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ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 A THESIS 8TO8JITTED TO THE BOARS Of TRUSTEES, PRESIDENT AHD FACULTT Of THE COLORADO SCHOOL 0? HHTS3 IH PARTIAL t M J K t X m 0? THE RSQUlRSsAa’To

f o r t h e i m R s E o p JHOTEBT “Of “SCIENCE ~

OOLDSR, COLORADO OOMTMTS

IHTRQDUCTTOH____

■a. LOCATION.------

REAS Oil FOR TE8T ABD EARLY TESTSIB THE AREA------3 THE DISCOVERY WELL. ___ 5

HISTORY. OF FIELD AFTER DISCOVERY-.------6 TOPOGRAPHY AHD DRAIHAQE— — — ------— 6

REGIOKAL RELATIQHS— — — — ------— S

LOCAL TOPOGRAPHY AHD DRAIHAGE-— 7

„

PERSOKHEL I£ FIELD------— -- — ------,— — — 10 m & m, ammmst ------■------i m a a s m m m is is . m m ------n GEOLOGY OF HOHTHEASTERH COLORADO -- ---— — — ------— 11

sasfca------■------14 WfffflRgJIfl. SZ& Sazlx VMsaaJA SLESSa — ----— 14 Cretaeeous 8y s tern—-—<■»——■ » » -■■

^ Dakota Group------15

gjLftSSS. S6fi3JSr-ww— — — ---- ~ * 2 l Foxhil,Xa. Sandstone a— ^ ------5 STRUCTURE------ii mu nop i m 0>i'm u* ** m «n m j mu «H I H i w » > >m mm n»i» < mm mu mm m mu rnmmmmmmmmmmmmm 31

GEOLOGIC HISTORY— ...... ______—35

PRE-CAMBRIAN TIME---- — ------— 35 PALEOZOIC ERA— --— — ---- ...------36

MESOZOIC ERA*1-.""-11 111111111. 111 ■■ 11— irn mi m i l mi m — n 1 ii 11 ...... —...... 37

CEHOZOIC ERA— — — — — ------— --- 38 mmm si mmm rn m iim ----- — ---- -

STRATIGRAPHY------*-- ~ ~ 4 X

48 im, ,a|pto M s m m k Baloir the Muddy aarig— ——— 49

SURFACE STRUCTURE— ------— SUBSURFACE STRUCTURE ---- — ------— -----— ,— 53 RELATION OF PRODUCTIVE AREAS TO GEOLOGIC STRUCTURE— 55

PAK'^HS----—— ------— ------— ------— 58

UNUSUAL CONDITIONS-— — — — -— — — ------— — 57 TYPICAL CASING AND CEMENTING PROGRAM— -----— — — 57

SHOOTING PROGRAM— — ------— ---- — — 58

AVERAGE COSTS FOR THE COMPLETED WELLS— ------— — 58 sassBg.

— .—■■I———— — —59

PRODUCT ION 3TAT 1ST IPS— 60 FOOT PER BARREL RAT 108— — — — --- — ---- — ---— 60

BOTTOM HOLE PRESSURES— — — ----— --- — — 63 METHODS OF PRODUCING WITH A DISCUSSION OF EACH ----63

Rep re s aur lng ------— — — 64 REPAIRS TO WELLS — — ------— -- -- ..— 68

OIL TREATING AND GAS SEPARATION— — — — ---- 65

WATER ENCROACHMENT.- — ------•--- ,— — 67

STORAGE AND TRANSPORTATION.------— — — — — — 67 THE COLORADO-WYOMING GAS COMPANY BOOSTER STATION -- .89 LIST OF MAPS. SKETCHES. CURVSS AND TABLES

TABLES AviD ffiflJj-LOOS TABLE I. GOTERALIZED GEOLOaiO SECTION - COLORADO PIEIMOHT JUSSA TABLE '4. X3LL3 OOIiPLETED, DRILLING AND ABANDONED BY LEASES TABLE 3. V7ELLS COMPLETED, DRILLING AND ABANDONED BY MONTHS TABLE 4. BRI3P PRODUCTION HISTORY - TYPICAL WELLS OP FIELD TABLE 5. PRODUCTION STATISTICS TABLE 6 . WELL LOGS - WELLINGTON FIELD, COLORADO

SKETCHES AND CURVSS PLATE X. FOOT PTO BARREL RATIO CURVSS

PLATS ,3. SKETCH OP HOOK-UP FOR PRODUCING WELL

PLATE 3. SKETCH OP HOOK-UP FOR REPRSSSURE WELL PLATE 4* SKETCH OP NORTH NTRAL GATHERING SYSTEM PLATS 5. SKETCH OP SOUTH CENTRAL GATHERING SYSTEM PLATS 6 . PLOT SHEET- CONTINENTAL COMPANY GASOLINE PLANT

PLATS ?. YEARLY PRODUCTION DECLINE CURVE - FOR 1 WELL PLATE 8 . TOTAL PRODUCTION CURVSS FOR FIELD

;taps PLATE 6 . TOPOGRAPHIC NAP- WELLINGTON OIL FIELD,COLORADO

PLATE 10. FIELD MAP - WELLINGTON OIL FIELD, COLORADO — /pLATE 11. SURFACE STRUCTURE HAP- WELLINGTON OIL FIELD,COLORADO

yPLATS 10. SUBSURFACE STRUCTURE '.IAP- WELLINGTON FIELD, COLORADO

/ PLATE 13. AREAL GEOLOGY MaP- COLORADO PIEDMONT AREA

PLATE 14. SECTIONS THROUGH WELLIjlGTON 9IL FIELD, COLORADO"

PLATE 15. GENERALIZED STRATIGRAPHIC SECTION- WELLINGTON FIELD

PLATE 16. GRAPHIC LOG OF DISCOVERY WELL- WELLINGTON FIELD THE WELLIHOTON OIL FIELD, COLORADO

IHTKQPPCTIQK

This thesis deals with the geology and the oil and gas production of the Wellington oil field, Colorado,

It is based? (1) on field work done by the writer during the summer and early fall of 1933; (3) upon geologic data obtained from various sources in the literature dealing with the area; and (3) on production data furnished by the

Continental Oil Company, The field work done by the writer included: (1) a plane table survey of the field and structure

(covering the topography, elevations and locations of oil wells, and elevations and locations of surface outcrops;; (2) a Brunt on survey of the dips of the outcrops. Considerable has previously been written regard­

ing the geology of the field in various scattered papers, but up to date the various geologic and production informa­ tion has not been compiled and assembled in one inclusive paper. The purpose in writing this paper has been to assemble, compile and correlate the various phases of geology, drilling and production pertaining to the field. a.

The writer is indebted to the following for

Information and assistance in preparing this paper5 (1) To Hr* A* 1, Bratnerd of the Continental oil Company, for geologic Information, and to Messrs. E# 8# Shannon, O.w. Whitaker, D.l* Jones, Oscar Johnson and H# Spence of the saw company, for information concerning production, and tte gasoline plant of the field; (8 ) to nr, liar Ball, for suggestions m to the geology of the field; {3} to Professor i*P* fiuleatt, for construct!** critic lam of some of the map®; (4) to Mr. Paul w, Stroud, for Information on the analysis of the oil of the field; (S) to Mrs# w.l.

Ingham, for assistance In some of the field work and computations; (6) to Professor B* 8* Boatright, for supervision and const m o t ire criticism of the parts on drilling, productIon, storage and transportation, and the gasoline plant; and (8) to Doctor r.it# fan Tuyl for general supenrislcm and const me t ire criticism of the thesis as a whole* 3.

LOOATIOW

The south and of the Wellington oil field is

located about 3 miles north and 2 miles west of the town

of Wellington, or about 11 miles north and 1 mile east of Fort Collins, in Larimer County, Colorado. (See accompanying maps.) It has a length of about 4 miles, and an average width of three-fourths of a mile. It covers parts of sections 6, 7, and 18 in T. 9 N., R. 68 W.; and parts of sections 30 and 31 in T. 10 If., R. 68 W. As can be observed from the maps, its long axis trends in

a north-south direotlon.

BMIfltt

REASON FOR TEST AM? EARLY TESTS II THE AREA

In 1907 or 1908, Junius Henderson of the Colorado Geological Survey, recognized the existence of anticlinal folding west of Wellington. During succeeding years his references to this folding led to a number of visits to the area by members of the survey, including the making of a sketch map in 1915 by R.C. Coffin. As a result, S.F. Rathvon, an oil operator of Boulder, Colorado, had the anticline checked and organized the "Poudre Oil and Gas Company? In 1915 he located and drilled a test well in the S. f. £ of

H. E. £ of section 31, T. 9 If., R. 68 W., at a point on the anticline where the dip in both directions is plainly visible.

Unfortunately, the location, though on the anticlinal axle, is in a saddle betm m n two d o m e and it not within a closed area. This well was drilled to a depth of about 4000 feet, ending In the Steele (lower

Pierre) shale after obtaining small showing® of gas and oil# tn a report dated m y 1916*, r#0« Oeoxge, state

Geologist, gave Mr. Rathvcm a. description of the Wellington structure, noting the crest in sect ion 31, f* 10 l.f R# SB t. and a southward plunge from- there to the Poudre Coopany well in seotlon 31, f. 9 if,, r. 68 w,, and definitely ©losing the structure to the north* However, he failed to recognise that the Ha&hwon well was outside the closed area, In the fall of 1917, John Bertram, while on a reconnaissance of the Hooky Mountain front for the Roxana Corporation, made an independent discovery of reverse dips and recommended further work in this area, A,f, spring,

Bertram*e assistant, was sent into the area ami reported an anticline running from near Fort Collins north for about 15 miles. Me outlined the area which Includes the fort

Collins ami tellingtom structures*

The Roxana Corporation promptly leased about

Hotel Superior figures refer to bibliography* 14,000 acres and started detailed work in this area, by

I.W* Kampert and O.H. Henley, under supervision of A.T. Schwennesen* The mapping was done in great detail and involved several months1 work* The resulting map has been

the basis for practically all activities in the region since that time, ami later careful checking has not modified

the work much.

In August 1919, the Roxana made an acreage

,v arrangement with the Keoughan-Hurst drilling Company for a test of the Hygiene sand of the Pierre shale. The well

was drilled near the high point of the anticline to a depth of 1312 feet and abandoned after obtaining some water and

a little oil in the Hygiene sand. As a result of the show of oil in the Keoughan-

Hurst well, the Roxana geologists recommended drilling to deeper sands, but the company abandoned Its leases in 1920

without fiirther drilling.

THE DISCOVERY WELL1

About 1933, T.A. Hairieon, Consulting geologist

of Denver, and his associates took new leases on the area,

and contracted with the llhlon oil Company of California for

the drilling of a test well. The type of lease used was

the Producers 88 form. This company located it© test well in the S. W.

of the N. W. £ of section 31, T. 10 N., R. 68 W., about 300 imt southwest of the itaoughaiwifurft bole, tii started drilling on March 30, 1933* Tbs will, which was drilled with cable tools, was- ex i s t e d on tfovesber 13, 1833, ms a gas well with ait estimated oap&oity of 83,000,000 etifele foot# The initial rook p t m & n m was about 1-300 to 1300 pound®* .4 graphic log of this well is shown cm Plats 10#

KiatORT OF Fltw M-FtWM OfSCOTORT

After the discovery mi l was brought in the union Oil Company of California obtained additional leases covering oost of the field, and during the next few years they developed the field, drilling most of the wells in it# In January 1939, the Continental Company took over the tmion oil Company of California1 e holdings and finlshed development of the field, drilling five additional wells and deepening two or three others.

