UINTAH AND OURAY RESERVATION Currently, the Ute Tribe, Ute Allottees, and the Ute Distri- Introduction bution Corporation in joint management hold 102,000 acres under lease, and more than 490 wells in production. The Utah Oil, Gas, and Mining Board conduct conservation spacing in cooperation COUNTY DAGGET The Uintah and Ouray Indian Reservation is located in the Uinta Ba- UINTAH COUNTY with the Ute Tribe. Spacing rules for the Altamont-Bluebell field COUNTY DUCHESNE sin, in northeast Utah (FIGURES UO-1 and UO-2). The terrain is High COUNTY Mountain desert in the central part of the basin, which is surrounded are set at a multi-well level allowing two wells per section, while undesignated field spacing is 40 acres for oil and 640 acres for gas. by mountain ranges on the edge of the basin. Elevation varies from SUMMIT approximately 5,600 feet to over 11,000 feet above sea level. The Some variations or exceptions exist by special ruling and order (Anderson, 1995). WASATCH area's main transportation conduit is U.S. Highway 40, which leads COUNTY east to Salt Lake City, Utah, and west to Denver, Colorado. The ba- STARR FLATS

sin covers approximately 11,500 square miles, and Ute Indian Tribe COTTONWOOD WASH Vernal jurisdiction comprises just over 4 million acres of this area, reaching BLUEBELL from the Utah-Colorado border west to the Wasatch Mountain range. ROOSEVELT WEST ALTAMONT TREND GUSHER ALTAMONT EAST GUSHER Mineral Ownership Fort Duchesne HORSE SHOE BEND FLAT MESA BLUE CEDAR BRENNER BOTTOM The Uintah and Ouray Indian Reservation is a checkerboard owner- RIM BENCH RANDLETT GYPSUM WONSITS ship reservation containing Ute Indian Tribe, Ute Indian Allotted, HILLS VALLEY CEDAR Duchesne STARVATION RED WASH Ute Indian Tribe and Ute Distribution Corporation Jointly Managed DUCHESNE REFUGE INDIAN WEST PLEASANT Ouray Indian Trust minerals, along with fee (privately owned) and federal RIDGE VALLEY WASATCH PARIETTE SOUTH CHAPITA minerals. Indian properties cover approximately 1.2 million surface- NUTTER BENCH WELLS CANYON CASTLE OURAY PEAK MONUMENT UTE TRAIL owned acres, and 400,000 mineral-owned acres within the 4 million- BUTTE RIVER

CHOKECHERRY BITTER acre jurisdictional boundary. Ute Indian Allottees, the Ute Indian CANYON CREEK Tribe, and the Ute Distribution Corporation own both surface and COUNTY UINTAH mineral properties in joint management.

UTAH COUNTY DUCHESNE COUNTY CARBON COUNTY

PETERS POINT 112O 111O 110O 109OO 108O 107O 41O WYOMING

GREEN Price FLAT MOUNTAINS ROCK UINTA RANGE AHUT CARBON COUNTY UINTAH COUNTY MERY COUNTY GRAND COUNTY MOON RIDGE TCH ASA TCH 40O COLORADO SEGUNDO W UINTA BASIN CANYON LEGEND ARCH CREEK

DOUGLAS N

U BOOK ASIN Oil Field TCH UNCOMP B TEA Gas Field AEL ASAW UPLIFT Reservation Boundary PLA AHGRE CLIFFS PICEANCE CREEK SWELL O 39 SAN RAF 0 5 10 20 30 0 50Miles Scale, miles 0 80Kilometers Figure UO-2. Index map showing the Uintah and Ouray Indian Reservation in yellow (modified after Anonymous, 1995).

Figure UO-1. Location of Uinta Basin and surrounding structural and physiographic features. Yellow area shows approximate boundary of Uintah and Ouray Indian Reservation (modified after Cashion, 1992).

UINTAH AND OURAY INDIAN RESERVATION Overview 1 UTAH Uintah and Ouray Reservation north, and northeast into the basin. The northwest-southeast trending major faulting, steep to overturned beds, and multiple unconformi- Petroleum Exploration and Development salt folds of the northern Paradox Basin plunge beneath the Book ties that allow youngest Eocene rocks to lie unconformably on top of Cliffs in the southernmost part of the basin, and the two downwarps Precambrian rocks. The basin axis is close to the mountain flank merge imperceptibly in this area. On the east, the Uinta Basin is sep- and moves northward with depth. The Uinta Basin is a rich source of many energy-producing minerals. arated from the Piceance Basin of northwest Colorado by the Doug- The Uinta Basin formed in Late Cretaceous and Paleocene time The greatest portion of the energy resources is hydrocarbons in the las Creek Arch, which parallels the Utah-Colorado border (FIGURE when, in response to rapid uplift and formation of the Uinta Moun- form of coal, oil, gas, oil shale, and bituminous sandstone and lime- UO-3). tains, the dominant north-south tectonic and sedimentation patterns stone. The basin is quite asymmetric. Beds on the north flank dip 10 to of Cretaceous time shifted to west-east. The Uintas impose a domi- Resources contained within the Uintah and Ouray Reservation Figure UO-3. Location and structural 35 degrees south, whereas beds on the south flank dip only 4 to 6 de- nant west-east trend through most of the basin; however, structures include conventional and unconventional hydrocarbon deposits of oil element map of the Uinta and Piceance grees north (Chidsey, 1993). The north flank is highly complex, with in the southeast portion have a strong northwest grain, reflecting the and gas, oil shale, and tar sands in major quantity; coal, uranium, sil- Basin Provinces (modified after Gautier et older buried Uncompahgre and Paradox trends. ver, copper, gold, gypsum, and phosphate are also present in minor to al., 1995). mid-economic quantities. o o 110 106o Cretaceous and older rocks contain many productive oil and gas UT WY 108 zones. However, the major portion of the energy production from the CO Uinta Basin is from Tertiary rocks, and the distribution of the hydro- MTNS. UPLIFT SANDWASH carbons and minerals is directly related to their depositional environ- UINTA BASIN ment. Uinta Basin production of oil and gas began in the late 1940's, with major development commencing in the late 1960's and expand- Vernal AXIAL ing in the late 1970's and early 1980's. Over 300 million barrels of UPLIFT Craig oil (MMBO) have been produced from the Greater Altamont-Blue- PROVINCE bell field alone. Conventional oil and gas deposits have been exten- BOUNDARY sively explored and developed. The Green River and Wasatch For- UINTA Rangely mations contain the bulk of the producing zones, with depth to these 40o BASIN zones ranging from 6,000 to 18,000 feet. This has resulted in the de- velopment of the Greater Altamont-Bluebell oil field, and numerous undesignated smaller fields (FIGURES UO-2, UO-6). BOOK PICEANCE The oil produced is high in paraffin content (pour point = 120 de- CLIFFS CREEK WHITEUPLIFT RIVER grees F), making it an excellent gasoline refining feedstock. It is ex- BASIN EAGLE tremely rich with associated natural gas, with values falling between Price 900 and 1700 British thermal units (Btu). Only one natural gas field Glenwood BASIN has been developed, and it is located east and south of the Green and DOUGLAS CLIFFS Springs White Rivers. It is bordered by the Natural Buttes Gas Field Unit, CREEK ARCH BOOK SAWATCH RANGE which covers 76,000 acres. Total Ute Indian oil production approximates 1,250 barrels per Grand Junction day, a level that has held for the last 10 years. New well development UNCOMPAHGRE UPLIFT and workover activity has been sufficient to offset the normal decline SAN RAFAEL of the many oil and gas fields within the basin and the reservation SWELL Green area (Anderson, 1995). River 0 25 50 MILES GUNNISON Geology of the Uinta Basin UT CO UPLIFT 025 50 KILOMETERS The Uinta Basin is a major sedimentary basin in the western-central Rocky Mountain province. It is bounded by the Uinta Mountain Up- EXPLANATION lift on the north and by the Wasatch Mountain Uplift and the eastern faulted margin of the Wasatch Plateau on the west. On the southwest o Upper Cretaceous rocks present and south, the San Rafael Swell and the Uncompahgre Uplift border 38 UPPER the basin (FIGURES UO-2 and UO-3). The southern basin edge is gen- Upper Cretaceous rocks absent CRETACEOUS erally considered to be the Book and Roan Cliffs, escarpments of Up- ABSENT BY per Cretaceous and Lower Tertiary formations which dip northwest, Thrust fault EROSION

UINTAH AND OURAY INDIAN RESERVATION Geology 2 UTAH The Uinta Basin is filled with 30,000 to 32,000 feet of sediment in its northern and deepest portion (Figs. UO-4 and UO-5). Although the majority of the rocks exposed on the reservation are of Tertiary age, some UTAH COLORADO pre-Tertiary age rocks are exposed on the northern and northwestern boundaries. Percentages of basin strata

are subdivided as follows: UINTA BASIN DOUGLAS CREEK PICEANCE BASIN AXIAL UPLIFT ARCH Tertiary (Eocene - Paleocene) - 55% Browns Park Fm.

Upper Cretaceous - 25% YTIARTER Duchesne River Fm. Uinta Fm. Triassic - Lower Cretaceous - 10% S Green River Formation Fm. Paleozoic - 10% tch Colton Fm. Wasa Wasatch Flagstaff Limestone S Fort Union Formations Currant Creek North Horn Conglomerate Lance Formation Formation S Lewis Shale Price Mesaverde Gp. River Fm. S Sego Sandstone S GEOLOGIC THICKNESS (ft.) GROUP AND CHARACTER OF BEDS Castlegate Sandstone TIME FORMATION EAST WEST Blackhawk Fm. S Mancos "B" S Quaternary Alluvium Alluvium, gravel surfaces, talus deposits, and Emery Sandstone Mancos Shale other windblown deposits S Pleistocene Glacial Deposits Glacial drift, alluvium, and terrace deposits 0-70 0-70 Ferron Sandstone Frontier Formation CRETACEOUS Tununk Shale S Miocene Bishop Conglomerate Conglomerate, boulders 1 to 6 feet in diameter, 0-500 0-500 sand and gravel S Mowry Shale S

y y Oligocene Duchesne River Formation Varicolored shale, sandstone, and conglomerate 1370 1500 Dakota Sandstone Significant oil production

tiar Eocene Uinta Formation Shale with sandstone interbeds 700-1650 1800-5400 Cedar Mountain Formation erT Green River Formation Green to white shale, sandstone, oil shale in Significant 1800-2400 0-5000 gas production middle of formation Morrison Formation Wasatch Formation Varicolored sandstone, shale, limestone 0-5000 S Source rocks Stump Formation S Curtis Formation S Paleocene deposits absent due to unconformity Cretaceous Currant Creek Formation Conglomerate, sandstone, and varicolored shale 0-4800 Preuss Formation Entrada Sandstone JURASSIC North Horn Formation Varicolored shale with sandstone interbeds 0-400 0-200 Twin Creek–Carmel Formation S Upper Mesaverde Group Upper section - Brackish-water sandstone, sandy 0-3000 1000-2200 Navajo Sandstone Cretaceous shale, carbonaceous shale, and coal Chinle Formation Gartra Member Lower section - Marine sandstone 0-500 300-1000 Ankareh Fm. Shinarump Conglomerate Mancos Shale (including Black marine shale, thick massive sandstone, 5000-6000 800-3500 Frontier Sandstone Member) shaly sandstone Thaynes Limestone TRIASSIC Moenkopi Formation State Dakota Sandstone Cross-bedded tan sandstone 30-50 30-50 Woodside Shale Bridge Fm. Jurassic Morrison Formation Varicolored shale with sandstone interbeds 780-800 780-800 S Park City Fm. (Phosphoria) Cutler Formation Triassic Chinle Formation Shale with minor sandstone and conglomerate 230 300-380 Upper Weber Sandstone Upper Weber Sandstone PERM. Moenkopi Formation Shale, sandstone, siltstone, and limestone 2300 800 Permian Park City Formation Argillaceous, sandy limestone 80-500 80-500 Lower Weber Sandstone Lower Weber Sandstone Maroon Formation Pennsylvanian Weber Sandstone Massive sandstone 1000-1500 1000-1500 Minturn

PENN. Morgan Formation Morgan Formation Varicolored shale and limestone with sandstone 300-800 300-800 Morgan Formation Formation Manning Canyon Shale Mississippian Round Valley Limestone Belden Shale S Humbug Formation S Great Blue Formation Interbedded shale, limestone, and sandstone 0-900 0-900 Manning Canyon Shale

Upper Molas Formation Humbug Fm. — Doughnut Sh. S ? Doughnut Formation Deseret Limestone MISS. Madison Formation Redwall Formation Leadville Limestone

er Leadville Formation Madison Formation

w Massive dolomite and limestone 0-1100 0-1100 Deseret Formation

Lo Chaffee Fm. Madison Formation Pinyon Peak Fm.

