture porosity. "A" Sand BLACKLEAF "A" SAND SAWTOOTH
DISCOVERY JURASSIC MADISON ANALOG FIELDS (*) denotes fields within the Reservation boundaries) UP CONTOUR DATUM "B" Sand DOWN T +1700 Reagan Field * � (Sweetgrass Arch)� 9.3 MMBO, 15 MMcf� 54 wells 37 N MADISON Blackfeet Field � (Sweetgrass Arch)� 1.6 MMBO, 3.0 MMcf� 8 wells oil, � � +400 DISCOVERY +1600 � � � � � � � � � 7 wells gas
Moulton Sand 4000 Gypsy Basin� (Sweetgrass Arch)� 504,783 BO, 3.1 MMcd� 4 wells
MISSISSIPPIAN +700
SUN RIVER DOLOMITE FACIES Red Creek� (Sweetgrass Arch)� 6.5 MMBO, 1.2 MMcd� 18 wells oil
+325 +600 Cut Bank Sand Top Ellis R6W +500 Blackfoot Field
Top Madison Glacier County, Montana +400 +350 Cutbank Sandstone Structure +375 +400 REAGAN FIELD C.I. = 10 feet Glacier County, Montana TABLE BF-1. Reagan Field Parameters 3-2 MADISON STRUCTURE 4-1 LEGEND Formation: � � � Madison�� � Average Depth:� � 3900 ft. (+375) 883 OIL WELL C.I. = 25 feet 891 Lithology:� � � Dolomite�� � Porosity:� � 12% DRY HOLE LEGEND R 7 W ABANDONED OIL WELL Injection Well Oil/Gas Column:�� � 52 foot oil column�� Permeability:� � 10 md Madison Oil Well 3-1 Madison Discovery Blackleaf "A" Sand Gas Well Dry Hole Blackleaf "A" Sand Discovery � � � � 68 ft. gas column (original)�Other Shows:� � Blackleaf "A" 890 Average Net Pay Thickness:� 20 feet�� � � � � Sand, Madison 4-2 5-1 DUNOCO 902 Figure BF-8.1. Source rock along the Sweetgrass Arch is thought to be the black, organic Bakken/Exclaw shale or marine Lodgepole limestone. Source rocks on the Arch 888 are considered mature, while those in the Montana disturbed belt are overmature. Typical traps are folded Madison rocks, with enhanced fracture porosity.
DUNOCO 3-3 6-1 I-1 Blackfeet Field Type Log 874 907 899 613 TYPICAL ELECTRIC LOG MURPHY CORP. A' Glacier County, Montana A MURPHY CORPORATION Muntzing 1-B (7-1) #1-B Muntzing Cutbank Sandstone Elev. 4191 WAGGNER-LANSFORD SUNBURST SAND MURPHY CORP. 3300 Madison Sun River Dolomite Gov't No. 1 (1-1) I-2 3150 Muntzing B-3 (7-3) Elev. 4243 Elev. 4173 SUNBURST SAND 917 CUT BANK 7-3 I-2x 3300 CUT BANK Moulton Sand 3300 878 3200 T 7-1 37 922 RIERDON 3400 3400 880 7-4 RIERDON N 890 Sunburst Sand 930 3250 910
920 900 3400 7-2 I-3 Cut Bank Sand 3400 U D 914 918 GAS 930 1-4
3300 3500 MADISON 3500 OIL 926 MADISON DUNOCO INC. Rierdon Belke No. 3 2-2 Elev. 4222 2-1 8-1 3350 Figure BF-8.3. 916 BLACKFOOT FIELD SUNBURST 3600 Structure contour map 919 CUTBANK GLACIER COUNTY, MONTANA of Blackfoot Field.
3400 Sawtooth CROSS SECTION A-A' Datum is top of Cut Figure BF-8.2. Type log from 9-1 Union Oil of California RIERDON Bank sandstone. DATUM - SEA LEVEL 3700 MUNTZING No. 1 (6-1) the Blackfoot Field showing Shows position of 906 Elev: 4225 production from both Madison 3450 cross-section A-A' in Madison carbonates and from younger Figure BF-8.4. GAS karst-related sandstone Figure BF-8.4. Cross-section A-A' showing the fault-assisted closure within the Blackfoot Field of the OIL deposits. Cut Bank sandstone.