RXOIOMt KJEUfXORS

this area lies in the Colorado Piedmont, which I® an undulating plain, sloping from an altitude of frost 6000 to 5500 feet along the foot of the mountain to about

40OO feet along its eastern margin#

The mountains rise abruptly shew* the foothills at the western edge, and on the north and east the Piedmont Is bordered by an Inward facing escarpment of Tertiary sediment 300 to 600 feet in height which separates it from the high plains.

The area is drained by the South Platt© river and

its tributaries. These include St, Vrain creek, Thompson creek, and Cache La poudre river. The latter flows in a southeasterly direction past Fort Collins,

The west margin of the Colorado Plateau is occupied by many low rounded hills, longer undulating ridges and Irregular or oval basins. Many of the basins contain lakes, ponds and reservoirs. The foothills at the west margin of the region are long narrow hogbacks or broader and lower asymmetric ridges aligned in a general north-south direction. The east slope of each ridge conform© more or lees closely to the dip of a resistant bed; the west slope is steeper. The master streams flow eastward from the mountains at right angles to the strike of the ridges. Many of the smaller streams are subsequent and flow in strike valley® between successive ridges. The higher crest of the foothills attain altitudes of 5700 to 6600 feet and stand 300 to 500 feet above the adjacent valley®. The easternmost ridges are lower and more gently ©loping.

LOCAL TOPOGRAPHY AID BRAIMAGE

This area which was mapped topographically with the plan# table by tb# writer {urn topogritpbio map* plate 0) has a regional slop# itom northwest to southeast of .about

180 feet in 3 mil## or SO feat par mil#* It slopes fro®

an elevation of over 5S0O feat in section 3S* f * 10 I.,

&♦ Si f** to about S310 fast elevation in section If, T* if**

H* 68 i* It hs# topographic high® In the northwest m m m 9 In soot ion 3§ T. 10 W*t E* 69 w , ,. and in the northeast comer In sootlem 39, T* 10 I., R* 60 v* fro® these areas there

are undulating ridges trending and eloping to the south# the northern part of the field Is in a topographic low, hut- the south part of the field* in sect ions 7 and 18* f* 9 !** a* SB f* is on a slight topographic ridge which

slopes off to the east and west and plunges southward* the area is drained by Bor Elder creek flowing through the north end of the field in a direct ion about south 30 degrees east* and by a few other small intermittent strews*

some of which drain into a eerie® of late® and reservoirs

which drain out southward*

aaai, m l aiiia

This region is typical of the central western Great Plain# in respect to climate and vegetation* The

temperature range i# great* being fro® «*30 degree® F# In winter to a® high as X00 or 110 degree® F. In summer*

the natural vegetation consists of grasses* sags* brush and greatewood* Oottcnwoods and willow® grow along the bank© of the streams, A considerable part of the area

Is irrigated by ditches from the lakes and reservoirs in the vicinity of the field. Abundant crops of sugar beets, alfalfa, wheat, corn and other cereals, in addition to cherries and other fruits grow here. However, much of the land is not Irrigated and here dry farming is practiced. Much of the land, particularly to the north, is used for cattle grassing. mm m m .

The drinking water for the field employees is' piped in from Fort Collins. This water is soft. The water used by the farmers and townspeople in the vicinity of Wellington is obtained from wells. This water is extremely hard, due to a high per cent of calcium and magnesium carbonates, sulphates and other mineral salts.

Formerly the water used for oil field operations was obtained from the lakes and reservoirs in the field. For the last few years it ha© been obtained from the oil wells themselves. m m mmzim ( m wm> sms.* u ju t t m m e m m m m j m m )

The nearest town from the field is Wellington, which is situated two miles east and three miles south of the south end of the field* Fort Collins is eleven miles south and one mile west of the south end. The small settlement, Waverly, 1 0,

le about on© and on©-half miles south and two miles west

of the south end of the field*

There are no company camps in the field operated by any oil companies, but the Continental Oil Company rents several of It® company houses in the field to some of its

employees. Their location may he noted from the field map. The roads in the area of the field are good graded dirt roads. These occur along most of the section lines

adjacent to the field, several trails run from these through

the field to the wells, tank farms, etc. The Colorado and Southern railroad runs north-south through Wellington, and a spur connects Wellington with the field. Hence, the transportation facilities are fairly good.

m m m m m m

Both the Wellington and Fort Collins oil fields

are controlled and operated by the Continental oil Company*

There are approximately 40 employees that work in the

Wellington and Fort Collins oil fields* They alternate in both fields to some extent, but there are more that work

in the Wellington field than in the Fort Collin© field,

Mr. D. L. Jones, of Fort Collins, is the field

superintendent for the Continental Oil Company at the

Wellington Field. They maintain a field office and warehouse

in the field*

TYPES Of QPEHATIQHi The Continental Oil Company pumps about 22 or 23 1 1 .

walls from 12 leases In the field. Two or three of the

wells in the field are used as key wells for repressuring. A few of the wells are shut down.

The company also operates an absorption gasoline plant which produces about 600 to TOO gallons of gasoline per day.

In addition to most of the field being leased and controlled by the Continental oil Company, the Colorado-

Wyoming Gas Company have a lease on a small tract, about

400 or 500 feet south of the Continental gasoline plant. This

tract is occupied by a booster station for their pipeline. Several years ago it was occupied by their compression gaso­

line plant. mssM, mm m man a i m m iiQ im i

On the edges of the Wellington field, the following

wildcat wells have been drilled, all of which had only a

small ©how of oil or gas or were dry hole®. All of these have been abandoned. They include: 1. The Union Oil Company of Colorado1s Warren Ho. 1,

in section 8, T. 9 N., R. 68 W. E. The Wyoming-111inois Oil Company1© LeRoy Ho. 1,

in section 30 T. 10 1., R. 68 f.

3. The Great northern Oil Company*e Ketterman Ho. 1,

in section 8, T. 9 H., R. 68 I.

4. The Great Northern Oil Company’s Harwood Ho. 1, jecT7»« r7f. 9 N., R. 88 W, In addition to these, the Union Oil Company of

California drilled several dry holes on the edge of the field,

that had only a small showing of oil or gas. These include the State Ho. 1, Hess Ho. 1, Thimmig Ho. 1, and Bobbles Lake lo. I. These wells are shown on the field map; all have been abandoned*

A wildcat well was drilled on the Douglas Lake anticline, by the Union Oil Company of California, several years ago. This was the Stats Land Ho. 1, which was located in section 36, T. 9 l., R. 69 W. It is located about three miles south and one and one-half miles west of the south end of the Wellington field. It is dry and abandoned after drilling to 4010 feet, and finding only a small show of oil. lo oil in commercial quantities has been discovered on the Douglas Lake structure. A well {dry and abandoned) wag drilled in 1919 by the Cactus Petroleum Company in section 13, T. 11 H., R. 69 w.

This is located about ten miles north and one mil® west of the north end of the Wellington field. It wa® drilled on an anticlinal fold, (the Round Butte structure) and deep enough to reach productive sands, but was found to be barren.

The poudre Oil and Gas Company, (as before mentioned), was drilled in 1915, in section 31, T. 9 If., R. 68 W,, in the saddle between the Wellington and Fort Collins fields.

The nearest productive oil and gas field, and the only one in the near vicinity of the Wellington field, is the Fort Collins oil field* This 1® located about eleven

or twelve mile® south of the Wellington field, in section® 19 and 30, T. 8 H., R. 68 f.

or smmMmims. (mmmi.

STRATIGRAPHY

The stratigraphy of northeastern Colorado as

described herein, is similar to that given by earlier reports on the area.

The rocks Include pre-©a©brlan crystalline rocks in the mountains and Carboniferous to Tertiary sediment© In the plains* (Be© table 1.)

The Cretaceous rock® are of major Importance on

account of their oil and gas production and possibilities. These include the Dakota group at the base with the "Muddy* sand at its top; the Penton shale, whose top member is the Oodell sandstone, {*1lobanton* of driller®); the Niobrara formation; Pierre shale, with thin sandstone beds; the Fox hill® sandstone and the Laramie formation. northeastern Colorado lies In a major structural depression called the Julasburg basin, of which the Denver basin is a part. The bedrock formations are concealed by

alluvial wash and wind blown ©and over wide areas, and the mantle makes the mapping of the area difficult.

Regional studies of the Cretaceous strata show that 1 4

there is an eastward thinning of the Pierre shale from the mountains eastward across the plains, pre-qaiabrftan Rooks.-The floor on which were deposited the sedimentary rocks of northeastern Colorado is exposed in the Colorado Front Range, where the crusta! movements elevated the Rockies thousands of feet above sea-level* From the Sherman mountains in the north in Wyoming, to the south end of the Rockies in lew Mexico, the basement complex consists of granite gneisses and schists* the granites were long ago intruded into ancient sedimentary rocks which were thereby metamorphosed Into marble, quart site, schist, etc* This complex mass was then eroded and through­ out large areas was redneed to a relatively plane surface before the beginning of Paleozoic time. Presumably, a similar complex of pre-Cambrian rocks forms the real floor of the Jules!)urg basin. Paleozoic, and Karlv ^ssosoie Strata,-The nature of these formations is known only from exposures along the foothill®, as n o wall® have been drilled into these older beds eastward on the plains. The Fountain formation rests on the crystalline floor among the eastern foothills of the Front Range. It consists of reddish variegated sandstone and conglomerate, and ranges in thickness from a few feet to many hundred. It

1® overlain by the Lyons sandstone, of Permian age, which is a fine grained, regularly bedded, cream colored sandstone, m

50 to 200 feet thick, Hext above is the Lykins formation which is a soft , yielding mass of shale and thin bedded sandstone with a few limestone bands* It aggregates about

400 to 800 feet in thickness. Above the tykins are the Sundanoe and Morrison formations* The Sundance, which is of Jurassic age, is a massive sandstone about 100 feet in thickness. The Morrison of this area is a non-marine accumulation of clay, marl, sandstone, and limey materials, of variegated reddish, greenish and gray colors. It is about

200 to 300 feet in thickness.

Cretaceous System

Dakota Group.-The Cretaceous system in the Foothills region consists of closely related, overlapping lenses of sandstone and shale, which are interpreted as a result of near-shore accumulation of sediments in the Cretaceous sea*

The massive resistant sandstones produce the prominent hogbacks in the foothills of the Front Range. Generally, the upper sandstone forms the highest hogback, but where the middle and lower sandstones coalesce, they may rise higher. The total thickness of the group is about 385 to 435 feet.