Devonian Sandstone, shale, carbonate 1000 2000 Figure UO-5. Diagram showing DEV. No identifiable Silurian or Ordovician deposits general correlation of rock units SIL. from the Uinta Basin, Utah, to the ORD. Manitou Fm. Cambrian Tintic Quartzite or Sandstone, shale, and carbonate 0-2000 0-2000 Lodore Formation Axial Uplift, Colorado, and Ophir Shale Dotsero Fm. Precambrian Uinta Mountain Group Quartzite with shale and conglomerate significant producing and source Sawatch Sandstone 12,000-20,000 CAMB. Lodore Sandstone Uncompahgre Suite Schist, gneiss, and granite horizons (modified after Spencer and Wilson, 1988) Precambrian p C

Figure UO-4. General stratigraphic column of the Uinta Basin (modified after Anonymous, 1995).

UINTAH AND OURAY INDIAN RESERVATION Geology Overview 3 UTAH ￿During Eocene time (38-50 million years ago) lar ge amounts of Uinta Formation sediment from adjacent higher areas were deposited in lacustrine and The Late Eocene Uinta Formation consists of fluvial deposits that R21E R22E 6 1 6 fluvial environments in the basin. These sediments, assigned to the overlie the Green River Formation from the last phase of Lake Uinta. Wasatch, Green River, and Uinta Formations, are perhaps more than Later, the lake filled up with volcaniclastic material, followed by 15,000 feet thick in the center of the basin, and contain important abundant bedded evaporites. Depths to the top of the formation mineral resources (FIGURE UO-6). range from 2,566 feet to 3,678 feet, with the average being 3,554 Horseshoe Bend ￿Much of the area no w occupied by the Uinta Basin was covered feet. Field boundary by a large lake during Eocene time. Lacustrine marlstone, oil shale, ￿Most of the production is from the Lo wer Uinta, which is a tran limestone, siltstone, and sandstone of the Green River Formation sitional unit between the Green River Formation and the fluvial Up T were deposited in the lake. During the lake's expansionary periods, per Uinta. The Lower Uinta is 350 to 450 feet thick in the Horse 6 Federal no. 3 fluvial sediments were deposited which are now beneath and periph shoe Bend field, a reservoir that has produced over 15 BCF of non- S eral to the lacustrine sediments. These fluvial deposits form the associated gas and 5,000 barrels of condensate. This is the only res shale, sandstone, and conglomerate of the Wasatch Formation. As ervoir that has produced at least 5 BCFG from the Uinta Formation, 1400 the lake receded, fluvial sediments were deposited on its periphery, although minor production exists elsewhere in the basin (FIGURES and eventually covered the entire area formerly occupied by the lake. UO-6 and UO-7). These deposits comprise the Uinta Formation (Anderson,1995).￿ ￿The primary dri ve mechanism is gas expansion and gravity, and 31 1600 WYOMING the trap is an updip stratigraphic 31 UTAH pinch-out. The average monthly gas D production has been increasing since 1800 N 1981 due to development drilling and 6 U MOUNTAINS new wells that were drilled in the ear ly to mid-1980s. UINTA COLORADO ￿The Uinta F ormation is rarely a 2000 primary drilling target, but it is a shal 2,3 Vernal low, low cost target with potential for Altamont Powder new discoveries (Morgan, 1993a). Walker Springs T 2200 Horseshoe Hollow 2 2 Bend ￿Green River Formation 7 Producing gas well 1 Cedar Rim S Wonsits ￿ 2,3 Bluebell Abandoned gas well 2,3 Valley The Eocene-Paleocene Green River 2 Rangeley Duchesne Formation is 2,000 to over 8,000 feet 0 1 2 3mi Monument thick. It accumulated in and around Butte 0 1 2 3 4km 2 ancestral Lake Flagstaff and Lake UINTA Uinta, along with the alluvial-fluvial 31 36 31 Natural deposits of the Wasatch Formation. Figure UO-7. Buttes Rock The Green River Formation was de Structure contour map of the BASIN 2,3 House average porosity of Green River reservoirs ranges from 5 to 20 per Horseshoe Bend area. Datum is the top of Unit A, posited as thick, regionally extensive 3 cent, and the permeability ranges from 0.1 to 42 millidarcies (mD). Uinta Formation with a contour interval of 200 ft. FERC stratigraphic sequences in marginal Tight formation ￿The source rocks for oil and associated g as found in the Green Only wells that have produced from the Uinta designated area and open lacustrine environments. River Formation are interbedded organic-rich carbonate mudstones Formation are shown (modified after Morgan, Depths to the top of the formation 1993a). located at depths of 8,500 to 12,500 feet in the north-central part of Maximum extent of range from 2,315 to 7,456 feet, and Uinta Basin plays the basin. Hydrocarbons, which were generated in deep overpres most wells produce from zones 3- UTAH COLORADO sured zones, migrated laterally along fracture systems to shallow 4,000 feet below the top. reservoirs located on the south and east flanks of the basin. ￿The majority of the producing ￿There are more than 60 kno wn reservoirs producing from the 0 10 20 30mi zones are channel sandstones about 10 Green River Formation, 9 of which have each produced more than 5 0 10 20 30 40 50km to 30 feet thick, but some reservoirs BCFG ( ). The Roosevelt reservoir was the first to pro produce from carbonate grainstones FIGURE UO-6 duce gas from this formation in 1949. Monthly production peaked in Figure UO-6 10 to 20 feet in thickness ( . The Uinta Basin with the maximum extent of play areas based on production and hy FIGURE UO- the mid-1970s, and decreased to a low in 1982. It has been increas drocarbon shows. Reservoirs are labeled: 1, Uinta Formation; 2, Green River Formation; and 3, Wa ). The porosity and permeability of 8 ing since then due to in-fill drilling programs in several reservoirs satch Formation. Note outline for Federal Energy Regulatory Commission (FERC) tight formation these zones can be either reduced or designated area (Wasatch/Mesaverde) in the east part of the basin. Hachured line indicates approx (Chidsey, 1993b). ￿ enhanced by diagenetic effects. The imate limits of Tertiary units in the Uinta Basin (modified after Chidsey, 1993a).

UINTAH AND OURAY INDIAN RESERVATION Producing Formations 4 UTAH Wasatch Formation There are more than 60 known res- Approximate base Natural Buttes Field ervoirs, 5 of which have produced at Coastal Oil Gas Corp. The Eocene-Paleocene Wasatch Formation is up to 3,000 feet thick. of Tertiary rocks least 5 BCFG (Figure UO-6). The first CIG 62D-36-9-22 It accumulated in and around ancestral Lake Flagstaff and Lake Uin- reservoir to produce from the Wasatch Formation Vernal nw sw sec. 36 T9S R22E ta in an intertonguing relationship with the Green River Formation. Colton Uintah County, Utah Formation was Peters Point in 1953. It was deposited as thick, regionally extensive stratigraphic sequen- asatch Co. K.B. 4949'

The total monthly gas production in- W ces primarily in an alluvial-fluvial environment peripheral to the an- Co. Duchesne Green River

creased between 1973 and 1982, and Utah cestral lakes. Depths to the top of the formation range from 3,147 to Formation S.P. Res. has been fairly constant since then 10,754 feet (FIGURE UO-9). er Formation Colorado (Chidsey, 1993c). Riv Most of the production comes from lenticular fluvial-alluvial Green channel and alluvial overbank sandstone deposits. The productive sandstones are usually isolated and encased in siltstones, mudstones, 4400 and shales (Figure UO-10). Porosity and permeability are generally

reduced by diagenesis, so production is enhanced near or along ma- Riv er jor fault and fracture zones. The average porosity ranges from 5 to Colton

Formation 4600 20 percent, and the permeability is 0.1 mD or lower. The source rocks for oil and associated gas found in the Wasatch Formation are organic-rich carbonate mudstones of the Green River

Formation, and are located at a depth of 8,500 to 12,500 feet in the 4800 north-central part of the basin. Source rocks for the non-associated Colton gas are organic-rich siltstones and mudstones, carbonate shales, and Perf. For ormation 4926'-6975' coals of the Mesaverde Group, located at depths of 6,000 feet or Price F (gross) mation

greater. 5000 IPF Green 1900 MCFGPD 0 1mi Carbon Co. Uintah Co. 3 BWPD 0 1km R17E Emery Co. Grand Co. 5200 N +8000 +1000 Alluvial-fluvial

20 Wasatch 5400

20 Alluvial-fluvial +1200 Marginal lacustrine N 5600

Wasatch Formation Wasatch 20 0 10 20mi Open lacustrine

20 0 10 20 30km 5800 T 30 10 9 +1400 20 Figure UO-9. Major depositional facies and distribution of formations at the Paleocene-Eocene boundary. Note S widespread Wasatch-Colton deposition in the Uinta Basin (modified after Chidsey, 1993).

10 6000

+1600 10 Figure UO-8. Structure contour map with isopach of single sandstone bed, Monument Butte reservoir, Duchesne and Uinta Counties, Utah. Structure con- tours (dashed lines with contour interval of 200 ft.) are based on a datum ap- 6200 proximately 150 ft. below the middle marker of the Green River Formation and Figure UO-10. Typical SP- show no structural closure. Net sandstone isopachs (solid lines with contour in- Uintah Co. resistivity log of the Natural

Duchesne Co. terval of 10 ft.) are based on one of many individual productive sandstone units

+1800 Buttes Wasatch reservoir, Mesaverde 6400 encased by shale or mudstone. Isopach geometry indicates deposition of sand- Uintah County, Utah (modified Group T.D. 7000' stone by meandering streams. The trap is created by updip pinch-out of chan- after Chidsey, 1993c). Completed: 4-26-81 nel sandstone to south along regional strike (modified after Chidsey, 1993b).