CONVENTIONAL PLAY TYPE 1 Blackfeet Reservation index topics Montan Fracture / Folded Anticline Mississippian Carbonate Play PAGE 8 of 13 map EAST PLAY TYPE 2 A WEST C-SE NE-NW C-NW NW-SW NE-SW SW-NE A' 20-35N-6W 13-35N-6W 19-35N-5W 11-35N-5W 19-35N-4W 3-35N-4W 1-35N-4W 3927 KB 3955 GL 4133 KB 4070 KB 4026 GL 4149 KB 4166 KB Jurassic/Cretaceous Sandstone Play TYPE LOG +1900 T 37 +1000 ELMER No. 1 N NE NW 3-36N-5W +1800 MOULTON General Characteristics - This play is the major producing interval on the +1100 +1700 Sweetgrass Arch. Stratigraphic in nature, typical traps are discontinuous fluvial +1200
2600 MOULTON sandstones in the Jurassic Sawtooth and Swift formations. Sandstones in the +1600 MOULTON Cretaceous Kootenai and Blackleaf intervals are also productive. +1500 T � Several traps are blanket sandstones that pinchout in an updip position along 36 MOULTON +1400 N structural trends. Numerous smaller fields are probably present on the flanks of
2700 ZONE RESERVATION BOUNDARY SAND +1300 the Sweetgrass Arch and the Kevin-Sunburst Dome. Source rock is thought to be SUNBURST GROUP SUNBURST BANK Cretaceous marine shales which are thermally mature across the region. +1200 DISCOVERY WELL A' CUT CUT BANK ELLIS GAS FIELD
+1500
+1400 2800 MADISON +1100 Analog Fields�(*) denotes fields which lies within the Reservation boundaries) MSL ELEVATION +1300 T 35 +1000 N A Reagan Field * � (Sweetgrass Arch)� Sunburst and Cut Bank Sands MOULTON SAND ELLIS +900 Blackfoot Field � (Sweetgrass Arch)� Cut Bank Sands 2900 CUT BANK FIELD Cut Bank*� (Sweetgrass Arch)� Cut Bank sands (est 15% with � � � +800 DISCOVERY WELL � � � � � � boundary)167.3 MMBO, 317 MMcf, 447 � �
Waterline in OIL FIELD BANK DIAGRAMMATIC CROSS SECTION A-A' MADISON +700 � � � � � � wells oil, 235 wells gas Cut Bank Sand Glacier and Toole Counties, Montana +1200 Kevin Sunburst� (Sunburst Dome)� � Cumulative production (1985) 74.9 T
3000 +600 34 � � � � � � MMBO more than 79.5 MMcf (1963) +1100 N CUT +500 � � � � � � Nisku (1 well), Madison (795 wells) � � � � � � Swift (25 wells) +400 0 100 Soberup Coulee�(Sweetgrass Arch)� 21,853 Mcf (abn'd) LIMIT 10 MV/DIV OHMS-M Figure BF-9.2. Cut Bank Field diagrammatic cross-section A-A' showing discontinuous nature of Gypsy Basin� (Sweetgrass Arch)� Sunburst Sand +700 sandstone development across structure (after T.G. Cully, Montana Geological Society, 1984). T 33 R 6 W N +800 +1000 4 3
+600
+666 EASTERN 7
2 2 BLACKFOOT INDIAN +632 +500 29 28 27 26 6 5 6 +633 1 CUT BANK FIELD +630 +649 T 32 GLACIER & TOOLE Co., MT T 4 N +900 2 5 APPROXIMATE GENERALIZED ELLIS STRUCTURE 32 Figure BF-9.1. Structure map of the Cut N CONTOUR INTERVAL = 50' 6 Bank Field, showing the structural and 4
stratigraphic position of Cut Bank 32 33 34 35 36 sandstone deposits related to underlying Karst development within the Madison carbonates (after T.G. Cully, Montana GLACIER COUNTY PONDERA COUNTY R 6 W R 5 W R 4 W Geological Society, 1984).