At the base of the Dakota is generally a gray, coarse-grained, massive and cross-bedded sandstone. It rests unconforraably on the channeled surface of the Morrison formation and varies greatly in thickness, being about 35 to to 75 feet thick*

.Above the lower conglomeratic sandstone is a variegated m M y shale. It is highly colored, in hues of rad, green, purple and blue, and about 35 t o '65 foot thick.

The middle sandstone member is gray, hard ouartsite, ©ven~hecMed and ripple-marked* there the lower shale is absent, this sandstone is difficult to distinguish fro© tbs lower sandstone* It Is generally about 10 to 15 fast thick* The upper shale Is a dark Mtunlnems marln®' shale, which 1® probably the chief source of oil in the Fort Collins and Wellington field®, as elsewhere in Colorado and Wyoming. It ranges fro® 110 to 340 feet thick in the western part, to somewhat less in the eastern part* The upper sandstone member is called the Muddy. Along the Front Range, where It is firmly cemented and hence almost a ouartslte, ft ordinarily occupies the crest of the Dakota hogbacks* At some place®, however, it 1® soft, granular and porous, and good for a reservoir rock* It contain® carbonaceous streaks and fragments' of fossil plant® as well a® a variety of markings, worn trail® and borings* It® thickness ranges from that of a knife edge to about 80 feet thick* This sand­ stone 1® the productive horlson of the Fort Collins and lelllngton fields* The cretaceous rooks of Western Kansas have been

.srteneively studied by 8&s®*3 In Hamilton County, Kansas, the Dakota sandstone consist® of irregularly bedded, light colored, fine-grained sandstone, sandy shale and shales in the v^pmt part; dark shale near the middle; and light tan

sandstone at the base, uneatpoeed rooks net separated from

the Dakota, here, may contain representatives of the purgatolrs format Ion of late Q m m m l m m age or the Morrison of Cretaceous age. The total thickness of about 400 feet is comparable to the thickness of the group as exposed, along the Front Range of Colorado and eastward across the plains.

Banftffs kh^le .-The .Benton shale includes the m m i m strata that overlie the Dakota group, awl are overlain by the flobmra format ion. The Benton and Hiobrara make tip the Colorado group. The Benton Is the equivalent of tbs Orsssros, Greenhorn and Carlisle format lane of southern Colorado and eastern Wyoming. At the base of the Benton shale are beds of dark shale and bentonite, resting on the Dakota, which are generally thin beds of shaly sandstone with carbonaceous

material. The top of the Benton Is marked by a thin tran­

sition m m , which separates the upper few inches of sh&ly

sandstone from the basal limestone of the Blobrara.

The Benton formation is exposed only in a narrow

outcrop in the depression between the hogbacks of Dakota and

MiObrara formations* It dips east and underlies all the northeast part of the state. there the Benton shale is exposed and not thinned by folding it measures about 600 feet thick. Along the

eastern front of the Rocky Mountain® in northern Colorado, the lit ho logy of these beds is so similar that the separation of it into the three formations recognized elsewhere is not satisfactory.

In general there are more numerous hands of bentonite and more fish scales in the lower 100 feet than above. The bentonite is usually in layers an inch or so

in thickness. Some of the shaly beds which contain fish

scales are decidedly limy, but except for these there is

little limestone in the lower 1/S of the formation. The middle portion of the Benton is commonly con­ cealed, for it occupies the central, flatter part of the inter hogback depressions. It is a thin-bedded dark shale. Between 450 and 500 feet above the base of the formation, there is a zone 20 to 30 feet thick which con­

tains fossils of Inoceramus labiatus in greater abundance

than above or below. Here the bentonite Is less abundant

and its place is taken to some extent by impure limestone beds or concretion zones a few inches thick. Throughout this zone and in the beds immediately above It, the odor of petroleum is conspicuous. In the upper 90 feet of the formation, beds of

shale free from sand are rare, and the limestone and bentonite both diminish. Alternations of sandy shale and mottled shaly

sandstone, (which are transitional), grade into a fine,

even-grained sandstone which forms the top of the Benton.

This sandstone, 3 to 2 0 feet or more thick, weathers to a light tint of buff. Because of its position at the top of the Benton, immediately beneath the Niobrara, it i© locally

called the Miofeenton sand. It is the Codell sandstone, which correlate® with the top of the Oarlile shale (the Carllie

sandstone) in western Kansas. In contrast to the difficult division of the Benton formation along the front range, Is the clear divisi­ bility in western Kansas, where, according to Bass3, it consist® of 30 to 40 feet of dark fissile shale with rusty beds, (the Graneros shale), at the base; 95 feet of limestone, shale and chalk, (the Greenhorn limestone), In the middle; and 330 to 360 feet of shale and chalky shale, (the Carlile

shale), at the top. the total thickness of about 450 feet here is not very different from 580 to 600 feet of Benton along the Front Range.

Niobrara Format Ion.-The Niobrara is the upper formation of the Colorado group. It rests conformably on the Benton shale and grades into the overlying Pierre shale. The contact at the base of the formation is dis­ tinct. the upper few inches of the massive Codell sandstone at the top of the Benton is shaly as is also the lower few

inches of the massive basal limestone of the Niobrara.

Where observed, the two formations are conformable and usually there Is a transition zone less than 10 inches thick, in which the cream colored limy paper shales of the Niobrara are replaced by non-calcareous flaky shales of the

Pierre. The outcrop of Niobrara is a narrow belt along the mountain front, topographically expressed by a series of low hogbacks separating valleys carved in the less resistant beds.

Although only two-thirds as thick as the Benton, it outcrops in a belt about as wide. It averages about 370 feet in thick­ ness. the Niobrara bed© are mostly light-colored limy ©hales interbedded with many layers of platy or shaly limestone, and a few zones of more massive oalcareous strata which form ridges. The lowest limestone, the Timpas, is generally the most massive. At the surface it weathers into angular blocks and releases rounded casts of Inoeexaaus deforms* ae large a© two fists. Thin limestone layers consisting of oyster shells are common at some horizons. Wear the top of the formation is a yellowish-buff zone which is generally somewhat conspicuous, in contrast to the dark dull gray or rusty brown part of the lower Pierre shale. The total thickness of the liobrara is not clearly exposed in Kansas, but from we11-log correlations by Bass3,

It is about 700 feet thick. The lower 50 to 60 feet is a prominent limestone, the Port Hays member, which is the equivalent of the Timpas lime in eastern Colorado. The thickness of the Timpas limestone increases- somewhat from west to east across the Colorado plains. In the vicinity of 31

Wellington it is about 30 feet thick, in the Fort Morgan area about 30 to 40 feet thick and near Wray about 60 to 70 feet in thickness* As the timpas is a very persistent bed through eastern Colorado and western Kansas, it makes an excellent marker,

PieffffS Shale.~0verIvIng the Niobrara formation is a thick series of marine shales and sandstones, which make up the Montana group and which are overlain by the Laramie formation. Variations in composition and appearance are common in successive layers and along individual beds.

Some authors consider the subdivision of the series into two distinct formations unwarranted but they are customarily so divided.

Although generally obscured, the contact of the Pierre with the underlying Niobrara is conformable. The upper beds of the Pierre and lower beds of the Foxhill® make a transition zone in which alternations of sandy shale and shaly sandstone occur.

Where sandstone predominates over shale, the base of the Foxhills sandstone is assumed to be reached. The fossils in the lower Foxhills and upper Pierre are similar.

The Pierre formation outcrops at the surface over a wide area along the west side of the Colorado Piedmont,

Near the east boundary of Larimer county It disappears beneath the Foxhills beds, and near the Colorado-Wyoming line it is covered by Tertiary beds. It Is exposed also at the surface throughout much of Morgan county and in adjacent counties on the south and east. 38,

Because of its gentle dip and many concealed intervals, figures representing its thickness cannot "be precise* Measurements3 along Fossil Creek, south of Fort l-

Collins indicate a total thickness of over 9000 feet. The total section has a thickness of about 8000 feet at the

Wellington field, but the top part has been eroded off, leaving but an actml thickness of about 3500 feet of the lower part of the Pierre. The formation thins eastward, to a thickness of total section of about 5000 feet in the Fort Morgan County area.

The absence of persistent and conspicuous key beds in the Pierre ©hale makes it impossible to determine from isolated outcrops the exact statIgraphie position of observed strata within this thick mass of sediments. In general, the lower fourth of this formation is largely made up of dark carbonaceous fissile ©hale, with a few thin sandy beds and a few thin seam© of bentonite. Irregu­ lar rusty bands, two or three inches thick, in which mud particles have been cemented by precipitation by iron oxides or carbonates, are common in the lower 300 or 300 feet.

Between 500 and 1000 feet above the base, there are in some places, particularly near the Wyoming line, a sandy sone containing a sandstone bed. Ball2 has suggested that it is the equivalent of the shannon sandstone member of

Wyoming. The middle 1500 to 2500 feet of the Pierre contains a larger proportion of sand than the higher or lower portions 23.

Most of the beds are sandy shale with some interbedded

sandstone*

The sandy shale here is lighter colored* less

carbonaceous, less definitely bedded and in thicker units than the shale above or below* At many localities clean sandstone with little or no mud interbedded, is found. Some of the sandstone zones can be traced for miles* The lowest member in this part of the Pierre shale is called the Hygiene sandstone* The type section was measured near the village of Hygiene, where the sandstone

Is typically developed. Some have assumed that there was only one prominent sandstone in the Pierre, and, therefore, the name has been frequently misapplied to other sandstones occupying different stratigraphic positions* Credit for the correct Interpretation of these several sandstones, according to Ball3 * is to be given to A.T. fchwennesen,

I.W. ICrampert, and C.H. Henley, formerly of the Boxana Corpora­ tion.

The Hygiene sandstone has been traced fairly continuously from a point northwest of Fort Collins to the vicinity of Boulder* It is best developed and best exposed between Boulder and Loveland. It is concealed or shaly between

Loveland and Fort Collins. Like the higher sandstones, it Is crossed bedded and limy. It is variable in color and coarseness, having usually shades of gray or greenish brown. At many places it contains bits of carbonaceous matter, and is rather abundant in marine fossils. It averages about 100 feet thick, neither llthologie&lly or faunally is it dis­ tinguishable from certain other Pierre sandstone®. Overlying the Hygiene sandstone is a zone of sandy shale about 200 to 400 feet thick. Capping this Is the Terry sandstone, which 1© about 10 to 20 feet thick. It form© part of the island in Terry Lake, which is two to three miles north of Fort Collins* and also helps to form part of the promon­ tories out in the lake. This is the type locality.

Above the Terry sandstone is a thicker mass of sandy ©hale about 300 to 600 feet thick, and capping this is the Rocky Ridge sandstone, which 1© about 50 to 100 feet thick. The type locality is around the Rocky Ridge reservoir and at Douglas Lake, the former being located about six miles north of Fort Collins and the latter about eight miles north of Fort Collin®.

Above the Rocky Ridge sandstone are sandy shale and shale bed® about I?0 feet thick. These are overlain by the Larimer sandstone which is 10 to 150 feet thick. The type locality is in the Larimer County canal in section 34, T. 8 I.,

R. 69 w. It also outcrop© along the C. & 8. railroad, east of Waverly, and along Fossil creek, south of Fort Collins.

Among the fossils collected in the outcrop at Fossil creek,

J. B. Reeslde, Jr.3 has identified the following* Inoceramu® sageneis (Say), Anleonnran oeqtj.ralft (Meek), Anlspmyffl eab-irataa 35.

