Plainview Prospeci

128 870W

Jefferson County, Colorado

Plainview Prospect

T2S R70W

Jefferson Co., Colorado

February 25, 1991R.Randy RayGeologist/Geophysicist

Copy No._ 10 _

1

Table of Contents

Executive Summary.

Introduction .

Regional Structure.

Golden Thrust Fault .

Lyons Sandstone .

Dakota and Muddy "J" Sandstones .

Niobrara Chalk '" .

Thermal Maturity .

Conclusions .

References .

Appendix I - Summary of P-Lyons Fields ..

Appendi x II - oi 1 Seeps .

2

Page

4

4

5

5

7

. . . . .. 8

. . . . .. 9

. . . . . . . . . " 10

10

11

15

16

Illustrations

List Qt Fiqures

1) Denver Basin after Tainter,19842) Generalized stratigraphic column after Leroy, 19553) Generalized tectonic map after Warner, 19804) Golden Fault structural Models after Domoracki, 19865) Geologic cross-section at soda Lakes, Berg, 19626) Golden Fault Seismic Line - Final Stack, Domoracki, 19867) Interpreted Golden Fault Seismic Line - Migrated Modified

from Domoracki, 1986, Interpreted by R.R.Ray8) State Highway 72 - Seismic Line - Final Stack from Domoracki,

19869) Interpreted State Highway 72 - Seismic Line - Final stack

from Domoracki, 1986, Interpreted by R.R.Ray10) Typical electric log Pierce Field Area and geologic cross­

section after Sonnenberg, 198411) "Pierce-Black Hollow" right-wrench zone after Stone, 198512) Seismic structure map on the Lyons Formation of the Pierce­

Black Hollow-New Windsor oil field complex, Weld Co.,Colorado after Stone, 1985

13) East-West electic log section from Eldorado Springs outcropto east side of Wattenberg Field after Weimer & Sonnenberg,1989

14) Index map of thermall y mature and oi1 productive Ni obraraformation after Rice, 1984

15) Geothermal gradients in the northern portion of Denver Basinafter Weimer & Sonnenberg, 1989

16) Photograph of fractured Ft. Hayes Limestone in outcrop northof Morrison, CO.

Plates

Plate 1 - Structural Cross-section A-A'Plate 2 - Geologic Map, 1"=2000'Plate 3 - stratigraphic Well-log Cross-section E-E'Plate 4 - Muddy "J" Structure Map, 1:100,000Plate 5 - Fox Hills Structure Map, 1:100,000Plate 6 - Prospect Leases, 1"=2000' showing pipelines and

proposed seismic program

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Plainview ProspectT2S R70W

Jefferson County, Colorado

~xecutive Summary

plainview Oil and Gas holds leases on a prospect 15 miles west ofthe center of downtown Denver. It is a combination gas and oilprospect located very close to market. An 8 inch intrastatepipeline passes across the lease.

Plainview Prospect is a structural trap formed at theintersection of regional fault trends along the Front Range. Theeastward thrusted Golden Fault is the dominant structural elementand hides the underlying basinal structure. It overlaps theIdaho Springs-Ralston shear zone which formed the ColoradoMineral belt and creates a regional fracture trend in the DenverBasin. Potential primary productive zones include fracturedNiobrara chalks, Dakota Sandstones and Lyons Sandstone.Secondary productive zones may incl ude the Terry, Hygiene andMuddy-J Sandstones. Potential reserves of up to 10 millionbarrels of oil are possible based on analog fields.

Further seismic definition of the prospect will be needed toconfirm the presence and size of a structure underneath thenorthern extension of the Golden Fault. An acreage block of 3088acres is presently held over the prospect and could be enlargedafter seismic definition.

Introduction

Plainview oil and Gas has acquired leases over an area that isattractive for oil and gas exploration. The acreage is locatednorthwest of Denver, between the towns of Golden and Boulder,along the Colorado Front Range (figs.l&3).

The acreage lies at the western margin of the Denver Basin as itabutts the structurally uplifted Front Range. The Denver Basincovers most of the eastern half of Colorado with the deepest partof the basin lying next to the mountains near Denver (fig.l).Because of its long producing history, the stratigraphy of thebasin is well known, both from subsurface and outcrop control. Adiagrammatic, generalized stratigraphic section prepared byLeroy, 1955, is shown in figure 2. Additional information hasbeen added which helps clarify the following discussions.

