FORT BERTHOLD RESERVATION List of Topics BACKGROUND Reservation Overview Production Overview GEOLOGIC OVERVIEW Geologic History Petroleum Systems Summary of Play Types CONVENTIONAL PLAY TYPES Play 1 - Folded Structure-Mississippian Carbonate Play￿ Play 2 - Mississippian Shoreline Play￿ Play 3 - Mississippian Lodgepole Waulsortian Mounds￿ Play 4 - Ordovician Red River Play Play 5 - Devonian Nisku-Duperow Play Play 6 - Pre-Prairie (Winnipegosis/Interlake Play) Play 7 - Post Madison Clastics (Tyler-Heath) Play 8 - Pre-Red River Gas Play Play 9 - Bakken Fairway/Sanish Sand Play￿ ￿ UNCONVENTIONAL / HYPOTHETICAL PLAY TYPES Play 10 - Niobrara Microbial Gas Play REFERENCES OVERVIEW there are approximately 10 formations proved to be productive in the Fort Land Status Berthold area. Of further note, the facies distribution during lower Mississippian ￿ The Fort Berthold Indian Reservation was established by the Fort Laramie FORT BERTHOLD RESERVATION Treaty of September 17, 1851, for the Arikara, Mandan, and Hidatsa Tribes of The Three Affiliated Tribes time strongly suggests that Lodgepole trends are present on the Fort Berthold Indian Reservation (USGS). Indians who later united to form the Three Affiliated Tribes. Executive Orders ￿ The Three Affiliated Tribes have purchased seismic data from lines located in and Congressional Acts have limited the reservation to its present boundaries. Tribal Headquarter: New Town, North Dakota the western portion of the Reservation, which may be examined by parties The act of June 1, 1910, 36 Stat. 455, opened unallotted and unsold reservation Geologic Setting: ￿ Williston Basin interested in oil and gas exploration. Some of the seismic data will be lands to non Indians, thus creating the "ceded and diminished lands" boundary. It reprocessed and may be correlated with borehole logs. Sections and data tapes was assumed by many that only the remaining lands comprised the Fort Berthold Introduction reside with the Division of Energy and Minerals Resources of the Bureau of Indian Reservation. A Federal appeals court (8th Cir. 1972), however, ruled that ￿ The Fort Berthold Indian Reservation is located in west-central North Dakota Indian Affairs located in Denver, CO. the 1910 Act did not change reservation boundaries and that the "homestead" approximately thirty miles southwest of the city of Minot. The Reservation (ceded) area remained a part of the reservation (City of New Town vs. United contains portions of Dunn, McKenzie, McLean, Mercer, Mountrail and Ward Area Location and Access States, 454 F 2d 121) Public Law 437 and the Act of July 31, 1947 (amended Counties and includes an area of about 1,530 square miles or 980,000 acres. ￿ Fort Berthold Indian Reservation comprises parts of Dunn, McKenzie, October 29, 1947) made provision for lands inundated by the Garrison Dam These lands are located 15 miles east of the center of the Williston Basin, a McLean, Mercer, Mountrail, and Ward Counties in west-central North Dakota reservoir. Table 1 summarizes the present extent of land holdings on the Fort geologic area where undiscovered accumulations of oil and gas may be located. (Figure 1), near the confluence of the Missouri and Little Missouri River valleys. Berthold Indian Reservation. Most of the north and northeast part of the ￿ Several studies have been published over the years which indicate high Total area is about 1,530 square miles, approximately 11 percent of which is reservation (the homestead area) is in private ownership. Land status data are potential for undiscovered oil and gas reserves on the Fort Berthold Reservation. covered by waters impounded by Garrison Dam (Lake Sakakawea). The lake from Bureau of Indian Affairs records. There has been past interest exhibited by oil companies, however, high royalties, divides the reservation into four distinct areas, here referred to as the western, ￿ Nearly 54 percent of the reservation's subsurface mineral rights are owned by high lease acquisition costs, inability to assemble large blocks of acreage, rights southern, eastern, and north-central segments. the Three Affiliated Tribes. Mineral rights in the diminished reservation area are to seismic data, Tribal Employment Rights Office (TERO) regulations, taxes, and ￿ Although reservoir waters somewhat impede travel between the four land all tribally owned with the exception of 164.09 acres owned by the Federal a 100 percent signature requirement imposed by the federal statute on Trust lands segments, most of the reservation is accessible over a system of State highways government. The Tribes also retain mineral ownership for 110,623.13 acres of have served as deterrents to oil and gas exploration on the Reservation. The 100 and local roads. Rail service is provided to the northern part of the reservation by the homestead area. Lands in the Garrison reservoir area were severed. percent signature requirement regulation has made exploration on Tribal Allotted the Soo Line Railroad. A main east-west line of the Burlington Northern passes Lands nearly impossible to carry out due to the high fragmentation caused by within 7 miles of the reservation, roughly paralleling the southern boundary. TABLE 1 - Summary of land ownership, Fort Berthold Indian Reservation, N. Dakota heirship. The Tribes are currently working to correct these problems to open the Percentage door for future gas and oil exploration and development. The Three Affiliated Physiography Classification ￿ Acreage of total Tribes are striving to work closer with oil companies to make oil and gas ￿ The Fort Berthold Indian Reservation includes land that ranges from rugged exploration on Fort Berthold competitive with lands outside of the Reservation. badlands to rolling plains. Altitudes range from about 1,850 feet at Lake Diminished Reservation Area Tribally-owned lands.￿ 57,954.20￿ 5.91 ￿ The Fort Berthold Reservation possesses all the requisites for commercial Sakakawea to over 2,600 feet on Phaelen's Butte near Mandaree. The reservation Allotted lands￿ 360,438.57￿ 36.76 petroleum development. According to an oil and gas study authorized by Joe H. is within the Northern Great Plains Physiographic Province and may be divided Government-owned land￿ 164.09￿ 0.01 Rawlings, source rocks and reservoir caprock combinations are in evidence from into four physiographic units: (1) the Coteau Slope; (2) the Missouri River trench Privately owned (alienated) land￿ 55,865.14￿ 5.70 the Antelope field located near the northwest corner of the Reservation. This (now flooded); (3) the Missouri Plateau; and (4) the Little Missouri Badlands. Subtotal￿ 474,422.00￿ 48.38 field produces both oil and gas from four different zones. The relatively new South of Lake Sakakawea the reservation has a bedrock surface with scattered Plaza field, located near the east exterior boundary, is also a major producing oil areas of glacial drift. North of the lake, glacial deposits predominate and only Reservoir Taking Area￿ 152,359.95￿ 15.54 field. Other fields were recently discovered on the Reservation while drilling the patches of bedrock crop out. The landscape reflects this distribution of sediments: Homestead (ceded) Area.￿ 353,792.59￿ 36.08 Bakken and Mission Canyon formations. This multiplicity of geologic structures south of the lake, hills and badlands are common; north of the lake the glaciated Total area of reservation.￿ argues the presence of the many deep traps. Regardless of the development of topography is mainly undulating to rolling. these fields, much of the Reservation has not been explored for accumulations of ￿ The reservation area north of Lake Sakakawea is part of the Coteau Slope, Contacts oil and gas. which has both erosional and glacial landforms with glacial predominating. Inquiries concerning oil and gas leases on the Fort Berthold Reservation may ￿ The Williston Basin, which encompasses the Reservation, has a long history Gentle slopes characterize 50 to 80 percent of the area and local relief ranges be directed to the Three Affiliated Tribes Natural Resources Department - of production. Much of the oil in this area was sourced by the organically rich from 50 to 200 feet. The Little Missouri Badlands lie adjacent to the Little telephone (701) 627-3627 or the Bureau of Indian Affairs, located in New Town, Bakken Formation. New horizontal drilling technology has made production Missouri River south and west of Lake Sakakawea as well as in a few restricted North Dakota - (701) 627-3741. from Bakken source rocks possible. A report written for the Bureau of Indian areas along the Missouri River. They consist of rugged, deeply-eroded, 85 980,574.54￿ 100.00 83 Affairs by Susan Race Wager, states that the Fort Berthold Reservation is hilly land in which gentle slopes characterize only 20 to 50 percent of the area Williams Mountrail 52 favorably located for exploration in the Bakken Formation. and local relief is commonly over 500 feet. Areas other than badlands south and McHenry Stanley ￿ According to George Long of the Bureau of Land Management (BLM), there west of the lake are part of the Missouri Plateau. In these areas, gentle slopes Minot have been 571 tests for oil and gas on or immediately adjacent to the Fort characterize about 50 to 70 percent of the area and local relief ranges from 300 to 2 Williston 8 Ward Berthold Reservation resulting in a total of 392 producing wells and 179 plugged 500 feet. 52 Watford City 73 New Town and abandoned wells; a 69% success ratio. The majority of these 179 plugged ￿ The Missouri and Little Missouri Rivers and their larger tributaries have cut 200 85 McLean and abandoned wells did report oil and gas shows. Of special interest, there deeply into the bedrock and glacial deposits of various compositions. The FORT BERTHOLD McKenzie Sheridan appears to be production potential in the Mississippian Charles Formation which Missouri River is 300 to 500 feet below the upland plain. Near the western Underwood has been bypassed in all of the wells drilled except those few that are too shallow boundary of the reservation, the Little Missouri River has eroded a channel more Mercer

to reach the Charles Formation located in the Mission Canyon. MONTANA than 600 feet deep. Occasional ridges and bare buttes extend as much as 400 feet 83 ￿ Water saturation calculations were made on 60 wells to evaluate possible above the plain. NORTH DAKOTA Billings Dunn Oliver bypassed production in the Mississippian Charles Formation. Possible oil and Burleigh

gas production was indicated in 52 of these 60 wells. According to the BLM, Beach 94 Belfield Dickinson Morton 94 Bismark