(Meek), eaouIlAee oompxeeeug (Say), and Soaphltgs notosua (Owen). These all occur throughout the Pierre ehale but are more abundant in the.Larimer sandstone, and this may help to dis­ tinguish it from higher and lower beds*

Above the Larimer sandstone i© about 70 to 150 feet of sandy shale, and capping it is the Richard sandstone member. It is about 35 to 50 feet thick and is ordinarily thin-bedded and limy with concretions. It forms a scarp around the east and northeast sides of the Wellington struc­ ture, forming dip slopes in places*

Above the Richard sandstone, the formation decreases in amount of sand and becomes more shalv* It contains a few unimportant thin sandstone lenses and dark iron stained calcareous conoretions are closely crowded in certain beds at some localities. Carbonaceous material is widely dissemi­ nated through the shale and give® it a dark color. The upper 3000 to 3000 feet of Pierre shale is almost free from sand.

The total thickness of the upper Pierre above the Richard sandstone member i® probably 3500 to 5300 feet.

EflSMU*. Saj4aipm«--T^ marine sandstones and sandy shales that overlie the Pierre shale, constitute the Foxhills sand­ stone. The beds consist of soft crumbly sandstone and sandy shale, with here and. there a bed of firmly Indaaratad-massive sandstone* At the base of the Foxhills sandstone, there Is a transition zone of variable thickness. It consists of gray or 36.

brownish gray sandy shale in layers airt«giBf- one-* eighth to one^fourth Inch thick,. The fossils to the upper Flerm and lower foxhills ax# m r r similar, and there is no sharp break either llthelogie&lly or famally between the Fierro and foxhills. B m m m r , the boundary line between the two f em o ­ tion© has been d r a m to Indicate the gradual change fro® no»*gritty upper Pierre shale to the sandy shale of the

Foxhills*

The top of the Foxhills m r k e the change front marine condition of the Foxhills to the brackish or fresh water conditions of the tarantle* The outcrop of foxhills sandstone f e m e a wide sen# trending in a general southerly direction along the eastern margin of tarlater County and curving down the T&lleys of

Cache la Poudre and South Platte risers alisost to creelcy#

Along the east aide of this outcrop s o b # the f m h ills strata disappear beneath the overlying farm®it. further east, the foxhills sandstone in again at the surface over wide areas in and near the west half of Morgan County.

At a u m b e r of hcriscne within the foxhills sandstone there are oonepieuoue and nae&lve sandstones which can be traced for miles and may be used for key beds in mapping geologic structure* The m e t persistent of the sandstone members of this group occurs at the top of this marine series* In places It is more than 50 feet thick and fonts conspicuous cliffs in places. It has been named the Milliken sandstone member, by

Henderson^, as its type locality is near the village of

Milliken, about one-half mile south of the Junction of the

Thompson and tittle Thompson creeks. The Milliken sandstone is not recognisable beneath the Laramie, at the margin of the Foxhills outcrop, where that format ion is again above the surface east of Greeley*

Other zones which can be traced for considerable distances in the field are marked by layers containing sand­ stone concretions. Certain of these concretion© contain large numbers of fossils m a nucleus, around which lime and iron are precipitated. Several collections of fossils have been identified by J,8, Reeside, Jr.s. it is reported that the faunas of the upper Pierre and lower Foxhills are indistinguishable. However collections from the upper half of the Foxhills are distinctive A typical collection of fossils from the upper

Foxhills, from the slop® of Wildcat mound, in section 28,

T. 4 I., R. 6? W., are as follows; Wucula planlmarginata (Meek and Hayden), Fterla nebraseensis (Meek and Hayden),

Card turn acecloe.ua (Meek and Hayden), Mactra for moss (Meek and

Hayden), Lunatla soberassa (Meek and Hayden), Fusus newberrvl

(Meek and Hayden), Lamna so. (Meek and Hayden). p Measured sections indicate that the Foxhills sandstone is about 1200 to 1800 feet thick in an area near the east half of Larimer County. The Foxhills sandstone has two definitions in this general area. Along the mountain front

it includes the transition zone and has the thickness a©

mentioned in Larimer county, with the Milliken sandstone

member at the top. In northeastern Colorado, the foxhills has been restricted by the Rocky Mountain Association of

Petroleum Geologists, (in order to facilitate mapping), to include only the sandstones and interbedded shales in the

upper 300 feet of the formation. Laraiaie *!ormat 1 on.-ConformabIv overlying* the Foxhills sandstone

is a variable series of fresh and brackish water shale© and

sandstones, with a few seams of coal* These deposits consti­ tute the Laramie formation. They represent the final deposits

of Cretaceous age made during the slow and irregular emergence of the Great Plains region, which was changing from sea to land. The base of the Laramie is a thin transition sore, a few feet thick, occupied by brackish and fresh water strata. The top of the Laramie formation is an erosion surface

representing the long interval of exposure to erosion before

the deposition of the overlying Tertiary sand, gravel and clay. This surface wag so irregular in places the Laramie strata formed hills in the midst of the Tertiary materials.

The Laramie is the surface formation over central and parts of Held County. It was mostly eroded from over

Morgan County. The Laramie formation consists of extremely variable beds of variegated shales and ©lay, interstratIfled with

irregularly bedded sandstone© which are of a light cream color. The shale Is generally lignltio ©nd contains a few seams of workable coal.

where the Laramie has escaped erosion before deposition of the overlying Tertiary bads, its thickness varies from 300 to 800 feet.

The common fossil® of the Laramie are species of Ostrea and Corbioula. At some places, oyster remains occur in irregular beds a few inches thick, composed almost entirely of shells. Tertiary Format ions.-The Tertiary is the surface formation over parts of the High Plains of northeast Colorado. It consists of an irregular mass of conglomerate, sandstone, shale and lignite. Two divisions of this formation have been recognised by geologists in this area; the White River at the base, and the Artkmree at the top. Ho attempt has been made- to differentiate them. At some localities the Tertiary consists of reworked sediment, derived largely from erosion of Cretaceous beds.

Under such conditions It is difficult to differentiate the base of the Tertiary and the top of the Laramie. Usually, however, the contact is a conspicuous surface. Generally the basal tertiary beds are conglomerates or coarse gritty sandstones containing a considerable amount of fresh feldspar. These beds are in striking contrast to the thoroughly decomposed and very fine particles that constitute the Laramie sandstone© and shales. At some localities, notably in the northeast part of Weld County, the conglomerate© of Tertiary age are firmly cemented and make conspicuous escarpments at the margin of the high plain®. At place© these conglomerate® are strung out in sinuous lines that are traceable for many miles in a general east-west direction. Quateypary Pecosit®.-The quaternary rocks of northeastern

Colorado are important only in that they conceal in many places the underlying solid rock®, and make more difficult the evaluation of the oil and gas resources -of the region.

They consist largely of windblown sands that cover many townships along the South Platte river. In many places sand dunes have been formed. Along the South Platte and its tributaries are extensive low terraces and flood plains, all of which are more or less covered with fluviatile deposits of silt, sand and gravel. Elsewhere, the poorly resistant shales of Pierre and Laramie age are deeply weathered and covered with a thick veneer of soil. Consequently there are many square miles of the Colorado Piedmont in which" the solid rooks are covered with soil. STRUCTURE

Hortheastem Colorado and adjacent parts of the Great Plains are underlain by a broad structural depression

called the Uulesburg basin. This basin has a length of about 400 miles in a north-south direction and a width of

about 300 mile®. Its limits are approximately outlined by the Cambridge anticline on the east, the Black Hill® on the northeast, the Laramie mountain® and Front Range on the west

and northwest, the Apishapa uplift on the south and the

Sierra Grande arch on the southeast. The deepest part of the Julesburg basin is the down-

fold of the Denver basin near its western rim, and which

parallels the mountain front from a point a little north of Pueblo to about 50 mile® north of the Wyoming line. Hear Greeley, the Dakota formation is depressed to about 4000 feet below sea-level. Hear the Larimer-We Id county line it is about at sea-level. From the bottom of this broad basin

near the west margin of Weld County, the strata rise steeply

to the west and gently toward the north, east and south. Thus, the Dakota sandstone passe® under Weld County and the counties to the north, east and south to reappear at the surface along

the encircling rim of the basin. dust east of the Front Range in this area, the

sedimentary rocks are upturned at varying steep angles upon

the east basal slopes of the Rocky Mountain®, flattening as they pass eastward under the plains. The beds are upturned at relatively steep angles all along the Front Range, and in place© are vertical or overturned* This monoeltnal condition is persistent along the west flank of the basin except where there are reversals causing local anticlines and domes. The strike of the upturned bed® is approximately north-south. Horth of the Cache La Poudre river, the Livermore and Red Mountain ©yncllne© extend far back into the mountain®f trending east-west. The anticline which lie® between the two, <* and also connect® them with the normal monocline to the north and south, ha® been eroded away, leaving a granite core exposed to the westward.

The uniformity in the direction of dip in the normal monocline through thousands of feet of strata, from the Carboniferous to the Upper Cretaceous, with almost no uncon- fortuity between, indicates a very long period of deposition on a uniformly subsiding sea bottom. East of Longmont, Berthoud, Loveland, Fort Collins and Wellington, the cretaceous bed® In range® 65, 66, 6? and 68 i.f dip toward the east without reversal* Further east on the plains the inclination decrease® regularly, until in the eastern half of this strip the bed® are nearly horizontal.

Still further east the regional dip 1© to the west* Rang©

65 W . is near the trough of a broad ©hallow syncline that trends in a general north-south direction through Greeley.

This syncline lie® along the axis, in the deeper part, of the

Julesburg basin. Along the east side of the Front Rang® between Longmont and the Wyoming line are a number of more or leg® well-defined en echelon folds. They trend in a northwesterly direct ion. The Fort Collins-fellington antieline is a well- defined, ©lightly sinuous fold which extend® from a point about two mile© northeast of Fort Collins in a general north direction for almost fourteen mile®. It is developed on the west flank of the Julesburg basin, about ©even miles from the foot of the mountain®. Two miles west of the saddle between the Wellington and Fort Collins anticlines, is a smaller fold, the Douglas Lake anticline. It has a similar trend, but is smaller than the Wellington and Fort Collins anticlines, having a closed area about two miles long in a north-south direction and one- half mile wide in an east-west direction. The closure is about 200 feet. The position of the axes of the Wellington, Douglas Lake and Fort Collins anticlines may be noted on the areal geology map. (See plate 13.) About nineteen miles south of Fort Collins and two miles west of Berthoud is the Berthoud dome. 'This is an elongated dome, with dips on the flank© ranging from about 3 to 15 degrees.

There is a ©mall dome about one and one-hamiles north of Round Butte or about sixteen miles north and two miles west of Wellington* This dome,, which Is called the Round Butte structure, is about a sails in diameter.