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Regional QiL~~lure

The Plainview acreage block is located at a unique intersectionof regional faul t and fracture trends (fig. 3) and therefore hasspecia I pot en tiaI for f0 rmi ngas izabIest ructu ra I trap. Thenorth trending Golden Thrust gradually disappears in outcropnorth of Golden. The last evidence of the thrust is roughlycoincidental with the cross-cutting Idaho Springs-Ralston shearzone. The Idaho Springs-Ralston shear zone is clearly evident asa zone stri king N55 E cut ting through Precambri an age rocks 0 fthe Front Range (fig.3). It is a Precambrian age fault zone thatwas reactivated during the Laramide orogeny and is attributedwith the formation of rich mineral deposits along the ColoradoMineral Belt (Tweto and Owen,1983). However, this regionalfracture zone appears to stop in outcrops along the mountainfront (see Plate 2 - geologic map) and is expressed as a zone ofNE trending faults in Cretaceous age Fox Hills and Laramieformations. Apparently the shearing is not visible in the wedgeof rock carried in the Golden Thrust block (hanging wall block).Therefore, the shearing probably occurred before the formation ofthe Golden Thrust and expresses fault block trends in the basin.

The continuation of the shear zone into the Denver Basin is

expressed as a higher heat flow area (Weimer andSonnenberg,1989,fig.15). A similar NE-SW trending right-lateralfault system emerging out of the Front Range (fig.11) controlslarge Lyons fields of Pierce, Black Hollow and New Windsor asnoted by Stone,198S.

Although there is an abundance of surface geologic informationthe exact geometries in the subsurface are still unclear. Mostof the surface geology may be reflecting structure in the hangingwall of a thrusted mountain front. (see Plate 1) The structureunderlying the thrust fault will have to be determined by seismicand drilling. However, the same structural grain of intersectinqNW-SE & NE-SW faults would be expected.

Q.Qld~Il Thrus t Faul t

The geologic interpretation of the Golden Fault has been studiedand debated since it was first described by Zieglar (1917).Various interpretations have ranged from low angle thrusting(Stewart,1953) to high angle fault / overturned fold (Berg,1962).(see fig.4)

The geometry of outcrop patterns indicates the nature of thefault may change along strike. In the outcrop between Morrisonand Golden the fault creates steeply east dipping to overturnedbeds associated with uplift of the Front Range to th'e west. Ageologic cross-section using well control and surface geology byBerg, 1962 (£ig.4) indicates the Golden Fault is a high angle(350 -500) thrust fault. He attributes the formation of structureat the Soda Lakes field to a combination of basement structureand compression along the leading edge of the fault. The field

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produced about 13,000 barrels of 11° ~PI. oil. from fractured .f...L,Hayes. Limestone member of the Niobrar~ For!:!tat~--,- Note also thezone of def orma tion wi th overturned sect ion wedged bet ween twoprimary faults that form the Golden Thrust. Displacement on thePrecambrian is about 6000 ft.

The northern extent of the Golden Fault is unclear from outcropinformation. In outcrop the Paleozoic and Mesozoic rockscontinue to have steep east dip all along the mountain front.However, at Superior the vertical to 600E dipping beds of the FoxHills sandstone flatten out and head off to the northeast.

The change in trend is coincident with the projection of theIdaho Springs-Ralston shear zone as it emerges from the mountainfront.

The Superior area has several NE trending faults exposed inoutcrop. The area has been mined for coal in the Laramie and FoxHills zones since the late 1800's. The faulting has beeninterpreted to be listric normal faults caused by sedimentloading associated with prograding Fox Hills deltas(Weimer,1973;Davis,1974;Davis,198S). This is probably asecondary structure created by the underlying wrenchingassociated with the Idaho Springs-Ralston shear zone.

New seismic data acquired by the Colorado School of Mines(Domoracki, 1986) helps to illustrate the geometry of the Goldenfault as a low angle (30°) thrust fault (fig.S). Displacement onthe Precambrian surface is about 10,000 ft. Using this new modelof the faulting it becomes clear that the Golden Thrust Fault isa low angle thrust which is losing throw and dying out to thenorth where it is overtaken by the wrenching associated with theIdaho Springs-Ralston shear zone. Th~ illi~~~~QiiQll gf ih~~~i£~.p..9.~i~ ~ll ~cell~ll.t. ar~~ 1Q g~ll~~~i~ .e.i~l!Qll!£~l.fQl9..:!:.llgLfaultinq ~llg fracturinq.

Even though the seismic evidence of the Golden fault zone isclear, the resolution of the footwall structure is more difficult(fig. 6). There is a large reflection time distortion caused byoverthrusted, high velocity Precambrian rocks. This causesvelocity pull-up which makes the reflections appear to be risingto the west. When properly corrected to depth, the basinal dipswould be flat lying to slightly eastward dipping.

With this new model in mind, the Colorado School of Mines seismicline down Highway 72 can be interpreted. This data was shot as12 fold vibroseis in 1977 (Davis and Young,1977), but has beenreprocessed by Domoracki,1986 (fig.7&8). When a 30° thrust faultis placed on the section it becomes clear that reflectionsunderneath the fault are probably associated with fault blocks inthe basin. of particular interest is an arching reflection justunderlying the leading edge of the thrust which appears to be ahigh faul t block. At this posi tion there is not much vel oci typull-up created since the thrust carries Pierre shale over thePierre shale in the basin. Velocity pull-up will begin to

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increase west of SP 15 where the Niobrara limestone is present Inthe overthrust block (see Plate 1).