Fort Berthold Reservation Page 1 of 18 North Dakota OVERVIEW at AntelopeFieldin1992. Condensate andgaswerediscoveredintheWinnipegDeadwoodFormations part oftheMississippianshorelinetrend,werediscoveredin1980's. PlazaandWabekFields, discovered in1953andextendsontothereservation. AntelopeField,asoutheastplunginganticline,was reservation boundary. Nessonislocatedabout50milesnorthwestofthe Nesson Anticlinein1951. GaswasdiscoveredatCedarCreekAnticlinein1916;oilon ￿ Mostofthereservationisunexplored. that total(1530sq.miles). than 143,000sq.milesandFortBertholdreservationcoversaboutonepercentof TheWillistonBasincoversmore has undergonemultipleexplorationcycles. Sincethelate1940's,industryhasfoundmorethan960fieldsandbasin ￿ clastic andcarbonatesedimentshavebeenpreserved. Largevolumesof and burialhistorythroughoutPaleozoicMesozoictime. among otherRockyMountainbasinsbecauseofitscontinuousbasinsubsidence TheWillistonBasinisdistinctive Cedar CreekAnticlines,andPoplarDome. EarlydiscoveriesweremadeonlargesurfacestructuressuchasNessonand ￿ Reservation Early ExplorationintheWillistonBasinandFortBerthold sedimentsanddeepPaleozoicsandstoneintervals. microbial gasinCretaceous Recentexplorationtargetsinclude primary focusofhydrocarbonexploration. CarbonatereservoirsinPaleozoicformationshavebeenthe reservation area. migration pathwaysarecriticaltosuccessfulfutureexplorationwithinthe Understandingthetrappingmechanismsand from thesesourceintervals. episodes ofmaturationandmigrationoccurredduringPermian-Cretaceoustime Multiple 1.69 TCFGfromundiscoveredresourcesinconventionalplays. TheWillistonBasincontainsanestimatedmeanvalueof650MMBOand ￿ of thebasin. including theworldrenownBakkenFormation,contributetoprolificnature Severalsourcerockhorizons, numerous explorationtargetswithinthisbasin. Thereservationisideallysituatedfor largest cratonicbasinsinNorthAmerica. Over700MMBOhavebeenproducedfromtheWillistonBasin,oneof ￿ Williston Basin North Dakota Fort BertholdReservation Fort BertholdReservation INTRODUCTION Nearby fields Fields withinreservationboundaries (1990) LuckyMound-1.4MMBO,890,670MCF,18wellstotal (1982) Mandaree-160MBO,147,325Mcf,2wellstotal (1982) SquawCreek-195MBO,328,546Mcf,1welltotal (1981) SpottedHorn-108MBO,36,234Mcf,(Abn'd) (1952) Croff-1.8MMBO,4.1Mmcf,3wellstotal (1957) BearDen-1.5MMBO,1.7Mmcf,2oilwells,1gaswell (1955) BlueButtes-46MMBO,29.2Mmcf,44wellstotal (1982) Wabek-5.4MMBO,3.9Mmcf,18wellstotal (1989) Plaza-2.9MMBO,3.9Mmcf,20wellstotal (1953) Antelope-41MMBO,19.2Mmcf,30oilwells,2gaswells 1996cumulativeproduction.Parenthesesindicatesdiscoveryyear Symposium Guidebook,1995). carbonate province(modifiedafterSeventhInternationalWilliston Basin numerous clasticpotentialreservoirintervals,theWilliston Basin isknownasa Whiletheotherbasinsareknownfortheir Paleozoic agecarbonatesediments. Basin isuniqueamongotherRockyMountainbasinsforits thickpackageof However,theWilliston intervals canbecorrelatedintoWyomingandMontana. Manyofthepotentialreservoir Figure FB-1.1.Producinghorizonlegend. U.S.G.S. GeologicProvince-WillistonBasin(031) GENERAL PRODUCTIONINFORMATION Tectonic Province-WillistonBasin Fort BertholdReservation Introduction

P A L E O Z O I C M E S O Z O I C CENOZOIC ERA

DEVONIAN MISSISSIPPIAN PENNSYLVANIAN PERMIAN TRIASSIC JURASSIC CRETACEOUS TERTIARY SYSTEM CAMBRIAN ORDOVICIAN SILURIAN S

Producing Horizon Legend(afterGeomapExecutive Reference Map, 1983) LOWER UPPER SERIES = SourceRock RDCN HRZN LEGEND PRODUCING HORIZON Opeche Madison Group Winnipegosis River Souris Duperow Nisku Three Forks Bakken Dawson Bay Niobrara Judith River ￿Morrison Fox Hills Eagle Stony Mountain Stonewall Big Snowy Group Tyler Fort Union Winnipeg Red River Amsden Minnelusa Dakota Group Greenhorn Nesson Ellis Group Deadwood Otter Interlake Interlake Lodgepole Lodgepole Kibbey Heath Spearfish Mission Canyon Charles Swift Piper Reirdon BASIN WILLISTON S

S S

S S B I O G E N I C C I N E G O I B BASIN POWDER RIVER Deadwood Jefferson White River Teckla Fort Union Morrison Morrison Gypsum Canyon Springs Sundance Fall River Muddy Mowry Goose Egg Englewood Dakota Teapot Niobrara Shannon Sussex Parkman Lance Wasatch Lakota Mesaverde Big Horn Interlake Interlake Chugwater Minnekahta Frontier Winnipeg Madison Minnelusa Spearfish

SOUTHERN MONTANA Madison WESTERN WYOMING Big Horn Tensleep Green River Wind River Fort Union Wasatch Flath Gall Darwin Amsden Weber ParkCity Dinwoody Gros Gannet Woodside Thaynes Ankareh Twin Creek Stump-Preuss Sundance Cloverly Bear River Muddy Mowry Frontier Shannon Cody Mesaverde Fox Hills Lance Morrison Morrison Niobrara Chugwater Lodgepole Lodgepole Mission Canyon Nugget Phosphoria Phosphoria Dakota Jefferson Darby Emerson Flathead Red River Fort Union Clagget Telegraph Creek Greenhorn Niobrara Eagle Judith River Hell Creek Blackleaf Big Snowy Group Ellis Group Tyler Morrison Morrison Frontier Madison Group Souris River Souris Duperow Nisku Three Forks Amsden Swift Sunburst Cut Bank Moulton Cat Creek Bow Island Kootenai Sawtooth Reirdon Mission Canyon Lodgepole Lodgepole Sun River Kibbey Heath Charles Charles Otter NORTHERN WESTERN MONTANA Page 2of18 Alberta Shel f REGIONAL GEOLOGY CANADA 98 97 114 113 100 99 112 111 110 109 108 107 106 105 104 103 102 101 BF Sweetgrass Bowdoin ￿ The Fort Berthold Reservation is situated near the deepest part of the Hogeland Dome UNITED STATES Bearpaw Basin Uplift Fault Poplar Williston Basin (see Fig. FB-2.1 A-A' and associated cross-sections). During Poplar Fault A BK FP Dome A' 48 OVERTHRUST Hinsdale Nesson Arch Little the Paleozoic and early part of the Mesozoic, the basin was a stable, cratonic

Anticline West East Rocky Mtns Judith BR Longitude Values (in degrees) Fort Berthold Reservation Blood A' Mtns Creek Cedar Creek NORTH DAKOTA depocenter which received over 15,000' of sediments. Fort Berthold A Big Syncline Little Anticline Snowy Cat Creek Fault Weldon-Brockton Fault 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 MONTANA BELT Belt Mtns reservation is located within the depocenter, near a major structural feature WILLISTON 0 Mtns Sumatra Wheatland Porcupine Cambrian Rocks Syncline Willow Syncline BASIN called the Nesson Anticline, which produces a significant percentage of PreCambrian Rocks Dome Cambrian Rocks Sands and Shales FaultCreek Miles City Crazy 1000 Sands and Shales Bull Arch hydrocarbons within the basin. Sweetgrass Arch Mountains Lake Mountains Basin Basin SR Nye-Bowler Fault Basin Fault ￿ Predominantly a carbonate depocenter in the Paleozoic, the basin is also 2000 Bearpaw Uplift Beartooth Pryor PreCambrian Rocks Mtns POWDER Mtns RIVER interbedded with clastics and evaporites. The clastic intervals are composed Poplar Dome Williston Basin 3000 Bighorn BASIN SOUTH DAKOTA of marine, organic rich shales which are the principal source rocks for the Rocky Mountain Trench Little Rocky Mountains AbsarokaBIGHORN Black Mtns BASIN Mtns Hills 4000 basin. In addition, some of the clastic intervals also include nearshore marine Overthrust Belt Uplift Owl Creek Casper or fluvial sandstone deposits. The carbonate and evaporite units are mainly Mtns Arch 5000 IDAHO Wind WIND RIVER tidal flat, bioherm/reef or sabhka deposits. Cyclic sedimentation of marine Fault River WYOMING BASIN Chadron Casper Mtn 6000 Mtns Sweetwater shales, limestones/dolomite, and anhydrites or salt are indicative of the Laramie Thickness of Sediment (feet) Uplift GREEN Mtns Hartville Arch RIVER Uplift Paleozoic section within the Williston Basin. 7000 RED HANNA BASIN DESERT BASIN NEBRASKA ￿ Potential reservoir intervals can be formed in the limestone or dolomite via ALLIANCE 8000 Rock BASIN MedicineLARAMIE Springs Bow BASIN UTAH Uplift BASIN primary or secondary porosity mechanisms. Porosity may be intergranular, Sierra Uinta Mtns WASHAKE Madre Mtns vuggy, intercrystalline or fractured or combinations of all types depending on Figure FB-2.2. Generalized time-slice cross-section along A-A'. Line of section along 48 BASIN Mtns COLORADO structural position and depositional environment. degrees latitude with selected points every 1 degree longitude. Datum is base Ordovician. EXPLANATION Anticline Precambrian Basement Uplifts Geologic History - Cambrian and older rocks Syncline Other Uplifts or Basins ￿ Precambrian age supracrustal sedimentary rocks are present in western Faults SR - Standing Rock BK - Fort Belknap Cenezoic Volcanic Fields BR - Fort Berthold BF - Blackfeet Montana and extend into Glacier National Park (see Fig. FB-2.1). These rocks A A' FP - Fort Peck Reservations X-section are estimated to be from 900 to 1400 million years old. No Precambrian rocks are exposed on the Fort Berthold Reservation. Figure FB-2.1. Present day structural features of the northern Rocky Mountain region. Includes ￿ During Cambrian time, a major seaway existed in western Montana and major fault zones, uplifts, basins, and reservation areas (modified after Peterson, 1987). eastern Idaho (see Figs. FB-2.2 & 2.4). This seaway gradually transgressed 110 105 100 from west to east across eastern Montana and the Dakotas. The dominant 0 100 40 20 0 source of coarse-grained clastics was to the east (from the Sioux Arch) and 100 A 60 WEST EAST A' 0 Fort Berthold gradually changed into shales and limestones to the west. Thickness of the 80 Antelope Longitude Values (in Degrees) Reservation 120 A A' Cambrian rocks varies from over 2000 feet in the Montana Disturbed Belt to less than 100 feet along the eastern edge of the Williston Basin. Cambrian 120 Fort Berthold Taylor Reservation 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 sediments buried under the Fort Berthold Reservation are about 300-600 feet 100 0 North Dakota Triassic Rocks thick and composed predominantly of coarse-grained sandstone. 120 80 Pennsylvanian Rocks 150 60 40 Bakken Shale Permian Rocks Montana 20 1000 Geologic History - Ordovician to Triassic 100 Williston Basin 60 40 Devonian Rocks ￿ A major depocenter evolved along the eastern edge of the Williston Basin 100 2000 Mississippian Rocks which was a stable, marine shelf area throughout much of the Paleozoic (see Fig. FB-2.3). Ordovician and Silurian rocks were deposited mostly in a Bearpaw Uplift 80 shallow tidal flat environment which resulted in alternating cycles of Cambrian and PreCambrian Rocks Cambrian Rocks older rocks exposed 3000 Bakken Shale Wyoming South Dakota Sweetgrass Arch Sands and Shales limestone/dolomite, marine shales, and evaporites. By the end of Silurian sandstone facies 40 0 time, a regional lowstand resulted in a basin-wide unconformity separating shale, sandstone and 20 Rocky Mountain Trench minor limestone facies 0 Ordovician Rocks Silurian and Devonian rocks. This unconformity influenced the development 4000 green shale facies Overthrust Belt of vuggy, karsted, carbonate sediments adjacent to this horizon. Present-day Little Rocky Mountains Prairie Salt 40 contour interval, in multiples of 10 feet thickness of Ordovician and Silurian rocks in the reservation area are 1200 5000 Thickness of Sediment (in ft) feet and 1000 feet , respectively. Figure FB-2.4. Map showing thickness of Cambrian-aged Deadwood and equivalent rocks along Poplar Dome Silurian Rocks ￿ Deposition during Devonian time proceeded much as it had in the Silurian with facies information, location of analog fields from Cambrian sediments, location of reservation, and location of regional cross-section A-A' (modified after Peterson, 1987). 6000 except for the development of highly organic-rich shales within the carbonate Cambrian Rocks intervals. Within the reservation boundaries, Devonian sediments are about Sands and Shales 1700 feet thick and include the regional Prairie Salt (500-700'), and the 7000 Bakken Shale (70-100'). The Prairie Salt forms a regional seal for the older Ordovician Rocks intervals and has been mobilized/dissolved out of this section near the western 8000 edge of the basin (105 degrees longitude). The Bakken Shale is thought to be one of the primary source intervals for Mississippian and younger production. Figure FB-2.3. Generalized time-slice cross-section A-A'. Triassic through Ordovician. Line of section along 48 degrees latitude with selected points every 1 degree of longitude. Datum is the base of Jurassic, Permian missing (from C.W. O'Melveny, July 1996).

