FORT BELKNAP RESERVATION List of Topics

BACKGROUND Reservation Overview￿ Regional Geologic Overview￿ GEOLOGIC OVERVIEW Geologic History￿ Summary of Play Types CONVENTIONAL PLAY TYPES Play 1 - Shallow Cretaceous Biogenic Gas Play Play 2 - Northern Plains Biogenic Gas Play￿ Plays 3,4,5 - Jurassic/Cretaceous and Mississippian Plays￿ UNCONVENTIONAL / HYPOTHETICAL PLAY TYPES Plays 6,7 - Fractured Bakken and Cambrian Sandstone Plays REFERENCES Historical Background of the OVERVIEW (i.e. joint ventures) in contrast to procedures and regulatory minimums imposed Assiniboine and Gros Ventre Tribes at Fort Belknap by the previous 1938 Minerals Leasing Act. The 1982 Act further provides that FORT BELKNAP RESERVATION ￿ The Fort Belknap Indian Reservation was created in 1887 as the home for the individual Indian allottees may join agreements negotiated for tribal lands. The Assiniboine and Gros Ventre Tribes Assiniboine and Gros Ventre Indian Tribes. The ancestors of these tribes have section entitled Operating Regulations discusses the procedures for obtaining lived on the northern plains for several centuries. The Assiniboine were allottee participance in the negotiated agreement. recognized by Europeans as part of the great Sioux Nation and speak a Siouan ￿ Principal components for the formal corporate proposal should include the TRIBAL HEADQUARTERS: ￿ Fort Belknap Agency, Montana language. However, their name is taken from a Chippewa word referring to area(s) of interest, type of contract, elaboration of proposed agreement terms, GEOLOGIC SETTING: ￿ Williston Basin "those who cook with stones." At some point in time the Assiniboine bands points of potential negotiation, diligence commitments (i.e. drilling), bonus broke with the traditional Sioux and allied themselves with the Cree. The tribe considerations, acreage relinquishments, tribal employment of training, etc. Also Location and Access settled along the Milk River and hunted between the Yellowstone River and an interested company or individual should provide evidence of experience and ￿ The Fort Belknap Reservation is located in southeast Blaine and western southern Canada. The Assiniboines quickly adopted horses, firearms and a ability to meet financial or diligence commitments. Phillips Counties of north-central Montana. The reservation lands are situated 45 reliance on commerce, thus completing their transition from an agrarian / miles east of Harve on State Highways 87 and 191 east of Great Falls. Tribal woodlands to a hunting/trading economic system. Joinder Agreement For Individual Indians headquarters are located at the Fort Belknap Agency, four miles east of Harlem. ￿ The Gros Ventre separated from the Arapaho and may be some of the original ￿ Pursuant to the 1982 Indian Minerals Development Act, Indian allottees may The Bureau of Indian Affairs Area Office is located in Billings. inhabitants of the western plains. French Canadian fur trappers gave the tribe join a tribal negotiated agreement. The Fort Belknap Community Council plan to their name, which translates to "big bellies", based on the tribal name in the solicit allottee interest once negotiations are underway to minimize company Topography Blackfeet and Shoshone languages. The Gros Ventre used the Blackfeet curative land acquisition. ￿ Most of the reservation is located on the northern Great Plains. The language in trade and were therefore considered part of the Blackfeet Nation. ￿ The BIA Area Office in Billings is currently developing an administrative southeastern portion, however, is located on the flanks of the Little Rocky This association resulted in the inclusion of the Gros Ventre in the Blackfeet process to streamline this effort and yet protect their trustee interest. A joinder Mountains. Most of the available acreage is located on the flat, easily accessible Treaty signed in 1855 with Governor Stevens of the Washington Territory. agreement was reviewed by the BIA Solicitor's Office in 1984. At that time the plains. Three prominent buttes dominate the western side. These are Twin Because of intertribal hostilities the Gros Ventre relocated near the Little Rocky Solicitor concluded "-- we see no reason why this agreement would not comply Buttes, Wild Horse Butte and Snake Butte. Elevations within the reservation Mountains. Although the federal government opened this new area, the Gros with all legal requirements." The 1982 Act provides for two legal requirements range from 2,300 ft. to 5,000 ft. Principal rivers are the Milk River, which forms Ventre remained between the Milk River and the Little Rocky Mountains. As for allottees to join a tribal mineral agreement: the northern reservation boundary, White Bear Creek, in the northwestern corner, indicated above, in 1887 the Gros Ventre were included with the Assiniboine in a and the east-flowing South Fork of Peoples Creek, which roughly divides the treaty establishing the Fort Belknap Indian Reservation. (1) all parties must consent reservation in half. (2) the Secretary must find that it is in the best interest of the individual to Competitive Negotiations for Mineral Agreements participate Land Ownership ￿ The Assiniboine and Gros Ventre Tribes of the Fort Belknap Reservation are ￿ The Fort Belknap Reservation consists of 980 square miles or approximately sincerely interested in working with energy companies and individuals towards The Secretary must evaluate within 180 days to approve or disapprove the 627,000 acres, of which, the tribes have mineral interest (BIA Trust Estate) in the development of the oil and gas resources underlying the reservations. The terms of any agreement regardless of allottee participation. about 61,000 acres. In addition to the reservation lands, the tribes at Fort acquisition of good oil or gas prospects through leasing or other agreements, the Belknap hold mineral interest in 25,5000 acres immediately west of the diligent exploration of prospects generated, and the ultimate production from the Requirement for Environmental Assessment reservation, referred to as submarginal lands. Approximately 21,000 mineral wells drilled are three compatible goals for all the parties. The Tribes may be ￿ A negotiated contract pursuant to the Indian Mineral Development Act will acres within the boundary of the reservation are under patented-in-fee or state amenable to a variety of arrangements to see that these goals are reached, and require an Environmental Assessment (EA) for the area under consideration for ownership. About 2,000 tribal mineral acres are withdrawn from development feel that competitive solicitations leading to negotiated contracts offers the oil and gas exploration and development activities. Generally the BIA requires activities due to religious significance and 26,800 tribal mineral acres are in the maximum flexibility to all parties concerned. the company to prepare this documentation which can equate to delays in the timber reserve. The latter acreage are in the Little Rockies and probably are not final review and approval process of the negotiated contract. Numerous previous of oil and gas interest since Paleozoic rocks outcrop. Available tribal minerals Authority to Negotiate Oil and Gas Agreements investigations exist that relate to the needed components of the EA. The tribes for an oil and gas agreement amount to about 58,000 acres. The Tribal ￿ The lands described in this Atlas are held in trust by the Bureau of Indian and CERT are in the process of assembling these reference studies for use by the Community Council with BIA concurrence could authorize an agreement for this Affairs. Therefore, oil and gas leases must be consummated pursuant to federal company and the BIA. Additionally, the tribes have requested that BIA initiate entire acreage or portions thereof. regulations. Authority to lease Indian trust lands through a negotiated agreement or fund the duration of this study to expedite the final approval process. For the ￿ Individual Indians (Allottees) have a mineral interest in approximately is provided in the Indian Minerals Development Act of 1982 (P.L. 97-382 ). initial submittal, the company need not concern themselves with the baseline data 535,000 acres although their surface interest is about 400,000 acres. The 1982 However, final regulation implementing the 1982 Act have not been promulgated acquisition but should give the tribe some idea about a plan of operations and Indian Mineral Development Act would allow allottees to joint a Tribal at this writing. The regulations governing the leasing of Indian lands under the precautions that will be taken to insure environmental protection and mitigation Agreement (25 U.S.C. Sec. 210(b)) which equates to possibly upwards of 1938 Mineral Leasing Act can be found in the Code of Federal Regulation, Title of damages to flora, fauna, air, water and property. 600,000 available acres. 25, Part 211 for tribal lands. The July 12, 1984 edition of the Federal Register ￿ Allottees normally must have their parcels individually offered in an has proposed regulations for 25 CFR, Part 225 Oil and Gas Mineral Contracts to administered lease sale prior to entering direct negotiations with a company. encompass the 1982 Indian Mineral Development Act. Therefore this proposal offers a unique opportunity for interested companies and ￿ Since the enactment of the Indian Mineral Development Act of 1982, tribes mineral owners alike. The conditions of allottee joinders to a Tribal Agreement have been afforded the opportunity to directly negotiate leases or other contracts will be discussed further in the section entitled Tribal Government and Operating Regulations.