Lyons Sandstone.

The Permian Lyons Sandstone is one of the primary objectives Inthe Plainview Prospect since it is an oil producing zone inseveral large fields. The outcrop of Lyons Sandstone in theBoulder to Morrison area has two major facies which interfingerwit h eachot her. The fir stis the whit e tor ed, fin e tom ediumgrained, cross-stratified, quartzose sandstone recognized aseolian dunes at the type section in Lyons, Colorado. The secondis a light colored, coarse grained, conglomeratic sandstonedeposited by fluvial processes (Weimer and Land,1973). Ingeneral, the Lyons Sandstone is dominantly eolian in Tl to 2S butbecomes more fluvial dominated and therefore, more conglomeraticsandstone in T3 to 5S (Thompson,1949; Weimer and Land,1973).

The Lyons Sandstone outcrops along the mountain front about 3miles west of the prospect area. It is reported to be 2~2 to 250feet thick, pale red to pink, fine to very fine grained, quartz­rich sandstone by Wells, 1967. The sandstone grains are well­sorted, rounded, frosted and coated with iron oxide. The rock isfirmly cemented by authigenic quartz overgrowths and can beclassified as an orthoquartzite.

In the subsurface, two wells have penetrated the Lyons Sandstonein the basin. The closest well is the Teton Energy Co. RockyMountain Fuel #1 in Sec.24,TIS,R70W. It hit the Lyons at 10,010ft.(-4451) and drilled 70 feet into the formation. No cores ortests are reported. The second well was the S.D. Johnson #1Farmers Highline and Canal Reservoir well in Sec7,T3S,R69W. Italso drilled 70 feet of Lyons Sandstone at a depth of 10,280(-4707) to 10,350 ft. Seven feet of core from the Lyons isdescribed as gray, fine-grained dense, quartzite with blackshale partings, horizontal and vertical fracturing, fair odor andslight Einpoint fluorescence throughout (see stratigraphic cross­section -E-E' ,Plate 3). Figure 10 is a typical electric logfrom the pierce field showing Lykins Formation limestones andanhydrites above the blocky Lyons Sandstone (Sonnenberg,1984).

The Permian Lyons Sandstone is oil productive in a number ofbasement fault controlled, anticlinal structures along the west·flank of the Denver Basin.ThePierce field was discovered in 1955

using seismic data. The field is a gentle anticlinal closurecreated by underlying basement fault blocks. There isapproximately 100 feet of closure at the Lyons level which trapsover 10 MMBO in an area of 2000 acres (fig.l0). Net pay averages27ft. of 11.6% porosity at a depth of 9200 feet(Sonnenberg,1984). Average well reserves for Lyons Sandstoneproducers are greater than 750,000 BO per well (see Appendix I ­Lyons Fields Statistics).

The color of the Lyons ranges from red to white.white color of the Lyons has been attributed to the

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The graypresence

orof

oil which reduced the red iron oxides to form gray colored Lyons(Levandowski and others,1973). Petroleum accumulations are foundwithin the reducing facies or gray colored sandstones.

Ston e has in die ate d that 1argeL yon s fie 1ds Pie rce (l0 .9 MM B0) ,Black Hollow (10.5 MMBO) and New Winsor (0.9 MMBO) are associatedwith a NE-SW trending right-lateral fault system emerging out ofthe Front Range (see fig.ll&12). The fault system probably has aPrecambrian ancestry similar to the parallel Colorado MineralBelt to the south.

As previously discussed, the seismic indicates a basement faultblock on the Plainview acreage. This basement structure could becreated by the wrench faulting of the Idaho Springs-Ralston shearzone analogous to the pierce or Black Hollow fields. Based onoutcrop and subsurface control, the Lyons Sandstone is presentand could be trapped in a low relief anticline under the leadingedge of the Golden Fault.

Dakog p.nd Muddy ~~~ Sandstones

l)Qtent~al for an extension of the Superior Gas Field is possiblein the prospect area. Production is primarily oil and wet gas­condensate from Dakota channel sandstones(see stratigraphiccross-section E-E'). The Muddy "J" Sandstone is generally thinand tight but does produce in a couple of the wells.

The Dakota interval is comprised of two to four channelsandstones in this area. Based on correlation to outcrop threemiles to the west, the lower channel is Lytle Sandstone. Itgenerally is not productive, testing wet. The middle channel isthe plainview Sandstone and it appears to be the most continuouschannel across the prospect area. It is productive and reaches amaximum of over 60 feet thick in wells closest to the plainview

Prospect area. The upper most channel is the El Dorado SpringsSandstone and it is also productive. It appears to be pinchingout to the south across the prospect area.

Gas production from the Dakota channels is at a rate of 25D~65QMCFPD per well. The sandstones completions generally includefracing and acidizing treatments. The wells closest to theprospect are all shut in and have no completion test information.