UINTAH AND OURAY INDIAN RESERVATION Producing Formations 5 UTAH Mesaverde Group 30 th Figure UO-11. Plot of core-plug porosity vs. reflectance for 25 25 th Gas from Mesaverde Group reservoirs is found in both structural and 75 porosity percentiles (joined by vertical lines) of nonmarine sandstone intervals of the Mesaverde Group, Uinta and Piceance 20 and stratigraphic traps. Some reservoirs, like those in Natural Creek Basins. Mesaverde data are compared with type curve and 90th percentile Buttes Field, are part of larger, basin-centered gas traps where the to 10th and 90th porosity percentiles representing sandstones in 15 gas collects downdip from more permeable water-filled reservoirs. general. Note that the porosity does not decrease within the win- Average depth to the top of productive reservoirs ranges from 1300 dow of hydrocarbon generation (Ro of 0.070-1.8%) (modified after Nuccio et al., 1992). 10 to >8500 feet. 9 The terminology of the Mesaverde Group is complex, due to fa- 8 cies changes that occurred as the Cretaceous Interior Sea trans- 7 gressed and regressed along its western margin in the Piceance-Uin- 6

ta Basin area. The Mesaverde consists of three dominant reservoir 5 facies: lenticular, fluvial sandstones of the Williams Fork Forma- 4

tion, coals that occur in the basal portion of the Williams Fork For- IN PERCENT POROSITY, mation, and extensive shoreline-marine sandstones of the Iles For- Type 3 curve mation. The fluvial sandstones of the Williams Fork Formation are ap- 10th percentile proximately 4000 feet thick in the eastern part of the Piceance Ba- 2 sin, thinning to <2000 feet on the Douglas Creek Arch and 2200- Figures UO-12A and 12B. Map showing the region (pink area) between R 25th to 75th PERCENTILES 2900 feet in Natural Buttes Field in the Uinta Basin. These sand- o 0.70 and 1.8%, where porosity of sandstones at the base of the Mesaverde stones are lithic arkoses and feldspathic arenites containing authi- Group does not decrease as a function of increasing Ro. This region defines genic quartz and carbonate cement. They have low porosities, rang- the area of optimum gas recovery for A, Upper Mesaverde; B, Lower Mesa- 1 ing from 7-12%, and low matrix permeabilities (<0.1 mD) due to verde (modified after Nuccio et al., 1992). 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.5 2.0 2.5 3.0 the abundance of authigenic clays. VITRINITE REFECTANCE, IN PERCENT

The shoreline-marine sandstones of the lower Mesaverde Iles 111o 00' 110o 45' 110o 30' 110o 15' 110o 00' 109o 45' 109o 30' 109o 15' 109o 00' 111o 00' 110o 45' 110o 30' 110o 15' 110o 00' 109o 45' 109o 30' 109o 15' 109o 00' Formation were deposited during transgressive and regressive cycles A B along northeast-southwest trending shorelines. These sandstones merge with fluvial facies to the northwest and the Mancos Shale to 40o 30' Vernal 40o 30' Vernal the southeast. The most productive members are the Cozzette, Cor- Jensen Jensen coran, and Castlegate Sandstones. Altamont Altamont UTAH The Castlegate Sandstone is a clean, fine-grained, subarkose to UTAH 2.00 COLORADO sublitharenite, with low porosity and permeability due to pore-filling COLORADO o 40o 15' authigenic clays. It was deposited along ancient shorelines or as 40 15' offshore bars. In the southeastern part of the Uinta Basin, 50-70 feet Duchesne Duchesne thick Castlegate sandstones produce from structural traps at depths of 8000 feet. Permeabilities range from 0.5-0.9 mD. All fields that 40o 00' 40o 00' produce from the Castlegate involve some type of structural closure, 1.50 and several close against faults. Production rates are enhanced by 1.10 the associated tectonic fractures. 1.10 Source rocks for gas produced from the fluvial sandstones at 0.75 o 39o 45' Natural Buttes Field are coals and carbonaceous shales. The source 39 45' for the shoreline-marine sandstones is probably the Mancos Shale. Porosities of the Mesaverde Group sandstones remain unusually sta- Price Price ble over a large vitrinite reflectance interval (FIGURES UO-11 and UO- o Green River 39o 30' Green River 12), implying that sparsely explored deep central basins may hold 39 30' some promise (Tremain, 1993). 0.75 0.60 39o 15' 39o 15' 0 10 20 30 MILES 0 10 20 30 MILES 0.65 0.50 0 10 20 30 KILOMETERS 0 10 20 30 KILOMETERS

UINTAH AND OURAY INDIAN RESERVATION Producing Formations 6 UTAH Mancos Shale

As of December 1990, almost 359.5 BCF of natural gas have been produced from Upper Cretaceous Mancos Shale reservoirs (FIGURE S Nat. Assoc. Pet N UO-13). Most of the production comes from the silty, tight gas sand- Argo Cities Service Govt. 1 Superior Texas Phillips G. E. Kadane sec 6 T3S, R102W stone reservoirs of the Mancos B (also called the Emery Sandstone) Unit 2-20 USA 1 Unit 3 Douglas Cr. 1 Unit B-1 Moran 1 in the middle of the Mancos Shale. Gas is also produced from the sec 20, T5S, R102W sec 7, T4S, R102W sec 1 T3S, R102W sec 9 T2S,R101W sec 18, T1S, R101W sec 2, T1N, R101W Mancos A/Morapos Sandstone, a conventional, clean sandstone S.P. R SP R S.P. R S.P. R S.P. R found in the upper transition zone between the Mancos Shale and the overlying Mesaverde Group (FIGURE UO-14). Mesaverde The Douglas Creek North Field has produced >5 BCFG from the Group Upper Mancos/Morapos Sandstone (figure 13). In this area, the Up- Anchor per Mancos consists of up to 34 feet of mud to coarse-grained, well- Mancos A sorted sandstone with 20% porosity and 100 mD permeability. It U. Sego S.P. R

Tongue 1000 was deposited as shelf sands in a marginal-marine setting, and is U. Sego L. Sego probably time-equivalent to the Castlegate Sandstone. L. Sego The Mancos B consists of 500 to >1000 feet of finely interbed-

ded and discontinuous claystone, siltstone, and very fine- to fine- 3000 Buck Tongue

3000 Mancos A 1000 grained sandstone, with an average net pay interval of 30-250 feet. It is characterized by low porosities and permeabilities, with porosities 1000 (Morapos) ranging from 10-11% on the Douglas Creek Arch, to <2% on the (Morapos) S.P. R flanks. Permeabilities are <0.1 mD on the average. Mancos B sedi-

ments were deposited on a northerly prograding submarine slope or 1000 foreslope, approximately 100 miles to the east of the time-equivalent Emery shoreline in Utah (Noe, 1993a). 1000 m Gas fields 2000 ft 00 00 <5BCF >5BCF

Rangeley Utah Colorado FERC tight sand areas Douglas Cr. N. 4000

Mancos Shale B' Silt Marker C' Philadelphia Cr.

4000 A' Approximate line of section 2000 100

2000 Lower Horse Draw Mancos Marine Mancos B Sandstone play Douglas Cr. W. Douglas Cr. (Emery) 500

Dragon Trail 2000 200 Mancos B 750

Cathedral 2000

A UINTA BASIN 300 1000

PICEANCE BASIN

B Datum 3000 ft above sea level

5000

5000 Douglas Creek fault UNCOMPAHGRE UPLIFT C 0 20,000 40,000 ft 0 6,000 12,000 m

DOUGLAS CREEK ARCH

UTAH Vertical exaggeration 50:1

COLORADO Grand Junction Figure UO-14. South to north structural cross section along the Douglas Creek Arch of the Mancos B interval and other sandstones in the transitional zone between the Mancos 0 10 20 30mi Mesa Shale and Mesaverde Group (modified after Noe, 1993a). PARADOX BASIN 0 10 3020 40 50km Delta

Figure UO-13. Gas fields of the Upper Cretaceous Mancos Shale (modified after Noe, 1993a)

UINTAH AND OURAY INDIAN RESERVATION Producing Formations 7 UTAH Dakota Sandstone, Cedar Mountain Formation, Figure UO-16. Three dimensional model Morrison Formation of Dakota Sandstone depositional environments at Hell's Hole Field The Dakota Sandstone, Cedar Mountain Formation, and Morrison (modified after Moretti et al., 1992). Formation are similar in lithologic succession. Each contains a bas- al, continuous, conglomeratic sandstone or conglomerate, like the Salt Wash Member of the Morrison Formation, the Buckhorn Con- glomerate of the Cedar Mountain Formation, and the lower part of VALLEY the Dakota Sandstone. This is overlain by interbedded shales and lenticular sandstones, like the Brushy Basin Member of the Morrison ALLUVIAL and the upper units of the Cedar Mountain and Dakota (Figure UO- PLAIN 15). The basal conglomeratic units are braided stream deposits, while the upper units of the Morrison and Cedar Mountain Forma-

tions are thought to be floodplain and meandering stream deposits. COASTAL The Upper Dakota was deposited in a complex coastal setting con- Distributary Channel FORSHORE TYPE LOG Braided Stream San Arroyo Field Coastal Plain with Marshes

SHOREFACE DAKOTA SILT Cross Bedding

Beach Ridges DAKOTA SANDSTONE Foreshore Sand

Figure UO-17. Structure contour map of the top of the Shoreface Slope and Sand 50 4800 CEDAR MOUNTAIN Entrada Sandstone, San Arroyo/Westwater area, FORMATION Grand County, Utah. The area that is productive from Highlands 25 FEET the Entrada Sandstone is colored in pink. The Bar X MILES 0 Field has produced less than 5 BCF of gas from the Buckhorn 0 123 Member Marine Shale Entrada Sandstone. Contour interval is 500 feet Brushy Basin MORRISON Member (modified after Morgan, 1993b). FORMATION sisting of coastal plain, fluvial, swamp, marsh, tidal flat, delta, beach, royo to 24% at Westwater.

5000 and nearshore marine environments (Fig. UO-16). Source rocks for San Arroyo and R 24 E R 25 E R 26 E Westwater Fields may have been or- D D The Morrison Formation is approximately 350-450 feet thick, U U U the Cedar Mountain Formation is approximately 0-150 feet thick, ganic-rich marine deposits of the Per- D and the Dakota Sandstone is approximately 40-250 feet thick (Noe, mian Phosphoria and Pennsylvanian T Salt Wash 1993b). Paradox Formations (Morgan, 0 1 2 3 4 mi -500 San Arroyo Member Entrada Sandstone 1993b). 1000 16 0 1 2 3 4 5 6 km 5200 S In northeastern Utah, the Entrada Sandstone consists of dune and in- 0 terdune eolian deposits associated with the northerly retreat of a Ju- R 23 E 500 rassic sea. The sandstones are gray to orange, fine- to medium- grained, well-sorted and cross-bedded. Bar X -500 0 Gas and some oil are produced from traps formed by anticlinal D 1000 5400 U D closures on Laramide structures. Three Entrada reservoirs have pro- 500 500 U D T duced >44 BCF gas; most of this production comes from San Arroyo Westwater U 17 ENTRADA Field (FIGURE UO-17). Average depth to the top of the reservoir var- S SANDSTONE ies from 5250 feet at San Arroyo to 6700 feet at Wilson Creek Field 500 in Colorado. Average net pay thickness in the Uinta Basin is 118 feet 1500 Figure UO-15. Type log from the San Arroyo at Westwater Field. Average porosity ranges from 16% at San Ar- 2000 2500 Field (modified after Hill and Bereskin, 1993).