5 4 3 Cut Bank Field Parameters 2 1 SW Cut Bank Field Parameters Formation:� Cretaceous Cut Bank Sandstone 400 � Colorado Group sands (Moulton, 500 � Sunburst, Lander) Formation:� Cut Bank � Mississippian Madison Lithology:� Cretaceous Cut Bank Sandstone, T Lithology:� Cretaceous Cut Bank Sandstone, � blanket sand which pinches out 31 8 300 9 10 11 12 � blanket sand which pinches out updip � updip N Average Depth:� 3900 feet (+375) Average Depth:� 3900 feet (+375) Porosity:� Moulton: 19-20% Porosity:� Moulton: 19-20% � Sunburst: 14-24% � Sunburst:14-24%
� Lander: 18-24% � Lander: 18-24% 13 � Cut Bank: 12-19% � Cut Bank: 12-19% � Madison: 10% Permeability:� Moulton - 200 md � Sunburst - not known Permeability:� Cut Bank: 1 to 450 md SW Cut Bank Field � Lander - 827 md Oil/Gas Column:� Information not available Glacier & Pondera Counties, Montana � Cut Bank - 110 md C.I. 20 ft. � Madison - not known Average Net Pay Thickness:� 27 feet STRUCTURE - ELLIS
Oil/Gas Column:� 52 foot oil column Figure BF-9.3. SW Cut Bank Field showing stratigraphic pinch-outs in the updip direction � 68 foot gas column (original) which correspond to the distribution of production (after W.L. Foley, Montana Geological Average Net Pay Thickness:� Variable with formation Society, 1981). CONVENTIONAL PLAY TYPE 2 Blackfeet Reservation index topics Montana Jurassic/Cretaceous Sandstone Play PAGE 9 of 13 map TYPICAL LOG R4W R3W R2W R1W R1E R2E KEVIN-SUNBURST FIELD PLAY TYPE 3 T Devonian / Mississippian Carbonate Play 36 SUNBURST N 1300 General Characteristics - Very little Devonian production has been found to MORRISON + 1400 date. Probably found on structures, and numerous shows have been recorded on SWIFT T deep tests at Kevin-Sunburst Gypsy Basin and Highview Fields. A Mississippian 35 + 1600 play on the Madison unconformity surface is also a distinct possibility. 1400 N Corresponds to the same United States Geological Survey play classification. + 1800 RIERDON Analog Fields (*) denotes fields within Reservation T 1500 34 N Gypsy Basin� � � 504,783 BO, 3.1 MMcf, 4 wells SAWTOOTH (Sweetgrass Arch)� � contain shows in Devonian rocks MADISON + 1800 + 2000 + 1600 T Kevin-Sunburst�� � Contains 1 Devonian Nisku producer 1600 33 Blackleaf Canyon N
Pondera Field� � � 22.5 MMBO, 224,702 Mcf, 361 wells DIAGRAMMATIC CROSS SECTION + 1400 KEVIN SUNBURST DOME (Sweetgrass Arch), 1984 Northwest Southeast T 32 N EAGLE COLORADO CRETACEOUS 3000 3000 BOW ISLAND KOOTENAI T 31 SUNBURST North South SAWTOOTH N BURWASH 2000 RIERDON 2000 5 MILES JURASSIC A A' SWIFT MADISON +2100 MORRISON
MISSISSIPPIAN 1000 1000 KEVIN - SUNBURST DOME NISKU (Oil & Gas) Toole County, Montana DUPEROW (CO2 ) OIL PRODUCING AREA +2000 STRUCTURE CONTOURS ON GAS PRODUCING AREA SWIFT SANDSTONE CAMBRIAN MADISON LIMESTONE 0 0 6 Miles Mean Sea Level C.I. = 100 FT
Figure BF-10.2. Typical log, Kevin-Sunburst Field and diagrammatic cross-section. Figure BF-10.3. Kevin-Sunburst Dome (after Montana Geological Society, 1985). +1900 SWIFT SHALE Shows both the Karst-related (Madison) distribution of sandstone reservoirs and development of channel-related (Cretaceous) sandstone horizons (from Montana Kevin-Sunburst Field Parameters +1850 RIERDON Geological Society, 1985).