On the east limb of the Julesburg basin there are several broad, low anticlinal uplifts*

The presence of anticlinal folds in the Cretaceous

formation In northeast Colorado may be inferred satisfactorily from the areal distribution of the'overlying Pierre, Foxhills and Laramie formations.

All of Morgan County, except the northwest and southwest corners, is occupied by Foxhills and Pierre beds, except Where covered in places by Tertiary and quaternary

gravels., ^Extending south from. Fort Morgan to southwest Washington County is a belt of Pierre shale five to fifteen miles wide, bordered on each side by Foxhills sandstone and shale. In all this region^. in Morgan and adjacent counties, the beds are nearly flat. Dip® of one-half to three-fourth® of a degree are the rule and they never exceed 2 degree®.

The exposure© in general are far apart. The Fort Morgan anticline is a broad, low flexure of Comparatively large extent, which trends southward from the southwest £ of T. 5 I., R. 5? W* to T. 2 8., R. 56 and

57 W. Its presence is indicated by the belt of Pierre shale

5 to 15 mile® wide, which extends southward from Fort Morgan through Morgan County to the southwest corner of Washington

County. 35.

flie Greasewood Lakes anticline I® indicated by the outcrop of Foxhills sandstone near Osgood, and to the great extent of Pierre and forbills outcrop® northwest of Goodrich and Weldona. This flexure curves southeast from the southwest corner of T* 7 N., R. 61 w. into the southwest i of T . S I . } B . 6 0 W* m m m am m

PBS^OAMBBIAH TBSE24

The Pre-Cambrian rocks of the Front Bangs of

Colorado, with their complex structure, present a period of long and varied history of sedimentation, metamorphism, igneous intrusion, d las trophism and erosion* Erosion through the ages ha® destroyed much of the record, while dlastrophlsm and metamorphism have partly obliterated and confused the remainder. During Pre^Oambrian time there was a long period during which a groat series of sediments were being deposited* These were formed of material derived from erosion of older rocks. Following this em o a time of diastrophism, causing folding,, faulting and mountain building. Intrusion of granitic material accompanied the mountain building. After this time of disturbance there was a long interval of diastrophle quiet during which erosion removed considerable of the cover from the buried metamorphosed sediments. Following this cam© a second period of folding, faulting and intrusion of granitic material* These affected the older materialst causing some metamorphism and forming a second series of pegmatitie intrusions and granitic masses.

The second period of mountain building and intrusion probably represented the close of the Archeozoic era. It m s followed by a long period of erosion.

PALEOZOIC SKA34

A study of northern and central Colorado shows that a considerable portion of the state m s submerged by epi­ continental sea® during the early Paleozoic, but any deposits laid down at this time were removed by erosion before the

Pennsylvanian period. The earliest Paleozoic sediments found in this area are those comprising the Fountain formation which suggests deposit© laid down by rapid streams along the flank© of the newly raised land* Judging from the character of the material© of thi® formation, it is probable that erosion, was rapid, and that semi-arid condition© prevailed. With the passage of time the land masse© were worn low, the streams decreased in gradients and the sediment© became finer. Seas were encroaching fro© the east, winds were forming ©and dune®, while■Inter­ mittent streams during the wet season brought in and transported some material. These deposits were partly reworked by the advancing sea and form tbs Lyons formation.

In by kins time the lands appear to have been low and 37. portions of the 'region were submerged beneath a ©hallow epl«eontlnent&l sea. Fine sediment© from the land were washed into the sea by streams, forming deltas, low and then portions of the sea were enclosed by deposits or minor uplifts, and in these limestone or gypsum was deposited*

Such conditions prevailed from the Pennsylvanian for some distance into the Trias sic, and during which time there, was a slow deposition of red beds*

i m o m m era34

Throughout the early part of the Meeosoic era there appears to have been considerable land area in the region now occupied by the Front Range, and during this time there w m continuous erosion and a stage of pe&eplan&tion was reached in early Jurassic time.

During Jurassic time the land masses were low, and in late Jurassic time a broad stretch of aplucentinemt&l sea advanced from the north from Montana and crossed Wyoming, depositing fosslliferou© marine beds as far south as the

Colorado-Wyoming line* The sea© withdrew near the close, of the Jurassic, leaving the area again a low swamp land. The Morrison formation was then formed, the deposits being of a sub^aerial and fluvatije nature, During the lower Cretaceous the sea© gradually encroached over the area. Basal conglomerates and quart© sands were then deposited, which famed the Dakota formation.

Throughout the Cretaceous to th© latter part of the Pierre the area was completely submerged by a sea which extended eastward from the Front Range. During Benton time most of the sediments transported from the adjoining lands were fine*

During the early Niobrara, limestones were formed, but in later Niobrara time land sediments again became of importance and throughout th© remainder of that and the Pierre epoch, they were deposited with remarkable uniformity. Th© Niobrara and early Pierre were times of maximum expansion of the Cretaceous seas. During the later Pierre and Foxhills, there occurred rejuvenation of some of the land masses frofc which the sediments were derived, and the withdrawal of the seas.

The sea had largely withdrawn by the beginning of Laramie time, leaving an area of swamps, lagoons, and low lying masses. During Laramie time, beds of peat formed in the swamps, and clays and sands were washed from the higher lands.

Hear the end of this epoch dlaatrophlsm became active, the seas were drained, the region was uplifted and mountain building commenced to the west.

c r a o a o ic e r a 3 3 * 3 4

Following the Lara® ids uplift, erosion was increased and the stream© in the higher portions of the new territory were loaded with sediment which they deposited over th© lower lands to the east. Great alluvial fans and piedmont plains were built out from th© edges of the new mountains forming Tertiary formations. Occasional lakes appeared on the plains surface, as well as many streams* With continued uplifts, vulcanism became active* Volcanoes appeared in the mountains and lava poured out in some places* The streams became loaded, largely with volcanic debris, so the Tertiary deposits laid down on the Piedmont plain were partly composed of andesitic material.

#Remnants of formerly extensive erosion surfaces within th© rang© commonly show four distinct ©rosiomal formsI

(1) Imperfectly developed peneplains; (2) stripped pediment-* like surfaces; (3) broad park^like areas, characterised by subdued remnant a of older erosion surfaces; (4) broad valley floors. "Four major erosion cycles *• two obviously compound «* gave rise to imperfect peneplains. These occur chiefly between elevations of 13,500 and 7,500 feet, and range in age from early Eocene to middle or late Miocene, as indicated by their relation to Tertiary sediments of known age. In addition, three Interrupted cycles of .minor importance have been recognised in the form of rock benches in the walls of major streams. Along the ©astern edge of the mountains they commonly lie between elevations of 7,000 and 8,000 feet. They p r o b a b l y developed in late Miocene and pliocene. During each erosional episode peneplanation was extensive on the soft sediments of the plains. 40

* The lack of warping of the surfaces suggests that uplift® of the rang© sine© early Tertiary time were of regional nature.*^

mam m wmssmmnm

PREVIOUS SURVEYS

The U.S.G.S. previously mapped this area topographically, using a 100-foot interval. The writer also mapped the area, July, 1933, more in detail, using a 3Q*foot interval* The details of th© topography are explained under the section on * Local Topography*, and by observing the accompanying topographic map. {See plate 9$

Various company surface geology surveys were made, as explained under * History* of the field* Mr. A, T. Schwenessen compiled a surface geology map of both the Wellington and

Fort Collins structures, from previous surveys* This map is shown in U.S.G.S. bulletin 796 3* Various subsurface maps of the Wellington oil field were also prepared by the Chian Oil Company of California and by th© Continental Oil Company from well-log data, eon* touring on various horizons.

The writer has. obtained a tracing of a subsurface map of the Wellington field, compiled from well-log data and contoured on the top of the 'Muddy sand, from th© Continental

Oil Company* This is Incorporated in the thesis. {See plate 13.)

This map was prepared by Mr* w. a. Gallagher of the Continental

Oil Company. STRATIGRAPHY

A generalized etratIgraphle section of the

Wellington-Fort Collins area has been obtained from the

Continental Oil Company. This was prepared by Hr# W« 0*

Gallagher of that company* A tracing made of it {with slight revisions), by the writer, is incorporated In this report* {see plate 15.)

The geologic formations of northeastern Colorado have already been described in general, under ffStratigraphy of northeast Colorado*, and so the formation® above the

Pierre shale or below the Dakota sandstone, (or those not penetrated by the drill in the Wellington field), will not be further described here.

The well section in the Wellington field extends from the middle Pierre formation at the surface down into the Muddy sand of upper Dakota age* The surface outcrops, including the Richard® sand­ stone at the top and the.Larimer sandstone about 100 feet below it, have already been described. The Richard sandstone member is at the top of the Hygiene group in the middle Pierre*. The Hygiene group average® about 1580 feet in thickness in this area and consists of five sandstone member® with inteibed&ed shale® and sandy shales. * ielow the Larimer sandstone is about 170 feet of 4 2 . gray shale and sandy shale which overlies the Rocky Ridge sandstone* This member consists of interbedded sandstone and shale with an aggregate thickness of about 350 feet* Underlying this is about 4S0 feet of interbedded sandy shale and gray shales, which overly the ferry sandstone, which is about 10 to 20 feet thick* Below this member is about 400 feet of interbedded gray ©hale and sandy shale which overlies the Hygiene sandstone* The Hygiene sandstone, which 1® the basal sandstone of the group Is about 50 to 80 feet thick*

Below the Hygiene sandstone is about 150 feet of sandy shale.

These sandstone members of the Hygiene group are all rather similar llthologloally. They are somewhat variable in color and coarseness, usually being shade© of gray or brown with a greenish tinge* They are rather eross^bedded, somewhat limy, and in places contain carbonaceous matter, and may b© rather abundant in marine fossils* These sandstone members are composed of poorly sorted angular to subangular quarts grain® and contain considerable amount® of heavy mineral® and glauconite* They also contain a rather large proportion of fine material and are cemented with calcareous cement.

Below the Hygiene group lie® the Steele group* This consist® of the lower shale group of the Pierre formation. The generalised section in the Wellington field shows th©

Steele group to have a total average thickness of approximately

233? feet. It oon®i®t® of inferbedded thin sandstones, thin 43,

shell beds and concretloimry limestones, silt stones, sandy shale, gray shales and bentonite seams.

Below the Steele group of the Pierre formation lies the Niobrara formation. In the Wellington field It has an average thickness of about 370 feet and consists of r 370 feet of gray limy shale (Aplqhana shale) at the top and * 80 feet of limestone (Time as limestone) at the bottom, •The Apishapa shale® consists primarily of grayish black laminated shale and dark gray calcareous shale with light gray to while specks. Some of the grayish black laminated shale is non-calcareous, but the greater part is calcareous. In general, the Apishapa shale can be distinguished from the overlying Pierre ©hales by it© marked increase in calcareous content and decrease in sand content,*

"The Timpas limestone®, which is persistent through** out eastern Colorado, is an excellent marker. It varies in color from white to grayish white or pale buff. Foraminifera are abundant in the Timpas limestone and on account of their transparency give it a somewhat speckled appearance, Th# upper part of the Timpas limestone Is fairly soft and in some place© approaches the consistency of hard chalk. The lower 30 feet of the Timpas Is relatively hard* Practically all the samples from th# Timpas limestone contain some shale with Apishapa characteristics* This ©hale may be partly from 44 the true Apishapa member and partly from thin shale members within the Tiinpas limestone itself*” The thickness of the

Timpas limestone in the Wellington field varies from about 25 to 85 feet* Below the Niobrara formation is the Benton formation. This has been subdivided by some geologists into the O&rllle,

Greenhorn and Graaeroe members. In the Wellington field the average thickness of the Benton formation is 538 feet. At the top and immediately underlying the Timp&s limestone is the Frontier or lio-Benton sand. This is called the C&rlile sand by some geologists.