UINTAH AND OURAY INDIAN RESERVATION Producing Formations 8 UTAH Weber Sandstone 724.7 BCF of associated gas and 772 MMBO. The Rangely Weber Gamma ray reservoir contributed 98.9% of the total gas production (FIGURE UO- (API units) Depth Density porosity Sedimentary Depth 0 150 (ft) 30 (%) 10 structure (ft) The Weber Sandstone is a fine-grained, subarkosic to quartz arenite 18). Average depth to the top of the Weber is 6500 feet, and the trap- 5600 of eolian origin deposited during Desmoinesian, Missourian, and ping mechanism in all Weber reservoirs is anticlinal closure (Hem- Fluvial

Wolfcampian time. In Rangely Field, productive eolian sands were borg, 1993). Dune Dune Extra deposited in dune, interdune, and extradune environments (FIGURE Extra UO-19). These sandstones are either cross-laminated or massively- Dune - 5800 bedded, the cross-laminated lithofacies being the major producer with Extra Dune an average porosity of 12%. Permeability along laminae averages 2 5700 Dune mD, while permeability across laminae averages 0.4 mD. Fluvial Cumulative production from the Weber Sandstone as of 1990 is Dune Extra Dune

Dune

o GREEN RIVER BASIN o o o Dune 111 110 109 108 Extra Henry's Fork fault WYOMING Extra 41o WYOMING - 5820 U 5800 UTAH lt inta fault COLORADO MOFFAT ROUTT fau h Flank Nort SAND WASH BASIN

5900 ry fault Split Mtn - 5840 nda WASA ou anticlines Extra TCH b Vernal x sin Danforth Ba Yampa fault Hills Craig ta Elk Dune in Wolf C Springs U re ek fault Moffat Dune Skull Cr. anticline

Maudlin Comple Dune Winter Thornburg Dune Ashley Valley Gulch 6000 Valley Fluvial Wil Creek Wonsits low fa Extra Altamont - Bluebell ult - 5860 N Valley Rangely Fluvial Red Wash Extra o UINTA 40 White River Fluvial BASIN AHUT uplift 6100 h c h PICEANCE Extra

DUCHESNE UINTAH COLORADO BASIN Douglas Fluvial - 5880 Creek Ar

RIO BLANCO Grand hogbac Dune >5BCF Weber associated gas fields Extra <5BCF Weber associated gas fields Uncompahgre k Extra 6200 Fluvial Major oil and gas fields without Weber production Dune Precambrian outcrop uplift Glenwood Fluvial Springs Weber Sandstone play

GARFIELD Extra Fluvial MESA - 5900 0 10 20 30 40 50 mi UTAH COLO 6300 0 10 40 60 80 km Fluvial Extra= Extradune Figure UO-18. Location map of Rangely Field and other major and minor Weber Sandstone reservoirs (modified after Hemborg, 1993). Horizontal Cross- Convolute lamination lamination lamination Burrows Root casts

Figure UO-19. Wireline log and core description of the No. 139Y UPRR, Rangely Field. Core shows one cycle of Weber deposition (modified after Hemborg, 1993)

UINTAH AND OURAY INDIAN RESERVATION Producing Formations 9 UTAH Play Ty es Play Summary Conventional Plays- Discr t d posits, usually bound d by a downdip wat r contact, from which oil, gas or NGL can b x- The United States Geological Survey identifies several petroleum plays in the Uinta-Piceance Basin Province and classifies tract d using traditional d v lopm nt practic s, including production at th surfac from a w ll as a cons qu nc of natural them as Conventional and Unconventional (Gautier et al., 1995). The discussions that follow are limited to those with pr ssur within th subsurfac r s rvoir, artificial lifting of oil from th r s rvoir to th surfac wh r applicabl , and th main- direct significance for future petroleum development in the Uintah and Ouray Indian Reservation t nanc of r s rvoir pr ssur by m ans of wat r or gas inj ction. (TABLE 1). Unconventional Plays- A broad class of hydrocarbon d posits of a typ (such as gas in tight sandston s, gas shal s, and coal-b d gas) that historically has not b n produc d using traditional d v lopm nt practic s. Such accumulations includ most continuous-typ d posits.

Reservation: Uintah and Ouray Total Production in Geologic Province: Uinta-Piceance Basin Province as of 1996 Uinta-Piceance Basin Undiscovered resources and numbers of fields are Province Area: 40,000 sq. miles (25.6 million acres) Oil: 486,712 MBO for Province-wide plays. No attempt has been made Reservation Area: 6250 sq. miles (4 million acres) Gas: 1,992,627 MMCFG to estimate number of undiscovered fields within the NGL: 40,262 MBNGL Uintah and Ouray Indian Reservation.

USGS Play Type Description of Play Oil or Gas Known Accumulations Undiscovered Accumulations > 1 MMBOE Play Probability Drilling depths Pay Thickness Porosity/Permeability Designation Field Size and Number (chance of success) (min., mean, max.) Field Size (median, mean) Uinta Tertiary Oil and Gas Gas (15 BCFG, 18.9 BCFG) Fluvial and lacustrine sandstones Gas Play Gas (917,288 MMCFG) Oil (2 MMBO, 2.8 MMBO) in the Wasatch and Green River Both (500, 3000, 6000)ft Variable 10-15%/v, low to 1000 md 2002 Oil (485,592 MBO) No. of Undiscovered Fields (min., median, max., mean) 1 Formations. Oil Gas (2, 6, 15, 7.1) (1000, 5000, 14000)ft 1 Oil (4, 13, 30, 14.7)

Upper Cretaceous Field Size (median, mean) Conventional Play Shallow sandstones of the Mostly Gas Gas (129,540 MMCFG) Gas (12 BCFG, 15.2 BCFG) Gas 2003 Mesaverde Group. No. of Undiscovered Fields (min., median, max., mean) 1 (500, 3500, 6000)ft up to 80 feet 8-18%/<0.1md 2 Gas (10, 23, 50, 25.9)

Cretaceous Dakota Field Size (median, mean) Fluvial Dakota Sandstone, Gas (10 BCFG, 13.1 BCFG) Gas 90% Gas Gas (579,169 MMCFG) Dakota - 25 feet to Jurassic Play 2004 discontinuous fluvial Morrison Oil (1 MMBOE, 1.5 MMBOE) (500, 3500, 6000)ft 10-25%/ 10% Oil 1 Buckhorn - 26 feet Sandstone, blanket eolian No. of Undiscovered Fields (min., median, max., mean) Unknown Permeability Oil Morrison - 11 feet Entrada Sandstone. Gas (3, 15, 25, 14.6) (1000, 4000, 6500)ft 3 Oil (1, 2, 4, 2.2)

Permian-Pennsylvanian Field Size (median, mean) Sandstones and Very high risk Oil (9 MMBO, 25.0 MMBO) 2005 Permian-Pennsylvanian Oil 11-14%/ Oil EUR (980.5 MMBO) No. of Undiscovered Fields (min., median, max., mean) 1 275 feet Carbonates Play sandstones and carbonates. Mostly Oil (6000, 10000, 12000)ft Unknown Permeability 4 Gas EUR (>706 BCFG) Oil (1, 4, 15, 5.7)

Basin Margin Field Size (median, mean) Oil Subthrusts Play Closures beneath thrusts, Oil (2 MMBO, 5.3 MMBO) Both N/A Gas (15 BCFG, 25.0 BCFG) (5000, 12000, 18000)ft Unknown 2014 reservoirs range from 0.18 (hypothetical) Paleozoic to Tertiary in age. No. of Undiscovered Fields (min., median, max., mean) Gas Oil (1, 2, 7, .05) (5000, 14000, 25000)ft 5 Gas (1, 3, 10, .07) Cretaceous Self-Sourced Fractured Shales Play Upper Mancos fractured shale. Best fracturing occurs in brittle Oil/Gas 10->50 feet 10-20%/0.01-100md (hypothetical, continuous) 2009 Both Oil EUR(14 MMBO) 1 siltstones, carbonates, and Per well EUR estimates vary (500, 2800, 6000)ft 6 calcareous shales. Tight Gas Uinta Medium- to fine-grained fluvial Tertiary East Play 2015 sandstones interbedded with Gas Gas N/A 1 up to 80 feet <5-9%/<0.1md (continuous) mudstones, siltstones, shales, N/A (3000, 6400, 10500)ft 7 and some coal of the Wasatch Fm.

Tight Gas Uinta Medium- to fine-grained fluvial Gas Tertiary West Play sandstones interbedded with Gas N/A N/A 1 (4500, 7500, 11000)ft up to 80 feet 4-8%/<0.01md (hypothetical, continuous) 2016 mudstones, siltstones, shales, 8 and some coal of the Wasatch Fm.

Basin Flank Uinta Mesaverde Play Based on widespread occurrence Gas 1 (hypothetical, continuous) 2018 of tight, gas-saturated continental Gas N/A N/A (8000, 9500, 15000)ft 4->12%/<0.1md 9 and marginal marine sandstone. Deep Synclinal Uinta Based on expected occurrence of Mesaverde Play Gas 3-8% Gas 1 N/A (hypothetical, continuous) 2020 gas-saturated tight Mesaverde N/A N/A (15000, 20000, 25000)ft Unknown permeability 10 Sandstone at depths >15,000 feet.

Table 1. Play summary chart. Conventional play type Unconventional/Hypothetical play type

UINTAH AND OURAY INDIAN RESERVATION Play Summary Table 10 UTAH Summary of Play Types Conventional Plays 260 MMBO and 378 BCFG; however, the field is being actively Analog Example: Greater Altamont - Bluebell Definition - Discrete deposits, usually bounded by a downdip water downspaced from 640 acres per well to 320 acres per well. This ad- Figures: UO-20 and UO-21 The United States Geological Survey has identified many petroleum contact, from which oil, gas, or NGL can be extracted using tradi- ditional drilling should significantly increase recovery. Location: T 1 N - 4 S, R 2 E - 7 W, on Reservation plays in the Uinta-Piceance Basin Province, classifying them as Con- tional development practices, including production at the surface Exploration status and resource potential: The conventional gas Producing formations: Wasatch and Green River Formations ventional and Unconventional. The discussions that follow are limit- from a well as a consequence of natural pressure within the subsur- part of this play is fairly well explored, but a maximum of 15 conven- Other significant shows: Mesaverde Sandstone, gas; ed to those plays with direct significance for future petroleum devel- face reservoir, artificial lifting of oil from the reservoir to the surface tional fields greater than 6 BCFG may be found, according to Uintah Formation, gas and oil opment on the Uintah and Ouray Indian Reservation. Most of the where applicable, and the maintenance of reservoir pressure by U.S.G.S. estimates (Table 1). Because of the very large volume of Lithology: Fluvial sandstone, lacustrine sandstones, following is extracted from USGS CD-ROMs DDS-30 and 35 (Gaut- means of water or gas injection. oil generated deep in the basin, a maximum of 30 oil fields greater limestones, dolomites ier et al., 1995). Table 1 is a summary of applicable USGS plays of than 1 MMBO may remain to be found. Type of drive: Solution gas the Uinta-Piceance Basin Province pertaining to the Uintah and Our- PLAY 1 - UINTA TERTIARY OIL AND GAS PLAY Net pay thickness: Multiple zones with variable thickness ay Reservation. The Uinta Tertiary Oil and Gas Play is based on oil and gas accumu- Porosity: 2-20%, average >10% lations primarily in stratigraphic traps in fluvial and lacustrine sand- Permeability: Variable in individual pay sections, ranges stones in the Wasatch and Green River Formations. The play area is from very low up to 1,000 mD in limited updip by the presence of brackish and fresh water in rocks unconsolidated sands near the outcrop. Estimated primary 316 MMBO, 360.5 BCFG, 330.2 MMBW recovery: Reservoirs: Reservoir sandstones of the Wa- satch and Green River Formations are Paleo- Other major analog fields: Greater Natural Buttes Monument Buttes o cene and Eocene in age and are predominant- WYOMING 41 Red Wash