MADISON Formation:� Mississippian Madison +1800 Pondera Field Parameters Lithology:� Dolomitic limestone, varies from dense, to coarse � crystalline to intragranular to vuggy to fracture NORTH-SOUTH STRUCTURE Formation:� Mississippian Sun River � porosity. Secondary porosity also is important CROSS SECTION � locally Impermeable - barren Lithology:� Light gray to buff, finely crystalline PONDERA FIELD � to sugary dolomite, 140ft. thick Average Net Pay Thickness:� 10 feet porosity Permeable - fluid bearing Illustrating hypothetical mode of structure and oil Average Net Pay Thickness:� 10 feet Other shows:� Bow Island Sand Burwash, Sunburst occurrence beneath pre-Jurassic unconformity � Swift, Reirdon, Sawtooth, Madison, Nisku, Oil - water contact Other shows:� Bow Island Sand � Duperow � Kootenai channel sands, Sun River Average Depth:� 1500 feet (+2000 msl) Figure BF-10.1. North-south structure cross-section, Pondera Field showing position of permeable, karsted Average Depth:� 1950 feet (+1820 msl) Madison carbonates. Porosity:� 20% Porosity:� 14% Permeability:� variable Permeability:� 82 md Oil/Gas Column:� from +1400 to 2150 feet in the Madison Oil/Gas Column:� 70 to 100 foot oil column
This field has numerous pay zones with both a structural and stratigraphic influence. This field is a pre-Jurassic truncation of folded Mississippian rocks, and part While the Kevin Sunburst Dome does not exist on the reservation, the local variations of a Laramide structural terrace.� in reservoir rock make smaller structural and stratigraphic traps likely possible.
Blackfeet Reservation CONVENTIONAL PLAY TYPE 3 index topics Montana Devonian / Mississippian Carbonate Play PAGE 10 of 13 map PLAY TYPE 4 R 12 W R 11 W SOUTH NORTH DISCOVERY A' WILLIAMS RAINBOW A RAINBOW UNION Montana Disturbed Belt - Imbricate Thrust 2-3 Federal Two Medicine 1-3 GREAT NORTHERN (Produces from Big Springs RAINBOW #588 Morning Gun (UK Greenhorn UK Greenhorn, 6766-7276') Blackleaf Tribal 1 completion) 1 6 Two Medicine #1-30 Two Medicine 1-19 RAINBOW -4645 Two Medicine 1-18 -3600 General Characteristics - Imbricate, or angled thrust sheets and corresponding EAST GLACIER FIELD 9260 TD 9453'TD 9244' TD 9559' 9383' TD TD HUMBLE anticlines between the Lewis Thrust Sheet, and the eastern edge of the Disturbed belt SHELL-UNION 10-Y Blackleaf Tribal Lewis 32x-10 -5879 -4612 summarize this play. Only three known fields exist in this province: the East Glacier -4373 DISCOVERY MONTANA POWER -3800 and Two Medicine complex and Blackleaf Complex. RAINBOW Two Medicine 1-11 Two Medicine 1-11 -4658 -4600 (Produces from A' � Potential reservoir rock is dolomitized Mississippian limestone between 200 and UK Greenhorn -4500 6900-7155') 500 feet thick. Permeability is low which may explain the small accumulation -4400 Sawtooth T -4300 -4000 Jurassic found. Lower Mississippian and Devonian rocks may have fractured reservoirs. RAINBOW 31 Two Medicine 1-18 -4700 N -4200 Jurassic and Cretaceous sandstones may produce. -4600 DISCOVERY UNION Sawtooth -4500 -4143 -4100 #588 Morning Gun � Source rock is thought to be either (1) the Flood member of the Cretaceous -4400 RAINBOW Two Medicine 1-19 -4042 -4200 Sun River Blackleaf formation (43 - 168 feet thick) with 1.1 % total organic carbon (TOC); (2) -4300 GREAT NORTHERN Mississippian Sawtooth Blackfeet TR 1 -4057 Sun shale member of the Jurassic Swift formation (6 - 32 feet thick) with 1.1 % TOC; or -4100 River (3) Devonian Bakken/Exshaw organic rich shale (10 - 40 feet thick) averaging 0.97 -4400 Sun River % TOC. TWO MEDICINE FIELD -4100 RAINBOW TWO MEDICINE Madison � Depths to potential reservoirs vary from 19,000 feet on the western side to less Big Springs Two Medicine 1-30 and TWO MEDICINE than 3000 feet on the eastern side. Carbon dioxide gas has been found in the -4237 EAST GLACIER -4600 FIELD A -4300 FIELDS Madison equivalent rocks in Canada. Some carbon dioxide has been found in smaller Glacier Co., Montana Glacier Co., MT structures in the Disturbed Belt. Madison SUN RIVER STRUCTURE CROSS SECTION 36 31 -4800 A-A' Analog Fields (*denotes field inside Reservation boundaries) Contour Interval = 100 ft Two Medicine� 11,510 BO � 275,000 Mcf (Abn'd)� (Montana Disturbed Belt) Figure BF-11.1. Two Medicine and East Glacier Fields (after James W. Garner, Montana Blackleaf � 33,748 BO � 7.0 MMcf (Abn'd) �� (Montana Disturbed Belt) Figure BF-11.2. Two Medicine Field (after James W. Garner, Montana Geological Society, 1985). Geological Society, 1985).