The Frontier sand varies from about 5 to 30 feet thick in the field, and is a good marker. "This sand5 consist© of relatively uniform sized grain* with maximum diameters of .18 to .21 millimeters. The grain© are largely angular but show some rounding. The sand is gray, compact and streaked with black shale, and is somewhat calcareous.

Small, rounded grains of glauconite are present in small amounts, and a little blotite is found in some samples. The Interval between the Frontier sand and the

Muddy sand of Dakota age cannot be definitely subdivided but, in general, it is subdivided Into a somewhat calcareous top member (correlated with the Greenhorn) and a lower non- calcareous member (the Mowry). The average thickness of the top calcareous meafeer, in the Wellington field, Is about 390 feet. It consists® of a variety of Interbedded grayish blaok sh&l©, dark gray shale, thin bedded, gray limestones and dark gray speckled shale, The grayish black shale is fine tortured, massive to poorly laminated and calcareous. The dark gray shale is massive, fine tortured and slightly gritty. It contains minute micaceous particles, and small black specks of organic matter. The dark gray speckled shale is massive, relatively hard and calcareous* Dark gray is the dominant color of the speckled shale but faint brownish shades are also present. The interbedded limestone where present is slightly crystalline, fossiliferous, medium texture and has a brownish luster. These characteristics distinguish it from the Timpas limestone and correlate it definitely with the Greenhorn.w

"The non-calcareous member® lies between the base of the calcareous member and the top of the Muddy sand. It consists of a dense* black, non-calcareous, fissile shale, This shale is very similar to the Mowry shale of Wyoming and is correlated with lt*lf The thickness of this member is

* 130 feet in the Wellington field* However, in the Wellington field there is often such a gradual vertical gradation between these two members (the calcareous and non-calcareous) that it is difficult or impossible to subdivide them.

Hie Dakota group can be divided into the upper sand, the Muddy, the middle sand, the Dakota, and the lower sand the Lakota, with intervening shales.

The Muddy ©and is the producing formation of oil and gas in the Wellington field, and practically all the wells of the field were- stopped in this horlson* A number of core samples from some of the typical wells of the field were examined by the writer* These were all cores from the Muddy sand (which were the only samples available) and Included samples from the Stuchell Ho. lt

Buckeye Ho, 6 t Oault^Piatt Ho* 1, Elder Ho. 1, Mitchell Ho* 2 and Yockey Ho. 1. The Muddy sandstone is rather similar llthologically throughout the field* In general it is of a light gray color and vitreous on fresh surfaces. The grains are variable in size, reaching a maximum of about *4© millimeters. Most of the grain® are angular to sub-angular, but a few are rounded,

A large number of the grains are transparent, but there are sufficient dull white and grayish grains to give the sand a light gray color* The principal constituent of the sandstone is quarts

grains, although a ©mall quantity,of black chert grains, magnetite, mica flakes and glauconite is present* There are apparently little or m organic constituents. The sandstone is rather tightly cemented with silica and a slight amount of iron oxide* It ha® a more or less variable porosity, ranging from about 12 to 18 percent pore space, as indicated by porosity tests made by the writer on core samples from 3 typical wells. Porosity tests made on these wells showed

the following results: Stuchell Ho. 1— 17.4 percent; Buckeye Ho. 6— 13.8 percent; Mitchell Ho. 3— 14.3 percent.

In the cor© ©maples, the interstratification of the sand with thin bands of black shale is very pronounced.

This sandstone formation is persistent and Is of fairly uniform thickness, varying from about 30 to 90 feet thick in th© field, with an average thickness of about 50 to 60 feet.

Th© Muddy sand is widespread and extends out beneath the plains across the Julesburg basin, where it i© folded

into a structural trap it is a favorable reservoir rock for oil and gas.

The Muddy sand is both overlain and underlain by rich carbonaceous shales. These are respectively th© Howry shale of lower Benton age and th© upper Dakota carbonaceous shales. These shales are probably the source rocks of the oil and gas in th© Wellington field as well a® in other field® in northeastern Colorado. The well log of State Ho. 1 of the Wellington field was the only one available of that field which penetrated below the Muddy sand. This log shows th© Muddy sand to have a thickness of 83 feet and to be underlain by 162 feet of

Interbedded dark bituminous shales, dark sandy shales, thin- bedded sand® and sandy limestones. These, In turn, are under­ lain by th® second, or Dakota sand. This is 30 feet thick her© and is decidedly different lithologically from the Muddy and Lakota sands. Its grains are colorless, transparent, vitreous, angular to round in form and variable in size, and is coarser than th® Muddy sand. Other characteristics of this sand are its secondary enlargement of th© grains by the addition of quarts, and by the dull whit© kaolin-like cementing material.

This sandstone Is underlain by 40 feet of interbedded light gray shale, dark sandy shale and sandy shell beds, beneath which is th© basal Dakota or Lakota sandstone. It has a thick­ ness of 23 feet here, and is similar lithologlcaliy to the Muddy sand. ff.aaftafA tto fiaatta a a i XM fitosm at zsaaaa&laaa.-*48 in dicated from the well records, the producing wells on the Fort Collins and Wellington anticlines reached the pay sand at depths of between 4300 feet and 4600 feet. These wells started in th©

Pierre shale, either just above or below the Larimer sandstone. In this general region the Pierre aggregates about 8500 feet at the Fort Collins field and 8000 feet at the Wellington field. Surveys mad© by a number of geologists, Including th© United States Geological Survey^, agree that the Muddy sand at the top of the Dakota wa® reached in the discovery well in th© Wellington field at a depth of 500 feet to 800 feet less than was indicated by calculations from surface data. 49*

It ha© been concluded that this has been due to thinning of the formations above the structures due to folding. Also the thinning above th© structures is probably partly due to th© fact that the Pierre did not begin to accumulate here until after the uplift began, and that the Pierre did not accumulate so thick above the fold.

A table of thicknesses^ of the Cretaceous formations in northeastern Colorado show that the Benton is fairly constant in thickness, being about 400 to 600 feet thick at points along the Front Range south of the Wyoming line and thickening slightly eastward in eastern Colorado and western Kansas. The Niobrara is likewise fairly constant in thickness, ranging between 335 and 600 feet, with an average of about 450 feet.

It also thicken© slightly eastward.

On the other hand, the Pierre formation is thickest near Fort Collins and Wellington and thins eastward to about

5OCX) to 5500 feet at Fort Morgan, go&§.aae, 2£p.

On th© other hand, th© basal sandstone of the Dakota, or the Lakota sandstone is about as thick a® the Muddy sand and widespread beneath the plains. It is possible that this sand say be an oil reservoir, although it is probably less favorable than the Muddy, due to th© less favorable adjacent source rooks,

the Sundance sand of Jurassic age and other older sands are also a possible oil reservoir in this area, although the older sands may be too deep to profitably drill.

The Nio~Benton or Frontier sand of the upper Benton is probably the only sand horison likely to produce oil in commercial Quantities above the Muddy, and even it has not been found to be a commercial producer in this area. This sand is about 3 to 30 feet thick. Its texture indicates It to be a good reservoir rock. It is overlain by carbonaceous shale. Good showings of oil have been obtained from it in drilling operations in the Wellington and Fort Collins fields, but no oil and gas in commercial amounts were developed. It

Is a possible source of oil in this area.

SURFACS STRUCTURE

The Pierre shale formation outcrops in the area including the Wellington field. In places it is covered by a thin veneer of recent ©oil or stream sand. The total thick-* ness of the Pierre in this area is about 8000 feet, but the top half ha© been eroded off, leaving a thickness of about 51*

3300 to 37GO feet of Pierre overlying th® Biobrara. Over the top of th® Wellington structure, the Pierre has been

somewhat thinned by folding and is about 3300 feet thick*

It increases in thickness down the flanks of the structure to about 3700 feet or more*

the middle 1500 to 2000 feet of the Pierre section contains some rather prominent sandstone members known as the Hygiene group, the two top members of the groupf the Richard

sandstone and the Larimer sandstone outcrop around the field! and are used a© key beds in surface mapping. the top member! the Richard sandstone, is about 25 to 50 feet thick and has a medium gray color. It is some­ what thin bedded and limy and contains some concretions. It grades vertically into soft sandy shale. It forms a scarp around the east and northeast sides of the Wellington structure, and also outcrops in places on the west, northwest, southwest and south sides of the structure. In some places it forms dip slopes.

About 110 feet below the Richard sandstone is the Larimer sandstone which outcrop© in place© around the field.

It ha© a thieknee© of about 10 to 20 feet in this area, but all but the top part of it 1© often concealed. It also forms dip ©lopes in places. Its thickness 1© rather uncertain due to the bottom part of it usually being concealed. The

Larimer sandstone is more abundantly foslliferous, i© slightly darker gray in color, more compact, and 1esc thin bedded than the Richard© sandstone, which helps to distinguish It from the latter member.

The writer measured dips around and in the field on these key beds, and also determined their elevations while mapping the topography and geology with the plane table. These elevation® were reduced to the Richard sandstone a® a datum. A surface structure map, based on these elevations and dip projections and checked against well-log data,was prepared. (See plate 11.)

The surface structure map was contoured on top of the Richard sandstone member, a 100-foot contour Interval being used. This surface structure map checks closely with previous ones mapped by other geologists*

It shows an elongate anticline trending in almost a north-south direction and with about 450 feet of closure. Th© closed portion of the anticline covers all of section 31, T. 10 s, R. 66 If. and section 6, T. 9 1., R. 68 W., the south part of section 30, T. 9 S., R. 68 W*# all but the west and east edges of section 7, T. 9 1., R. 68 W., and the north-central part of section 18, T. 9 I., R. 68 W., or about 3 and one-half sections in all. The highest part of the anticline lies in the central part of section 31, T. 16 I., R. 88 W. and the north part of section S, T. 9 H*, R. 68 f. As shown on the map, the dips vary from about ? t© 53.

12 degrees on th© ©mat side of th© structure and from about 12 to 23 degrees on the west side of the structure. In sec­ tion 19, T. 9 H., E. 68 I., at the south end of the anticline, the structure plunges gently to the south, the dip® at the south side of the lake there being about 2 or 3 degrees.

West of th© anticline and paralleling it, is an elongated sync line, with its axis trending roughly in a north- south direction and passing through the east one-third of sections 35 and 36 of T. 10 N., R. 69 W. and sections 1 and 12 of T. 9 l., R. 69 w. A reversal occurs along this line, and a little westward through the central parts of th© above sections, the dips are eastward, the Larimer sandstone here having dips of 7 to 11 degrees east.