Fort Berthold Reservation GEOLOGY OVERVIEW Page 3 of 18 North Dakota Geologic History WEST Longitude Values (in Degrees) Fort Berthold EAST removed any evidence of these rocks west of longitude 104 degrees. Permian rocks Reservation within the reservation are about 500 feet thick. Triassic-aged sediments are also A A' Cretaceous present and of continental origin. Estimated thickness of Triassic rocks across the 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 0 Epeiric Seaway reservation are about 400-500 feet thick.

Alaska Greenland 1000 Geologic History - Jurassic to Cretaceous Volcanics A tectonic structural reorganization of the North American continent occurred during Upper Cretaceous Jurassic-Cretaceous time. This resulted in a major change in depocenter position of 2000 the Williston basin, shifting from the east to the western side (Figure 4.3). The inital (Niobrara and Eagle Formations) pulses of the Sevier and later Laramide thrusting resulted in dominantly clastic deposition in the Cretaceous Seaway during this time (Figure 4.4). 3000 ￿ Thickness of Jurassic rocks across the reservation area are estimated to be about 1200 to 1400 feet thick and are comprised of a complex mixture of nearshore marine, 4000 fluvial, and evaporitic deposits. Early Cretaceous-aged continental/fluvial sediments Jurassic Rocks Canada are about 300-400 feet thick. Provenance for these sediments are thought to have Lower Cretaceous 5000 been from the southeast in what is present day South Dakota. (Mowry) Cretaceous Poplar Dome Epeiric Seaway ￿ The Mowry/Skull Creek Formation is about 400-500 feet thick within the Mississippian and Older Thickness of Sediment (in ft) reservation area and was deposited in a transgressive marine sequence which 6000 Rocks United States Lower Cretaceous extended from western Montana eastward into the Dakotas; from Texas northward (Kootenai) Bearpaw Uplift 0 into Canada. Numerous clastic sandstone deposits are present within this sequence Cretaceous 7000 Sweetgrass Arch Epeiric Seaway and are the result of variations in sea level and clastic influx into the seaway. Williston Basin ￿ During Upper Cretaceous time thrusting and crustal loading from the west had Rocky Mountain Trench subsided enough to allow the re-establishment of carbonate deposition within the 8000 Mexico Cuba seaway. Extensive chalk deposits of the Greenhorn/Niobrara Formations were Overthrust Belt deposited as well as thousands of feet of marine carbonate/clastic shale. Upper Figure FB-3.2. Generalized cross-section A-A' - Cretaceous and Older Rocks. Line of cross-section Cretaceous rocks in the area are more than 2500 feet thick. As the Laramide Orogeny along 48 degrees latitude with selected points every 1 degree of longitude. Datum located at the top of and associated thrusting began to exert influence, nearshore marine and fluvial the Cretaceous. sandstones began depositing along the shorelines of the seaway.

Figure FB-3.3. Paleogeographic map of North America during Late Geologic History - Tertiary and Quaternary Cretaceous time, showing the extent of the Cretaceous seaway (after As the orogenic uplifts of the Laramide Orogeny occurred during Late Cretaceous to 110 105 100 Rice and Shurr, 1980). Tertiary time, older Cretaceous rocks were uplifted and eroded. Only the central 200 A portion of the Williston preserved the swamp/peat deposits during the Paleocene and 600 A'

Eocene. Coal deposits of the Fort Union and equivalent rocks are the result. These 400 GEOLOGIC HISTORY (continued) 600 Ft. Berthold sediments can be up to 1750 feet thick across the reservation. Alpine glaciers existed 0 600 Reservation 600 Dickinson Field 0 in Montana during Quaternary time and extensive glacial lakes and ice sheets covered 1000 400 Geologic History - Ordovician to Triassic 600 800 the reservation area. 400 North Dakota By Mississppian time, the western portion of the Williston Basin was 200 continuously receiving carbonates and evaporites in a shallow, marine shelf 0 environment (see Figure BF-3.1). Most of the producing reservoirs in the Montana basin are from these cyclic marine shales, limestone/dolomite porosity horizons, and evaporitic carbonate sequences. Eventually, the Charles Salt Wyoming horizon would cover the entire basin and part of eastern and central Cambrian and Montana. By late Mississippian time, deposition of shales and mudstones older ricks exposed South Dakota were mainly confined to the central Williston area and the Big Snowy sandstone and sandy trough in central Montana. Total thickness of Mississippian rocks within shale facies the reservation boundaries is about 2400-2800 feet. green, gray, and red shale ￿ Another major lowstand at the end of the Mississippian time led to with minor limestone widespread erosion and karstification of the underlying carbonate intervals. 200 200 foot contour interval Pennsylvanian sediments are confined to the center of the Williston basin and central Montana. Pennsylvanian rocks are about 400 feet thick. ￿ Permian deposits are confined to the central Williston basin area and Figure FB-3.4 Isopach map showing thickness and facies distribution of late Mississippian and are predominantly sandstone/shale and evaporite sequences. As the Pennsylvanian sediments of the Tyler and Big Snowy Group suite of rocks. Location of Fort Berthold Williston basin became filled to base-level, only shallow marine/terrestrial Reservation, any analog fields, and older basement rocks also shown (modified after Peterson, 1987). sediments were deposited. This also resulted in numerous unconformities in this horizon. A major unconformity at the end of Permian time has

Fort Berthold Reservation GEOLOGY OVERVIEW Page 4 of 18 North Dakota Geologic History Petroleum Systems ￿ Bakken Shale - Known as a world-class source interval, the Bakken has an average of Madison Group Subcrop 11.33 wt. % organic carbon. Oil generation was probably initiated about 75 mya with initial Region of Prairie Petroleum Province expulsion occurring about 70mya (late Cretaceous). Calculations based on pyrolysis data Formation salt ￿ Accumulations of hydrocarbons owe their genesis to several critical factors: generation preservation A suggest that between 92.3 - 110 billion barrels of oil have been generated from the Bakken. and migration from source intervals, structural/stratigraphic trapping mechanisms, porous Except for a few fields utilizing the Bakken as the reservoir, significant volumes of Bakken reservior rocks, and the appropriate timing of formation/generation of these factors. At least sourced oil have not been discovered to date. Some researchers suggest that most of the Saskatchewan Manitoba four petroleum systems are present within the Williston Basin with numerous underexplored expelled Bakken oil is probably lost into the drainage system, where it remains dispersed, at potential hydrocarbon exploration targets. This discussion focuses on the source intervals. very low saturations (see Figures 2.2 and 2.3 below). Most of the larger structures in the Williston Basin contain mixtures of Lodgepole (Madison) and Bakken oils with the latter at Poplar Source rocks: Generation and Expulsion low relative concentrations. Nesson Anticline Dome At least four source intervals have contributed to the hydrocarbon generation and B Petroleum Province accumulation patterns within the Williston Basin and all are present in the reservation area. ￿ Lodgepole source interval - This zone contains predominantly carbonate source horizons with relatively low initial yields; 8 kg HC/t rock. However, large volumes of oil have been 7000 ￿ Ordovician Winnipeg shale - A very organic rich shale which exceeds richness values of discovered typed to this source interval, especially within the Nesson Anticline Petroleum Cedar Creek Anticline the Bakken shale in some cases. This interval first entered the oil window in latest Province. This horizon seems to be geographically restricted to the central and southern Petroleum Province 5000 North Dakota Cretaceous/Paleocene time. Peak generation and expulsion occurred between 55-38 mya and portions of the Williston Basin. It appears that migration and trapping efficiencies were much some generation continues today. Oils typed to this source are found in the Cedar Creek higher in this horizon when compared to the Bakken. This may be due to advantageous South Dakota anticline, eastern Montana, and western North Dakota. However, structures which formed in timing of structure development relative to expulsion/migration. Montana 3000 latest Eocene or after (such as the Nesson Anticline) could not trap the oil migrating from this 0 200km source. This suggests that much of Winnipeg- sourced oil migrated to the northeastern flank ￿ Winnipegosis source interval - The rich, basinal carbonate horizons within this unit (47 Wyoming Depth of base Madison (ft) of the Williston Basin where undiscovered oil resource may be present in Ordovician and kg HC/t rock) are restricted to a starved, Devonian which begins along the northern end of the Silurian strata. This source interval is aerally restricted to the southern and central portions of Nesson anticline and continues north into Canada. This interval charges many of the Figure FB-4.1 - Location of the Williston Basin with major petroleum provinces the basin. and line of section for burial history diagrams indicated. Structural contours are Waulsortian mounds found in some of the Mississippian-aged sequences. drawn on the base of the Madison Group (after J. Burrus, K. Osadetz, S. Wolf, et al, 1995).

A Distance (km) B A Distance (km) B 50 100 150 200 250 300 50 100 150 200 250 300

0 0 Bakken thickness exaggerated x 2.5 HC saturation HC saturation 1 1 TR=.10 < 2% TR=.10 < 2%

2 - 5% 2 - 5% TR=.20 TR=.20 2 5 - 10% 2 Winnepegosis 5 - 10% Madison TR=.65 thickness exaggerated TR=.65 Depth (km) Depth (km) x 2.5 between 0-250km 10 - 80% Lodgepole Northern limit of Duperow 10 - 80% Ordovician source 3 TR=.90 > 80% 3 TR=.90 > 80% Potential in Potential in Ordovician source & Interlake Prairie Winnipegosis & Prairie Winnipeg source Bakken interval Bighorn salt horizon Lodgepole salt horizon 4 4 0Ma 0Ma Figure FB-4.2 - Burial history model with patterns of transformation ratio (TR) at the present and distribution Figure FB-4.3- Burial history model with patterns of transformation ratio (TR) at the present and distribution of of oil saturations, calculated using a finite model, two-dimensional computer model that simulates oil oil saturations, calculated using a finite model, two-dimensional computer model that simulates oil generation, generation, expulsion, and migration. Generation kinetics determined by experimental data from Williston expulsion, and migration. Generation kinetics determined by experimental data from Williston Basin source Basin source rocks. Thermal history model constrained by both present temperature and source rock rocks. Thermal history model constrained by both present temperature and source rock maturity data. maturity data. Saturations compared to known patterns of hydrocarbon accumulation within the basin. Saturations compared to known patterns of hydrocarbon accumulation within the basin. Saturations between Saturations between 2-5% represent dispersed oil; saturations above 10% represent oil accumulation or 2-5% represent dispersed oil; saturations above 10% represent oil accumulation or depleted source rocks. depleted source rocks. Arrows show patterns of active oil migration (after J. Burrus, K. Osadetz, S. Wolf, et Arrows show patterns of active oil migration (after J. Burrus, K. Osadetz, S. Wolf, et al., 1995). al., 1995) Fort Berthold Reservation Page 5 of 18 North Dakota Petroleum Systems Schematic Diagram of Play Types - Fort Berthold Reservation Play Summary WEST EAST The diagram and summary charts are coded to the play type number Upper Cretaceous and provide a quick reference to the Play Types - Explanation discovered and undiscovered 1. Madison Structure Play resource for the reservation area. Niobrara 10 10 2. Madison Shoreline/Truncation Play Also listed are USGS (1996) risk Jurassic 3. Mississippian Lodgepole estimates and designations for each Waulsortian Mound Play Triassic of the play types. A qualitative brief 4. Ordovician Red River Play Permian review of the summary aspects of 5. Devonian Nisku/Duperow Play Pennsylvanian each play are also shown. 6. Silurian Interlake Play 1 7 2 2 7 7. Pennsylvanian Tyler-Heath Play