The Muddy "J" Sandstone is productive to the north and south.Wattenberg Field with reserves in the order of 1 TCFG from theMuddy "J" Sandstone is about 15 miles to the northeast. To thesoutheast, the Teton Energy Co. Church Estate #22-1 well testedoil and gas from the "J" even though it is currently shut-in.Most Muddy "J" production is classed as from stratigraphictraps, but subtle paleo-structure and unconformities have alsocontrolled the petroleum accumulations (Weimer and Sonnenberg,1989) .

A structure map on the Muddy "J" Sandstone (Plate 4) indicates aprominent NW-SE trending nose on the south end of Superior Field.

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The nosing may be related to a NW-SE trending fault as seen Inthe Precambrian outcrop. The structural discontinui ty is shownin the shallow Fox Hills structure map also (Plate 5). A secondNW-SE trending structural nose is also contoured by Van Horn,1976, through the Teton Energy Church Estate #22-1 well. Thisstructural trend could be part of the trapping mechanism for "J"in the well even though it is structurally much lower than wellsin the Superior Field. This structural trend may also beindicating a basement flexural trend that would create closureunder the Golden Thrust.

Niobrara Chalk

The Cretaceous age Niobrara Chalk interval is the other prlmaryobjective in the Plainview Prospect. It is an attractive oil andgas producing target when developed using horizontal drill holesto intersect vertical fractures. The britt.le chalks in theNiobrara have a tendency to naturally fracture due to compactionand burial as well as local tectonics. As articulated in the

R~gj_Qnal Structure and Golden Thrust Fault sections, preceeding,the Idaho Springs-Ralston SW-NE trending basement shear zoneintersects the north-south trending Golden Thrust Faultunderneath the Plainview Prospect acreage block. This shouldenhance the fracturing at depth.

Figure 16 illustrates the intersecting vertical fracture patternof the Fort Hayes Limestone member of the Niobrara as exposed inoutcrop north of Morrison (Sec.26,T4S,R70W). The outcrop dipsabout 45° east and shows prominent north trending fracturesspaced on average about one foot apart. These are intersected bycross fractures trending NW-SE spaced every 2-6 feet apart.

Oil produced from the Niobrara chalks is sourced from thesurrounding organically-rich shales. The shales like the chalkswere deposited in shallow to deep marine environments. Whenthermally mature the Niobrara shales generate hydrocarbons thatmigrate into the fractured chalks. The plainview prospect is inthe thermally mature, oil generating part of the Denver Basin(Tainter,1982) and is in the area where wells produce oil and wetgas condensate from the Niobrara (Rice,1985). (see fig.14)Weimer and Sonnenberg, 1989, have noted higher geothermalgradients associated with an extension of the Colorado MineralBelt trend (fig.15). The deep burial depths and higher heat flowassociated with the Idaho Springs-Ralston shear zone createthermally mature rocks in the Niobrara.

The Sod a Lakes 0i 1 fie 1d pro duced 13 I 000 BOa nd fl~_red un toldquantities of associated gas after its discovery in 19~5. It wastrapped in a structure along the Golden Thrust similar to theP Iainvie w Pro spect. The S. D . Johns on #1 Li 11ie Pa I1a0 r0 we 1I(see Plate 3) indicates the Q£oduction was from the f..9n Hqy'~_e.Lif!l.estoneinterval .in ihe basal Niobrara chalk formatiof).-'.

i:

Imm ediate 1y ad j ace nt tot he PIa invie w Pro spect I

drilled Martin Exploration. Carrucci #1-33 well

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theblew

verticallyout three

times; twice while drilling the top 120 feet interval in theNiobrara and once while drilling the basal Fort Hayes member. Inaddition, several wells (Sec.13&25) in the Superior Field producefrom the Codell interval immediately underlying the Ft. HayesLimestone. Electic logs run on wells in the vicinity show highelectrical resistivities through a large part of the Niobraraformation. High resistivity readings like these correspond to--\producing areas in the Austin Chalk trend of south-central Texas

(Hinds&Berg,1990) and in the QilQ_ Fiel--9,of §'.Quthe~st RLQ.ming..,

!herm~ Maturity

The Plainview Prospect is located in a part of the Denver Basinwhich has oil and gas generating source rocks present (fig.14).The mountain front between Boulder, Golden and Morrison liesjuxtaposed to the deepest part of the Denver Basin (Tainter,1982,fig.1). Marine shales of the Benton, Niobrara and Pierreformations are thermally mature and source hydrocarbons for oilproduction in the Denver Basin. Numerous oi I seeps and showshave been reported (Stewart, 1955, see Appendix II) along theFront Range. These are undoubtedly sourced from the shalesunderlying the Golden fault.

The geothermal gradients mapped by Weimer and Sonnenberg,(fig.lS), indicate an extension of the Colorado Mineral(Idaho Springs-Ralston Creek) trend into the basin acrossPlainview Prospect. This should enhance oil generationfracturing over the prospect.