Fort Belknap Reservation RESERVATION OVERVIEW Page 1 of 13 Montana Operational Regulations Operating Regulations

Tribal Government ￿ The reservation lands available for oil and gas leasing or other types of mineral agreements are largely allotted lands (86.5%) with the Tribes holding Fort Belknap Indian Reservation, the home of the Gros Ventre and Assiniboine mineral rights to 9.8% of the reservation lands and all of the submarginal lands. Tribes was created by treaty on October 17, 1885 and by an Act of Congress on Therefore, the governmental authorities for the disposition of the contracts will May 1, 1888. The business and governmental affairs of Fort Belknap are be the tribal councils, allottees, and the trustee, the Bureau of Indian Affairs, conducted under the authority of a constitution and bylaws ratified by members acting in behalf of the Secretary of the Interior. Environmental assassments are of the Tribes on October 19, 1935, and approved by the Secretary of the Interior currently being prepared by the BIA to aid in rapid implementation of a contract on December 13, 1935, pursuant to the Indian Reorganization Act of 1934. after economic analysis and approval by the BIA. Subsequently, a corporate charter for the Fort Belknap Indian Community was ￿ The Tribes have not enacted any specific codes, ordinances, regulations nor ratified by members of the Community on August 25, 1937. mineral taxes relating to oil and gas exploration and development, therefore the ￿ The principal decision-making body for the Reservation is the Fort Belknap chief regulations governing oil and gas activities are those of Title 25 of the Code Community Council, consisting of six Assiniboine and six Gros Ventre members. of Federal Regulations (CFR) Subchapter 1 - Energy & Minerals (Part 225 Each council member serves for a four year term. Every two years, each of the applicable to P.L. 97-382 CFR, Part 216 (applocable to revenue reporting and three voting districts--Milk River and Lodge Pole elect an Assiniboine and a payments) and Title 43 CFR Part 3160 (applicable to production reporting and Gros Ventre memeber to the Council. On the first Monday in January following operating procedures. each election, a president, vice-president and secretary/treasurer are elected from ￿ The Bureau of Indian Affairs Billings and Aberdeen Area Offices have within the twelve council members. Council officers serve for a period of two entered into a memorandum of understanding with Montana State Office of the years. The current officers were elected January 1984. Any council memeber or Bureau of Land Management (BLM) whereby BLM will provide certain oil and officer may serve as long as he/she is re-elected to office. gas management operations on Indian lands. ￿ The Tribal President appoints standing committees which meet monthly as needed. Negotiation for an oil and gas agreement would be conducted by the Tribal Community Committee. Any oil and gas development agreement would have to receive final approval from the Tribal Council.

CANADA 15 MONTANA Toole Hill Blaine 233 Havre Shelby 2 Harlem CONTACT Liberty ROCKY Malta Conrad FORT BELKNAP Delmer Bigby, Land Specialist 87 BOY'S Fort Belknap Indian Community Gros Ventre & Assiniboine Tribes Ft. Benton Chouteau Phillips P.O. Box 249 Rural Route #1 Box 66 89 Great Falls Harlem, MT 59526 Fergus 15 Cascade 191 TEL: 353-2205 x423￿ Fax: (406) 353-2797 87 19 Petroleum Lewistown Judith Grassrange 89 Basin 200 Meagher 87

Fort Belknap Reservation OVERVIEW Page 2 of 13 Montana Regional Geology Alberta Shelf C A N A D A 98 97 49 114 113 100 99 ￿ The Fort Belknap Reservation is situtuated on the northern flank of the Little 112 111 110 109 108 107 106 105 104 103 102 101 BF Sweetgrass Bowdoin Hogeland Dome UNITED STATES EXPLANATION Rocky Mountains, an early Tertiary intrusion. (see figure 1 cross-section and Bearpaw Basin Uplift Fault Poplar Poplar Fault 48 Precambrian Basement Uplifts A BK FP Dome A' map). The reservation is west of the Bowdoin Dome, east of the Bearpaw Uplift OVERTHRUST Hinsdale Nesson Arch Little Anticline Other Uplifts or Basins PRODUCING HORIZON LEGEND Judith Rocky Mtns BR and south of the Hogland Basin. Blood Mtns Creek Cedar Creek NORTH DAKOTA Cenezoic Volcanic Fields Big Syncline 47 Anticline Little Snowy Cat Creek Fault ￿ The geologic section is represented by Pre-Cambrian metamorphics, Paleozoic MONTANA Belt Weldon-Brockton Fault BELT Mtns WILLISTON Reservations WESTERN & Mtns Sumatra POWDER RIVER WESTERN WYOMING Wheatland WILLISTON NORTHERN carbonates and Jurassic and Cretaceous sandstones. The Paleozoic rocks are Porcupine BASIN ERA BASIN BASIN Syncline Willow SynclineDome Anticline SOUTHERN MONTANA

SERIES MONTANA FaultCreek Miles City 46 SYSTEM mainly dolomites and limestones deposited within the Williston Basin and Crazy Bull Syncline Mountains Arch Lake Mountains White River Basin Basin SR Green River Alberta Shelf depocenters. Jurassic and Cretaceous rocks vary from continental Nye-Bowler Fault Basin Faults BeartoothFault Wind River Pryor 45 Mtns POWDER A Wasatch to marine sandstones and shales. Mtns A' X-section Wasatch RIVER TERTIARY

CENOZOIC Fort Union Bighorn BASIN Fort Union Fort Union ￿ Most of the reservation is overlain by Quaternary alluvium deposits, SOUTH DAKOTA SR - Standing Rock Fort Union AbsarokaBIGHORN BR - Fort Berthold B Black 44 Cretaceous Bearpaw shale (high bentonite content) and Judith River sandstones Mtns BASIN Mtns FP - Fort Peck Hills Lance Lance Hell Creek I BK - Fort Belknap Uplift Teckla O and siltstones. Owl Fox Hills Fox Hills Judith River Creek Casper BF - Blackfeet Mesaverde Clagget Mtns Arch Mesaverde G Wind Judith River WIND Teapot Eagle IDAHO 43 Parkman Cody RIVER Eagle Telegraph Creek E River Fault

WYOMING UPPER Sussex Shannon BASIN Chadron Niobrara Exploration History Casper Mtn Niobrara Shannon N Mtns Niobrara Greenhorn Sweetwater Niobrara Laramie Greenhorn Frontier Frontier C I GREEN Uplift ￿ Only 10 wells have been drilled to date on the reservation with no commercial Mtns Hartville Frontier Arch Uplift RIVER HANNA RED Dakota Group success. However, significant gas shows have been encountered in 3-4 wells just BASIN BASIN NEBRASKA Mowry Mowry Blackleaf DESERT Bow Island Rock Medicine ALLIANCE Muddy BASIN LARAMIE CRETACEOUS Muddy Springs Kootenai S outside the reservation boundary. Bow BASIN Bear River UTAH Uplift BASIN Dakota Cat Creek Sierra Dakota Mtns LOWER Moulton Uinta Mtns WASHAKE Madre Fall River Structure contours BASIN Mtns Cloverly Sunburst S COLORADO Z O I C 100-1000' Lakota Cut Bank Gannet Intrusions, Precambrian Morrison Morrison Morrison Morrison or Tertiary Syenite Porphyry Figure BK-2.1. Present day structural features in the Rocky Mountain region (after Peterson, 1987). Ellis Group Ellis Group T Sundance Sundance

COUNTY Swift COUNTY Swift Intrusions, Tertiary Volcanics -600 32 Canyon Springs N Reirdon Stump-Preuss Reirdon JURASSIC Piper Gypsum Spring Sawtooth Faults - thrust, normal Twin Creek Nesson Structural Geology M E S O Reservation boundary Nugget -500 Chugwater Chugwater ￿ The Fort Belknap Reservation is dominated by the Little Rock Mountains of Paleocene- Ankareh T D Thaynes U 31 Eocene age. The Little Rocky Mountains are a series of igneous intrusions (Seyenite Woodside N TRIASSIC D Spearfish Spearfish U -300 Porphyries) that have generated numerous structural domes (over 50) of various sizes (see Dinwoody Snake Butte detailed structure map). Several domes have been breached by erosion and expose the -400 Minnekahta igneous core. Others have Paleozoic rocks exposed at the surface. Dips within the complex Goose Egg Phosphoria T 30 area are steeply tilted to vertical. Dip decreases away from the dome to about 80 feet/mile. Opeche N The southern end consists of several domes, averaging two to three miles in diameter. Small PERMIAN Park City BLAINE PHILLIPS -100 intrusions are present on the western edge of the reservation (Snake Butte, Wild Horse Butte). Minnelusa Weber