N o o o ly litharenites and feldspathic litharenites over Walker Hollow UTAH most of the basin. Some lacustrine limestones Wonsits Valley 111 110 109 uplift produce in the deeper part of the basin. Po- Uinta rosities range from <10 percent in the deep Altamont-Bluebell field area to >15 percent at A A' shallower depths (<4,000 feet). SW Altamont - Bluebell fields NE AHUT Source rocks: The source rocks for much of

Vernal COLORADO the non-associated Wasatch gas in the basin 9000 are the underlying Cretaceous Mesaverde gas- prone coals, shales, and mudstones, but some 6000 A' may have a Tertiary origin. In the northern Duchesne River Fm. 9000' North Horn Fm. Uinta and Duchesne part of the basin, oil is the predominant hy- Colton Fm. Green River Fm. 3000 Duchesne River outcrop drocarbon. This oil comes from lipid-rich la- 8000' custrine shales and marlstones in the Green (par Uinta Fm. 40o SL River Formation. A complex mixing of oil t) 7000' and gas from different sources has resulted in -3000 more gas fields at shallower depths and pre- 6000' North Horn Fm. W dominantly oil in deeper reservoirs. This is asatch Fm. Colton 5000' Colton Fm. -6000 outcrop the opposite of what occurs in many other ba- 4000' (part) & Mesa Price sins. A -9000 3000' Timing and migration: The Mesaverde ft m ver North de Gr Horn Group began generating gas in the Early Terti- Green 6000 2000 oup outcrop River ary, and the Green River Formation began Area of fluid-pressure Green gradients >0.5 psi/ft outcrop River generating oil and gas in the Middle Tertiary 1000 outcrop to the present. The deep (>10,000 feet) Terti- 3000 Paleozoic-Mesozoic rock ary oil fields are highly overpressured as a re- 4 8 12 16 20 mi Wasatch sult of present-day hydrocarbon generation. 0 0 outcrop Traps: The traps are mostly stratigraphic, but 5 10 15 20 km 0 10 20 30mi 39o some structural-stratigraphic traps occur, such 0 10 20 30 40 50km as the Red Wash Field area (EUR 175 MMBO, 373 BCFG). The largest producing Figure UO-21. Generalized southwest to northeast cross section of Tertiary rocks in the Uinta Basin showing major facies, Figure UO-20. Combined thickness of the Green River, Wasatch/Colton, and North Horn intertonguing relationships, and stratigraphic names. Area of fluid-pressure gradients >0.5 psi/ft indicated in red. Line of section is area is the greater Altamont-Bluebell area, Formations with outcrop areas indicated. Contour interval is 1000 feet. Cross section A- shown in Figure UO-11 (modified after Chidsey, 1993a). A' is shown in Figure UO-21 (modified after Chidsey, 1993a). which has an estimated ultimate recovery of

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY TYPE: Uinta Tertiary Oil and Gas Play 11 UTAH A A' Figure UO-23. Diagrammatic UPPER CRETACEOUS CONVENTIONAL PLAY R21E R22E R23E 31 MILES west-east cross section showing GREEN RIVER FM. stratigraphy of the Greater Natural This is primarily a gas play in sandstones of the Mesaverde Group at R18E er Riv Buttes Field and position of shallow depths in both the Piceance and Uinta Basins; however, dis- White Wasatch producing sandstones covered fields are mostly in the Piceance Basin. Fields are localized WASATCH FM. that overlie the Mesaverde. Line T A' by structure, but stratigraphic traps have also been found. The play 2000 FT. of section is shown in Figure UO- 9S is limited downdip where the reservoirs become unconventional 14 (modified after Osmond, 1992). Green (tight) and is limited updip by fresh-water flushing. The Mesaverde River part of this play has some areal overlap with tight Mesaverde reser- A voirs. The tight rocks are generally beneath and/or downdip of con- T NORTH HORN FM. ventional Mesaverde reservoirs. 10S

Reservoirs: The reservoir rocks are Cretaceous Mesaverde Group GROUP VERDE sandstones deposited in marginal-marine, fluvio-deltaic, and fluvial MESA FT. 2500 environments. Some very fine-grained sandstone and siltstone reser- T Outline of gas field N 0 6mi ONE 0 10km SANDST voirs were deposited in a shallow-marine shelf environment seaward Outline of oil field 11S CASTLEGATE of, and in part beneath, the Mesaverde Group. These reservoirs in- Line of cross section

clude the Mancos Shale "B" and equivalents, but much of the Man- Fault (E-W) dashed where uncertain MANCOS SHALE cos "B" fields are tight and developed by drilling, although there is Gilsonite vein (NW-SE) dashed where uncertain some potential for field growth. Figure UO-22. Map of the Greater Natural Buttes Gas Field (modified after Osmond, 1992). PRODUCTION UINTA Gray-Green Shale and Fluvial Sandstone Source Rocks: The Mesaverde Group source beds are organic FM. Horseshoe Bend shales (including some coals) interbedded with sandstones. SURFACE 0-1700 12 Miles N of GNB

Timing and Migration: Time of generation is Late Tertiary to pres- Gilsonite ent. Veins Traps: Traps are predominantly structural-stratigraphic and strati- R 20 E R 21 E R 22 E R 23 E Lacustrine and Marginal Lacustrine Gray-Green Shale, GREEN graphic. Accumulations are found at depths of <1,000 feet to 6,000 Marlstone and Sandstone

feet, with a median depth of 3,500 feet. T RIVER 8 S Exploration Status: The conventional part of the play is well ex- FM. MAHOGANY OIL SHALE BED Field Outline 3800' White River, 5 Miles North of GNB

plored in the Piceance Basin and only moderately explored in the EOCENE - 500 OIL with ASSOCIATED GAS Uinta Basin. Because of the large volume of gas generated by Me- Uintah Special Meridian 'H' MARKER Red Wash/Wonsits to N and NE Salt Lake Meridian Monument Butte and Other Fields to W saverde source beds, the U.S.G.S. estimates that a minimum of 10 GAS +_0 DOUGLAS CREEK MEMBER and a maximum of 50 conventional fields may be discovered (Table Greater Natural Buttes, T SE Red Wash/Powder Springs +500 9 1). S 9 Miles NE of GNB - 500 Analog Field Greater Natural Buttes +1000 WASATCH Red Shale and Fluvial Sandstone Greater Natural Buttes Peters Point, 20 Miles SW of GNB Figures: UO-22 to UO - 25 +_0 FM.

T 2000' NORTH HORN - FLAGSTAFF Location: T 8-10 S, R 19-23 E (SLB&M), 1 Varicolored Shales, Fluvial Sandstone, 0 West S Lacustrine Limestone and Coal T 36 S, R 25-26 E (SLPM), Uinta County, +500 CENE 'OHIO CRK CGL' - BEDS AT DARL CYN' Utah, on Reservation PALEO- Sandstone with Dark Chert Pebbles

Producing formations: Green River Formation, Wasatch Formation Farrer FM. Tight Sands and Siltstones, Mesaverde Group +1000 Datum: Top Wasatch Formation Gray Shale and Coal MESAVERDE IMMATURE FOR GAS Contour Interval: 500 feet T Other significant shows: None 1 1 S GROUP Greater Natural Buttes Lithology: Fluvial and lacustrine sandstones, MATURE limestones, dolomites Figure UO-24. Structural contour map of Natural Buttes Field. Bold line depicts approximate 2200' - 2900' Type of drive: Pressure depletion Reservation boundary (modified after Hill and Bereskin, 1993). NELSEN FM. - 700FT. Net pay thickness: Individual sands may be up to 80 feet in COAL BEARING East thickness Porosity: 8-18%, average 12% (logs) Upper Level for Gas Generation CRETA CEOUS CRETA Permeability: Generally less than 0.1 mD MANCOS SHALE - 5000' Cuts Down, Stratigraphically, Eastward Across GNB from 1000' +- Estimated ultimate recovery: 0.5 BCFG (Marine) Above Mesaverde to below the Other major analog fields: Devil's Playground Figure UO-25. Stratigraphic column for Greater Natural Buttes Base of Mesaverde; Dakota Sandstone Based on Coal Rank Book Cliffs 30 Miles S of GNB Red Wash (GNB) Field, showing formations which produce oil and gas in High Volitile A Bituminous Ro 0.85% (Fluvial) (Nuccio and Johnson 1986) Wonsits Valley GNB and nearby fields (modified after Osmond, 1992).

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY TYPE: Upper Cretaceous Conventional Play 12 UTAH CRETACEOUS DAKOTA TO JURASSIC PLAY TYPE LOG R 24 E R 22 E R 23 E San Arroyo Field 26 25 30 29 28 FENCE CANYON FIELD This is primarily a conventional reservoir play, but tight reservoirs from the Dakota Group (including Uintah and Carbon Counties, Utah are mixed with the conventional rocks. The discovered fields are - 710 the Cedar Mountain Formation) and DA KO TA SILT mostly structurally controlled. Based on known fields, it appears to TEXACO the Jurassic Entrada Sandstone (FIG- 3 FENCE CANYON - 753 - 342 SP IEL be predominantly a gas play (90 percent gas, 10 percent oil). The URES 27 and 28). Many of the fields - 990

7800 DA KO TA Cretaceous Dakota Group (including the Cedar Mountain Formation) 35 36 31 32 33 MANCOS SANDSTONE have significant amounts of nitrogen SHALE and the Jurassic rocks were combined into one play by the U.S.G.S. and CO (as much as 25 percent). DATUM 2 T 7900 - 600 - 617 DAKOTA because many fields produce from rocks of both ages and any struc- - - 523 400 SILT 15 - Exploration status and resource 800 MARKER -1570 - 1000 ture drilled has the potential for accumulations in both. The Wilson - 1200 4800 CEDAR MOUNTAIN S - 1400 - - 828 OOOOOOO potential: The play is maturely de- - 1600 8000 Creek Field is the southeasternmost structure along a series of pro- DAKOTA SS FORMATION CEDAR MTN. FM. veloped for large fields, but subtle UINTAH CO ducing structures that includes the Maudlin Gulch Field. The down- 31 32 33 34 CARBON, CO 35 BUCKHORN OOOOO structures and stratigraphic traps 8100 CGL. Buckhorn dip limits of the play are where the rocks become tight and reservoirs T Member MORRISON may contain as many as 25 signifi- 15.5 3 FENCE CANYON FM. Brushy Basin MORRISON are unconventional (>6,000 feet). Member cant accumulations (TABLE 1). S 8200 FORMATION Reservoirs: The Cretaceous Dakota reservoirs vary from lenticular - 1121 - 351

6 5 4 3 2 5000 to continuous, and are predominantly fluvial in the play area. The PERFS: 7978-8016 Ft. 8079-8106 Ft. Jurassic reservoirs range from discontinuous fluvial sandstones of T 91 IPF: 877 MCFGPD the Morrison Formation to blanket eolian sandstones of the Entrada 16 COMPLETED: 9-29-61 Sandstone. Porosities range from <11 percent to about 25 percent. S - 13 GEOLOGY BY JOHN OSMOND Salt Wash Source rocks: Source rock data for this play are lacking in the pub- Member STRUCTURE MAP 0 2000' 4000' 1 MILE

lic record, but some dark shales, mudstones, and thin coals are pres- 5200 DATUM: TOP OF DAKOTA SILT ent in the Dakota Group. The overlying marine Cretaceous Mowry and Mancos Shales are both known source beds (mostly oil prone). Figure UO-26. Structure map and typical electric log from Fence Canyon Field (modified after Hill and Bereskin, 1993). Timing and migration: The hydrocarbons were probably generated in Late Cretaceous to Early Tertiary time, and some may have mi- grated into younger Tertiary structures.