~onclusions

1989Belttheand

The Plainview Prospect is a potential structural andstratigraphic trap in the deep portion of the Denver Basin. Areview of available surface geology, well control, seismic andpublished articles shows it has potential for trapping petroleumin multiple reservoirs. It will require further seismic definition_using modern highfold Vibroseis data. A program of about 13miles should be acquired to detail the structural strike and diporientations (see Plate 6). The lines should be designed toaccomodate the expected structural complexity and still be ableto get good data.

R. Randy RayGeologist/Geophysicist

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Geologic Maps

LeRoy, L.W., 1955, Summary of Surface Stratigraphy; in FieldConference on Geology of Front Range Foothills West ofDenver: Rocky Mountain Association of Geologists, p.15-24.

Scott, G.R. and Cobban, W.A., 1965, Geologic andBiostratigraphic Map of the pierre Shale Between JarreCreek and Loveland, Colorado: U.S. Geol. Survey Map 1-439.

Scott, G.R., 1972, Geologic Map of the MorrisonJefferson County, Colorado: united StatesSurvey Map 1-790A, Scale 1:24,000.

Quadrangle,Geological

Sheridan, D.M., Maxwell, C.H. and Albee, A.L., 1967, Geologyand Uranium Deposits of the Ralston Buttes DistrictJefferson County, Colorado: U.S. Geol. Survey Prof. Paper520, 121 p.

Stewart, W.A., 1953, Structure and oil possibilities of thewest flank of the Denver Basin north-central, Colorado:PhD thesis, Colorado School of Mines, T-777, 121p.

Stewart, W.A., 1955, Structure of the Foothills Area West ofDenver, Colorado; in Field Conference Guidebook: RockyMountain Association of Geologists, p. 25-30.

Van Horn, R., 1957, Bedrock Geology of the Golden Quadrangle,Colorado: U.S. Geol. Survey Map GQ 103.

Van Horn, R., 1972, Surficial and Bedrock Geologic Map of theGolden Quadrangle, Jefferson County, Colorado: U.S. Geol.Survey Map 1-761-A.

Structure

Berg, R.R., 1962a, Subsurface Interpretation of the GoldenFault at Soda Lakes, Jefferson County, Colorado: Am.Assoc. Petroleum Geologists Bull., v. 46, p. 704-707.

Berg, R.R., 1962b, Mountain Flank Thrusting in Rocky MountainForeland, Wyoming and Colorado: Am. Assoc. PetroleumGeologists Bull., v. 46, n. 11, p. 2019-2032.

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Davis, T.L., and Young, T.K., 1977, Seismic Investigation ofthe Colorado Front Range Zone of Flank DeformationImmediately North of Golden, Colorado; in Veal, H.K., ed.,Exploration Frontiers in the Central and Southern Rockies:Rocky Mountain Association of Geologists, p. 77-88.

Davis, T.L., 1985, Seismic Evidence of Tectonic Influence on

Development of Cretaceous Listric Normal Faults, Boulder­Wattenberg-Greeley Area, Denver Basin, Colorado: TheMountain Geologist, v. 22, n. 2, p. 47-53.

Gries, R., 1983, Oi 1 and Gas Prospecting Beneath PrecambrianForeland Thrust Plates in Rocky Mountains: 1I.m. Assoc.Petroleum Geologists Bull., v. 67, n. I, p. 1-28.

Stone, D.S.,Tectonics:

1969, Wrench Faulting andThe Mountain Geologist, v. 6,

Rocky Mountainn. 2, p. 67-79.

Stone, D.S., 1985, Seismic profilesand Black Hollow fields, WeldExploration of the Rocky Mtn.Atlas, p. 79-87.

ln the area of the Pierce

Co., Colorado: SeismicRegion, RMAG & DGS 1985

Warner, L.A., 1980, The Colorado Lineament; in Kent,Porter, K.W. eds., Colorado Geology: RockyAssociation of Geologists, p. 11-21.

H.C. andMountain

Weimer, R.J., and Davis, T.L., 1977, Stratigraphic and SeismicEvidence for Late Cretaceous Growth Faul ting, DenverBasin, Colorado; in Payton, C.E. ed., SeismicStratigraphy - Applications to Hydrocarbon Exploration:American Association of Petroleum Geologists, Memoir 26,p. 277-300.

Lyons Sandstone

Blood, W.A., 1970, Upper Portion of the Fountain Formation andthe Lyons Formation at Morrison, Colorado: Mtn. Geol., v.7, no. 1, p. 33-48.

Dimelow, T.E., 1972, Stratigraphy and petrology,Sandstone, northeastern Colorado: Colo. Sch. ofunpub. M.S. thesis #1158.

LyonsMines,

Levandowski,D.W., Kaley,M.E., Silverman,S.R., and Smalley,R.G.,1973, Cementation in Lyons Sandstone and its role in oilaccumulation, Denver basin, Colorado: Am. Assoc. PetroleumGeologists Bull., V.57, p.2217-2244.