Wild Horse -200 ￿ The Bearpaw Uplift, located west of the reservation, is also Tertiary in age and consists of T Butte Amsden Minnelusa Tensleep Amsden 0 29 a series of intrusions and complex thrust and normal faults. As the Bearpaw intrusion was C

500 N emplaced, the paleo gas field that existed in the Cretaceous sands was broken, carried by Amsden 0 I Tyler Darwin Tyler S landslides into downdip positions. The Bearpaws' contain large, shallow gas fields trapped in PENNSYLVANIAN 200 Big Snowy Group Big Snowy Group 300 100 Heath

these "landslide" fault blocks. O -100 0 Heath Madison Otter T Otter 500 Kibbey Madison Kibbey 28 ￿ The northern part of the reservation is mainly of gentle dip, although a major thrust fault Madison Group Madison Group Mission Canyon Sun River N Z 400 Charles Charles 100 (present at the surface) trends northwest to southeast. It's orientation suggests it is related to Mission Canyon Lodgepole

MISSISSIPPIAN Mission Canyon 500 0 200 the fault systems that were created during the Bearpaw intrusive episode. Smaller folds and Lodgepole Englewood Lodgepole

O Bakken 300 faults have been identified from surface geology. Three Forks Three Forks S T Jefferson Jefferson 400 Nisku -500 27 Duperow Nisku N E 500 D Souris River Darby Duperow DEVONIAN U Most Likely Hydrocarbon Zones Dawson Bay Souris River 1000 Winnipegosis ￿ Based on current gas shows and regional hydrocarbon production, regional cross-sections P A L SYNCLINE 3000 and depositional maps, the most likely plays to develop on the Fort Belknap Reservation are: Interlake Interlake

T SILURIAN 2000 U 26 D 1) Cretaceous rocks-Upper Cretaceous section is very thick; gas shows; D N Stonewall U Big Horn Big Horn Red River 0 high potential for Eagle sand biogenic gas accumulations. 1000 2000 Stony Mountain 4000 2) Cretaceous rocks-discontinuous reservoir rocks encased within marine shales; Bowdoin, Red River Winnipeg CREEK 0 ORDOVICIAN T Virgelle sandstones and Greenhorn Limestone. Biogenic gas accumulations are possible. 25 3) Jurassic and Lower Cretaceous rocks-no shows reported, but lack of well control does not Winnipeg Emerson COW N Gallatin preclude biogenic gas potential. Deadwood Deadwood Gros Ventre Flathead Flathead CAMBRIAN R 23 E R 24 E R 25 E R 26 E Note: Paleozoic rocks are not considered prospective due to exposure at the surface in the Little Rocky Mountains at the south end of the reservation. Those rocks are open to the S = Source Rock DETAILED STRUCTURE MAP FORT BELKNAP Base of Colorado Shale RESERVATION atmosphere and would be charged with fresh water. The Mission Canyon Limestone is cavernous where exposed, and is an excellent aquifer. Other Paleozoic units penetrated by Figure BK-2.3. Detailed stratigraphic column of Fort Belknap area (after Peterson Figure BK-2.2. Detailed structure map of Fort Belknap Reservation (after et al, 1987). Knechtel, 1959). well control have been found wet.

Fort Belknap Reservation GEOLOGY OVERVIEW Page 3 of 13 Montana Regional, Structural Geology A Longitude Values (In Degrees) A' GEOLOGIC HISTORY Blackfeet West Fort Belknap Reservation East 4 2 6 0 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 ￿ One generalized structural cross-section (see cross-section A-A') 6000 10 2 Ft. Belknap 12 Ft. Peck 0 has been constructed to summarize present day tectonic provinces and A 15 older paleostructure. The cross-section uses rock thickness values A' 5000 Ft. from each of the geologic periods. Section A runs along the 48 degree Berthold 0 Early Tertiary Intrusions Bearpaw Uplift latitude line and values were selected at one degree longitude intervals. 10 4000 ￿The western end of the section, near the Blackfeet Reservation is 10 Little Rocky Mountains 3000 dominated by high relief (greater than 5000 feet). The Cretaceous and 4 Poplar Dome older Paleozoic section is about 11,000 feet thick. Major basement 8 NORTH 2000 Upper Cretaceous DAKOTA uplifts, such as the Sweetgrass Arch and the Bearpaw Uplift, 15 Rocks SOUTH Standing Rock influenced sedimentation throughout geologic time. 12 Tertiary Rocks DAKOTA 6 1000 Niobrara and Eagle Fort Union and Golden Valley ￿ The eastern side of the cross-section is dominated by the Williston 10 8 8 2 0 Basin, a stable cratonic depocenter which contains more than 15,000 10 MONTANA 0 10 WYOMING feet of sediments. The center part of the illustration is influenced by Upper Cretaceous the Bearpaw Uplift and the Little Rocky Mountains Tertiary intrusions. - 1000 Rocks

EXPLANATION Elevation (in Feet) Lower Cretaceous Rocks Lower Cretaceous The southern end of the reservation is located on the Little Rocky Mowry Niobrara and Eagle Cambrian and older rocks 12 Kootenai exposed at land surface - 2000 Mountain intrusion.

Sandstone Facies ￿ To better illustrate the geologic history of the region, which has Shale, Sandstone and Minor Jurassic Rocks Limestone Facies 0 - 3000 been influenced by all of these tectonic provinces, a series of paleo Jurassic Green Shale Facies Rocks cross-sections are shown. Each section summarizes a particular time Mississippian Rocks Oil Field, Cambrian NEBRASKA - 4000 Triassic Rocks interval; Cambrian and older rocks, Ordovician to Triassic and Reservoir Cretaceous to Jurassic. Since Tertiary sediments are present only in - 5000 Devonian Rocks Permian Rocks the Williston Basin, no paleostructure section is shown. Figure BK-3.1. Thickness in hundreds of feet and rock facies map of Deadwood Formation or equivalent rocks. Cambrian Rocks Sands and Shales ￿ A paleo cross-section attempts to show what the subsurface (Cambrian and Lower Ordovician) - 6000 PreCambrian Rocks Pennsylvanian geology may have looked like within that time interval. For the sake Cambrian Rocks Rocks Sweetgrass Arch of space, only the particular interval is shown; no rocks older than it - 7000 Sands and Shales Rocky Mountain Trench Mississippian Rocks are illustrated. The rock units above the interval have not yet been Overthrust Belt - 8000 deposited; the top of the section is the datum. The datum is flat, Bakken Shale representing the paleo ground surface.

- 9000 Line of Section along 48 degrees of latitude with selected points every 1 degree of longitude. Cambrian and Older Rocks Generalized X-Section A-A' Devonian - 10,000 Rocks ￿ Oldest rocks exposed at the Fort Belknap Reservation are Longitude Values (in degrees) Present Day Structure Prairie Salt Fort Belknap Reservation metamorphosed sedimentary and igneous rocks. These rocks are - 11,000 West A A' East Silurian Rocks mainly biotite schist and gneiss. Some metavolcanics are present as hornblende gneiss and amphibolite. 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 Cambrian Rocks Ordovician - 12,000 0 Datum : Sea Level Scale : 1 deg = about 50 miles Sands and Shales Rocks ￿ During Cambrian time, a major seaway existed in western Montana Cambrian Rocks PreCambrian Rocks and eastern Idaho. This seaway gradually transgressed from west to Cambrian Rocks Sands and Shales - 13,000 Nesson 1000 Sands and Shales Anticline east across eastern Montana and the Dakotas. The major source of Sweetgrass Arch Williston Basin coarse-grained clastics was to the east (from the Sioux Arch) and 2000 Bearpaw Uplift Figure BK-3.2. Generalized cross-section A-A' PreCambrian Rocks graded into shales and limestones to the west. Thickness of the Poplar Dome Williston Basin Cambrian rocks varies from over 2000 feet thick in the Montana 3000 Disturbed Belt to less than 100 feet thick at the eastern edge of the Rocky Mountain Trench Little Rocky Mountains Williston Basin. Cambrian rocks at the Fort Belknap Reservation are 4000 Overthrust Belt Generalized X-Section A-A' represented by the Flathead Sandstone and are about 1000 to 1100 feet Cambrian and Older Rocks thick. There is no evidence of any structural features at this time.