The producing portion of the structure is within the area of closure, In sections 30 and 31, T. 10 If., R. 68 W., and sections 6, 7, and 18, T. 9 M., R. 68 W., as may be observed from the map. Ho surface faulting was observed in mapping th© structure. Other details of th© surface geology may be noted by inspection of the surface structure map.

SUBSURFACE STRUCTURE

The Wellington structure was mapped from we 11-log data and contoured on the top of the Muddy sand, by Mr. W. G.

Gallagher of the Continental Oil Company. This subsurface structure is®p indicates the shape and extent of the structure to be similar to that shown by the surface structure map.

However, the suhsurface map shows a hinge fault

cutting diagonally across the structure, striking in a

direction about north 30 degrees west. It passes through the

northeast com er of section 36 T. 10 H., H. 69 w*, the south­ west corner of section 31, T. 10 H. , R. 68 w., the center of section 6, f. 9 8., R. 88 f., and the northeast m r m t

of section 7, T. 9 8., R. 68 f. The upthrow side la to the northeast. The maximum displacement is at the northwest end

in the northeast corner of section 36, T. 10 jr., ft. 69 w., where it amounts to about 450 to 500 feet. The displacement decreases more or less uniformly to the southeast end of the

fault in the northeast corner of section 7, T. 9 1., R. 68 f., where it is about 80 feet. This fault apparently cuts the lower Cretaceous beds here, Including th© Dakota, Benton and Niobrara groups, but dies out in th© overlying thick and more or less plastic Pierre shales.

This subsurface structure map shows a closure

similar to that shown by the surface structure map. The high point of the subsurface structure coincides with that of the surface structure, occurring in the central parts of section 31 T, 10 H., R. 68 jr., and section 6, T. 9 1.,

R. 68 w. The producing well® are within the closed area* Further detail® of the structure may he noted by observing the accompanying subsurface structure map. (Bee plate 13.)

RELATION OF PRODUCTIVE AREAS TO 0I0L0GI0 STRUCTURE

In northeastern Colorado, oil production 1® closely related to anticlinal structures. The producing Wellington and Fort Collins fields are both situated on anticlines! and the producing wells are located within the closed area of the structure®.

On th© other hand, tests drilled on the Douglas Lake anticline failed to produce oil in commercial amounts. The reasons for failure to produce may be that the drainage area and amount of closure was too small to trap the oil in commercial amounts* It is about two miles long and one-half mil© wide and hm about 300 feet closure. Other reasons may be that th© oil has been flushed out of the Muddy sand by ground water, since it Is near the mountaims; or that the Wellington and Fort Collins structures have trapped the oil before it reached the Douglas Lake structure. Th© Round Butte anticline, several miles north of the Wellington structure, has not proved favorable for oil production. Accumulation of oil there may have been prevented by a fault sson© to the east of It which may have checked the oil, or it may have been prevented by the tight©ning of the

Dakota sand® at the structure. T m t of tlm Welllagtoa-Fort Qollim district, oil un& gau field® are new boi^g developed in the Greaeeweotl lake snd lew rs&ywer areas# The structure I® m t well tinitirsfood in these m o m owing to the feet that the fltrurtwro of the iitaddjr sand ie net tlie m m ® m that of the For Hills formatlen on the surface.

fffljC L L D P

« S m i ,

cable tools have beta need for drilling the wells in this field, a® they were considered m o m pmeiieal than rotary tools In this area. All th# well# except deott Ho# 4 and Seott Ho* S, Hltohell Ho* 3# Elder Wo# 3 and Fleming no# 1 were trilled by the Stolen oil Company of California# The above five m m drilled by the Continental oil Company who took over the Union oil Company of California property in thie field in 1939* All the well® except the last two brought to (seott So# 4 and doott Ho* S) m m drilled with company tools and labor# Th# last two m m drilled by contract, though eonpany tool® m m need* The time neoooeary for drilling and com- plotlag the®# well® varied from three to six months. OTOTTJAJ, CONDITIO®©

Very few drilling difficulties were encountered in the field. Occasionally, bentonite oaves were found in well© in the north end of th© field. Th© four water ©and© commonly found did not cause an appreciable amount of trouble.

There seems to have been but little trouble with lost circulation. No coal seam© were found in any of the well©.

TYPICAL CASING AND CEMENTIHO PROGRAM

The casing seats were at convenient depths on more or less hard or impervious formations. There seems to have been no definite plan followed as to when to cement and when not to. Practically all the holes were started with 30-inch casing, which was used only as conductor pipe and set between

30 and 100 feet. The next string was 15 and one-half inch,

70 pound, D.8.X. casing with plain shoe, which was run to between 600 and 800 feet and later pulled.

The most persistent water sand in the field is the

Hygiene sand, occurring at depths of 850 to 1200 feet. This water ©and 1© ©hut off by the next string of casing, which Is

12 and one-half inch, 50 pound, D.3.X. casing with plain shoe.

It is run to between 1100 and 1400 feet, and cemented with from

25 to 126 sacks of cement, either with or without 5 to 9 gallons of "Konast". Th© 12 and one-half inch casing shuts off a few variable lenticular surface water fcands which occur between the surface and the Hygiene Band* Hext,a strins of to inch, 43 pound, D.3.X. casing with plain*, or Baker shoe was run to between . 100 and *.-500 feet and 8<«v,but not cemented, Folio wing this a string of 8 1/4*1*101!

30 pound, D.B.X., casing ^ith plain or Baker shoe, was run to between -50 '*) and 4-00 feet and net, arid u 3U-.-j.ly cemented, Over half of the wells wore cemented .srith nbout . 0 or 5 3 sacks of cement and tne casing used to shut off occasional lenticular water sands at 1 40.' feet or deeper. Finally the oil string, the t 6 and one-fourth inch, pound, D.B.X., casing with plain shoe was run to the top of the producing sand (the Ifud&y). In a couple of wells, another string of 4 and one-half inch casing was run, although this string was the exception.

'ilfOOTIHS F.tiAttbU

Only nine wells in this field were shot. In most oases these wells were snot once with frotn so to 40 quarts of nltro. However, a. shots were used in the H.P. Stuohpil Ho. a,

3 in the Buckeye U.P. Mo. 7, 4 in the 3cott Ho. 3, and 5 in the U.H. Foster Ho. 1.

AVERAGE COST FOR IHS X3PLSKO V/MX.3

Ho exact figures as to the oost of the various operations and as to tao completed wells were available, but each well cost between C?5,0'0 and to complete. ©

INDIVIDUAL SELL LOGS

Individual well log® for eaeli well drilled in the field are shown on separate sheets. (See table S.) These well logs show for eaoh well the thieSmess* depths and descriptions for formations penetrated* water, oil and gas sands| location of wells* time commenced and completed; sur­ face elevations; total depth; and casing and shot records.

FLUID CHARACTER 1ST 108

Th© oil from the field Is a medium gravity oil averaging about 34 degrees A.P.T. The gas produced is wet, running about 1 6. P.M. An analysis cf the oil by Mr. W.I* white and Mr, i r . S . Cor lew, under Mr. Paul Stroud of Colorado School of hincs, shows the following results: The analysis was run by a method used at the Colorado School of uinea from the following data obtained:

Volume of charge % 4000 o.c* Volume recovered - 2655 e.c.

Volume of residue * 1276 o.c. Loss x 69 o.c. x 1*7 percent

Or. of residue ~ 13*3 A,P.I* at SO degress s\

Precipitation number of residue * 18.0 ea

Th© Analysis

G&eolin® 1.4 $• S$>* Or. 0*844

ferostne I4.£$. gp. Or. 0.875 Flash point 130*,

Gas oil and Gas oil 19*9$; yiscosity BOilCO; gp.Or. 0.914; F.F. 300°.

Lube fractions huh© oil 19.9$; Iflseosity 500^100; 8?*Gr« 0*935;P.P. 375®.

Residu© 30.3$; precipitation #18.0; 8p« Or. 0.978*

PRODUCTION STATISTICS

The oil production record for each well or lease of the field was obtained from the time the wells were brought

in up to September l t 1933, but th® gas and water production

record was available only sine© January 1, 1930* {See table 5,)

FOOT PER BAKBJSL RATIOS

The foot par barrel (F/B) curves on the separate

sketch (plate 1) show the gas oil ratio® (F/B) of sir different typical lease® in the field, by months from January, 1930,

to July, 1933. These run about 50 to 3000 cubic feet of gae

per barrel of oil, with an average ratio- of between 500 to 1000 cubic feet to 1 barrel. The F/B ratio for th© other wells

of the field show an average also of approximately 500 to 1000.

The well having the highest F/B ratio is the Buckeye Ho. 2, which has a ratio varying from about 44,000 to

175,000. This well produced about 50 to 1000 barrels of oil m. .

par south End 10 to 10 mid lion r'ijh:a feet of gas , during

ite life to date. The ©roessively high gas production 1©

partly due to the well1© location on the top of th© structure

and partly to it© he ire one of the first well© brought in. Th# discovery rail, Buckeye Wo. '1, also ©howed a very high F/B ratio itp until th© middle of 1930, when it m e shut down.

It a F/B ratio was between 40,000 to 80,000. If also was situated on the high part of the etrnetixre.

Welle ©hewing a low F/B ratio are the Yockey Ho. lf whooe average F/B. ratio i« about BOO or 300, and th© lament

Ho. 1, whose ratio is so low it has not been recorded, Th©

latter well hao not produced any appreciable amount of ga© during ft© life. These well© are located fairly well dowr- on the east flank of the ©t me t we . Tar i at ion in the F/B ratio curve© may be due to a number of different factor®. Formally, there will be a decline 5r the F/B ratio after a period of time, due to the drop of

rook ore®sure, and in the production of gas 'fmm the field.

Increases in the F/B ratio for a well or leas® isay b© dueto shutting the well down for a time and allowing th®

gas pressure to build up again. This is illustrated in th©

Too key Ho. 1 eitrv© # which shows a great increase in the F/B ratio- Auguet and September, 1931. < During this time th© well

was not pumping a great deal of th® tl»® and the gas pm®©nr® built up. h little later the F/B rati© dropped again. 83.

Another factor is the effect of a nearby key well feed for repressuring. this may increase the gas production at nearby wells. For example, the F/B cur re for the Dumonts Oook Ho. 1 well, shows a decline to January, 1932. Shortly before that time they began to use the nearby Stuohell Ho. 3 well a® a repressure well. Beginning with January, 1933, th®

Bnmont^Oook Ho. 1 Increased its F/B ratio for almost a year. During the life of an average oil well, the F/B ratio is higher when first produced, then it gradually declines for some time and finally as the well approaches the end of its life, the F/B ratio rises.

BOTTOM HOLE PRK8SURKS

At the beginning of th® life of the field th® bottom hole pressures were between 1300 and 1300 pounds. How the average pressures have dropped to about 750 pounds.