9 8. Pre-Red River Gas Mississippian 3 Winnipeg/Deadwood Clastics 5 3 Mississippian Devonian Bakken Shale 9. Fractured Bakken Play 6 9 Red River 4 10. Shallow Microbial Gas Play Interlake 8 Winnipeg Deadwood

No scale implied - drawing is approximate width of Reservation Dolomite Precambrian Fluvial/Clastic dominated shorelines

Limestone Sandstone Clastic/calcareous shale

Organic-rich Limestone shorelines shale or Waulsortian Mounds

Oil Gas

Figure FB-5.1. Schematic diagrams of play types at Blackfeet Reservation

Reservation: Fort Berthold Total Production ( by province-1996) Williston Basin Undiscovered resources and numbers of fields are Geologic Province: Central Wiliston Basin Oil: 1496 MMBO for Province-wide plays. No attempt has been made Province Area: Williston Basin (143,000 sq. miles) Gas: 1735 BCFG to estimate number of undiscovered fields within the Reservation Area: 1530 sq. miles (980,000 acres) NGL: 192 MBNGL 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 (chance of success)

Madison, structure 3101a folded structures, primary Both 878 MMBO Median: 600 MMBO(30 fields @ 20MMBO) 1 3,000 - 12,000 ft 1) confirmed play; excellent 1) lack of well control and secondary porosity 916.5 BCFG Field Size (> 1 MMBOE) high production within reservation 2) rough topography in carbonates 77.9 MMBNGL 2 MMBO (min), 20 MMBO (median), 5.3 MMBO(mean) 2) thermally mature source rocks 3) porosity and facies may be (numbers include 1, 2,& 3) No. of undiscovered fields (> 1 MMBOE) 3) source rocks and reservoir present highly variable 1 9 (min) 30 (median) 60 (max) 31.9 (mean) 4) seismic delineation is useful numbers include plays 1, 2, & 3

Madison shoreline/ 3101b Cyclic evaporite/ carbonate Both 878 MMBO Median of 600 MMBO (30 fields @ 20MMBO) 1 3,000 - 12,000 ft 1) confirmed play; excellent 1) lack of well control truncation play sequence, structure/stratigraphic 916.5 BCFG Field Size ( >1 MMBOE) high production within reservation 2) rough topography updip pinchout, multiple shoreline 77.9 MMBNGL 2 MMBO(min) 20 MMBO(median) 5.3 MMBO(mean) 2) thermally mature source rocks 3) porosity and facies may be cycles (numbers include 1, 2,& 3) 3) source rocks and reservoir present highly variable No of undiscovered fields (> 1 MMBOE) 4) trend extends into reservation 4) seismic may not be able to 2 9 (min) 30 (median) 60 (max) 31.9 (mean) 5) mostly shallow drilling depths delineate shoreline trends numbers include plays 1, 2, & 3

Miss. Lodgepole/ 3101c Mound buildups; 'reefs', small Both 878 MMBO Median of 600 MMBO (30 fields @ 20MMBO) 1 3,000 - 12,000 ft 1) confirmed play; trend probably 1) lack of well control Waulsortian Mound play but prolific structures; excellent 916.5 BCFG Field Size ( >1 MMBOE) high extends to reservation 2) rough topography porosity and permeability 77.9 MMBNGL 2 MMBO(min) 20 MMBO(median) 5.3 MMBO(mean) 2) thermally mature source rocks 3) small areal extent, may (numbers include 1, 2,& 3) 3) source rocks and reservoir present be difficult to explore for No of undiscovered fields (> 1 MMBOE) 4) seismic may be very useful 3 9 (min) 30 (median) 60 (max) 31.9 (mean) numbers include plays 1, 2, & 3

Ordovician Red River Median of 250 MMBO (25 fields @ 10 MMBO) 3102 Cyclic evaporite/ carbonate Both 188.3 MMBO 1 7,000 - 12,000 ft 1) confirmed play; 1) lack of well control Play sequence, structure/stratigraphic 555.7 BCFG Field Size ( >1 MMBOE) high production within reservation 2) rough topography updip pinchouts; multiple shoreline 70.5 MMBNGL 2 MMBO/10 BCFG(min) 10 MMBO/35 BCFG(median) 2) thermally mature source rocks 3) possible small exploration cycles 2.1 MMBO/11.7 BCFG(mean) 3) source rocks and reservoir present targets 4 No of undiscovered fields (> 1 MMBOE) 4) seismic useful in locating 5 (min) 25 (median) 50 (max) 26 (mean) structures

Table FB-5.1. Play summary chart

Fort Berthold Reservation Page 6 of 18 North Dakota Play Types Reservation: Fort Berthold Total Production ( by province-1996) Williston Basin Undiscovered resources and numbers of fields are Geologic Province: Central Williston Basin Oil: 1496 MMBO for Province-wide plays. No attempt has been made Province Area: Williston Basin (143,000 sq. miles) Gas: 1735 BCFG to estimate number of undiscovered fields within the Reservation Area: 1530 sq. miles (980,000 acres) NGL: 192 MBNGL 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) Median 250 MMBO (25 fields @ 10 MMBO) Nisku and Duperow 3103 Cyclic evaporite/carbonate Both 160.5 MMBO 1 8,000 - 12,500 ft 1) confirmed play; 1) lack of well control sequences. Structural and 159.2 BCFG Field Size (> 1MMBOE) high production within reservation 2) rough topography stratigraphic pinchouts. Excellent 12.7 MMBNGL 2 MMBO/10 BCFG 10 MMBO/60 BCFG 2.1 MMBO/13.1 BCFG 2) thermally mature source rocks porosity and permeability No.of undiscovered fields (> 1 MMBOE) 3) source rocks and reservoir present 5 9 (min) 25 (median) 60 (max) 26.9 (mean) 4) seismic delineation is useful

Silurian Winnipegosis Median 225 MMBO (15 fields @ 15 MMBO) 3105 Cyclic evaporite/ carbonate Both 55.5 MMBO 1 8,000 - 12,500 ft 1) confirmed play; 1) lack of well control and Interlake sequence, erosional surfaces. 180 MMCFG Field Size (> 1MMBOE) mod.- high production within reservation 2) rough topography Primary and secondary porosity. 24.8 MMBNGL 3 MMBO/15 MCFG(min) 15 MMBO/90 MMCFG(median) 2) thermally mature source rocks 3.3 MMBO/19.7 MMCF(mean) Structural and unconformity related 3) source rocks and reservoir present 6 trapping mechanisms No. of undiscovered fields (> 1 MMBOE) 4) seismic useful in prospect 5 (min) 15 (median) 25 (max) 15 (mean) delineation

Post Madison 3106 Fluvial and nearshore sandstones Both 133.5 MMBO Median 16 MMBO (8 fields @ 2 MMBO) 1 5,500 - 9,000 ft 1) Thermally mature source rocks 1) No production within Penn. Tyler/Heath with structural closures. Traps may 28.8 BCFG mod.-high 2) source rocks and reservoir present reservation also occur as discontinuous sandstone Field Size (> 1MMBOE) 3) shallow drilling depths 2) rough topography lenses. 2 MMBO 10 MMBO 2.1 MMBO 3) lack of well control 4) depositional area within 7 No of undiscovered fields (> 1 MMBOE) 4 (min) 8 (median) 15 (max) 8.6 (mean) reservation may be marine instead of shoreline

Ordovician Pre-Red River 3107 Clastic sequences, fluvial and NGL and low no information Median 50 BCFG (5 fields @ 10 BCFG) 1 10,000 - 16,000 ft 1) confirmed play; 1) lack of well control Play nearshore blanket sandstones. BTU gas available moderate production within reservation 2) rough topography Large, faulted structures Field Size (> 1MMBOE) 2) thermally mature source rocks 3) low BTU, contains 10 BCFG 25 BCFG 13.1 BCFG 3) source rocks and reservoir present nitrogen 8 No. of undiscovered fields (> 1 MMBOE) 4) seismic useful in locating 1 (min) 5 (median) 20 (max) 7.3 (mean) structures 5) high volume reserves

Fractured Bakken 3111 Organic rich shale, marine siltstone; Both No information available not estimated 1 7,500 - 11,100 ft 1) confirmed play; 1) lack of well control fractured; thermally mature oil shale Oil shows from Sanish sandstones 70.3 MMBO/ sq. mile generated hydrocarbons 0.2 (20%) production within reservation 2) rough topography 56.24 MMCFG/ sq. mile generated hydrocarbons 2) thermally mature source rocks 3) Probable narrow bands of Area of play = 8185 sq. miles 3) source rocks and reservoir present potential fractured reservoir 9 7806 sq. miles untested 4) seismic delineation is useful zones

Niobrara Microbial 3113 Niobrara limestone and other Microbial gas Only production to date is from not estimated 1 500 - 4500 ft 1) large volume play 1) lack of well control Gas Play shallow reservoirs, self-sourced; Cedar Creek Anticline and 180 MMCFG/160 acres (median) 0.5 (50%) 2) shallow drilling depths 2) rough topography porosity decreasing with increasing Bowdoin dome. These fields are 256 MMCFG/160 acres (mean) 3) accumulations in structural 3) reservoir continuity is depth. Large volume accumulations from shallow Eagle Formation Area of play = 55,000 sq. miles traps, seismic may be useful problematic 10 possible sandstones, not Niobrara. 29,958 sq. miles untested (mean) in delineation of traps 4) areal extent may be small

Table BR-6.1. Play type summaries. Conventional play type

Unconventional/Hypothetical play type

Fort Berthold Reservation Page 7 of 18 North Dakota Summary of Plays (continued) R 96 W R 95 W A A.P.C. A.P.C. A.P.C. A' Blue Buttes Field Parameters A.P.C. #3 M Aura #1 Aura #2 Selliseth Texaco #20 Sivertson Se Sw Sec. 19 Se Se Sec. 19 Se Sw Sec. 20 #4 Gov't-Dorough 1 6 1 Se Se Sec. 20 Formation: ￿ Mississippian Madison KB 2346' KB 2388' KB 2495' Se Sw Sec. 21 KB 2493' KB 2690' Lithology: Interbedded limestones -6600 and dolomites. 7 12 -6500 Average depth: 9200 feet GR Last LL 9000 Charles (in reservation area) T

9100 Salt 9100 -6600 18 13 151 9300 -6700 N 9000 LL Mississippian Porosity: ￿ averages 7.7% GR 9100 -6600 9200 Madison Permeability: ￿ 0.1-8 md, 9200 -6700 19 24 9400 average is 3 md. A A' 9100 Gamma Ray Marker Formation 9200 9300 Oil/gas column: ￿ oil 280 feet -6800 -6700 Top Blue Buttes Pay 9300 9500 Average net pay: ￿ variable 30 25 9200 9300

9400 -6900 9400 9600 Other Formations with shows: Kibbey sandstone, 36 31 36

9300 Kibbey limestone and Charles Formation 9400 -7000 9500

9700 1 6 1

Blue Buttes Field Structural Cross-Section 7 -6800 12 T 150 Figure FB-7.1. Blue Buttes Field structural cross-section (after Connelly, North Dakota Geological Society, 1962). N 18 13 Analog Fields