Thickness of Sediment (feet) 5000 Line of section along 48 degrees latitude with selected points every 1 degree of longitude. 6000 Datum: Base of Ordovician

Figure BK-3.3. Generalized time-interval cross-section for Cambrian and older rocks along line of section A-A'.

Fort Belknap Reservation GEOLOGIC OVERVIEW Page 4 of 13 Montana Geologic History Ordovician to Mississippian Rocks Fort Belknap Longitude Values (in Degrees) From late Cambrian through most of the WEST A A' EAST Ft. Belknap Reservation Paleozoic, the Williston Basin on the east side of the 800 Ft. Belknap 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 cross-section was the dominant receiver of sediments 1000 2200 0 1200 Triassic Rocks (see cross-section A-A', and Figures BK-4.1. and

1400 2000 Pennsylvanian Rocks Bakken Shale Permian Rocks 1800 1600 1000 BK-4.2.). The Williston Basin has been a stable, Montana 1800 1400 shallow marine shelf through most of the Paleozoic 1200 North Devonian Rocks 1000 Dakota 1600 2000 Mississippian Rocks Era. Ordovician and Silurian rocks were deposited in 1400 800 1200 South Bearpaw Uplift a tidal flat environment with alternating cycles of 1000 600 400 200 Dakota PreCambrian Rocks 3000 Sweetgrass Arch Cambrian Rocks Bakken Shale limestone/dolomite, marine shales and evaporites. At Sands and Shales 800 Standing Rock Rocky Mountain Trench the end of Silurian time, a regional unconformity 800 4000 Ordovician Rocks extended across the Williston Basin and to the west. Overthrust Belt Mississippian or older Wyoming 600 Little Rocky Mountains Prairie Salt rocks exposed at land Approximate limit of Present thickness of Ordovician rocks on the Fort surface 400 the Madison Limestone 5000 Generalized Cross-Section A-A' Poplar Dome Belknap Reservation are from 120 to 300 feet. The Thickness in feet of Triassic through Ordovician Silurian Rocks 400 Silurian is not present (either having never been Madison Limestone 6000

Thickness of Sediment (in ft) Line of cross section along 48 degrees Cambrian Rocks deposited or having been completely eroded). Dolomite facies latitude with selected points every 1 degree of longitude Sands and Shales 7000 ￿ Devonian deposition was similar to that in Primarily limestone and Nebraska DATUM: Base of Jurassic - Permian missing shaly limestone facies Ordovician time. Within the reservation boundaries, Ordovician Rocks 8000 Limit of Charles salt these rocks are about 600 to 1100 feet thick, Williston Basin thickening northward, and include the Jefferson Limit of anhydrite in middle part of Madison Limestone Figure BK-4.2. Generalized time-interval cross-section of Triassic through Ordovician rocks. Group (possible Duperow rocks) and the Three Forks shaly limestone facies Shale. ￿ Mississippian rocks thicken southward towards the Big Snowy trough. Included within the period are Lodgepole Limestone and Figure BK-4.1. Thickness in feet and generalized rock facies of the Madison group (Mississippian) and equivalent Mission Canyon Limestone. The Mission Canyon is coarse grained rocks (modified after Peterson, 1981, 1984). WEST Longitude Values (in Degrees) EAST with numerous solution cavities at the top of the unit. Total thickness Fort Belknap of Mississippian rocks varies within reservation boundaries from 700 to A Reservation A' 1100 feet thick. 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 ￿ A major unconformity at the end of Mississippian time led to 2 3 4 0 2 1 0 Blackfeet5 3 widespread erosion and karstification. Pennsylvanian sediments are 3 3 4 confined to the center of the Williston Basin and are in central Montana 1000 Volcanics Ft. Belknap3 4.5 south of the reservation, in the Big Snowy trough. No Pennsylvanian, A 0 Ft. Peck Upper Cretaceous 2000 Permian or Triassic rocks are present at Fort Belknap. 3 4 Ft. A' (Niobrara and Eagle Formations) Berthold 0 0 Jurassic to Cretaceous Rocks 1 3000 In Jurassic time, the Williston Basin was still the major depocenter 3 0 2 for clastic and marine carbonate/evaporite sediments although the focus 4000 5 Jurassic Rocks of deposition shifted to the west (Figure BK-4.4) Thickness of Jurassic 5 5 NORTH 4 6 DAKOTA Lower Cretaceous rocks is estimated to be about 400 to 700 feet, thickening northward 3 5000 (Mowry) 2 Standing 1 0 SOUTH into the Hogland Basin. 1 DAKOTA Rock Thickness of Sediment (in ft) Poplar Dome 0 4 Mississippian and Older ￿ Early Cretaceous rocks (Lower Kootenai) are about 150 to 300 feet MONTANA 5 6000 Rocks WYOMING 1 Lower Cretaceous thick at the reservation. The early lower Cretaceous is thought to have 3 (Kootenai) 5 2 Bearpaw Uplift 1 7000 been a time of continental to nearshore deposits. Source area for these 6 0 Sweetgrass Arch 0 Williston Basin deposits (i.e., Lakota Formation) is thought to have been to the EXPLANATION 6.5 Rocky Mountain Trench southwest in Montana and northern Wyoming. 8000 Pre-Cretaceous rocks The late, Early Cretaceous rocks (Colorado Group-Mowry/Skull exposed at land surface 0 Overthrust Belt 0 6 3 1 Creek) are about 70 to 800 feet thick. These rocks were deposited in a 1 4 5 2 3 Figure BK-4.4. Generalized time-interval cross-section of Cretaceous and older rocks along A- transgressing marine sequence that extended from western Montana Tertiary rocks present NEBRASKA A' line of section. eastward into the Dakotas and from Texas into Canada. These rocks 0 Gas field (Cretaceous reservoir) 0 are represented by the Thermopolis, Mowry, and Warm Creek Shales. All are marine shales and impermeable. ￿ Upper Cretaceous rocks (Montana Group) are from 3500 to 4000 Figure BK-4.3. Thickness of Cretaceous rocks in thousands of feet, showing areas where Tertiary rocks are present. Gas feet thick at Fort Belknap. These rocks thicken southward into the fields producing from Cretaceous sandstones are outlined (modified after McGookey et al. 1972). Rocky Mountain trough. These units contain the Eagle and Judith River sandstones. The Bearpaw Uplift began to form at this time and created large scale gas traps.

Fort Belknap Reservation GEOLOGIC OVERVIEW Page 5 of 13 Montana Geologic History Tertiary and Younger ￿ In early Tertiary time (Paleocene or Eocene), a large mass of syenite porphyry intruded the Precambrian basement rocks into a dome about 10 miles in diameter. Smaller intrusions formed to the northwest and include, Twin Buttes, Wild Horse Butte and Snake Butte. Erosion has since removed much of the sediment cover and exposes the syenite porphyry (Fig. BK-5.1). ￿ The nearby Bearpaw Uplift was intruded by intense igneous activity which produced extrusive deposits (lava flows). Extensive landslides occurred on both the north and south Km MDOC PC flanks of the uplift. Subsurface well control shows volcanic flows resting on Lower KJKe Colorado Shale. The landslides formed both normal and thrust faults (at the head and toe Kt Kjr Kc Ke Kw of the slides). The displaced gas migrated to these new traps. ￿ By Pliocene (mid-Tertiary) time, erosion had reduced both the Little Rocky Mountains and Bearpaws to low-lying hills. Detrital material extended many miles outward from the uplifts and were reworked as alluvial terraces. Pleistocene glaciation covered most of the reservation, although glaciers never overran the Little Rocky Mountains. After the retreat of the ice, glacial material was dropped, forming hummocky, poorly drained topography.