T R 9 W R 8 W T R 9 W R 8 W 27 27 -830 N Williams Exploration N -830 2-5 Blackleaf Unit Williams Exploration 2-5 Blackleaf Unit 1000 D 1000 2 1 6 U 5 4 G/W 2 1 6 5 4 G / W Blackleaf Canyon Field Parameters Two Medicine Field Parameters -46 -46 Williams Exploration -500 Williams Exploration 500 1-5 Blackleaf Unit 1-5 Blackleaf Unit +1500 -1000 Formation: � Mississippian Sun River +1000 Formation: � Cretaceous Greenhorn, Mississippian Sun River -1000 U D -1500 Gulf Oil -1500 -497 -497 Gulf Oil 1Teton Knowlton Lithology:� West Sun River dolomite, �continuous, 450 feet 11 Lithology: � Greenhorn - fractured sandstone and shale, 600 � 0 1 Teton Knowlton G / W 12 7 8 9 11 12 7 9 +12 DISCOVERY � East Sun River, 420 feet � feet. Continuous except when faulted + 12 Rainbow Resources DISCOVERY 1-16 Blackleaf Fed. Rainbow Resources Average depth: � West Sun River "A" thrust sheet � Sun River - fractured dolomite, 225 feet 1-8 Blackleaf Fed Burlington Northern Burlington Northern � 3900 feet. (+1537 feet MSL) � Continuous except when faulted +1545 11-18 Blackleaf A -500 11-18 Blackleaf A -408 T -575 T � West Sun River "B" thrust sheet 5700 feet Average Depth:� Greenhorn - 7000 feet (-2000 feet MSL) No. Natural Gas -575 26 DISCOVERY 26 14 13 18 17 14 13 18 17 16 1 Blackleaf Fed. A N +535 No. Natural Gas � (-200 feet MSL) -1208 Williams Exploration Williams Exploration N � Sun River - 8800 feet (-4050 MSL) General Pet. 1 Blackleaf Fed. 1-16 Blackleaf Unit I-16 Blackleaf Unit � East Sun River 5028 feet (-28 feet MSL) General Petroleum 1 Blackleaf -300 Porosity: � Greenhorn - 15% Sun River - 9% average 1 Blackleaf Porosity: � West Sun River 3.5% matrix porosity -200 -130 +1608 � matrix Williams Exploration Williams Exploration � East Sun River 3.5% matrix porosity 1-19 Blackleaf Unit I-19 Blackleaf Unit Permeability: � not known 23 24 -100 20 21 23 24 19 -86 19 20 21 Permeability: � not known +1459 DISCOVERY Northern Natural Gas Oil/Gas Column:� Greenhorn - 375 feet (water contact not known)� Woods Petroleum No. Natural Gas Woods Pet. Blackleaf Fed B Oil/Gas Column: � West Sun River "A" (100 feet MSL) #1 Volcano Reef � �Sun River- 125 feet (water contact not known) Blackleaf Fed. B #1 Volcano Reef � West Sun River "B" (350 feet +1450 MSL) -500 G / W Average Net Pay:� Greenhorn - 100 feet Sun River - 90 feet -1000 � East Sun River 350 feet (-450 feet MSL) -1500
26 25 29 28 26 25 30 29 28 Average Net Pay: � Sun River 350 feet thick
+1500
35 36 31 -200 32 +1000 35 36 +500 31 32 BLACKLEAF CANYON G/W FIELD BLACKLEAF CANYON
LEWIS AND CLARK NATIONAL FOREST T FIELD 25 SUN RIVER STRUCTURE T SUN RIVER STRUCTURE N "A" THRUST SHEET LEWIS AND CLARK NATIONAL FOREST 25 5 "B" THRUST SHEET 2 1 6 Contour Intervals: 100 & 500 ft N 2 1 6 Contour Interval: 500 ft BLACKLEAF UNIT Mobil BLACKLEAF UNIT 5-1 Federal Mobil 5-1 Fed
Field BF-11.3. Blackleaf Canyon Field (after James W. Garner, Figure BF-11.4 Blackleaf Canyon Field (after James W. Garner, Montana Geological Society, 1985). Montana Geological Society, 1985).