(*) denotes fields within Reservation 24 19 24 Figure FB-7.2. Structure contour map PLAY TYPE 1 Antelope* - ￿ 39 MMBO￿ 18.9 Mmcf of Blue Buttes Field showing location R 96 W R 95 W (includes Bakken, Duperow, and Interlake) of cross-section A-A'. Structure on top Note: Only Madison penetrations Blue Buttes Field Folded Structure - Mississippian Carbonate are shown of Lower Charles Salt. Play Blue Buttes -￿ 45 MMBO￿ 28.3 Mmcf Top Lower Charles Salt (includes Duperow, Interlake, and Red River) Structure Map CI = 20 feet General Characteristics - The Mississippian Madison play is primarily a structural play combined with superimposed Bear Den -￿ 1.4 MMBO￿ 1.5 Mmcf A.P.C. #1 Swenson Heirs A.P.C. #1 AB Fleming Estate A.P.C. #1 T Larson Tract 1 A.P.C. #1 Antelope Unit 'A' A.P.C. Gulf #1 J Strand A.P.C. Carter #1 Reed-Norby Unit (Madison, Duperow) C Se Ne 11-152N-95W C Nw Nw 12-152N-95W C Se Sw 1-152N-95W Ne Se 1-152N-95W S/2 Nw/4 6-152N-94W Lot 2 6-152N-94W facies/porosity changes and pinch-outs. This play is the dominant 2242 KB 2210 KB 2136 KB 2117 KB 2129 KB 2198 KB B B' hydrocarbon producer in the Williston basin. The Madison is Croff -￿ 1.7 MMBO￿ 4.0 Mmcf -5000 -5000' subdivided into several producing horizons (see cross-sections (Madison, Duperow) -5603 -5589 -5557 -5494 Kibbey -5619 below), based on porosity zones. These zones are overlain by Kibbey -5838 -5794 -5889 -5882 -5908 -5876 evaporite or shale seals. The Charles Salt horizon is a regional Charles Charles -6161 evaporite seal which overlies most of the Madison Formation. -6575 -6492 -6466 -6409 Madison -6536 Madison -6809 ￿ Reservoir rocks are generally dolomitized carbonate rocks with Antelope Field Parameters Lodgepole TD -6866 TD -6908 either algal, oolitic, crinoidal, or micritic components. Source Bakken TD -7212 rocks are thought to be either of Bakken origin or cyclic marine Formation:￿ Mississippian Madison shales within the evaporite-carbonate cycle. Onset of oil Lithology:￿ Limestone, brown, dolomitic, fossil -8081 -8226 Three Forks - Nisku generation and migration is modeled to begin in the Late fragments, occasional chalky horizons. R 94 W -8367 TD -8255 -8555 Duperow B' TD -8570 Cretaceous. Average depth: ￿ 9100 feet -8770 Souris River -8997 Dawson Bay-Prairie Evaporite (in reservation area).￿ -9273 A Fort Berthold Reservation Winnipegosis- Elm Point - Ashern Porosity: ￿ 4.7% gross, intergranular, vuggy unconformity -9631 horizons Permeability: ￿ info. not available T 152 Silurian Oil/gas column: ￿ highly variable N -10779 Stony Mountain Average net pay: ￿ variable -10993 Structural Cross Section

Other shows: ￿ Sanish, Duperow, Interlake. Red River Antelope Field McKenzie Co., North Dakota Other information: contains 4.7% H2S -11632 Winnipeg

-12274 Index Map Cambrian ?

-13012 PreCambrian

Figure FB-7.3. Antelope field cross-section (after North Dakota Geological Society, 1962).

Fort Berthold Reservation CONVENTIONAL PLAY TYPE 1 Page 8 of 18 North Dakota Folded Structure - Mississippian Carbonate Play PLAY TYPE 2 Canada Carnduff Mississippian Shoreline Play Elmore Analog Fields U.S.A. North Dakota (*) denotes fields which lie within reservation Mouse General characteristics - This play is an extension of the northeast shelf play River Burke which produces from Sherwood and Bluell porosity cycles. In an eastward Park Bottineou direction the Mississippian interval subcrops the following formations: Midale, Renville Plaza* - 2.6 MMBO, 1.7 Mmcf out of 20 wells, 3-4 MMBO ultimate (Bluell) Nesson, Bluell, Sherwood, Mohall, Glenburn, Landa, Wayne, and Lodgepole. Lake Reservoirs are dolomitized carbonates of either algal, oolitic, or bioherm banks Wabek* - 5.1 MMBO, 3.6 Mmcf, out of 18 wells, 6-7 MMBO ultimate (Sherwood) Darling along the shoreline trend. The updip seal can either be an evaporite or a shale. Source rocks are likely contained within the Bakken or other marine shales R 88 W R 87 W within the evaporite sequence. Lone Ward McHenry Tree Mountrail T 153 Wabek Wabek N Plaza Sherwood Field Shoreline Plaza Field Parameters

(Sherwood Prod.) Lucky Mound A' McLean Formation: Mississippian Mission Canyon, Bluell subinterval Centennial Index Map Lithology: Light brown-brown, peloidal, oolitic 0 12 24 miles pisolitic, intraclastic and -5200 composite wackestone-grainstone Average depth: ￿ 7400-7500 feet A Study Area Porosity: ￿ intergranular, vugular, intraparticle; 6-16% Permeability:￿ no information Plaza Field North Dakota Oil/Gas column:￿ at least 120 feet, no oil/water contact known (Bluell Production) Average net pay: 6 feet T Figure FB-8.1. Sherwood shoreline trend and position of 152 major oil fields ( after Sperr et al, 1993). N

B B' -5300 A Se Se 3 Se Nw 2 Sw Sw 32 A' B Ne Ne 20 Ne Ne 21 Ne Ne 22 B' SW 152N-88W 152N-88W 152N-87W NE West 152N-88W 152N-88W 152N-88W East -5500

GR CNL/FDC GR CNL/FDC GR CNL/FDC GR CNL/FDC GR CNL/FDC GR CNL/FDC 7300 -5400 7200 7200 7400 DEN DEN DEN

DEN POR DEN POR 7300

DEN POR 7200 Rival NEU POR Rival NEU POR NEU POR NEU NEU NEU

Figure FB-8.2. Structure map of the Sherwood subinterval - Plaza and Wabek 7300 7400 7300 fields (after Sperr et al, 1993). 8 7300 8 8 8 L. Bluell 8 L. Bluell 8

Wabek Field Parameters Sherwood Sherwood 7500 Formation: Mississippian Mission Canyon

Mohall 7600 Sherwood subinterval 7400 Mohall 7500 Lithology: ￿ Light brown-brown, peloidal, oolitic,

pisolitic intraclastic and composite 7500 7500

Glenburn 7600 wackestone-grainstone D & A Glenburn Average depth: ￿ 7300-7500 feet IPF 308 BO, 134 MCFG & DST: Rec. 45' SO&GCM, 7700 IPP 34 BO, 15 MCFG & IP: Non-commercial 0 BWPD 270' GCW 57 BWPD Perfs: 7388-7402, 7408-7412 Porosity: ￿ intergranular, vugular, intraparticle Perfs: 7324-7366 Perfs: 7415-7424,7436-7438 7416-7422 6-26%, ave.=10% IPF 259 BO, 129 MCFG & Permeability: ￿ no information IPP 29 BO, 45 MCFG & 0 BWPD Intershoal Mudstone 65 BWPD Perfs: 7354-7390 Perfs: 7482-7484, 7490-7496 Oil/Gas column: ￿ at least 100 feet Plaza Field Cross-section Wabek Field Cross-section Average net pay: ￿ 26 feet Figure FB-8.3. Wabek Field cross-section showing position of productive interval. Datum is Figure FB-8.4. Plaza field cross-section showing position of productive interval. Datum is top of top of Sherwood horizon (after Sperr et al, 1993)). Sherwood horizon (after Sperr et al, 1993). Fort Berthold Reservation CONVENTIONAL PLAY TYPE 2 Page 9 of 18 North Dakota Mississippian Shoreline Play WILLISTON BASIN PLAY TYPE 3 Lodgepole Buildups Mississippian Lodgepole West East S Waulsortian Mounds sea level S S ? General Characteristics - No production has been CANADA ? established within the reservation, however, there is a 100 productive trend in neighboring Stark County. Similar 300 500 mounds have been found in outcrop in the big Snowy ? Fort Berthold ? Mountains, Montana. Montana 900 ￿ Waulsortian facies within the Lodgepole formation LB Trough 700 Montana 500 BS are lens-like buildups of massive limestone with Trough shelf basin shelf 500 abundant crinoid and bryozoan fragments. Potential slope B ? 300 reservoir intervals are boundstones whose framework 500 constituents consist of crinoids, bryozoans, and lesser Explanation amounts of mollusks and corals. Inter and intra-particle Approximate erosional limit of Madison Formation porosity is the result of leaching and alteration of these Grainstone-packstone beds on flanks of mound particles. Bryozoan-crinoid buildup facies (potential hydrocarbon reservoir) Postulated Waulsortian mounds Mudstone-wackestone core facies of mound Known Waulsortian mounds Wackestone-packstone buildup facies

Figure FB-9.2. Generalized isopach map (c.i.=200') of the Lodgepole Formation, Williston Basin in Figure FB-9.1. Diagrammatic cross-section of Waulsortian Mounds within the Williston Basin, shows relation to the Fort Berthold Reservation. LB=Little Belt Mountains, B=Bridger Range, BS=Big Snowy facies distribution and general location within the basin (after Burke and Lasemi, 1995). Mountains, D=Dickinson Lodgepole Field, S=Saskatchewan (modified from Burke and Lasemi, 1995).

CONOCO, INC. Figure FB-9.4. Generalized Lodgepole Kadramas 75 section depicting Waulsortian Mound Dickinson Field, Lodgepole Formation NW SE 31-140-96 Buildup (after Burke and Lasemi, 1995). Stark Co., N.D. Williston Basin DLL Mission GR oolitic, pelletal, light yellow-brown, Canyon 9200 dolomitic, skeletal packstone to wackestone R 97 W R 96 W Lodgepole Dickinson Field Lodgepole Parameters T 9300 140 N 240 Formation:￿ Mississippian Lodgepole Supra Mound Lithology: primarily fossiliferous grainstones 9400 medium to dark gray-brown slightly with minor amounts of dolomite argillaceous and cherty skeletal wackestones and mudstones boundstones, packstones 255 262 Average depth: ￿ 9800 feet 9500 368 378 260 Porosity: ￿ 9.4-10% mound core up to 15% in mound flanks 9600 Permeability: ￿ variable, up to 460md Oil/Gas column: ￿ no information log marker 9700 234 303 Average net pay: ￿ at least 50 feet T 139 Other shows: ￿ no information Lower Mound Core N 9800 light to medium gray-brown mottled Lodgepole with dark brown, bryozoan baffle and oil/water boundstones with grainstone, packstone, contact and wackestone matrix; abundant coarse (-7365) calcite cement 237 9900

10000 Bakken black shale interbedded with 20' Contour Interval argillaceous mudstone and calcareous siltstones light brown gray dolomite interbedded with Three Forks 10100 gray green shale Figure FB-9.3. Isopach map of lower Lodgepole at Dickinson Field (after Burke and Lasemi,1995).

Fort Berthold Reservation CONVENTIONAL PLAY TYPE 3 Page 10 of 18 North Dakota Mississippian Lodgepole Waulsortian Mound Play PLAY TYPE 4 110 105 100 Ordovician Red River Play A 300 A' General Characteristics: This is the second most productive formation in the 500 Williston basin. Reservoirs are dolomite intervals and dolomitic limestones 100 300 Antelope Ft. Berthold formed from bioclastic mounds and tidal flat deposits. Cyclic deposits of Blue Buttes Reservation 500 700 carbonate, evaporite, and organic rich shale provide reservoir, source, and seal. 100 Major accumulations are found on structural noses such as Nesson and Cedar Creek Anticlines. Smaller fields are found in fold structures draped over 500 North Dakota Montana 500 basement fault blocks, or small carbonate mounds. 300 ￿ The source intervals are thermally mature to overmature at the basin center, 300 and become somewhat immature along the basin flanks. Winnipeg shale and marine shales in the Red River Formation are thought to be the primary source of the reservoir oil. Hydrocarbon generation and migration is estimated to have

300 begun in late Paleozoic time.