EXPLANATION

Sandstone Shale and sandstone Siliceous shale Shale Limestone and dolomite Shale and argillaceous Metamorphic rocks Syenite porphyry limestone Figure BK-5.1. Schematic section through the Little Rocky Mountains, showing the laccolithic intrusion of syenite porphyry and the doming of the sedimentary rocks. Tsp, syenite porphyry; Kjr, Judith River Formation;Kc, Clagget Shale; Ke, Eagle Sandstone; Kw, Warm Creek Shale; Km, Mowry Shale; Kt, Thermopolis Shale; KJKe, Kootenai Formation and Ellis Group; MDOC, limestone and sandstone of Mississippian to Cambrian age: and PC, Precambrian rocks.

Fort Belknap Reservation GEOLOGY OVERVIEW Page 6 of 13 Montana Geologic History Play Types Explanation

(1) Shallow Cretaceous Biogenic Gas Play

(2) Northern Great Plains medium and low potential Biogenic Gas Play SOUTH NORTH (3) Jurassic / Cretaceous Sandstones

+ (4) Fractured / Folded Anticlines Mississippian Jurassic Ellis + Carbonate Play Kootenai + Mowry ShaleThermopolis Shale Eagle Warm Creek Shale + Gravity-Slide Faults (5) Mississippian and Devonian Carbonate Play Clagget Shale + + Judith River + Bearpaw Shale (6) Fractured Bakken + + + + + 1 + (7) Cambrian Sands + + 1 + + + Seyenite Porphry + + + + + 2 + + + + 2 + + + + + + + 3 4 Sandstone Limestone + + + + + + + 3 Shale Dolomite + 5 + + + + + + + + + + Shales, sands + + Mississippian Mission Canyon + Bakken / 3 Forks Shale and siltstones + + + Igneous/ + 6 4 6 + + + Metamorphics + + + Precambrian 5 Devonian Jefferson Limestone 7 + + + + Ordovician Bighorn Dolomite Gas + Volcanics Metamorphic Rocks + Cambrian Flathead Sandstone7 + + + + Oil + + + Intrusions Little Rocky Mountains Hogeland Basin Gravity Slide Sandstone No Scale - Drawing is approximate length of Reservation Thrusts Lenses Figure BK-6.1. Schematic diagram of play types at Fort Belknap Reservation.

Reservation: Fort Belknap Total Production Undiscovered resources and numbers of fields are Geologic Province: North Central Montana ( by province-1996) North Central Montana for Province-wide plays. No attempt has been made Province Area: North Central Montana (62,500 sq. miles) Oil: 440 MMBO to estimate number of undiscovered fields within the Reservation Area: 947 sq. miles (606,080 acres) Gas: 1.1 TCFG Fort Belknap 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) Shallow Cretaceous 2809 Porous and permeable Biogenic Gas Probably equivalent to Median: 280 BCFG (14 fields @ 20 BCFG) 1 700-3000 ft 1) gas shows southern end of 1) no production on reservation Biogenic Gas Play sandstones of accumulations at Tiger Field Size (>1 MMBOE) 0.50-0.70 reservation 2) lack of well control Ridge. 2) shallow drilling 3) reservoir rock unknown Upper Cretaceous age 20 BCFG median 27.4 BCFG max 3) structures present; domes 4) size of accumulation unknown (Eagle and Judith River) 504,000 MMCF # of undiscovered fields (> 1 MMBOE) faults Biogenic gas accumulations. from numerous fields in 5 (min) 14 (median) 26 (max) 14 (mean) 4) source rock-self source 1 Province

Northern and Great Plains 2811 Accumulations in Upper Biogenic Gas None known at this time. Median gas estimates 1 700-3000 ft 1) gas shows north and west 1) no production on reservation 2812 Cretaceous units; tighter 0.50-0.70 of reservation, near Tiger 2) lack of well control Medium and Low Potential 17,366 BCFG median siltstones and sandstones. 20,479 BCFG mean Ridge 3) reservoir rock unknown Biogenic Gas May be equivalent to Eagle 2) structures present; domes, 4) size of accumulation unknown and Judith River formations. Low gas estimates faults. Source rock/ self 12,409 BCFG median source 2 15,353 BCFG mean

Jurassic, Cretaceous 2808 stratigraphic traps; Both 134 MMBO Median: 30 MMBO (15 fields @ 2 MMBO) 1 1000-4000 ft 1) Gas shows north and west 1) no production on reservation Sandstones discontinuous sands, undip 318 BCFG not estimated west of reservation 2) lack of well control pinchouts. Fluvial and 9 MBNGL Field Size (>1 MMBOE) 2) structures present; domes, 3) reservoir rock unknown nearshore sandstones. (Most from Cutbank) 2 MMBO 9 MMBO 2.5 MMBO faults 4) size of accumulation unknown # of undiscovered fields (> 1 MMBOE) 3) source rock/ self source 3 6 (min) 15 (median) 28 (max) 15.8 (mean)

Table BK-1. Play summary chart.

Fort Belknap Reservation Page 8 of 13 Montana Play Summary Reservation: Fort Belknap Total Production Undiscovered resources and numbers of fields are Geologic Province: North Central Montana ( by province-1996) North Central Montana for Province-wide plays. No attempt has been made Province Area: North Central Montana (62,500 sq. miles) Oil: 440 MMBO to estimate number of undiscovered fields within the Reservation Area: 947 sq. miles (606,080 acres) Gas: 1.1 TCFG Fort Belknap 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 estimated 9 MMBO (9 fields@ 1 MMBO) 1 1,000-6,700 ft. 1) structures exsist; folds 1) no production on reservation anticlines in controlled by matrix or 21,506 MMCFG Field Size (>1 MMBOE) not estimated faults, domes 2) rocks exposed to atmosphere Mississippian fractures 585 MBNGL 1 MMBO 3 MMBO 1.2 MMBO 2) reservoir rock exists at Little Rocky Mountains; (numbers include No of Fields (>1 MMBOE) 3) regionally thermally mature strong hydro. gradient-flushed? Carbonates Mississippian and 3 (min) 9 (median) 17 (max) 9.4 (mean) 3) lack of well control 4 Devonian play)

Mississippian and 2805 1) Jurassic/Mississippian Both (see numbers from estimated 48 MMBO (12 fields @ 4 MMBO) 1 1,300-7,000 ft. 1) structures exsist; folds, 1) no production on reservation regional unconformity traps Mississippian) Field Size (>1 MMBOE) not estimated faults, domes 2) rocks exposed to atmosphere Devonian Carbonates 2) Devonian Structural Traps 4 MMBO 21 MMBO 4.8 MMBO 2) reservoir rock exists at Little Rocky Mountains: 3) regionally thermally mature strong hydro. gradient-flushed? No of Fields (>1 MMBOE) 3) lack of well control 5 3 (min) 12 (median) 21 (max) 12 (mean)

Fractured Bakken 2804 Bakken/Exshaw Shale Oil Not applicable 0.25 5,000-10,000 ft. 1) Bakken regionally exists 1) no existing production within Not estimated High organic content, 0.2 2) thermally mature province 18,000 BO / square miles 47,520 / square miles thermally mature; fractured 3) structures and flexures exist 2) no Bakken at southern end 5328 sq. mi. untested reservoir of reservation 6 3) no deep well control

Cambrian estimated 2 MMBO (2 fields @ 1 MMBO) 2802 Coarse sands trapped as Both Not applicable 0.5 1,700-7,000 ft. 1) structures exist; folds, 1) no existing production within Sands pinchouts or on deeper Field Size (>1 MMBOE) not estimated faults, domes province structures 1 MMBO 5 MMBO 1.3 MMBO 2) reservoir rock exists 2) rocks exposed to atmosphere No of Fields (>1 MMBOE) at Little Rocky Mountains: 1 (min) 2 (median) 4 (max) 1.1 (mean) strong hydro. gradient-flushed? 3) source rock unknown 7 4) thermal maturity unknown 5) lack of well control

Table BK-2. Play summary chart (continued)

Conventional Play

Hypothetical Play

Fort Belknap Reservation Play Summary (continued) Page 8 of 13 Montana PLAY TYPE 1