SAN ARROYO FIELD 5400 Traps: The known traps are predominantly structural, and some R25E R26E have stratigraphically modified the accumulation. Many of the fields Figure UO-28. Type log from the ENTRADA are situated on surface anticlines; they tend to be large and were dis- San Arroyo Field (modified after Hill SANDSTONE covered relatively early in the exploration cycle. San Arroyo-East 1200 and Bereskin, 1993). Canyon (EUR 174 BCFG) was discovered in 1955 and produces 1300 1700 Figures: UO-27, UO-28

Analog Example: Fence Canyon AHUT Figure 26 Location: T 16 S, R 25-26 E, (SLPM), Grand County, Utah, just east of Reservation Location: T 15-16 S, R 22-23 E, (SLB&M), 1400

1600 Producing formations: Dakota Sandstone COLORADO Uinta and Grand Counties, Utah, on Reservation T 1500 Other producing zones: Castlegate Sandstone, Cedar Mountain and Buckhorn Producing formations: Dakota Sandstone, Buckhorn Conglomerate, 16 Conglomerate Members of the Cedar Mountain Morrison Formation S 1 7 0 0 Formation, Brushy Basin and Salt Wash Members of Other significant shows: Cretaceous Mancos Shale 2000 1900 the Morrison Formation, Entrada Sandstone Lithology: Sandstone, white, fine-medium grained, 1800 Other significant shows: None conglomeratic Lithology: Interbedded sandstone and shale (Dakota), Type of drive: Gas expansion variegated mudstone with sandstone lenses (Cedar Mountain), sandstone to conglomerate (Buckhorn Net pay thickness: Dakota - 25 ft., Buckhorn - 26 ft., Morrison - 11ft. SAN ARR ANTICLINEBAR-X Member), shale with occasional sandstone beds Porosity: 10-16% ANTICLINE (Morrison), sandstone (Entrada) Permeability: Unknown OYO Type of drive: Gas expansion Estimated ultimate recovery: 10 BCFG Net pay thickness: 13-80 feet, variable Other major analog fields: Evacuation Creek, Hell's Hole, Park DATUM: TOP OF DAKOTA SILT SAN ARRO YO UNIT CONTOUR INTERVAL: 100 FT. Porosity: 10-20% Mountain, San Arroyo Figure UO-27. Structural contour map of San Arroyo Field (modified after Hill and Bereskin, Permeability: NA 1993). Estimated primary recovery: Not calculated

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY TYPE: Cretaceous Dakota to Jurassic Play 13 UTAH Analog Field: Greater Hell's Hole Figures: UO-29 to UO-31

Location: T 10 S, R 25 E, (SLB&M), Uinta County, Utah; T 1-2 S, R 104 W, Rio Blanco County, Colorado, east of Reservation Producing formations: Dakota Group VALLEY Other significant shows: Mesaverde shales and coals, Mancos Shale (B), Weber Sandstone (Maroon), Leadville

Lithology: Sandstone ALLUVIAL PLAIN Type of drive: Gas depletion Net pay thickness: 25 ft. average, max 57 ft., min 5.5 ft. A L ASTCOAL Porosity: 14-18% Permeability: 0.1-10 mD Distributary Channel Estimated ultimate recovery: 26.2 BCFG, 65,000 BC FORESHORE Braided Stream

COMPOSITE TYPE LOG Coastal Plain with Marshes SHOREFACE HELL'S HOLE FIELD Cross Bedding

Beach Ridges 6600

Foreshore Sand Dakota Silt Figure UO-30. Three dimensional model Marine Shale Shoreface Slope and Sand 50 of Dakota Sandstone depositional environments at Hell's Hole Field. Highlands 25 Upper Dakota A FEET (modified after Moretti et al., 1992). MILES Shoreface to Foreshore 0

Marine Sands Marine Shale 0 123 6700 O O O O O O 107 107 108

Upper Dakota B 109 O 111 110 41 Shoreface Marine Sands Middle Dakota C DAGGET SAND WASH Coastal Plain, Fluvial Channel, MOUNTAINS BASIN UINTA Overbank MOFFAT

6800 AXIAL ARCH Lower Dakota D UINTAH Braided Alluvial Rangely AH Channels ALTAMONT Field DUCHESNE UT COLORADO RED WASH

PICEANCE O UINTA 40 NATURAL BUTTES RIO BLANCO BASIN PICEANCE CR. 6900 Hell's Hole N. DOUGLAS Area Figure UO-29. H CARBON C R Composite type log for A GARFIELD K the Dakota section at E Morrison E R Continental Hell's Hole, Rio Blanco C BASIN S Mud, Silt, and Sand GRAND A County, CO, and Uintah L WYOMING G MESA County, UT (modified U O after Moretti et al., D

7000 O Figure UO-31. Map showing the Hell's Hole TD 1992). 39 UTAH COLORADO area (modified after Moretti et al., 1992). 0 100 200 20 30 10 0 -10 01020 50mi.

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY TYPE: Cretaceous Dakota to Jurassic Play 14 UTAH PLAY TYPE 4 The two producing fields in the play are Ashley Valley Field in Analog Example: Rangely PERMIAN-PENNSYLVANIAN Utah (EUR 25.5 MMBO) and Rangely Field in Colorado (EUR 955 Figures: UO-18, 19, 32, 33 MMBO, 706 BCFG). Ashley Valley produces from about 4,000 feet Location: Rio Blanco County, Colorado, east of Reservation SANDSTONES AND CARBONATES PLAY Producing formations: Weber Sandstone and Rangely from 5,500 to more than 6,000 feet. The play depths Other significant shows: None for undiscovered accumulations range from 6,000 to 12,000 feet. This is primarily a play for structural and stratigraphic traps in Per- Lithology: Sandstone mian and Pennsylvanian sandstones and carbonates. The objective The play below 8,000 feet is relatively unexplored by drilling, but is Type of drive: Combination reservoirs were deposited in predominantly marine and eolian envi- Net pay thickness: 275 feet ronments. Some redbeds occur, but are not part of the prospective Porosity: 15% facies. Permeability: 25 mD The eastern part of the play is bounded by the expected limit of Estimated ultimate recovery: 904 MMBO Other major analog fields: Ashley Valley, Thornburg porous sandstone. The southern boundary is limited by expected presence of structural and stratigraphic traps in the Uinta Basin; the 112o 111o 110o 109o 108o 107o northern limit is based on the expected limit of conventional reser- 41o voirs. This play is thought by the U.S.G.S to be very high risk. FRONT RANGE UPLIFT Reservoirs: The Permian-Pennsylvanian reservoirs are both sand- WEBER SANDSTONE stone and carbonate. The sandstones have good reservoir quality at Salt Lake City shallow depths (<8,000 feet). The carbonates are expected to be po- WEBER Gore rous at least as deep as 12,000 feet. The shallow sandstones (Weber SANDSTONE Craig Sandstone) have about 11-14 percent porosity in the only two dis- Vernal covered fields in the play. Source rocks: The source rocks for the discovered oil fields are not OQUIRRH fault known, but the Park City (Phosphoria) Formation was probably the GROUP

source, requiring long-range migration. Some local Pennsylvanian z o one marine shales may also be a source. 40

AH MAROON Timing and migration: The hydrocarbons must have migrated pri- FORMATION MAROON or to Tertiary tectonism, so generation was probably during the Up- UT FORMATION per Cretaceous.

COLORADO Glenwood Springs Price Exploration status and resource potential: Only two fields have been found in the province, both of which are related to anticlinal Garmesa FRYINGPAN closures, and both of which produce oil. The play is for oil with as- fault MEMBER sociated gas, but it is possible that some gas fields of less than mini- U zone loessite nc mum size (6 BCFG) may also be found. Several Pennsylvanian om ELEPHANT p SAWATCH sandstone and carbonate reservoirs produce on closures just outside a PAKOON CANYON hg Grand Junction UPLIFT re the province in the Maudlin Gulch Field area (Danforth Hills Anti- o DOLOMITE FORMATION f 39 Green River au UNCOMPAHGRE cline). lt Salina zo CUTLER ne UPLIFT FORMATION

Highland area of high to moderate relief Sabkha, playa, restricted shallow- marine setting 0 30 mi 60 mi Highland area of low to moderate relief Shallow- or nearshore-marine 0 50 km 100 km sand-rich environment Alluvial fan, alluvial plain, delta plain Offshore-marine sand-rich environment

Eolian dune field Carbonate shelf, platform, or reef

Figure UO-32. Map showing the Early Wolfcampian paleogeography of the Uinta-Piceance Basin Region during maximum transgression (modified after Johnson et al., 1992).

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY TYPE: Permian-Pennsylvanian Sandstones and Carbonates Play 15 UTAH Eastern Era System Series Piceance Basin Uinta Basin PLAY TYPE 5 rocks containing more than 1 percent total organic carbon (TOC) are found in the (FIGURE UO-33) Park City Fm Park City BASIN MARGIN SUBTHRUSTS PLAY (HYPOTHETICAL) Lower Tertiary, Upper Cretaceous, and Pennsylvanian Belden Shale . Leonardian Fm The Jurassic Curtis Formation may be a local source bed. This play is primarily for closures beneath high- to low-angle thrusts. Figure UO-3 Schoolhouse Tongue shows some of the flanking thrusts present along the northern to eastern part of the Timing and migration: The timing is uncertain, but most of the thrusting took place Wolfcampian Weber Maroon province. The play is hypothetical, and both oil and gas should be present. The only during the Laramide Orogeny. Ss PERMIAN Ss Fm Fm Weber Maroon nearby analog is the Tepee Flats Field in the eastern Wind River Basin-Casper Arch area. Here, thick, unfractured Cretaceous marine shale provides a seal for an oil and Traps: Traps are most likely structural and structural-stratigraphic (FIGURES UO-34 Virgilian gas accumulation in the Upper Cretaceous Frontier Formation. and UO-35). Play depths should range from 5,000 feet to as much as 25,000 feet.