R 96 W R 95 W Ordovician or 100 South Dakota older rocks exposed Blue Buttes Field Parameters 11,300 Dolomite facies - Red River Wyoming Limestone and dolomite facies Formation: Ordovician Red River 1 6 1 Red River Lithology: black to dark gray dolomite, limestone 11,400 very fine grained to crystalline ￿ 400 contour interval, 200' 11,400 occasionally sucrosic texture 7 12 Figure FB-10.1. Map showing thickness of Ordovician Red River Formation within the Williston basin and surrounding area, Average depth: ￿ -11,300 MSL 11,500 location of analog fields and reservation, and location of regional cross-section A-A' (modified after Peterson, 1987). Porosity: ￿ 9.8% T 11,500 18 13 151 Permeability: ￿ 1.0 md N R 95 W R 94 W Oil/Gas column: ￿ unknown

19 24 Average net pay thickness: ￿ 23 feet 11,600

30 29 28 27 26 Other shows: ￿ Kibbey Sandstone, Kibbey Limestone -11,000 Charles Formation T T 30 25 153 -11,145 153 Other information:￿ Initial IP 564 BOPD, API 58 N N 2928 Mcfgpd-discovery well

31 32 33 34 35 36 31 36 -11,200 -11,080

-11,100 -11,000 11,300 1 6 1 3 2 1 6 5 4 Antelope Field Parameters T T -10,993 152 7 12 152 Formation: Ordovician Red River T N N 11,400 150 Lithology: black to dark gray limestone/dolomite N 7 8 9 10 11 12 very fine grained to crystalline Fort Berthold Reservation 11,500 Occasionally sucrosic texture 18 13 Average depth: ￿ 13,480-13,490 feet Porosity: ￿ 12% log density porosity R 95 W R 94 W 24 19 24 Permeability: ￿ not known Note: Wells shown are Red River penetrations only. Oil/Gas column: ￿ no information R 96 W R 95 W ANTELOPE FIELD Average net pay thickness: ￿ 10 feet Note: Only Red River penetrations Blue Buttes Field Red River production was established at are shown Antelope Field in 1989 with the 30-23 Mckeen Red River Structure Map Other shows:￿ Minnelusa and Charles Formations Red River Structure Map well in section 30, T 153 N, R 94 W Cumulative production: (1995)￿ 94 MBO, 1.15 Mmcf API 56.2, IP 113 BC, 1452 Mcfgpd CI = 25 feet C.I. = 50 feet Figure FB-10.3. Red River Structure Map - Blue Buttes Field. Shows Figure FB-10.2. Structure contour map of the Red River Fm., Antelope Field. trend of Anticline development and production. Contours show the general trend of anticline/fold development.

Fort Berthold Reservation CONVENTIONAL PLAY TYPE 4 Page 11 of 18 North Dakota Ordovician Red River Play 110 105 100 PLAY TYPE 5 Analog Fields (*) denotes fields which lie within Reservation 1200 1200 1600 Devonian Nisku-Duperow Play 2000 1000 1800 A 800 1000 A' Antelope*- ￿ 39 MMBO, 18.9 Mmcf (includes Bakken, Duperow, 800 General Characteristics- This play consists of a carbonate evaporite sequence and Interlake) 600 Antelope 1400 Ft. Berthold interbedded with cyclic marine shales. Reservoir rocks are typically dolomite or Bear Den Reservation 400 dolomitized limestone. Source rock for the oil is thought to be from the Bakken Blue Buttes - ￿ 45 MMBO, 28.3 Mmcf (includes Duperow, Interlake, 600 and Red River) 200 interval which is mature-overmature in the central portion of the basin and 400 immature on the flanks. Oil migration and generation are estimated to have Bear Den - ￿ 1.4 MMBO, 1.5 Mmcf (includes Madison, Duperow) 200 North Dakota 200 begun in early to late Cretaceous time. 600 Montana ￿ Traps are gentle folds and closures related to carbonate bank deposition on Croff - ￿ 1.7 MMBO, 4.0 Mmcf (includes Madison, Duperow) paleohighs or shelf areas. These paleostructures are present on regional

200 structural trends such as the Nesson Anticline and Antelope Anticline.

R 95 W R 94 W

South Dakota Silurian and 30 29 28 27 26 older rocks exposed T Limit of Bakken source T rocks Wyoming 153 153 Limit of Prairie salt N N

31 32 33 34 35 400 contour interval, 200'

Figure FB-11.1. Map showing thickness of Devonian rocks, limit of Prairie salt, limit of Bakken source rock, location of analog R 95 W R 94 W fields and reservation, and location of regional cross-section A-A' (modified after Peterson, 1987). -8100 3 2 1 6 5 4 Bear Den Field Parameters T T -8200 152 152 R 96 W R 95 W N Formation: Devonian Duperow N Ne Ne Sec. 36, T 149 N, R 96 W Lithology: microcrystalline dolomite with fair GR Laterolog -8900 7 8 9 microsucrosic porosity 10 11 12 Fort Berthold Reservation 23 24 19 Average depth: ￿ 11,300 feet Birdbear -8300 -8600 -8950 Porosity: ￿ variable, microsucrosic

Duperow Permeability: ￿ not known 18 17 16 Oil/Gas column: ￿ variable 15 14 13 11,250 -9000 T Average net pay thickness: 13 feet 26 25 30 149 N Other info: ￿ no H2S -8400 11,300 -8900 18 20 21 Limestone 22 24 Antelope Field Parameters Shale Dolomite 35 36 31 Formation: ￿ Devonian Duperow Lithology: ￿ dolomite, brown, finely Souris River crystalline, granular to vugular 30 29 28 Bakken dolomite limestone intervals, fossiliferous evaporite Bear Den - Devonian Field Average depth:￿ 10,750 feet shale Mckenzie County North Dakota Porosity: ￿ variable, granular, vuggy ANTELOPE FIELD TOP DUPEROW STRUCTURE Permeability:￿ not known CI= 50' Oil/Gas column:￿ variable Devonian Duperow Figure FB-11.2. Bear Den - Devonian Field. Shows position of dolomitic intervals relative to the Average net pay thickness:￿ variable Devonian Structure Map Duperow interbedded evaporite seals. Productive interval indicated in black. Other shows:￿ Madison, Interlake, Sanish Other information:￿ No H2S C.I. = 100 feet

Figure FB-11.3. Structure map of Antelope Field. Shows general anticlinal fold trend to the southeast. Inset shows position of Bakken relative to Duperow Formation.

Fort Berthold Reservation CONVENTIONAL PLAY TYPE 5 Page 12 of 18 North Dakota Devonian Nisku - Duperow Play Ft. Berthold PLAY TYPE 6 110 100 105 Reservation Pre-Prairie ( Winnipegosis/Interlake Play) Antelope Field Parameters A 1100 A' General Characteristics - Regional carbonate units of lower Devonian Antelope and Silurian age are overlain by the Prairie Evaporite which acts as a seal Formation:￿ Silurian Interlake 900 rock. Typical reservoirs in the Winnipegosis are reefs or dolomitized Lithology: dolomite, cream to dark brown 700 carbonate mounds. Unconformity traps are thought to exist in the Silurian possible algal forms, 0 microcrystalline and vugular in part 500 Interlake Formation which can result in dolomitized reefs, minor karsting, 0 Average depth: ￿ -9600 feet MSL North Dakota and dissolution porosity in tidal deposits. 300 ￿ The Ordovician Red River shales are thought to be the source rocks for Porosity:￿ variable, granular, vuggy, 7.5% South Dakota this play and are thermally mature within the basin center. Typical traps Permeability:￿ 1.3md 100 consist of gentle folds with flexure faulting associated with the regional Oil/Gas column:￿ variable Montana structure. Stratigraphic traps (either pinch-outs or porosity variations) may Average net pay thickness:￿ variable Wyoming exist as well. Other shows:￿ Madison, Duperow, Sanish

Silurian and Blue Buttes Field Parameters older rocks exposed

Limey dolomite facies Formation:￿ Silurian Interlake Lithology:￿ Dolomite dolomite facies Average depth:￿ 12,300 feet (-9967 MSL) 100 contour interval, 200' Porosity:￿ 12% Figure FB-12.1. Map showing thickness of Silurian Interlake Formation, facies type, location of analog field and reservation, Permeability:￿ not known and location of regional cross-section A-A' (modified after Peterson, 1987). Oil/Gas column:￿ not known Average net pay thickness:￿ 30 feet Borehole Compensated Sonic Log R 95 W R 94 W Amerada Hess 9-43 Jones Laterolog with Gamma Ray -9759 ne se 9-150n-95w T Interlake: 12,315-12,356 30 25 12,372-12,394 152 Amerada Petroleum 30 29 28 27 26 12,404-12,418 -9898 N -9733 1 Antelope Unit 'A' T -9702 T ne se 1-152n-95w -9755 NDE 153 153 NDE Silurian 11,727-11826 -9694 NDE N N 32 36 NDE 31 32 33 34 35 NDE -9650

-9951 NDE NDE NDE 12200 5 1 -9722 -9600 -9917 -9653 NDE -9997 3 2 1 6 5 4

NDE NDE 11700 -9800 -9700 -9600 T 8 12 T 152 152 -9615 NDE NDE N

12300 N -10027 T -9967 Fort Berthold Reservation Productive NDE 7 8 9 17 13 151 10 11 12 interval -9996 N Productive NDE NDE -9935 Interval

-10022 -9880

12400 20 24 R 95 W R 94 W 11800 Note: Wells shown are deeper than Devonian Blue Buttes Field 25 Interlake Structure Map ANTELOPE FIELD Fort Berthold Silurian Structure Map

12500 C.I. = 25 feet R 96 W

Figure FB-12.3. Structure contour map of Interlake interval, C.I. = 25 feet Figure FB-12.2. Example of wireline log Blue Buttes Field. Shows anticlinal nose development with Figure FB-12.4. Example of Antelope Field wireline through Silurian interval in Blue Buttes production located somewhat off structure. This indicates a Figure FB-12.5. Silurian structure map, Antelope Field. Shows anticlinal fold trend to the log in the Silurian interval. Field. strong stratigraphic component which assists trapping southeast with production strongly coincident with structure. mechanism.