+2331 Shallow Cretaceous Biogenic Gas FO +2092 +2113 +1995 +2212 22 FO U FO D D +1977 +1922 +2362 General Characteristics - This play is characterized by gravity-slide traps that +1853 FO +2208 FO U +2113 +2187 +1969 U +2140 +1500 +1779 T formed during Tertiary time due to emplacement of igneous intrusions. Biogenic D +1962 FO +2256 FO +1480 27 gas is trapped by fault blocks in Eagle and Judith River sandstones. Well control +2172 +2110 +2130 FO FO +2142 +2171 +1966 D FO N is sparse on the reservation, therefore, reservoir quality is speculative. FO FO +2365 U +1960 +1471 FO FO +1846 U ￿ Reservoir rock at Tiger Ridge and other nearby fields is a fine to medium +1983 +1930 D +1986 +2207 FO D U U A +2061 D T U D FO U +2039 +2052 grained marine sandstone with porosities of 16-20% and permeabilities ranging FO D +2489 +1683 27 D +2202 FO +2134 FO +1855 from 9.5 to 110 millidarcies. Eagle sandstone thickness varies from 45 to 150 U FO N FO +1692 FO +1278 FO FO FO FO feet thick. FO U FO FO +1605 U 33 31 +1611 31 +2157 D 36 D FO +1566 FO +2189 +2168 ￿ The north half of the reservation has surface expressed thrust and normal FO FO A' D FO FO U faults. Gas shows are present in areas south, west and north of the reservation boundaries. R 15 E R 15 E LINE OF R 15 E CROSS-SECTION A-A'

LEGEND BLAINE CO. Analog Fields (Outside reservation)

CHOUTEAU CO. Bullwacker U +1692 TOP OF EAGLE FORMATION UP THROWN D FAULT BULLWACKER FIELD Leroy DOWN THROWN FO EAGLE FORMATION FAULTED OUT Blaine & Chouteau Counties, Montana Tiger Ridge

IGNEOUS INTRUSIVES LINE OF SECTION A - A' Havre

Figure BK-8.1. Bullwacker Field, Blaine & Chouteau Counties, Montana (after G.W. Shepard).

A A' ROLAND BOND; LONE STAR EXP. ROLAND BOND; LONE STAR EXP. THE MONTANA POWER CO. 9 - 26 EARL WEAVER STATE 16 - 36 14 - 31 ROKANSON C SE 26 - 27N - 16E NE SE 36 - 27N - 16E SE SW 31 - 27N - 17E

KB 3918'

TOP JUDITH RIVER Fm STRUCTURAL CROSS SECTION A - A' Table BK-3. Bullwacker Field Parameters BULLWACKER FIELD DATUM: +2600 MEAN SEA LEVEL BLAINE & CHOUTEAU COUNTIES, MONTANA Formation: ￿ Upper Cretaceous Eagle Sandstone JUDITH RIVER FM Lithology: continuous unit of fine to medium grained calcareous, marine sandstone, about 150 ft. thick TERTIARY VOLCANICS Porosity: ￿ 16 percent Permeability: No information available CLAGGETT SHALE

Oil/Gas Column: ￿ No information available JUDITH RIVER FM Average Net Pay: ￿ 40 feet net thickness TOP EAGLE FM JUDITH RIVER FM Other formations with shows: ￿ Eagle gas shows and Judith River gas shows 1800 Other information: Published literature suggests that permeabilities are low. Reservoir 1900 must be fractured before production. TOP TELEGRAPH

CREEK Fm TOP CLAGGETT SHALE 2000

EAGLE FM CLAGGETT SHALE 2100 COLORADO SHALE

DST 1690 - 2070' 2200 GTS 1 min @ 50 MCFD Top Eagle Fm

DST 2150 - 2284 rec 20 Mud COLORADO SHALE

Figure BK-8.2. Structural cross-section A-A', Bullwacker Field (after G.W. Shepard).

Fort Belknap Reservation CONVENTIONAL/HYPOTHETICAL PLAY TYPE 1 Page 9 of 13 Montana Shallow Cretaceous Biogenic Gas Play PLAY TYPE 2 Northern Great Plains Biogenic Gas Play Cretaceous Epeiric Seaway (Medium - Low Potential) General Characteristics - This play is characterized by very fine to fine-grained sandstones and siltstones within the Alaska Greenland Upper Cretaceous section of the reservation area. These rocks are equivalent to Eagle and Judith River sandstones at Tiger Ridge Field on the Bearpaw uplift (Figure BK-9.2 and 9.3). No production has been found to date within the Fort Belknap area. Tight gas sandstone production is present in nearby Leroy Field. ￿ Reservoir rock at Tiger Ridge Field and other fields in the area is fine-medium-grained marine sandstones with high porosities and permeabilities. It is assumed that lower porosity and permeability values will be present within the reservation area. Potential reservoir intervals may be enhanced by location on paleostructure.￿ Series Southeastern North-Central ￿ Trapping mechanisms could include fault traps, domes, and discontinuous sandstone lenses. Potential seal intervals Alberta Montana may be sporadic and too porous for efficient gas trapping. The north half of the reservation has surface expressed Frenchman Fm. thrusted and normal faulted horizons. Gas shows are present in areas south, west, and north of the reservation Hell Creek Fm. Battle Fm. Canada boundaries. It is unclear whether they are of thermogenic or microbial origin. Whitemud Fm. Eastend Fm. Fox Hills SS. Edmonton Group Cretaceous Epeiric Seaway Bearpaw Shale Bearpaw Shale

United States Oldman Fm. 0 Judith River Fm. Cretaceous

Belly River Group Foremost Epeiric Seaway

180 Mi Pakowki Fm. Claggett Shale A 90 Mi 150 Mi A' Upper Mexico Cuba GLACIER NAT'L PARK Cretaceous Gammon MARINE SHALE & Milk River Equiv. Eagle SS. WILLOW CREEK NONMARINE ROCKS SILTSTONE Shale FM (PART) First White Specks Telegraph Creek Fm. ? COASTAL SANDSTONE CHALK & LIMESTONE CALCAREOUS SHALE Niobrara Fm. ? ST MARY RIVER FM BEARPAW Medicine Hat MTNS SS. Carlile Shale Figure BK-9.1. Paleogeographic map of North America during Late WEST FLANK WILLISTON BASIN ? Cretaceous time, showing the Cretaceous seaway (after Rice and HORSETHIEF DOWDOIN Shurr, 1980). BEARPAW SHALE SANDSTONE FOX DOME Second White Specks ? HILLS SS HELL CREEK FM. Fm. horn ? Mosby SS. Mbr. 113 112 111 110 109 108 107 Green- FOX HILLS SS Second White BEARPAW SHALE Specks SS. Belle Fourche Shale ? 51 JUDITH RIVER FM Colorado Group Fish Scale SS. ? PIERRE Lower Suffield SHALE Cretaceous Mowry Shale Block CLAGGETT SHALE ARDMORE BENTONITE BED Bow Island Fm. Muddy SS.. Medicine EAGLE SS 50 Hat Field TWO MEDICINE FORMATION Presently producing gas interval Nonmarine Rocks VIRGELLE SS GAMMON TELEGRAPH SHALE CREEK FM. NIOBRARA FM ? Interval with potential for gas Marine Sandstones CARLILE SHALE production from low-permeability Marine Siltstones and MARIAS RIVER SHALE reservoirs BELLE FOURCHE SH GREENHORN FM CANADA Shales 49 Alberta Saskatchewan Upper Cretaceous MOWRY SHALE UNITED STATES Montana Bowdoin Lower Cretaceous Figure BK-9.4. Correlation chart of selected Cretaceous rocks in north-central Field Montana and southeastern Alberta showing currently productive intervals and Tiger Ridge SKULL CREEK SHALE those with potential for gas production from low-permeability reservoirs. Field VAUGHN MUDDY SS MBR 48 BLACKLEAF FM

Figure BK-9.3. Distribution of shallow gas fields in north-central Montana, southeastern Alberta, and southwestern Saskatchewan. Bowdoin field and large area in Canada produce from low- Figure BK 9.2. Diagrammatic sequence of selected Cretaceous Rocks from Glacier National Park permeability reservoirs. Tiger Ridge field produces from structural to the west flank of the Williston Basin, Montana (after Rice and Shurr, 1980). traps of conventional reservoirs.