? Reservoirs: The reservoirs for this play range in age from Paleozoic to Tertiary. Exploration status and resource potential: The play is almost unexplored by drilling and only moderately explored by seismic mapping. Based on the abundant Missourian ? Maroon Reservoir quality may be poor, especially for prospects deeper than 12,000 feet. The

Ss Fm fields near the thrusts in the Uinta Basin, a median field size of 2 MMBO and 15 BCF Weber Mississippian carbonates are expected to be porous in most parts of the play. Weber PALEOZOIC PALEOZOIC Ss of non-associated gas, and a maximum field size of approximately 50 MMBO and 150 Desmoinesian Source rocks: The source rocks are within the subthrust section. Possible source BCFG are estimated for this play. Fm

Morgan Mintum

Fm Morrison Fm

PENNSYLVANIAN PENNSYLVANIAN Atokan A A' Figure UO-33. Nomenclature and WEST Pineview Field EAST

Morgan Fm correlation for the Weber Sandstone in Round Belden Sh Valley the East Uinta and Piceance Basins. Evanston Fm (Te) Morrowan 1 Newton Sheep 3-3 UPRR 2-1 Bingham Ls Unconformities indicated by white 4-10S 2-5 Bingham, patches (modified after Hemborg, 1993). Wasatch Fm (Tw) 1 Pineview 3-2 UPRR 3-9 UPRR 2-1 A +8000'

Kk R 7 E +6000' Evanston Fm (Ke) Tw-Tf Wasatch Fo T wkes? Te Te 32 35 3 Frontier Fm (Kf) +4000' Ke N Ke Jsp Oil-Water contact (-3415') Kk Aspen Sh (Ka) +2000' -3800 Kk -3600 Kelvin Fm (Kk) -3400 Kk -3200 Sea level -3000 Jsp -2800 -3800 -3600 5 A-2600 -2000' -2400 Stump/Preuss Ss (Jsp) Jsp Oil -2800 T Twin Creek Ls (Jtc) Water -4000' -3000 -3000 2 -3200 -3200 Nugget Ss (Jn) -3400 N -3400 R a) Hilliard Sh (Kh) Oil-Water Ankareh Fm (T -6000' -3600 contact thrust N -3800 (-3415') R t) 8 Thaynes Ls (T Absaroka 0 1 mi -8000' Dry Hole Twin Creek and Nugget completion Twin Creek completion Nugget completion er Fm Frontier Fm (Kf) Ka 0 1km

Bear Riv -10000' Figure UO-34. Typical geometry of a shallow east-trending structure, Pineview Nugget Reservoir, (Kbr)

Summit County, Utah (not on reservation). Gas is trapped in an asymmetrical thrusted anticline in Woodside Sh (TR w) the hanging wall of the Absaroka Thrust system. Structure contour map of the top of the Nugget B Sandstone (modified after Hjellming, 1993). Figure UO-35. Cross section through the reservoir. Line of section shown in Figure UO-34 (modified after Hjellming, 1993).

UINTAH AND OURAY INDIAN RESERVATION CONVENTIONAL PLAY: Basin Margin Subthrusts Play (Hypothetical) 16 UTAH DEFINITION: Unconventional Plays tural flexures is considered quite high, perhaps more than 50 percent; 112 o 111o 110o 109o 108o Unconventional Play- A broad class of hydrocarbon deposits of a also, there is high potential for finding many areas of small produc- T BEL T WYOMING type (such as gas in "tight" sandstones, gas shales, and coal-bed gas) tion, and perhaps as many as 10 larger fields (Table 1). 41o that historically has not been produced using traditional development SAND WASH practices. Such accumulations include most continuous-type depos- UPLIFT BASIN its. Analog Example: Greater Douglas Creek UINTA FIGURES UO-13, UO-14 Location: Rio Blanco County, Colorado Cretaceous Self-Sourced west of Reservation Producing formations: Mancos, Mancos (B) Shale Fractured Shales Play (Hypothetical) OGENIC PICEANCE Other significant shows: Morapos Formation o 40 OR Oil is produced from fractured Upper Cretaceous Mancos Shale and Lithology: Sandstone UINTA BASIN its equivalents. The best fracturing occurs in brittle siltstones, carbo- Type of drive: Pressure depletion and water drive CREEK NB SC nates, and calcareous shales. Net pay thickness: 30-250 feet er The play outline is based by the U.S.G.S. on the known occur- Porosity: 2-20% Riv rence of production and the tectonic features associated with known Permeability: 0.01-100 mD BOOK BASIN and suspected potential. In the play, the best open fractures occur at

U

the maximum flexure on anticlines or monoclines. Fractures also TCH produce well where shear zones or faults occur. The play boundary TIGHT GAS UINTA TERTIARY EAST PLAY o TEA CLIFFS is fairly easy to define except in the area between Rangely and the 39 ASA W UNCOMP PLA AEL Axial Uplift, where proprietary seismic data indicate the presence of This play is based on well-established gas production from the Ute- SEVIER several subsurface thrusts, including thrusts associated with the land Butte, Chapita, and Buck Canyon zones of the Tertiary Wasatch White River Field structure. Formation. Updip to the south and east, the play limit is based on an SWELL AHGRE Reservoirs: The reservoirs are open fractures in brittle siltstones, increase in reservoir quality and a change to mostly conventional res- SAN RAF ervoirs that have gas-water contacts, which are included in the Uinta carbonates, and calcareous and siliceous shales. The producing inter- UPLIFT vals vary from 10 feet to more than 50 feet thick. The fracturing is Tertiary Oil and Gas Play. Downdip to the north, the play boundary HENRY Green highly variable, and one well in the play has produced over 1 is defined as the point where it becomes predominantly an oil play MOUNTAINS and is included in Play Type 1. The western limit is along the Green MMBO. 38o River drainage, where the play becomes higher risk and has been as- CIRCLE Source rocks: The enclosing marine shales are the source rocks. sessed separately by the U.S.G.S. as Tight Gas Uinta Tertiary West CLIFFS

The richness varies from about one percent to more than four percent UPLIFT AHUT Play (Play Type 8). The overall Wasatch tight gas plays (7 and 8) are TOC, based on unpublished information. based on vitrinite reflectance (Ro) levels in the underlying Creta- Timing and migration: The oil was probably generated in the Late ceous Mesaverde Group. Rice and others (1992) and Fouch and oth- COLORADO Tertiary during maximum burial. ers (1992) showed that Wasatch gas has migrated upward from the Traps: The traps are formed by the enclosing unfractured, more Mesaverde Group and that the play occurs between the basal Mesa- plastic shale, which contains less silt and carbonate than the brittle verde Ro limits at 1.1-1.5 percent. 0 30 mi 60 mi 100 km facies. The largest accumulation in the play is found in Rangely Reservoirs: Reservoir rocks are generally medium- to fine-grained 0 50 km Field (EUR 14 MMBO). The highest concentration of oil wells pro- feldspathic litharenites and litharenites deposited primarily in fluvial EXPLANATION ducing from the Mancos Shale at Rangely is along the south flank of environments. They are interbedded with mudstones, siltstones, the structure at the point of maximum flexure. shales, and some coal. Porosity ranges from less than 5 percent to Tertiary volcanic and intrusive Contact Exploration Status and Resource Potential: The play is moderate- more than 9 percent. The reservoirs range in depth from about 3,000 rocks ly well explored by vertical wells but nearly unexplored by slant- and feet to about 10,500 feet, having a median depth of 6,400 feet. Tertiary sedimentary rocks Fault horizontal-hole drilling. The U.S.G.S. assumed a low success ratio Source rocks: The predominant source of the gas is in the underly- Precambrian sedimentary Thrust fault for the overall play area. Although this play is classified as a contin- ing Mesaverde Group (Fouch and others, 1992; Nuccio and others, rocks uous-type play (e.g., tight gas), production should be localized by in- 1992; Rice and others, 1992). Gas well that provided dividual fractured structures and fracture trends. Precambrian metamorphic rocks core samples: Precambrian intrusive rocks NB, Natural Buttes field EUR estimates per well are extremely variable and, although the play is treated as a continuous-type occurrence, the U.S.G.S also simulat- SC, Southman Canyon field ed individual undiscovered fields or "sweet spots" within it to assist Figure UO-36. Generalized geologic map of the Uinta Basin Province showing location of cored wells (modified after in assessment. On this basis, the success ratio in well-mapped struc- Pitman et al., 1986)

UNITAH AND OURAY INDIAN RESERVATION UNCONVENTIONAL PLAY TYPE: Cretaceous Self-Sourced Fractured Shales Play (Hypothetical) 17 UTAH Play 8: TIGHT GAS UINTA TERTIARY WEST PLAY Play 9: BASIN FLANK UINTA MESAVERDE PLAY (HYPOTHETICAL) (HYPOTHETICAL)

This play is the western extension of Tight Gas Uinta Tertiary East This play is based on the widespread occurrence of tight, gas-saturated Play (Play Type 7) and is separated from Play 7 along the Green Riv- continental and marginal marine sandstone. The south, east, and west er drainage. Although the river is a surface feature, it more or less limits of the play are based on thermal maturation levels in the basal coincides with a westward decrease in drilling activity and reservoir 1890 1280 part of the Mesaverde Group. The reservoirs grade updip into more quality. It is higher risk than Play 7 and, on this basis, it was decided A B conventional Mesaverde reservoirs having gas-water contacts (see Up- by the U.S.G.S to use separate assessment parameters. per Cretaceous Conventional Play Type 2). Mesaverde burial depths greater than 15,000 feet designate the downdip (north) play boundary Reservoirs: This play draws on the same reservoirs as Play 7, yet (Fouch and others, 1994). porosities are somewhat lower here, ranging from less than 4 percent Carbonate to about 8 percent in reservoir sandstones. The play depths range 1910 1300 marker Reservoirs: The reservoirs are fine- to medium-grained litharenites to from about 4,500 feet to 11,000 feet, with a median depth of 7,500 feldspathic litharenites, becoming coarser to the west. Most reservoir feet. permeabilities are <0.1 md. Porosities range from <4 percent to >12 percent, averaging about 8 percent (FIGURES UO-11 and UO-12) (Nuccio

Source rocks: The underlying Mesaverde Group is the gas source. t) and others, 1992). Play depth varies from 8,000 feet to 15,000 feet, The play limits approximately coincide with maturation levels of Ro having a median of 9,500 feet. 1.1-1.5 percent in gas-prone source beds in the basal part of the Me- 1930 1320 saverde Group. Source rocks: Source rocks are gas-prone, thermally mature coals, carbonaceous shales, and mudstones of the Mesaverde Group (FIG-

Timing and migration: METERS URES UO-11 and UO-12) Gas generation began in the Late Tertiary . and may be continuing presently in the Mesaverde in the deeper parts

of the basin; however, it is possible that vertical gas migration from IN Timing and migration: Gas generation began in the Tertiary and may mation

the Mesaverde may not be as effective as it is in Play 7. mation (upper par be continuing to the present in the deeper parts of the play. The basal 1950 al 1340 vinter Mesaverde has a thermal maturity greater than Ro 1.1 percent. Traps: Traps are both stratigraphic and diagenetic. al v al

DEPTH Traps: Traps are both stratigraphic and diagenetic. Exploration status: There is considerably less drilling activity in Tuscher for Tuscher asatch for this play relative to Play 7. The play is only sparsely to moderately inter Exploration status: The play is essentially unexplored due to depth,

W explored by drilling. 1970 Cored 1360 economics, poor reservoir quality, and the fact that it is mostly overlain by oil- and gas-producing rocks of the Tertiary Green River Formation. Cored

1990 1380

1 10 100 1 10 100 RESISTIVITY, OHM-M 2/M

Figure UO-37. Electric log profile of cored wells (modified after Pitman et al., 1986).