Blackfeet Reservation CONVENTIONAL PLAY TYPE 4 index topics Montana Montana Disturbed Belt - Imbricate Thrust PAGE 11 of 13 map Ft. Peck o 110 Reservation o o Figure BF-12.1. Thickness of 105 100 Blackfeet 25 Bakken formation (uppermost 50 75 Blackfeet 50 100 25 Devonian and lowermost Ft. Belknap 25 4 2 o Mississippian) (modified after A MONTANA 48 6 0 50 Peterson, 1981,1984). A' 10 Ft. Peck 2 0 Ft. Belknap 12 0 Ft. Berthold A 15 0 75 0 A' 0 Ft. 0 25 0 Approximate limit of the Berthold Bakken Formation 0 NORTH DAKOTA 10 0 o 46 10
Standing Rock 4 NORTH 8 15 DAKOTA SOUTH Standing Rock 12 DAKOTA WYOMING 44 o 6 EXPLANATION SOUTH DAKOTA 10 8 8 Mississippian or 2 0 older rocks exposed 10 MONTANA at land surface 10 WYOMING 25 Thickness in feet of Bakken Formation NEBRASKA EXPLANATION o Cambrian and older rocks 12 42 exposed at land surface
Sandstone Facies Shale, Sandstone and Minor Limestone Facies 0 PLAY TYPE 5 Green Shale Facies
Fractured Bakken Shale Play Oil Field, Cambrian NEBRASKA General Characteristics - The Devonian Bakken, one of the probable source rocks for the Madison, is an Reservoir organic rich marine shale, regionally equivalent to the Alberta Shelf, Exchaw shale. The Bakken is considered to be thermally mature across the Sweetgrass Arch, and varies from less than 10 feet thick to Figure BF-12.2. Thickness of Deadwood and equivalent rocks, location of analog fields. Blackfeet reservation and location of over 75 feet thick in the northern portion of the Blackfeet Reservation. Depths vary from 1500 to 6000 regional cross-section A-A' (modified after Peterson, 1981, 1984). feet deep. Fractures would occur along hinge lines in the basin or on the crests of structures.