Fort Belknap Reservation CONVENTIONALl/HYPOTHETICAL PLAY TYPE 2 Page 10 of 13 Montana Northern Plains Low Potential Biogenic Gas Play PLAY TYPE 5 112o 110o 108o 106o 104o 102o 100o 98o PLAY TYPE 3 Mississippian and Older Carbonates ALBERTA MANITOBA Jurassic / Cretaceous Sandstones BLACKFEET 500 General Characteristics- This play is characterized by possible traps in the Mississippian, Devonian 250 250 FORT FORT SASKATCHEWAN o and Ordovician carbonate units. No production has been established to date at either Fort Belknap or BELKNAP PECK 48 General Characteristics- This play is on the adjacent Bearpaw Uplift. FORT characterized by possible traps in the Jurassic BERTHOLD ￿ Trapping mechanisms include discontinuous porosity zones and structural traps. One problem may MONTANA NORTH DAKOTA Swift / Ellis sandstone units and in the Lower 500 1250 be breached Mississippian and older units exposed to the atmosphere in the Little Rocky Mountains, Cretaceous Kootenai formation. No production at the southern edge of the reservation. The top of the Mission Canyon is cavernous and forms an 1000 has been established to date at either Fort Belknap 750 excellent aquifer. This strong, hydrodynamic flow from south to north may have "flushed", 750 or on the adjacent Bearpaw Uplift. Oil shows 250 46o hydrocarbons from the older rocks. (Fig. BK-10.3 and BK-10.4) 500 have been found in Jurassic rocks at Tiger Ridge 500 STANDING ROCK Gas Field. CANADA MONTANA 750 ￿ Trapping mechanisms include discontinuous SOUTH DAKOTA Explanation sandstone lenses and sandstone pinchouts. One 2500 WYOMING 500 250 problem may be breached Jurassic / Cretaceous 3000 Contact -- Line represents upper EXPLANATION 44 o Fort Belknap Agency contact of Madison Group along 3200 Saco # some mountains and general Jurassic and older rocks units exposed to the atmosphere in the Little # area of outcrop in some exposed at land surface 3400 Rocky Mountains, at the southern end of the 3200 localities. 500 Sandy facies, 3500 Swift Formation reservation. A strong, hydrodynamic flow from 3400 Carbonate facies, Lodgepole # Warm Spring Generalized potentiometric Reirdon Formation 500 south to north may have "flushed", hydrocarbons contour -- Shows altitude at Little Rocky Mnts. which water level would have Evaporite facies from the system. 3200 3500 stood in tightly cased wells NEBRASKA 42 o

3800 Spring Giant Springs 3600 Figure BK-10.1. Thickness of Jurassic rocks in feet, showing approximate distribution of carbonate facies and Great Falls Hydrology mapped in 1977 # North Moccasin evaporite facies (modified after Peterson, 1972). Mtns. Map adapted from Montana Hilger Bureau of Mines and Geology 3200 Warm Springs # Hydrologic Map 2, 1980. South Cat Creek fault zone 3400 Judith Mnts. 3400 Moccasin Mtns. Lewiston # Big Springs PLAY TYPE 4 Judith Basin Little Belt Mnts. 4000 Central Montana Uplift Fractured, Folded Anticlines in Big Snowy Mtns. 4200 Mississippian Carbonates 3800 3600 4400

Willow Creek fault zone 800 General Characteristics - This play is 1000 2200 1200 characterized by possible traps in the Mississippian, 1400 2000 Mission Canyon carbonate units. No production Figure BK-10.3. Potentiometric surface of water in the Madison Group, central Montana. 1800 1600 Montana 1800 has been established to date at either Fort Belknap CANADA 1400 MONTANA 1200 North or on the adjacent Bearpaw Uplift. Trapping Explanation 1000 Dakota 1600 25 to 50 1400 800 mechanisms include discontinuous porosity zones percent South Contact -- Line represents upper 1200 contact of Madison Group along 600 400 1000 200 Dakota and structural traps. Fort Belknap Agency some mountains and general # area of outcrop in some One problem may be breached Mississippian and 3000 Saco # localities. 800 3000 50 to 75 percent older units exposed to the atmosphere in the Little 800 3500 Mississippian or older Wyoming 600 Rocky Mountains, at the southern edge of the 25 to 50 percent Line of equal dissolved-solids Lodgepole # Warm Spring concentration -- Interval 2000 rocks exposed at land Approximate limit of reservation( refer to Figure BK-10.2). percent mg/1 400 Little Rocky Mnts. surface the Madison Limestone 0 to 25 ￿ The top of the Mission Canyon is cavernous and percent Thickness in feet of 0 to 25 Madison Limestone forms an excellent aquifer. This strong, 3000 Ratio lines -- Separates areas of Dolomite facies hydrodynamic flow from south to north may have Giant Springs 0 to 25, 25 to 50, and 50 to 75 Great Falls # North 25 to 50 percent percent Na+K+Cl to other Primarily limestone and "flushed" hydrocarbons from the older rocks. Moccasin dissolved constituents. Nebraska Mnts. 50 to 75 percent shaly limestone facies Warm Spring Hilger 5000 Judith Basin # Limit of Charles salt of South Spring Judith Mnts. Cat Creek fault zone informal subsurface usage 3000 Moccasin Geochemistry mapped in 1977 Mnts. Limit of anhydrite in middle # Big Springs 1000 Lewiston Map adapted from Montana part of Madison Limestone Bureau of Mines and Geology Little Belt Mnts. Hydrologic Map 3, 1980. Big Snowy Mnts. Central Montana uplift 5000 1000 50 to 75 percent Figure BK-10.2. Thickness in feet and generalized rock facies of the Madison Group (Mississippian) and equivalent 3000 0 to 25 percent Willow Creek fault zone rocks (modified after Peterson, 1981, 1984b). 25 to 50 percent

Figure BK-10.4. Dissolved solids concentration and ratio of sodium, potassium, and chloride to dissolved solids concentration in water of the Madison Group, Montana. Fort Belknap Reservation CONVENTIONAL / HYPOTHETICAL PLAY TYPES 3, 4, 5 Page 11 of 13 Montana Jurassic/Cretaceous and Mississippian Plays Canada United States o o ? PLAY TYPE 6 110 105o 100 Fort Fractured Bakken Play 1200 1200 1600 Belknap 100 2000 1000 1800 A 800 ? 200 1000 A' General Characteristics - This play involves 800 Fort 600 Antelope 1400 225 possible fracture production from the Belknap Ft. Berthold Bear Den 125 Reservation ? 250 Bakken/Three Forks shale. No production 400 600 Immature has been established to date within the Fort 200 225 "Low-Resistivity" Belknap area or adjacent Bearpaw uplift. The 400 Approximate Limit Of Bakken Formation 200 Bakken Shale North Dakota 200 (Modified from Sandberg, 1962) Three Forks shale is poorly exposed in the 200 Organic-rich rocks 600 Montana have not yet generated Mature "High" Resistivity Bakken Shale 150 Little Rocky Mountains at the southern end of 175 Organic-rich rocks have generated hydrocarbons - matrix hydrocarbons-matrix porosity is porosity is water saturated. the reservation. Organic content (quality and Resistivity oil saturated. quantity) and thermal maturity are unknown. 200 Control Point (Induction or Laterolog) ￿ Trapping mechanisms could include North Dakota discontinuous fracture zones and possible structural closures. The northern end of the South Dakota Silurian and South Dakota reservation is on the southern flank of the older rocks exposed Hogeland sub-basin, where it is possible that Limit of Bakken source Wyoming Montana the Bakken/Three Forks shale is better rocks 0 developed and thermally mature. Limit of Prairie salt

Figure BK-11.1. Areas of "high" and "low" electrical resistivity in Bakken shales, with subsurface isotherm contours 400 contour interval, 200' (degrees) and interpreted area of source-rock maturity (after Meissner, 1987). Figure BK-11.3. Map showing thickness of Devonian rocks, limit of Prairie salt, limit of Bakken source rock, location of analog fields and reservation, and location of regional cross-section A-A' (modified after Peterson, 1987). ? West East