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Momper, J.A., 1963, Nomenclature, Lithofacies and Genesis of

Permo-Pennsylvanian Rocks, Northern Denver Basin: RockyMtn. Assoc. Geol. Guidebook, 14th Ann. Field Conf., p. 41­67 .

Sonnenberg, S.A., 1984, The Pierce Field Structure: TheMtn. Geologist, v.21, nO'.l, Jan.1984, p.l-·4.

Thompson, W.O., 1949, Lyons Sandstone of Colorado Front Range:Am. Assoc. Petroleum Geologists Bull., v. 33, p. 52-72.

Weimer, R.J., and Land, C.B., 1973, Lyons Formation (Permian),Jefferson County, Colorado: A Fluvial deposit: TheMountain Geologist, v. 9, nos. 2-3, p. 289-297.

Muddy J Sandstone and Dakota Sandstone

Weimer, R.J. and Sonnenberg, S.A., 1989, Sequence StratigraphicAnalysis of Muddy (J) Sandstone Reservoir, WattenbergField, Denver Basin, Colorado: Rocky Mountain Associationof Geologists, 1989 Guidebook, p. 197-220.

Niobrara Formation

Smagala, T.M., Brown, C.A. and Nydegger, G.L., 1984, Log­derived indicator of thermal maturity, Niobrara Formation,Denver Basin, Colorado, Nebraska, Wyoming: HydrocarbonSource Rocks of the Greater Rocky Mtn. Regi on, RMAG 1984Guidebook, p. 355-363.

Upper Cretaceous

Weimer, R.J., 1973, Guide to Uppermost Cretaceous Stratigraphy,Central Front Range, Colorado: Deltaic Sedimentation,Growth Faul ting and Earl y Laramide Crustal Movement: TheMountain Geologist, v. 10, no. 3, p. 53-97.

Thermal Maturation

Hinds, G.S. and Berg, R.R., 1990, Estimating organic maturityfrom well logs, upper Cretaceous Austin Chalk, Texas Gul fCoast: Gulf Coast Assoc. Geol. Soc. Trans. - 40th Annual

Mtg., p. 295-300.

13

Rice, D.D., 1989, Relation of hydrocarbon occurrence to thermalmaturity of organic matter in the Upper CretaceousNiobrara Formation, eastern Denver Basin: Evidence of

biogenic versus thermogenic origin of hydrocarbons; in J.Woodward, F.F. Meissner and J.L. Clayton, eds.,Hydrocarbon Source Rocks of the Greater Rocky MountainRegion, RMAG 1984 Guidebook, p. 365-368.

Tainter, P.A., 1984, Stratigraphic and Paleostructural Controlson Hydrocarbon Migration in Cretaceous D and J Sandstonesof the Denver Basin; in J. Woodward, F.F. Meissner andJ. L. Cl ayton, eds., Hydrocarbon Source Rocks of theGreater Rocky Mountain Region, RMAG: p. 330-354.

Seismic Data

Davis, T.L., 1974, Seismic Investigation of Late CretaceousFaulting Along the East Flank of the Central Front Range,Colorado: Ph. D. thesis, Colorado School of Mines, T-1681,65 p.

Money, N.R., 1977, A Seismic Investigation of the North GoldenArea, Jefferson County, Colorado: M.S. thesis, ColoradoSchool of Mines, T-1849, 56 p.

Nelson, K. J., 1977, A Reflection Seismic Investigation ofGolden Quadrangle Area, Jefferson County, Colorado:thesis, Colorado School of Mines, T-1990, 55 p.

theM.S.

Ray, R.R., Gries, R., and Babcock, J.W., 1983, AcousticVelocities, Synthetic Seismograms, and Lithologies ofThrusted Precambrian Rocks, Rocky Mountain Foreland; inLowell, J. D., ed., Conference on Rocky Mountain Forel andBasins and Uplifts: Rocky Mountain Association ofGeologists, p. 125-135.

Shuck, E.L., 1976, A Seismic SurveyJefferson County, Colorado: M.S.of Mines, T-1835, 45 p.

of thethesis,

RalstonColorado

Area,School

Young, T.K., 1977, A Seismic Investigation of Nor'th and SouthTable Mount.ains near Golden, Jefferson County, Colorado:M.S. thesis, Colorado School of Mines, T-1947, 54 p.

14

,';~. :. 'f't . .' .-

.Q1-EJ us 21 N~ 11 s

_ f!,'.~:- t.( ..II. ~ I.

field l'!ame

Black HollowNew WindsorPierceFort CollinsLake CanalLovelandKeotaLaPorteBerthoud

Douglas Lake

No-,-Wells

113

15611113.1

Cum " Prod.!...I:. r -, ~ 84-C:

l'{}-~~Hf f ?: Zj-

I ';~4I" ;..:; .. ~).I"'O

10, 93-Y ,'4456327,321

2,7175,939

12,816141

306,820,J1J-21.?

111

141oooo3o

PRPRPRPR,PRPRPRPRPR

PI\L

1 S. I.

- 7-/\/- ( ~ w: !.'!