UINTAH AND OURAY INDIAN RESERVATION Unconventional Play 8: Tight Gas Uinta Tertiary East and West Plays 18 UTAH DEEP SYNCLINAL UINTA MESAVERDE PLAY Source rocks: Gas-prone organic material interbedded with sandstone 111o 110o 109o 108o (HYPOTHETICAL) has generated large volumes of gas. Salt Lake City Timing and migration: Gas generation commenced in the Tertiary, UINTA MOUNTAINS Oil field This play is based on the expected occurrence of gas-saturated, tight and may be continuing at the present time. The thermal maturity of WASA

Mesaverde sandstones at depths greater than 15,000 feet. The limits the Mesaverde is in excess of Ro 1.5 percent, and the deeper rocks MTNS Vernal Gas field TCH of the play are based on depth and reservoir quality. This play bor- exhibit >Ro 2.0 percent. B' Greater A Greater Red Wash ders Play 9 and involves the same suite of rocks. field Traps: Traps are both stratigraphic and diagenetic. Lake Mtns Altamont- Roosevelt Bluebell Reservoirs: Reservoir rocks are sandstones interbedded with mud- Duchesne Exploration status: The play is not well explored, due to the fact field Pariette River WHITE stones, siltstones, shales, and some coals. Porosity is generally lower o that primary interest in the area is in the overlying Tertiary reservoirs. 40 Bench Rangely Utah field than in Play 9, and although there is almost no drilling, the U.S.G.S. A' Lake PICEANCE R expects porosity to be <8 percent to about 3 percent, having a median B Island IVER field Natural CREEK of 5-6 percent (Table 1). Reservoir depths are >15,000 feet, as deep BOOK Buttes CLIFFS BASIN Green field UPLIFT as 25,000 ft, and have a median of 20,000 feet (FIGURES UO-42 through U Price UINTA h Sunny- rc A Parachute TEA side Tar Sand Glenwood UO-44). Creek PRICE Douglas Creek Rifle Springs PLA CANYON BASIN BOOK CLIFFS

A A'

H o CLIFFS ELK 39 AEL UPLIFT Grand M TC Green BOOK Junction OUNT Altamont- Pariette River AINS

SA Bluebell Bench Island AW SAN RAF UNCOMP Approximate outline of AH 1 2 3 4 5 6 7 8 Uinta and Piceance Creek 0 25 50 Kilometers UT UPLIFT Basins AHGRE Colorado River COLORADO 0 20 40 Miles

0.50% Rm

Figure UO-38. Index map of the Uinta and Piceance Creek Basins area showing location of cross-sections A-A' 0.75% Rm (Figure UO-43) and B-B' (Figure UO-44) (modified after Nuccio et al., 1992).

1.10% Rm Eocene Paleocene Figure UO-40. Cross section B-B', which ex- B B' tends from outcrops on the southwest flank of Sunnyside Tar Sand the Uinta Basin through the Altamont-Bluebell Natural Buttes Altamont - Bluebell fields (A-B) Field. Producing intervals for some of the basin's Pariette Bench Redwash Field (RW) Island fields are projected into the line of section. See Duchesne, Monument 9000 Horseshoe Bend Figure UO-42 for line of section (modified after Tertiary verde Group verde Cretaceous 6000 Nuccio et al., 1992). Duchesne River Fm. North Hor Colton Fm. 2.0% Rm Mesa Green River Fm. 3000 n Fm. t) Tertiary Upper Cretaceous (par Uinta Fm. SL Nonmarine Green River Fm. Open Lake; Type I Tuscher and Farrer Fms. -3000 Braided and meandering fluvial; Type III North Horn Fm. AB W Green River Fm. asatch Fm Marginal Lacustrine Neslen Fm. BW Colton Fm. -6000 Mixed Lake and Fluvial Coastal Plain; Type III (part) & Mesaverde Group

Type I, II, and III . -9000 Colton and Wasatch Fms. Marine ft m Alluvial; Type III Sego Sandstone 6000 2000 Tertiary and U. Cretaceous Shore, nearshore North Horn Fm. Figure UO-39. Cross section A-A' through the Mancos Shale 3000 1000 Paleozoic-Mesozoic rock Alluvial and minor lake Uinta Basin, Utah, showing types of kerogen Type I, II, and III Open marine; Type II and III 4 8 12 16 20 mi GAS found at various stratigraphic intervals, levels of Gas Well Buck Tongue of 0 OIL & GAS Mancos Shale thermal maturity (Rm lines), and associated 0 5 10 15 20 km Oil Well Oil producing zone Castlegate SS and 650 ft hydrocarbon producing zones. See Figure UO- Dry Hole Gas producing zone Blackhawk Fm.; Type III; 42 for line of section (modified after Nuccio et al., 0 Littoral and shelf 16 mi 1992).

UINTAH AND OURAY INDIAN RESERVATION UNCONVENTIONAL PLAY: Deep Synclinal Uinta Mesaverde Play (Hypothetical) 19 UTAH REFERENCES co Bureau of Mines and Mineral Resources, Socorro, New Mex- County, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., ico, p. 104. Jr., eds., Hydrocarbon and Mineral Resources of the Uinta Ba- Anderson, R. C., 1995, ed., The Oil and Gas Opportunity on Indian sin, Utah and Colorado: Utah Geological Association Guide- Lands: Exploration Policies and Procedures, Bureau of Indian Hill, Bradley G., and Bereskin, S. Robert, eds., 1993, Oil and Gas book 20, Salt Lake City, Utah U.S.A. Affairs. Fields of Utah: Utah Geological Association Publication 22, Salt Lake City, Utah, U.S.A. Pitman, J.K., Anders, D.E., Fouch, T.D., and Nichols, D.J., 1986, Anonymous, 1995, Uintah and Ouray Reservation, in Anderson, Rob- Hydrocarbon Potential of Nonmarine Upper Cretaceous and ert C., ed., The Oil and Gas Opportunity on Indian Lands: Explo- Hjellming, Carol A., ed., 1993, Atlas of Major Rocky Mountain Gas Lower Tertiary Rocks, Eastern Uinta Basin, Utah, in Spencer, ration Policies and Procedures, 1995 Edition, Bureau of Indian Reservoirs: New Mexico Bureau of Mines and Mineral Resour- Charles W., and Mast, Richard F., eds., Geology of Tight Gas Affairs, p.93-106. ces, Socorro, New Mexico. Reservoirs, AAPG Studies in Geology #24.

Cashion, W.B., 1992, Oil-Shale resources of the Uintah and Ouray In- Johnson, Samuel Y., Chan, Marjorie A., and Konopka, Edith A.,1992, Rice, D.D., Fouch, T.D., and Johnson, R.C., 1992, Influence of dian Reservation, Uinta Basin, Utah, in Fouch, T.D., Nuccio, V.F., Pennsylvanian and Early Permian Paleogeography of the Uinta- source rock type, thermal maturity and migration on composi- and Chidsey, T.C., Jr., ed., Hydrocarbon and Mineral Resources Piceance Basin Region, Northwestern Colorado and Northeast- tion and distribution of natural gases, Uinta Basin, Utah, in of the Uinta Basin, Utah and Colorado: Utah Geological Associ- ern Utah: U.S. Geological Survey Bulletin 1787-CC. Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., Jr., eds., Hydrocar- ation Guidebook 20, Salt Lake City, Utah U.S.A., Utah Geologi- bon and mineral resources of the Uinta Basin, Utah and Colora- cal Association. Moretti, George, Jr., Lipinski, Paul, Gustafson and Slaughter, Arville, do: Utah Geological Association Field Symposium, 1992, 1992, Dakota Sandstone deposition and trap door structure of Guidebook 20, p. 95-109. Chidsey, Thomas C. Jr., 1993a, Uinta Basin [UN] Plays-Overview, in Hells Hole Field , eastern Uinta basin, Utah and Colorado, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., Jr., eds., Hydrocar- Spencer, Charles W., and Wilson, Robert J., 1988, Petroleum Geology Reservoirs: New Mexico Bureau of Mines and Mineral Resour- bon and Mineral Resources of the Uinta Basin, Utah and and Principal Exploration Plays in the Uinta-Piceance-Eagle Ba- ces, Socorro, New Mexico, p. 83. Colorado: Utah Geological Association Guidebook 20, Salt sins Province, Utah and Colorado: U.S. Geological Survey Lake City, Utah U.S.A. Open-File Report 88-450-G. Chidsey, Thomas C. Jr., 1993b, Green River Formation, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: Morgan, Craig D., 1993a, Uinta Formation, in Hjellming, Carol A., Tremain, Carol M., 1993, Mesaverde Group, in Hjellming, Carol A., New Mexico Bureau of Mines and Mineral Resources, Socorro, ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mex- ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mex- New Mexico, p. 85-86. ico Bureau of Mines and Mineral Resources, Socorro, New ico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 84. Mexico, p. 97-98. Chidsey, Thomas C. Jr., 1993c, Wasatch Formation, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: Morgan, Craig D., 1993b, Entrada Sandstone, in Hjellming, Carol A., New Mexico Bureau of Mines and Mineral Resources, Socorro, ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mex- New Mexico, p. 87. ico Bureau of Mines and Mineral Resources, Socorro, New Mexico, p. 104. Fouch, Thomas D., Nuccio, Vito F., Osmond, John C., Macmillan, Logan, Cashion, William B., and Wandrey, Craig J., 1992, Oil Noe, David C., 1993a, Mancos Marine Sandstones, in Hjellming, and gas in uppermost Cretaceous and Tertiary rock, Uinta Basin, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.D. Jr.ed., Hy- New Mexico Bureau of Mines and Mineral Resources, Socorro, drocarbon and Mineral Resources of the Uinta Basin, Utah and New Mexico, p. 99-100. Colorado: U.S. Geological Association Guidebook 20, Salt Lake City, Utah U.S.A. Noe, David C., 1993b, Dakota Sandstone, Cedar Mountain Forma- tion, and Morrison Formation, in Hjellming, Carol A., ed., Atlas Fouch, T.D., Schmoker, J.W., Boone, L.E., Wandrey, C.J., Crovelli, of Major Rocky Mountain Gas Reservoirs: New Mexico Bureau R.A., and Butler, W.C., 1994, Nonassociated gas resources in of Mines and Mineral Resources, Socorro, New Mexico, p. 101- low-permeability sandstone reservoirs, lower Tertiary Wasatch 102. Formation, and Upper Cretaceous Mesaverde Group, Uinta Ba- sin, Utah: U.S. Geological Survey Open-File Report (in press). Nuccio, V.F., J.W. Schmoker, and T.D. Fouch, 1992, Thermal maturi- ty, porosity, and lithofacies relationships applied to gas genera- Gautier, Donald L., Dolton, Gordon L., Takahashi, Kenneth I., and tion and production in Cretaceous and Tertiary low permeability Varnes, Katherine L., eds., 1995 National Assessment of United (tight) sandstones, Uinta Basin, Utah, in Fouch, T.D., Nuccio, States Oil and Gas resources- Results, Methodology, and Sup- V.F., and Chidsey,T.C., Jr., eds., Hydrocarbon and mineral re- porting Data: U.S. Geological Survey Digital Data Series DDS- sources of the Uinta Basin, Utah and Colorado: Utah Geologi- 30 1995. cal Association Field Symposium, 1992, Guidebook 20, p. 77- 93. Hemborg, H. Thomas, 1993, Weber Sandstone, in Hjellming, Carol A., ed., Atlas of Major Rocky Mountain Gas Reservoirs: New Mexi- Osmond, John C., 1992, Greater Natural Buttes gas field, Uintah

UINTAH AND OURAY INDIAN RESERVATION References 20 UTAH