Fort Berthold Reservation CONVENTIONAL PLAY TYPE 6 Page 13 of 18 North Dakota Pre-Prairie (Winnipegosis/Interlake Play) 110 105 100 Dickinson Field - Heath Pool R 97 W R 98 W 200 A 600 A' 6 1 6 1 400 600 Ft. Berthold 0 Reservation 600 600 Dickinson Field 0 1000 400 600 800 400 North Dakota 200 T 140 0 Montana N -5380

-5360 -5320

-5340 -5300 31 -5280 36 Cambrian and 31 36 -5240 older rocks exposed Gamma Ray / Neutron Log UNITEX Ltd. 6 - 1 Walton sandstone and sandy Wyoming South Dakota ne ne 6 - 139n - 96w 6 -5260 6 1 shale facies 0 HEATH 7,800- 7,832 FT -5260 green, gray, and red shale T with minor limestone 139 CI = 20 ' 200 200 foot contour interval N

Figure FB-13.1. Thickness of Upper Mississippian - Lower Pennsylvanian Big Snowy Group interval (Tyler-Heath), location of Fort

Berthold Reservation, Dickinson Field (analog), and location of regional cross-section A-A' (modified after Peterson, 1987). 7500

PLAY TYPE 7 Post Madison Clastics (Tyler-Heath) Figure FB-13.2. Structure map of Dickinson Field, top of Heath. Complex structural configuration reflects the depositional patterns associated with fluvial, deltaic and nearshore marine environments (after Williston Basin Field General Characteristics - Regional deposition of fluvial, deltaic, and nearshore marine Summaries, 1984).

sandstones and carbonates provides the potential reservoirs for this play type. Dark gray 7600 to black, organic rich, marine shales of the Tyler are considered to be the main source Dickinson Field Parameters rock which charge these reservoirs. The shales are thermally mature in the center of the basin and immature along the flanks. Onset of oil generation and migration is thought to Formation: ￿ Pennsylvanian Tyler have occurred in late Cretaceous to early Tertiary time. Mississippian Heath ￿ Lateral discontinuity of potential reservoirs in the well-sorted fluvial and nearshore Lithology: Interbedded sandstones and marine sandstones is the norm. In general, areal extent of reservoirs is limited with possible internal porosity and permeability barriers. Overall porosities may be quite good shales 7700 (10-16%). Tyler sandstones are roughly time equivalent to the Morrow sandstones of the Average Depth: ￿ 7800 feet mid-continent. Porosity: ￿ 12% Permeability: ￿ 194 md Oil/Gas Column: ￿ not known Average net pay: ￿ variable Other Shows: ￿ shows in deeper Mississippian intervals￿ 7800 Productive interval

Figure FB-13.3. Well log example from Dickinson Field. Upper Mississippian - Lower Pennsylvanian

Fort Berthold Reservation CONVENTIONAL PLAY TYPE 7 Page 14 of 18 North Dakota Post Madison Clastics (Tyler-Heath) 110 105 100 PLAY TYPE 8 0 100 40 20 0 Pre-Red River Gas Play A 100 60 A' 0 80 Antelope 120 General Characteristics - Production has been established from Ordovician Ft. Berthold (Winnipeg) and Cambrian (Deadwood) sandstones. These units are located 120 Reservation Taylor within the thermally mature or overmature hydrocarbon window of the Williston 100 Taylor Field - Winnipeg Pool basin. Both gas and condensate are produced. R 93 W R 92 W North Dakota 120 80 ￿ Reservoir intervals contain a 'clean' quartz sandstone, silica cement, and T 150 60 40 enhanced fracture porosity. Source rock is considered to be a marine shale either -9650 140 Montana N 20 within the Deadwood or the Winnipeg sandstone. Hydrocarbon generation is 100 -9600 60 40 thought to have occurred in late Cretaceous to early Tertiary time. Traps are 100 generally asymmetric folds associated with major structural fault zones or hinge -9550

lines. -9500 80 ￿ Locations of the fields used as analogs for this play type are noted on the -9550 TA Cambrian and -9450 older rocks exposed regional facies map. Fort Berthold reservation is bracketed by these fields and in

Wyoming South Dakota an optimum facies position for possible plays of this type to occur within the -9400 -9362 TA sandstone facies -9453 TA Taylor Field T 40 0 boundary of the reservation. Area 139 shale, sandstone and 20 -9500 -9400 N minor limestone facies 0 Compensated Densilog-Compensated -9336 -9350 green shale facies Neutron-Gamma Ray Log -9322 Gulf Oil 40 contour interval, 20' 1-24-1C Ogre -9450 se nw 24-139n-93w -9300 Figure FB-14.1. Thickness of Deadwood and equivalent rocks, location of analog fields, location of -9248 reservation, and location of regional cross-section A-A' (modified after Peterson, 1987). -9400 11400 11400 -9250

-9350 Antelope Field Parameters T -9300 -9200 R 95 W R 94 W -9250 138 Formation: Ordovician Winnipeg N

and Cambrian Deadwood -9200 -9150 30 29 28 27 26 Lithology: very fine to fine grained, 11500 CI=50 ft T -12,044 T occasionally medium grained 153 153 quartz sandstone, occasionally Figure FB-14.4. Taylor Field, Winnipeg Structure. Production strongly correlated to major N N carbonaceous and pyritic fault with associated anticlinal nose development to the northwest (from Williston Basin Summaries, 1994). 31 32 33 34 35 -11,622 Average Depth:￿ 13,900 feet

-11,700 Porosity:￿ 12-18% depending upon interval -12,000 GR

-11,830 Permeability: ￿ no information 11600 3 2 1 6 5 4 Oil/Gas column:￿ no information -11,647 T Average net pay: ￿ 40-50 feet T Taylor Field Parameters 152 152 Other shows:￿ no information N N Formation: ￿ Ordovician Winnipeg and Cambrian 7 8 9 Other information: 1-32 Brenna-Lacy (1992) completed in Deadwood 10 11 12 Fort Berthold Reservation Winnipeg-Deadwood. IPF 8BCPD, 5924 MCFGPD. SI for gas. Cumulative production - (1995) 3037 BO, 5.4 MMCF. Lithology:￿ Interbedded shales and sandstones Sandstone consists of very fine grained 11700 quartz R 95 W R 94 W (based on Richardson Field core, N Gulf Oil Leviathan 1-21-B Note: Gas wells shown are Winnipeg/Deadwood penetrations only. Average depth: ￿ 11,760-11,780 feet ANTELOPE FIELD D Winnipeg/Deadwood production was Porosity: ￿ variable, 12-14% density log porosity established at the 1-32 Brenna Lacy well in Winnipeg Structure Map Permeability: ￿ no information section 1, T 152 N R 95 W. Cumulative Productive Oil/gas column: ￿ no information production (1995) is 3037 BO and 5.3 MMcf. 11800 interval C.I. = 100 feet Average net pay: no information Other shows: ￿ no information Figure FB-14.2. Structure contour map of the Winnepeg Fm., Antelope Field. Figure FB-14.3. Example of Winnipeg- Shows Winnepeg production correlated with anticlinal fold trend to the southeast. Other information: Discovery well for Taylor Field, 120 BCPD, 4.54 MMCFPD, 57.9 Deadwood formation log signature from API. Cumulative production (1995) 128,730 BO, 5.3 MMCF. Taylor field.

Fort Berthold Reservation CONVENTIONAL PLAY TYPE 8 Page 15 of 18 North Dakota Pre - Red River Gas Play Canada PLAY TYPE 9 controlled by fractures; matrix porosity and permeability are low. United States Bakken Fairway/Sanish Sand Play Different fairways are assumed to exist. The areas with the highest ? potential have elevated thermal maturity, proximity to subcrop, close General Characteristics - The fractured Bakken Formation can fracture spacing and proximity to basin flexure hinge lines. Vitrinite 100 be subdivided into three distinct rock types. The upper and lower reflectance should be greater than 0.9-1.02. ? 200 zones are black shale with a high organic matter content. The middle ￿ The United States Geological Survey considers Antelope field a zone is a relatively lean organic shale/siltstone. U.S.G.S. analyses of special category of Bakken fairway production. The Sanish sand is 225 ? 125 the Bakken indicates that 11.5-12.1 weight percent of the shale is locally developed, brown, dolomitic, friable, and a slightly 250 organic carbon. Evidence suggests that the Bakken has generated argillaceous sandstone with about 6-7% porosity. Immature 225 hundreds of billions of barrels of oil. "Low-Resistivity" Approximate Limit Of Bakken Formation 200 ￿ The Bakken Fm, where it exists, is thermally mature (see map). It Bakken Shale Antelope Field Parameters (Modified from Sandberg, 1962) Organic-rich rocks forms a continuously sourced, self-sealed reservoir. Production is have not yet generated 150 Mature "High" Resistivity Bakken Shale 175 hydrocarbons - matrix Antelope Field - Sanish Pool Formation:￿ Bakken shale/Sanish Organic-rich rocks have generated porosity is water R 94 W sandstone interval Resistivity hydrocarbons-matrix porosity is saturated. Control Point oil saturated. Lithology: ￿ sandstone, dolomitic, (Induction or -8362 brown, friable, slightly Laterolog) Borehole Compensated -8350 argillaceous North Dakota Sonic Log William C. Kirkwod -8483 Average depth:￿ 10,525 feet South Dakota 42-8 Melby T se ne 8-152n-94w Porosity: ￿ 7.4 average -8404 153 N Permeability:￿ low, changes across Caliper Limestone SPHI -8450 6.0 16.0 6.300 -0.100 structure with the sand/silt Montana GR DT 0.0 100.0 96.00 40.00 -8400 content

-8375 Oil/Gas column: ￿ no information

Figure FB-15.1. Areas of "high" and "low" electrical resistivity in Bakken shales, with subsurface isotherm contours (degrees) and -8425 Average net pay: variable interpreted area of source-rock maturity (after Messiner, 1984). Other formations Mission Canyon,

-8450 with shows:￿ Devonian and Winnipegosis

10500 CANADA -8475 Other information: Discovery well was Woodward Star- Fort Berthold reservation is T USA 151 Tribal, sw se 21 T152N R 94 W; 550 BOPD (1953) ideally situated for mature -8468 N caliper Bakken production. The -8477 -2000 Bakken source interval is -2000 GR Figure FB-15.4. Structure map of the Sanish Pool, Antelope thought to have generated over Rockton-FroidFault Zone field (from Williston Basin Field Summaries, 1984). 1 billion barrels of oil but -9000 10600 production/migration from the -3000 interval is problematic. Weldon Fault ? -4000 DT West East Mechanisms for emplacement -5000 South Limit -8000 Jurassic outside the Bakken interval are Ø Jurassic Bakken Shale Big Snowy Group Nesson Axis Triassic described below in the -7000 -6000 of Bakken interval -3000 -4000 -5500 west/east cross-section. -6000

Production within the Bakken Formation 10700 Madison Group (L-M Miss.) Charles Formation must be concentrated in -5000 Devonian

-4000 North Mission Canyon Fm. intervals where fractures -5000 (original or induced) can -5500 -5000 SouthDakota Dakota Source Rock Bakken Formation Lodgepole "Maturity" remain open to fluid flow. -3000 (Upper and Lower Bakken Shales)

Nisku Fm. Poor Porosity Oil and/or Gas Production -2000

Mont. Good Porosity Contour Interval 500 Feet -1000

-2000 Interbedded Salt, Anhydrite and generally Black organic-rich Shale: Upper and "Maturity" -1000 dense "tight" Dolomite and Limestone: Lower Bakken Shale Members Charles Formation Hydrocarbon Accumulation Figure FB-15.3. Example of log Migration Flow Direction Light-colored generally porous Limestone and Dolomite- Calcareous-dolomitic Siltstone: Middle signature from Antelope Field oolitic, pelletal and skelletal i.p.: Mission Canyon and Bakken Siltstone Member Wyoming showing Bakken shale interval Nisku Fms. Dark-colored generally dense "tight" Shaley Limestone- Grey-green-red Dolomite, Shale, and Overpressure Cell with sand/silt development Siliceous (tr iangle), i.p.: Lodgepole Formation Siltstone: Three Forks Formation Figure FB-15.2. Williston Basin with structure contours on the base of Mississippian strata and limit of Fractures Bakken Formation (after Webster, 1987). Figure FB-15.5. Schematic east-west section across the Williston Basin showing source-rock maturity, fluid over-pressure, fracture, migration and hydrocarbon accumulation patterns in the Bakken formation and adjacent units (after Messiner, 1984).