-~ f ;1./ .- /•..•....; .•.•u/,/ ~. .' ,:...~/~'..

TOTALS 43 23,008,975 30 PR, 2 S.!., 11 P&A

All Wells Avg. 535,092 BO/WELL

f i~LQ Name

PierceBlack HollowBerthoudNew WindsorFt. Collins

TOTALS

1411

311

30

~um~ frod '-

10,933,95210,515,313

306,820825,522

Q,L 718

22,588,325

j." , ~~ . i i ~~

, , , ~ f; ~! {:

. .I

Producing Wells Avg. 752,944 BO/WELL

The two largest fields only

Black Hollow& pierce 25 21,449,265 -

Best Wells Avg. 857,971 BO/WELL

15

Appendi~ liNOTE: This is a 11st of the 011 seeps campi 1ed by W.

stewart, 1953, structure and Oil Possibilities of theFlank of the Denver Basin North-Central , Colorado:Sch. Mines PhD Thesis #777, 121p. My comments arein brackets [*]. oil seeps are plotted on Plate 5.

Direct Indications 9f Natural Hydrocarbons

AlanWest

Colo.added

There are at least nine known occurrences of bituminous materialin the foothills belt between the Ralston Reservoir and DutchCreek. They consist of live oil seeps, dead oil residues,asp ha Itic san dston es, sol id , brittl e bit um ens and show sin 0i 1and water wells. An index map recording these localities isshown in Figure 19. The nature of the individual occurrences isdiscussed by index number below:

Local ity

1)This locality is a live oil seep occurring in a gulch emtyinginto Golden Gate Canyon about 1 1/2 miles northwest of Golden.The seep occurs in metamorphic rocks and is located one-half milewest of the crystalline-sedimentary contact. The stream gravelsin the bottom of the gulch are locally cemented by asphalticresidue. In summer when the stream has nearly dried up, pocketsof live, green, high gravity oil accumulate in the gravels. Itis believed that this oil rises through fractures in thecrystallines from sedimentary rocks underthrust below them in thefootwall of the Golden Fault. [* Probably sourced fromCretaceous age rocks. Cretaceous oil is generally green, 44-480API gravity, paraffinic, 40°F pour point. ]

2 )

About 1 1/4 miles northeast of the first locality, a live greenoil seep was encountered when the Denver Fire Clay Company drovean adit into the Dakota sandstones to open up a fire clay seam(Van Tuyl, p.744, 1932).

3)Van Tuyl (oral communication) reports an occurrence of highgravity petroleum in a water well drilled near the Fountain­Basement contact, west of Morrison and south of Red Rocks Park.

4)An oil show in the Dakota sandstone is recorded in the driller'slog of the Midas Oil and Gas Company, No.2 well, near Morrison inT5S, R69W (Barb, p.134, 1946).

16

5)Van Tuyl (oral communication) states that a construction crewdriving the pilot tunnel for the first tunnel on U.S. Highway 40in Clear Creek Canyon, encountered a pocket of heavy, black, deadoil in th joints of the metamorphic rocks. This locality isabout three-fourths of a mile west of the Fountain-Basementcontact. [*probably sourced by Paleozoic rocks. Paleozoic oilis generally black, 36-41° API gravity, paraffinic, OOF pourpoint. ]

6)LeRoy (p.31, 1946) describes occurrences of a black brittle,bituminous substance in the shales and limestones of the basal

Lykins formation in Glennon Canyon south of Morrison.

7 )LeRoy (p.31, 1946) reports a similar occurrence in a limestone,15 feet above the Lyons-Lykins contact on Ralston Creek.

8)Heavy, black, brittle bituminous material was observed by VanTuyl (personal communication) in a road cut near the parking lotbehind the amphi theater at Red Rocks Park. This material wasfound in the four to five feet of the basal Fountain and in

joints of the underlying crystal lines.

9)South of the Turkey Creek water gap in the Dakota hogback, thereis an old quarry developed in an occurrence of bituminoussandstone at the top of the Dakota formation. An attempt wasmade once to extract the bitumen by a hot water or steam process.

All of the foregoing occurrences are located in the hanging wallof the Golden Fault. The source of many of these hydrocarbonscould be the 9,000 foot section of marine limestones and shalesof the Benton, Niobrara and Pierre formations in the footwall ofthe fault. Trap possibilities are almost negligible in theupthrown block and commercial accumulations, if present, areexpected on the downthrown side of the fault.

17

(2) Area Of Mature Source RocksC.1. = 500'

Figure 14. Structure on J Sandstone at present, datum Is sea level.after Tainter, 1984

POG fig. 1

ERAAGEFJ FORMATIONa·'.· ...• _ ..... :,,__ . '.U 00 o~ GREEN MOUNT A!N

LOWER ' ..... '.,N U) ;•.6.~ ..... ' .