Jurassic Jurassic Big Snowy Group Nesson Axis Triassic

PLAY TYPE 7

Madison Group (L-M Miss.) Cambrian Sandstone Play Devonian Charles Formation 110¡ General characteristics - The Cambrian 105¡ 100¡ 0 Mission Canyon Fm. 100 Flathead sandstone may be a potential production 40 20 0 A 100 Source Rock Bakken Formation Lodgepole "Maturity" horizon. No production has been established to 60 A' 0 (Upper and Lower Bakken Shales) date within the Fort Belknap Reservation or 80 Antelope Fort 120 Ft. Berthold Nisku Fm. adjacent Bearpaw Uplift. The Flathead interval Poor Porosity 120 Belknap Reservation Good Porosity is well exposed in the Little Rocky Mountains at Taylor the southern end of the reservation. It is a fine- 100 grained sandstone with some interbedded North Dakota Interbedded Salt, Anhydrite and generally Black organic-rich Shale: Upper and "Maturity" 120 80 Lower Bakken Shale Members dense "tight" Dolomite and Limestone: Hydrocarbon Accumulation conglomeratic lenses and thick shale intervals 150 60 40 Charles Formation Migration Flow Direction Montana Calcareous-dolomitic Siltstone: (Fig. BK-11.4). 20 Light-colored generally porous Limestone and Dolomite - 100 oolitic, pelletal and skelletal i.p.: Mission Canyon Middle Bakken Siltstone Member 60 and Nisku Fms. Since the Cambrian Flathead sandstone is 40 100 Grey-green-red Dolomite, Shale, and exposed at the surface to meteoric influx, a Dark-colored generally dense "tight" Shaley Limestone- Overpressure Cell Silliceous (triangle), i.p.: Lodgepole Formation Siltstone:Three Forks Formation Fractures hydrodynamic flow gradient from south to north may have flushed hydrocarbons from the older 80 Figure BK-11.2. Schematic east-west section across the Williston Basin showing source-rock maturity, fluid over- rocks. Cambrian and pressure, fracture, migration and hydrocarbon accumulation patterns in the Bakken formation and adjacent units Trapping mechanisms would include structural older rocks exposed (from Messiner, 1984). Wyoming South Dakota domes, fault traps, and sandstone pinchouts. sandstone facies 40 0 shale, sandstone and 20 minor limestone facies 0 green shale facies

40 contour interval, 20'

Figure BK-11.4. Thickness of Deadwood and equivalent rocks, location of analog fields, location of reservation, and location of regional cross-section A-A' (modified after Peterson, 1987).

Fort Belknap Reservation HYPOTHETICAL PLAY TYPES 6 & 7 Page 12 of 13 Montana Fractured Bakken and Cambrian Sandstone Plays Fort Belknap Reservation Indian Land Areas, 1992, United States Department of the Interior-Bureau of General References Indian Affairs. Erdmann, C.E. and V.K. Koskinen, 1953, "Preliminary Structure Contour Map Anderson, Robert C., 1995, The Oil and Gas Opportunity on Indian Lands- of Blaine, Northern Chouteau and Hill Counties ans Adjoining Areas, Clayton, Lee, et al., 1980, Geological Map of North Dakota Survey. Exploration Policies and Procedures, Bureau of Indian Affairs, Division of Montana", Guidebook, 4th Annual Field Conference, Little Rocky Energy and Mineral Resources, General Publication G-95-3, 158 p. Mountains, Montana, Southwestern Saskatchewan, Billings Geological Darton, N.H., et al., 1951, Geologic Map of South Dakota, United States Society. Geological Survey. Beeman, William R., et al., 1996, Digital Map Data, Text and Graphical Images in Support of the 1995 Assessment of United States Oil and Gas Resources, Ervin-Cleveland, Malanie and George W. Shepard, 1985, "Bullwacker Field", Ross, Clyde P., et al., 1958, Geological Map of Montana, Montana Bureau of United States Geological Survey, Digital Data Series DDS-35, CD ROM. Montana Oil and Gas Field Symposium, Montana Geological Society, Mines. Billings, Montana, pp. 297-300 Charpenteir, Ronald R., et al., 1996, Tubular Data, Text, and Graphical Images in Support of the 1995 National Assessment of United States Oil and Gas Feltis, Richard D., 1993, "Hydrogeology of the Madison Group in Central Resources, United States Geological Survey, Digital Data Series DDS-36, Montana", Energy and Mineral Resources of Central Montana, Montana CD ROM. Geological Society, Billings, Montana, pp. 239-242

Gautier, Donald L., et al., 1996, 1995 National Assessment of United States Oil Knechtel, Maxwell M., 1959, "Stratigraphy of the Little Rocky Mountains and and Gas Resources - Results, Methodology, and Supporting Data, United Encircling Foothills, Montana", Contribution to Economic Geology, USGS States Geological Survey Digital Data Series DDS-30 Release 2. Survey Bulliten 1072-N; includes Geologic Map.

______., et al., 1995, 1995 National Assessment of United States Oil ______, et al., 1944, "Oil and Gas Possibilities of the Plains Adjacent to and Gas Resources, Overview of the 1995 National Assessment of Potential Little Rocky Mountains, Montana", Plains Adjacent to the Little Rocky Additions to Technically Recoverable Resources of Oil and Gas - Onshore Mountains, Montana, Oil and Gas Investigation Map, 0004, United Stated and State Waters of the United States, United States Geological Survey Geological Survey. Circular 1118, 20 p. Maher, Patrick D., 1969, "Eagle Gas Accumulations of the Bearpaw Uplift Area, Mallory, William Wyman, et al., 1972, Geologic Atlas of the Rocky Mountain Montana", Eastern Montana Symposium, Montana Geological Society 20th Region, Rocky Mountain Association of Geologists , 331 p. Anniversary Field Conference Guidebook, pp. 121-127.

Peterson, James A. and MacCary, Lawrence M., 1987, "Regional Stratigraphy Maughan, Edwin K., 1993, "Stratigraphic and Structural Summary for Central and General Petroleum Geology of the U.S. Portion of the Williston Basin Montana", Energy and Mineral Resources of Central Montana, Montana and Adjacent Areas", Williston Basin: Anatomy of a Cratonic Oil Province, Geological Society, Billings, Montana, 1993, pp. 3-20. Rocky Mountain Association of Geologists, pp. 9-43. Rice, Dudley D., 1980, "Coastal and Deltaic Sedimentation of Upper Cretaceous Rice, Dudley D. and Shurr, George W., July 1980, "Shallow, Low-Permeability Sandstone, Relation to Shallow Gas Accumulations, North-Central Reservoirs of the Northern Great Plains - Assessment of their Natural Gas Montana", American Association of Petroleum Geologists Bulliten, Volume Resources", American Association of Petroleum Geologists Bulletin, 64/3, March, pp. 316-338. Volume 64/7, pp. 969-987. Rowley, Arthur E., 1985, "Leroy Field", Montana Oil and Gas Field Willette, Donna C., et al., 1996, "Oil and Gas Atlas on Indian Lands", Indian Symposium, Montana Geological Society, Billings, Montana, pp. 689-692. Resources Building Partnerships, Sixth Annual Energy and Minerals Conference, Bureau of Indian Affairs, Division of Energy and Mineral Shurr, George W., et al., 1993, "Regional Pressure Patterns as Evidence for Resources, p. 10. Fractured Reservoirs in the Bowdoin and Phillips Sandstones on the Bowdoin Dome, Montana", Energy and Mineral Resources of Central Fort Belknap - Fields and Articles Montana, Montana Geological Society, Billings, Montana.

Alverson, Douglas C., 1965, "Geology and Hydrology of the Fort Belknap Fort Belknap - Map References Indian Reservation, Montana", Water Supply of Indian Reservations; Accession Number 65-18877, pp. F1-F59 Executive Reference Map 334, 1985 edition, Extended Area, Northern Rocky Mountains, Geomap Company. Bennett, Steve, 1985, "Tiger Ridge Field"; Montana Oil and Gas Field Symposium, Montana Geological Society, Billings, Montana, pp. 1123- Executive Reference Map 321, 1983 edition, Southern Williston Basin, Geomap 1126 Company.

Fort Belknap Reservation REFERENCES Page 13 of 13 Montana