PLAY TYPE 6
180 Mi 90 Mi 150 Mi Cambrian Sandstone Play A 112û A' 110 108 106 104 102 GLACIER NAT'L PARK CANADA MARINE SHALE & 48 WILLOW CREEK NONMARINE ROCKS SILTSTONE UNITED STATES General Characteristics - Cambrian sandstones are more than 2000 feet thick in FM (PART) COASTAL SANDSTONE SWEETGRASS CHALK & LIMESTONE HILLS the Disturbed belt part of the Reservation. Reservoir rocks are quartz and lithic CALCAREOUS SHALE A BEARPAW MTNS BOWDOIN A' DOME sandstones from the Flathead formation. Depth to Cambrian is between 3000 ST MARY RIVER FM BEARPAW POPLAR MTNS DOME ANTICLINE and 8000 feet. Source rock is thought to be dark gray marine shales in the 48 WEST FLANK LITTLE ROCKY WILLISTON BASIN MTNS Cambrian Gordon formation. No information is available on source rock organic HORSETHIEF DOWDOIN BEARPAW SHALE SANDSTONE FOX DOME content or thermal maturity. Traps could be structural closures or pinch-outs. HILLS SS HELL CREEK FM. CAT CREEK ANTICLINE WESTERN LIMIT
FOX HILLS SS CEDAR CREEK ANTICLINE BEARPAW SHALE 47
JUDITH RIVER FM CENTRAL MONTANA PIERRE PLAY TYPE 7 UPLIFT SHALE OF PORCUPINE WILLISTON BASIN Biogenic (Low, Medium, High Potential) Gas Play CLAGGETT SHALE ARDMORE BENTONITE BED DOME EAGLE SS ND 46 TWO MEDICINE FORMATION VIRGELLE SS GAMMON General Characteristics - Shallow biogenic (methane rich) gas produces at TELEGRAPH SHALE SD CREEK FM. NIOBRARA FM Bowdoin Dome and Cedar Creek Anticline from the Cretaceous Eagle and Judith CARLILE SHALE PRYOR MARIAS RIVER SHALE UPLIFT NORTHERN LIMIT River sandstones. Traps are stratigraphic and consist of coarse clastic sands BELLE FOURCHE SH GREENHORN FM BIG HORN POWDER RIVER BASIN Upper Cretaceous MTNS grading to fine sands and silts. Methane is generated soon after burial and is MOWRY SHALE MT Lower Cretaceous 45 WY preferentially trapped in the coarse facies. The reservoirs are shallow and tight SKULL CREEK SHALE and look poor on well logs. A pay section may not yield gas shows when drilled. VAUGHN MUDDY SS BLACK HILLS MBR UPLIFT BLACKLEAF FM "Sweet spots" on structural highs (with paleothinning) probably localized better reservoirs. This potential for traps in fine grained reservoir rocks also exists. 44 Figure BF-12.3. Thickness of Bakken formation (uppermost Devonian and Figure BF-12.4. Major structural elements of northern Rocky Mountain Region and location of lowermost Mississippian), in feet (modified after Peterson, 1981,1984). Cretaceous cross-section (after Rice and Shurr, 1980). UNCONVENTIONAL / HYPOTHETICAL PLAY TYPES 5, 6, 7 Blackfeet Reservation index topics Montana Bakken, Cambrian Sandstone and Biogenic Gas Plays PAGE 12 of 13 map ______, 1985, "Gypsy Basin North Field", Montana Oil and Gas Field Blackfeet - Map References BLACKFEET RESERVATION Symposium, Montana Geological Society, Billings, Montana, pp. 577-578. Executive Reference Map 334, 1985 edition, Extended Area, Northern Rocky General References ______, 1985, "Highview Field", Montana Oil and Gas Field Mountains, Geomap Company. Symposium, Montana Geological Society, Billings, Montana, pp. 615-616 Anderson, Robert C., 1995, The Oil and Gas Opportunity on Indian Lands- Executive Reference Map 321, 1983 edition, Southern Williston Basin, Geomap Exploration Policies and Procedures: Bureau of Indian Affairs, Division of Cully, Timothy G., 1985, "Cut Bank Field (Gas)", Montana Oil and Gas Field Company. Energy and Mineral Resources, General Publication G-95-3, 158 p. Symposium, Montana Geological Society, Billings, Montana, pp. 407-408 Indian Land Areas, 1992, United States Department of the Interior-Bureau of Beeman, William R., et al., 1996, Digital Map Data, Text and Graphical Images Dyman, T.S., 1996, "North-Central Montana Province (028)", Tabular Data, Indian Affairs. in Support of the 1995 Assessment of United States Oil and Gas Resources, Text, and Graphical Images In Support of the 1995 National Assessment of United States Geological Survey, Digital Data Series DDS-35, CD ROM. United States Oil and Gas Resources, United States Geological Survey, Clayton, Lee, et al., 1980, Geological Map of North Dakota Survey. Digital Data Series DDS-36, CD ROM. Charpenteir, Ronald R., et al., 