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POG fig. 2

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Figure 4. Generalized tectonic map of northeast Front Range foothills and adjacent Denver basin, Colorado. Compiled from varioussources, including Burbank and others (1935)" Fisher (1946), Lovering and Goddard (1950), Hunter (1955), Parker (1961),

Spencer (1961),Abbott (1970), Punongbayan (1972), Nesse (1977). ft W 1980a er arner,

paG fig. 3

E.I~~~~~~~_-_6_0_00_Figure 5. Golden fault structural models: A-Ziegler(1917, Fig. 6), through Golden; B-Stewart (1953, Plate10), near Golden Gate Canyon, SP indicates shotpoint; C­Birdsall (1956, Fig. 19), along Golden Gate Canyon; D­Bieber (1983, Fig. 5), near Ralston Creek; E-Money(1977, Fig. 14C), one mile north of Golden Gate Canyon.Ty=Tertiary; Mz=Mesozoici Pz=Paleozoic; pC=Precambrian.

EAST+l' :0< 10,000'

APPROXIMATE SCALE

6000

Sea Level

pz

pz Mz

c.

after Domoracki, 1986

POG fig. 4

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rigure 6. Geologic cross-section at Soda Lakes (fromBerg, 1962a, rig. 4).

Canyon. HorizontalGr-surface trace

~Figure ~7. Final stackscale is compressed 2:1.or Golden fault; LB-line

~Golden GateMF-mountain front;

bend. after Domoracki, 1986

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Figure 18. Golden Gate Canyon. Migrationafter Domoracki, 1986

POG fig. 7

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Figure 21. Final stacks - state Highway 72. Display scaleis near 1: 1. after Domoracki, 1986. Interpretation by R.R.Ray. See also Plate 4.

Pf 9201-9210, Pumped 317 BOPD

-4000 ft

-5000 ft

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Figure 2. Typical electric log Pierce field area showing Lykinsand Lyons Formations (California Co. # 1 Priddy, NW SWSec. 23, T8N, R66W).

after Sonnenberg, 1984

o : 1.41I

Figure 5. Structural cross section through Pierce structure. Notehow sublle the structure is on true scale cross section.

:••••

WY.i..........., + 4'-

301

tNI

10 20! I

m

ol

tD

~U)-2

c o.ARE A of

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9DENVE R

o 10 20 30 40 50I I I I I I

km

Figure 1: Index map showing area of Figure 2 from Stone, 1969, Pi. I, with New Windsor anticlinal

axis added. R-I2 is the "Pierce-Black Hollow" right-wrench zone, here called the Windsor Fault. R-IIlsthe "Colorado Mineral Belt." after Stone, 1985

POG fig. 11

Figure 2: Seismic structure map on the Lyons Formaticn of the Pierce-Black Hollow-New Windsor oilfield complex, Weld County, Colorado. after Stone, 1985

POG fig.12

Weimer and Sonnenberg

TETON ENERGY CONTINENT Al MARTIN BRYAN

Sequences Formations Members HE SE 13; is - lOW SE HE SW 5: 1S - 69W SEHE2; 1S-69W HE HW 13: is - 68W

PIERRE~ 4--; .~

------

~ <:~> l0

0

5Smoky~-~

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3

=<~

NIOBRARA

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J

Hill

->

x - BENTONITE

-- Ft. Hay"

TnLn

TnLa ••

WATTEN

Lincoln Ls.

Hartland Sh.

Bridge Creek Ls.

GRANEROS

~ CARLILE

Za:oJ:ZUJUJ

a:"

4

3

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MUDDY (J)LSI!:2SKULL

CREEKT'I:[~PLAINVIE\ILS!!:1

LYTLE~~ MORRISON

\JoG)

(Q

....•

c.u Figure 15. East-west electric-log section from Eldorado Springs outcrop (modified from MacKenzie,1971) to east side of Watten berg Field (see Figu re 3 for section location). Lithologic symbols for surfacesection are shown on Figure 7. after Weimer and Sonnenberg, 1989

DUDLEY D. RICE

olr

o

50 kilometersJ1

30 miles

after Rice, 1984

FIgurE! 1. Index map of Denver basin showing present-day depth of burlal to top of Niobrara Fom1atlon (modified from Shurr, 1980~ Contourvalues are In meters. Location of wells from which gas samples were analyzed are labeled by numbers and from core sampleswere analyzed are label&d by letters.

POG fig. 14

;;@.L_"tJ'"? I KANS

~"O i~~t.;.o I

I / ~'--,!C/ 0::' 2.5

F/100 ft

Plainview ProspectGradients

')."

AREA OF MATURESOURCE ROCKS (TAINTER. 1984)

~~~ AREA OF VITRINITE

REFLECTANCE VALUES GREATER

~ _." THAN 0.75 (HIGLEY 01 01 •• 1985)

. Figure 24. Geothermal gradients in n-orthernportion of Denver Basin, in FO per 100 ft.C.M.B. is Colorado Mineral Belt, a Precambrianstructural trend with a zone of Tertiary intru­sions, exposed in the Front Range Uplift.after Weimer & Sonnenberg, 1989.

POG fig. 15