Fort Berthold Reservation UNCONVENTIONAL PLAY TYPE 9 Page 16 of 18 North Dakota Bakken Fairway/Sanish Sand Play R44W 43 42 41 40 39 38 R37W PLAY TYPE 10 Formations T Vernon 1

Series Niobrara Microbial Gas Play System 2000 S Cretaceous Beecher (Low - High Potential) Low Epeiric Seaway Fort Union Formation 2000 Island Tertiary Paleocene 2 Hell Creek Formation Alaska Greenland General Characteristics - Upper Cretaceous Niobrara 2100 Fox Hills Sandstone is a chalk and calcareous shale that covers most of the Cherry

Low Creek, East 3 Bearpaw Shale western interior from Kansas and eastern Colorado into Armel St. Francis Kansas

2000 Colorado the Dakotas. It is assumed that a Niobrara gas play 2200 Judith River Formation similar to the eastern Denver Basin (Beecher Island Wheeler 4 Claggett Shale Pierre Field, Goodland Field) exists in the southern Williston Shale basin. Eagle

Upper Low Benkelman Sandstone Gammon ￿ Niobrara production in the Denver Basin is 5 Shale considered a self-sourced, continuous extent gas field. Cheyenne Co.

Niobrara Formation Estimated thickness of the Niobrara would be greater Sherman Co. Canada 2200 Carlile Shale than 100 feet, and depth of burial is less than 1000 feet. Area of subcrop or outcrop might affect gas generation. 2100 Greenhorn Formation 2400 Cretaceous Cretaceous Areal extent of production might be as small as 25 2300 2500 Epeiric Seaway Belle Fourche Shale square miles. Mowry Shale United States

Muddy Sandstone 2500 unconformity Skull Creek Shale 0 nonmarine 2600 Cretaceous Fall River Sandstone rocks Epeiric Seaway coastal sandstones 2800 2800 Kootenai Formation calcareous Lower rocks Sunburst SS Mbr. marine siltstones and shales Mexico Cuba Cut Bank SS Mbr. Figure FB-16.5. Structure map on top of the Niobrara Formation, unconformity northwestern Kansas showing a Niobrara gas field (in red). Contour interval

Morrison Formation is 100 feet. Hypothetical or unconventional play for Fort Berthold reservation

Upper (after Lockridge and Sholle, 1978). Jurassic Figure FB-16.3. General correlation chart of Cretaceous rocks (after Rice and Shurr, 1980).

Figure FB-16.1. Paleogeographic map of North America during Late

Cretaceous time, showing the extent of the Cretaceous seaway (after Rice 112 110 Canada 108 and Shurr, 1980). 106 104 102 20 United States 49 Resistivity Gamma Ray Porosity mv 1.0 10 100 40 240 45 30 15 0 Montana Non North 1450 1450 3000' Marine Area Dakota Rocks 48 Gamma SP Ray Density of Porosity

burial PIERRE RILD Neutron South RLL8 Porosity below Dakota Sharon Springs Mbr. 4000' burial > 3000' 47 Beecher Island perforated Wyoming Ø could be interval <35% Gas Zone Nebraska Legend for Facies Map North burial between 10 5 0 3000-4000' non marine rocks Dakota Core Permeability 1550 1550 (md) Ø could be 46 Colorado Niobrara Fm. coastal sandstones Kansas 30-35% of interbedded shelf sandstone

and shales South NIOBRARA CAOF 2100 MCFGPD siltstones and shales occurrence Montana Dakota

New of Oklahoma chalk and limestone 45 Smoky Hill Member Mexico Wyoming Limit Figure FB-16.6. Type logs for Niobrara producing well, Beecher Island area, Kansas Nebraska No. 44 1-32 Whombie, sec. 32, T2S, R43W (after Lockridge and Sholle, 1978).

Figure FB-16.4. Regional distribution of diagenetic and petrophysical facies of the Niobrara. Figure FB-16.2. Map showing depth of burial of the Niobrara Formation. Area within 3000 feet or less of burial should contain chalks with porosity greater than 35%. Across reservation area porosity could be <35% (after Rice and Shurr, Areas between 3000 and 4000 feet of burial should average 30-35% porosity (after Rice and 1980). Shurr, 1980).

Fort Berthold Reservation UNCONVENTIONAL PLAY TYPE 10 Page 17 of 18 North Dakota Niobrara Microbial Gas Play General References ______, 1984, "Blue Buttes-Red River Pool-McKenzie County, North Fort Berthold Reservation Dakota", Williston Basin Field Summaries, Petroleum Information. Editors, North Dakota Geological Society, 1962, "Antelope Field-Sanish", Oil Anderson, Robert C., 1995, The Oil and Gas Opportunity on Indian Lands- and Gas Fields of North Dakota-A Symposium , North Dakota Geological ______, 1984, "Dickinson Field Heath Pool-Stark County, North Exploration Policies and Procedures, Bureau of Indian Affairs, Division of Society, Bismark, North Dakota, pp. 21-22. Dakota", Williston Basin Field Summaries, Petroleum Information. Energy and Mineral Resources, General Publication G-95-3, 158 p. ______, 1962, "Antelope Field-Sanish", Oil and Gas Fields of North ______, 1984, "Taylor Field-Winnipeg Pool-Stark County, North Beeman, William R., et al., 1996, Digital Map Data, Text and Graphical Images Dakota-A Symposium , North Dakota Geological Society, Bismark, North Dakota", Williston Basin Field Summaries, Petroleum Information. in Support of the 1995 Assessment of United States Oil and Gas Resources, Dakota, pp. 23-24. United States Geological Survey, Digital Data Series DDS-35, CD ROM. Gordon, Ian R., 1995, (Abstract) "Stratigraphy and Structure of an Early ______, 1962, "Antelope Field-Duperow", Oil and Gas Fields of North Mississippian Waulsortian Bioherm in the Lodgepole Formation, Dickinson Charpenteir, Ronald R., et al., 1996, Tubular Data, Text, and Graphical Images Dakota-A Symposium , North Dakota Geological Society, Bismark, North Field, North Dakota", Seventh International Williston Basin Symposium, in Support of the 1995 National Assessment of United States Oil and Gas Dakota, pp. 25-26 Montana Geological Society, Billings, Montana, pp. 449. Resources, United States Geological Survey, Digital Data Series DDS-36, CD ROM. ______, 1962, "Antelope Field-Interlake", Oil and Gas Fields of North Peterson, James A., 1996, "Williston Basin Province (031)", Tabular Data, Text, Dakota-A Symposium , North Dakota Geological Society, Bismark, North and Graphical Images In Support of the 1995 National Assessment of United Gautier, Donald L., et al., 1996, 1995 National Assessment of United States Oil Dakota, pp. 27-28. States Oil and Gas Resources, United States Geological Survey, Digital Data and Gas Resources - Results, Methodology, and Supporting Data, United Series DDS-36, CD ROM. States Geological Survey Digital Data Series DDS-30 Release 2. ______, 1962, "Antelope Field-Madison", Oil and Gas Fields of North Dakota-A Symposium , North Dakota Geological Society, Bismark, North Shurr, George W., et al., 1995, "Tectonic Controls on the Lodgepole Play in ______., et al., 1995, 1995 National Assessment of United States Oil Dakota, pp. 21-22. Northern Stark County, North Dakota- Perspectives from Surface Studies", and Gas Resources, Overview of the 1995 National Assessment of Potential Seventh International Williston Basin Symposium, Montana Geological Additions to Technically Recoverable Resources of Oil and Gas - Onshore ______, 1962, "Bear Den-Madison", Oil and Gas Fields of North Society, Billings , Montana, pp. 203-208. and State Waters of the United States, United States Geological Survey Dakota-A Symposium , North Dakota Geological Society, Bismark, North Circular 1118, 20 p. Dakota, pp. 31-32 Sperr, J.T., et al., 1993, "Wabek and Plaza Fields: Carbonate Shoreline Traps in the Williston Basin of North Dakota", North Dakota Geologic Survey Field Mallory, William Wyman, et al., 1972, Geologic Atlas of the Rocky Mountain ______, "Bear Den-Devonian", Oil and Gas Fields of North Dakota-A Study, No. 1, p. 24. Region, Rocky Mountain Association of Geologists ,331 p. Symposium , North Dakota Geological Society, Bismark, North Dakota, pp. 33-34 Webster, Mark and Thomas Van Arsdale; 1995, "Geochemical Microseep Survey Peterson, James A. and MacCary, Lawrence M., 1987, "Regional Stratigraphy of the Plaza and Wabek Productive trends, Mountrail and Ward Counties, and General Petroleum Geology of the U.S. Portion of the Williston Basin ______, 1962, "Blue Buttes-Madison", Oil and Gas Fields of North North Dakota", Seventh International Williston Basin Symposium, Montana and Adjacent Areas", Williston Basin: Anatomy of a Cratonic Oil Province, Dakota-A Symposium , North Dakota Geological Society, Bismark, North Geological Society, Billings, Montana, pp. 57-65. Rocky Mountain Association of Geologists, pp. 9-43. Dakota, pp. 49-52 Fort Berthold Reservation - Map References Rice, Dudley D. and Shurr, George W., July 1980, "Shallow, Low-Permeability ______, 1962, "Croff-Madison", Oil and Gas Fields of North Dakota-A Reservoirs of the Northern Great Plains - Assessment of their Natural Gas Symposium , North Dakota Geological Society, Bismark, North Dakota, Executive Reference Map 334, 1985 edition, Extended Area, Northern Rocky Resources", American Association of Petroleum Geologists Bulletin, pp. 77-78 Mountains, Geomap Company. Volume 64/7, pp. 969-987. ______, 1962, "Croff-Devonian", Oil and Gas Fields of North Dakota-A Executive Reference Map 321, 1983 edition, Southern Williston Basin, Geomap Willette, Donna C., et al., 1996, "Oil and Gas Atlas on Indian Lands", Indian Symposium , North Dakota Geological Society, Bismark, North Dakota, Company. Resources Building Partnerships, Sixth Annual Energy and Minerals pp. 79-80 Conference, Bureau of Indian Affairs, Division of Energy and Mineral Indian Land Areas, 1992, United States Department of the Interior-Bureau of Resources, 10 p. Editors, Petroleum Information, 1984, Antelope Field-Sanish Pool - McKenzie Indian Affairs. County, North Dakota", Williston Basin Field Summaries, Petroleum Fort Berthold Reservation-Fields and Articles Information. Clayton, Lee, et al., 1980, Geological Map of North Dakota Survey.

Anderson, Robert C., 1995, "Fort Berthold Reservation-The Three Affiliated ______, 1984, "Antelope Field-Devonian Pool-McKenzie County, North Darton, N.H., et al., 1951, Geologic Map of South Dakota, United States Tribes", The Oil and Gas Opportunity on Indian Lands-Exploration Policies Dakota", Williston Basin Field Summaries, Petroleum Information. Geological Survey. and Procedures, Bureau of Indian Affairs, Division of Energy and Mineral Resources, General Publication G-95-3, pp. 29-42. ______, 1984, "Antelope Field-Silurian Pool-McKenzie County, North Ross, Clyde P., et al., 1958, Geological Map of Montana, Montana Bureau of Dakota", Williston Basin Field Summaries, Petroleum Information. Mines. Burke, Randolph B. and Zakaria Lasemi, 1995, "A Preliminary Comparison of Waulsortian Mound Facies in the Williston and Illinois Basins", Seventh International Williston Basin Symposium, Montana Geological Society, ______, 1984, "Blue Buttes-Silurian Pool-McKenzie County, North Billings, Montana, pp. 115-128 Dakota", Williston Basin Field Summaries, Petroleum Information.

Fort Berthold Reservation REFERENCES Page 18 of 18 North Dakota