1996, Tubular Data, Text, and Graphical Images Darton, ., et al., 1951, Geologic Map of South Dakota, United States Geological in Support of the 1995 National Assessment of United States Oil and Gas Editors, 1985, "Cut Bank South Central Sand Unit Field", Montana Oil and Gas Survey. Resources, United States Geological Survey, Digital Data Series DDS-36, Field Symposium, Montana Geological Society, Billings, Montana, CD ROM. pp. 407-408. Ross, Clyde P., et al., 1958, Geological Map of Montana, Montana Bureau of Mines. Gautier, Donald L., et al., 1996, 1995 National Assessment of United States Oil ______, 1985, "Reagan Field", Montana Oil and Gas Field Symposium, and Gas Resources - Results, Methodology, and Supporting Data, United Montana Geological Society, Billings, Montana, pp. 937-939. States Geological Survey Digital Data Series DDS-30 Release 2. Foley, W.L., 1958, "SW Cut Bank", Montana Oil and Gas Symposium, Montana ______., et al., 1995, 1995 National Assessment of United States Oil Geological Society, Billings, Montana. and Gas Resources, Overview of the 1995 National Assessment of Potential Additions to Technically Recoverable Resources of Oil and Gas - Onshore Garner, James W., 1985, "Blackleaf Canyon Field", Montana Oil and Gas Field and State Waters of the United States, United States Geological Survey Symposium, Montana Geological Society, Billings, Montana, pp. 251-256. Circular 1118, 20 p. ______, 1985, "Two Medicine (East Glacier) Field", Montana Oil and Mallory, William Wyman, et al., 1972, Geologic Atlas of the Rocky Mountain Gas Field Symposium, Montana Geological Society, Billings, Montana, Region, Rocky Mountain Association of Geologists , 331 p. pp. 1139-1143.
Peterson, James A. and MacCary, Lawrence M., 1987, "Regional Stratigraphy Hedglin, Bill, 1985, "Blackfoot Field", Montana Oil and Gas Field Symposium, and General Petroleum Geology of the U.S. Portion of the Williston Basin Montana Geological Society, Billings, Montana, pp. 243-246. and Adjacent Areas", Williston Basin: Anatomy of a Cratonic Oil Province, Rocky Mountain Association of Geologists, pp. 9-43. Jones, M.K., 1985, "Kevin Sunburst Field", Montana Oil and Gas Field Symposium, Geological Society, Billings, Montana, pp. 655-660. Rice, Dudley D. and Shurr, George W., July 1980, "Shallow, Low-Permeability Reservoirs of the Northern Great Plains - Assessment of their Natural Gas Leskla, Willard, 1958, "Pondera Field", Montana Oil and Gas Field Symposium, Resources", American Association of Petroleum Geologists Bulletin, Montana Geological Society, Billings, Montana, pp.885-888. Volume 64/7, pp. 969-987. McCourt, J.H., 1958, "Reagan Field", Montana Oil and Gas Field Symposium, Willette, Donna C., et al., 1996, "Oil and Gas Atlas on Indian Lands", Indian Montana Geological Society, Billings, Montana, pp.203-205. Resources Building Partnerships, Sixth Annual Energy and Minerals Conference, Bureau of Indian Affairs, Division of Energy and Mineral Nordquist, J.W., 1958, "Gypsy Basin Field", Montana Oil and Gas Field Resources, p. 10. Symposium, Montana Geological Society, Billings, Montana, pp.154-155
Perry, William J., 1996, "Montana Thrust Belt Province (027)", Tabular Data, Blackfeet - Fields and Articles Text, and Graphical Images In Support of of the 1995 National Assessment of United States Oil and Gas Resources, United States Geological Survey, Anderson, Robert C., 1995, "Blackfeet Indian Reservation- Blackfeet Tribe"; Digital Data Series DDS-36, CD ROM. The Oil and Gas Opportunity on Indian Lands-Exploration Policies and Procedures, Bureau of Indian Affairs, Division of Energy and Mineral Reed, W.G., Jr., 1958, "Blackfoot Field"; Montana Oil and Gas Field Resources, General Publication G-95-3, pp. 7-11. Symposium, Montana Geological Society, Billings, Montana, pp.73-75
Chamberlain, Virgil R., 1985, "Gypsy Basin Field"; Montana Oil and Gas Field Tonneson, John J., 1985, "Soberup Coulee Field"; Montana Oil and Gas Field Symposium, Montana Geological Society, Billings, Montana, pp. 573-576. Symposium, Montana Geological Society, Billings, Montana, pp. 1081 1083.
Blackfeet Reservation REFERENCES index topics Montana PAGE 13 of 13 map