METHODS OF FROBTJ0IMG WITH A DISCUSSION OF EACH

Brief description of the production methods used for 15 wells of the field were obtained. These were the only ones available that contained this type of data, but may be considered as typical of the field. (See table 4.) Separate sketches show a typical well hookup for a repressure well, and typical flow line hookup for a producing well. (See plate© 2 and 3.) A typical composite decline curve, constructed by Cutler*s mathematical method, shows the decline of oil pro-* duct ion for the field. This Is a family decline curve based on all the wells of the field* (See plate 7.)

Another sketch shows total production decline curves for the field, for oil water aid gas. This sketch show© the production decline of oil since the field was opened up, but the production decline curves for gas and water only since January, 1930, the figures being unavailable for gas and water previous to that time. (See plate 8.)

Flowing?.-* During the early life of the wells, most of them flowed for a short time, which varied from a few days to a few months; hydrostatic head and gas pressure being th© source of energy. These wells flowed through the 8 and one*fourth inch casing or through tubing. A® the production declined or the wells ceased to produce, they were flowed through a one-half inch to 1 and three-fourth© inch choke or bean. Swabbing.* During the early life of the well®, some of them were swabbed occasionally to keep up production or to increase production. (See table 4.) Gas Lift.-Gas lift was used in Mitchell Ho. 3 from October,

1927, to April, 1938. It is the only well in the field which used this method of production, and it was probably used experimentally. Ho other data was available concerning detail® of th© gas lift method used. After April, 1938, this well was pumped. 64

lumping.-At present all the productive wells, except 3 key

wells which are being used for represserlug, are being produced by pumping through a a and one-half or 3 inch tubing. (See table .)

miking beam® are used for pumping all the producing

wells in th© field, *silta Barrel*1 pumps were used extensively in the early history of the field, because they could be pulled and replaced quickly, A few ”Ellis Barrel” pumps and ffEpeo Liner” pumps are still used in the field, but they are

rapidly changing to th© MAxelson Liner Insert” pumps. Most of these Axelson pumps have a 9-foot length, with a 48-Inch plunger and a 3 and one-half inch diameter. All the well® are

counter balanced. It takes about 8 hour® to pull the xsd® in a well or about 3 day® for a tubing job.

ReBreiaurlng.-sttiehell to. 3, Scott Bo. 3 and Mitchell Bo. 3

are being used a® key wells for representing the field, at present, Stuchell Ho* 3 is taking about 2 to 3 million cubic feet of gas per day under 750 pounds pressure and Scott Bo. 3 about 4 to 6 million cubic feet-■under 3000 pounds pressure*

Mitchell Ho, 3 is used a® a reserve key well for represser ing.

A compressor unit of 166 H.P. (type 10 Bessemer) furnished compressed gas to the well® through a 2 and one-half inch high pressure line. REPAIRS fO WELLS

Hot many repair® are necessary for the well®. The equipment ha© been installed for several year; in most cases,

since the well© were completed. There la but little clutch trouble or other repairs to be done. Occasionally, however, the cups of th® pimps have to be repaired. The head well® are pulled ©very 3 to 8 weeks; the others on an average of every 3 to 6 months.

OIL TBEATIIfGr AMD GAB SEPARATXGI

The oil is treated at two central gathering systems, one near the south end of the field on the Diaaont-Cook lea©©; the other a little north of the center of th© field on the

Mitchell lease.

The oil 1© treated by a combination of Tretolite, Lorraine gas traps, ”Gun Barrels” and wHay Tanks”, the latter which act as scrubbers and are cylindrical tanks of about 130 to 300 barrels capacity, and containing hay or straw used as filters. A small amount of Tretolite is used to break down the emulsions of oil and water and basic sediments produced.

The Tretolite cut© the film® of th© emulsion* Statistics for the first 6 month© of 1933, on the amounts and costs of tretolite used in the field*were obtained and show the following averages:

Average number of drums of tretolite used per month (in the f l a i d .017

Average cost of tretolite used per months*— ****~|1.81

Average number of barrels of ©lean oil (per month) Average cost per barrel of ©lean oil ^

The oil# gas and water all come mixed more or less from the flow line of each well to the separator or gas trap at thecentral gathering system. In the operation of th© Lorraine separators, the fluid level is controlled by means of a float. The oil, water and emulsion enters the trap at the top and falls down over a series of conical baffles to the bottom of th© trap at a greatly reduced velocity. During t the descent, th© gas is liberated free th© oil and flows out through a pipe at the top to th© absorption gasoline plant.

Excessive gas pressure within the trap i© prevented by a safety valve. The oil and water emulsion flows out a pipe a little above the basic sediment and water outlet to the corresponding

®gurn barrel* where it is heated and then goes through th© corresponding *hay tank*. The Tretolite outs or breaks down the emulsion and th©' hay tank acts as a scrubber which separates out the water and basic sediments. The latter drains off near the bottom and the remaining oil flows out to th© corres­ ponding leas© tank where the oil from that least is gaged. 67.

Ho paraffin© trouble of any consequence is encountered in handling the oil*

WATER EHCHOACHMEHT

During the early life of the field and when the wells were first brought in* the water production was compara­ tively small. However* at present there Is a ratio of about 3 barrels of water per barrel of oil produced. This has in­ creased gradually since 1927-1928* due to the opening up of the gas more at that time* and the resultant gradual encroachment of the water*

The ratio of water to oil produced varies greatly in the different wells* a few of the® producing mostly oil and gas with but little water* but most of them produce an excess of water as shown in the production statistics of the f leld* msm m

There are two gathering systems In the field* The south one is located in th© south part of section 7* T, 9 I,,

R. 68 w* * on the Dumont-Oook lease. The production from th© two south sections in the field* Including the wells from the

Elder* Gault and Piatt* Gault-?iatt^Puleston* Dumont-Cook*

Stuchell Lake* Yockey and D'ment leases is collected there.

The north gathering system is located in the north part of section 8# T, 9 I., R. 68 w ., on the Mitchell lease. The production from the three north sections in the field* including the wells from the Scott, Fleming* Mitchell* Buckeye* Plummer and Foster leases* is collected there* The locations of these two gathering systems are shown on the field map. (See plate 10.) Separate sketches show a plan view of the storage tanks, separators and pumps, with the tank capacities of the two gathering systems, (iee plates 4 and 5.) The loading rack is also shown on the field map. it is in the southwest part of section 6* T. 9 H. *

R. 68 W.* at the Continental Oil Company camp at Orcutt* which is on a spur of the Union pacific railroad out of Fort Collins. The oil* gas and water is pumped from the wells to the gathering systems. There it. is run through the separators and the oil, gas and water separated out. There the oil is pumped into leas© tanks of 250 or 500 barrel capacities each, and from there piped to the loading rack. From the separators at the gathering systems* th© water is drained off into lakes* and th® gas is piped to th© Continental Oil Company absorption gasoline plant in the field. Here* part of the gas is manufactured into gasoline and the excess dry gas is partly used for fuel in th© field and partly for reptessurlng through th© three key wells.

On© 4-inch flow line run© from each producing well to the central battery or gathering system. Leas® production is gauged at the lease tanks at the central system* 4 or 6-inch

flow lines are used to transport the oil from the central

gathering systems to the shipping racks* 8-inch flow lines

run from the separators to the gasoline plant, and 8-inch flow

lines are used for gas pipe lines, carrying the dry gas out of the field.

xa mmmtmmM m msm aaaaa wmm

In the S.W. $ of E*I* i of section 8, f. 9 H*, E. 08 W., is a ©mall tract about 800 feet by 000 feet in area, leased by the Colorado-Wyoming Gas Company, the location Is

shown on the field map* (See Plate 10)

Several years ago it was occupied by this company* s compressor gasoline plant, but it ha© been partly dismantled and shut down for over a year. Formerly it contained 4 twin compressors and 4 single compressors of the Cooper-Bessemer type (80 H.P. engines with 18-Inch stroke and 30-Inch diameter

pistons); two cooling towers, and other auxiliary equipment for manufacturing casinghead gasoline by the compression method* It used to handle 8 to 10 million cubic feet of gas per day

from the field.

At present, however, the remains of this plant consist of the 4 single compressors, and it is now used as an inter­ mittent booster station for the Colorado-Wyoming Gas Company to boost pressure® when necessary In the pipe line running through the field from Fort Collins to Cheyenne. she smmmrn, m mmm mm m mm.

The. Continental Oil Company has a gasoline plant located in the west center of H.E. £ of section 8, T. 9 l.t

E. 88 w* # on the Mitchell lease. It is situated just a little north aid west of Mitchell He* 1 well. The location Is shown on the field map. {See plate 10.)

It is an absorption type gasoline plant with maximum capacity of about 8 million cubic feet of gas, or 10,000 gallons of gasoline per day. At present it is producing about

600 to TOO gallons of gasoline per 3-4 hours from about 600,000 cubic feet of wet gas, the gas produced in the field. A separate sketch shows this absorption gasoline plant layout and the flow sheet. (See plate 6.) The explanation of the flow sheet in making gasoline in this plant is as follow®*

The gas comes in from the separator® at the central gathering systems through the gas meter (1), and on the com­ pressors (2), where it is compressed to a pressure of 100 pound® per square inch. It then flows to the lower part of the absorber tower®(3). There it meets the mineral seal oil which flows downward over the baffle plates. The outgoing excess gas flows out to the gas line where it is used for fuel or repressuring. The absorb ant or mineral seal oil with the absorbed vapors from the gas is then pumped by the low pressure p m p (4) , to the pre-heater and heat exchanger (5). Here It is heated by n .

live steam in the pre-heater to about 330 degree® F, and partly

vaporised, it passe® through the heat exchanger, heating the mineral seal oil flowing to the absorption towers which partially vaporises. The abeorbant next passes to the regenerating tower

over the still (6)t and is heated to ©bout 330 degrees F.f which

completes its vaporisation. Next, the gasoline vapor® pass from the still to the * knockout box* (7). this is a condenser consisting of a series of coil® which cools the vapors to about SCO degree® F.

and condenses out some gasoline which flow® to the receiving house. It also remove® part of the water and oil from the gasoline vapors. The gasoline vapors then flow to the reflux

tower (8), where the remainder of the water, oil and residue is removed from the gasoline- vapor®. Here, some more of the vapors are condensed to gasoline and flow to the receiving

' house •

The gasoline vapors from the reflux tower then flows on to the gasoline condensing colls (9). Here, condensation of

the vapors 1® obtained through air cooled pipes with water

sprayed over them. The excess dry gas flow® out from the condensing coils into the gas line. The gasoline comes out

of the gasoline condensing colls at about 100 degrees F. and flows to the receiving house (10). The combined gasoline

condensates from the knock-out box {?), reflux tower (2) and

condensing coils (9), la gauged in the receiving, house and flows

from there into the storage tanks (11). The water and residue is drained off from the knock* out box and reflux tower, and the reflux oil or unvaporlzed mineral oil from the reflux tower, knock-out box and. still, circulate back and is pumped by pumps (13), to the teat ex­ changer. Here it loses part of its heat to the absorbant, and it flows on to cooling colls (14), where it loses more heat, and flows back into the absorbing towers, and so complete® the cycle.

The mineral seal oil or absorption oil is a light amber colored oil of light gravity. It is used over and over again. There is some loss, possibly 5 percent* occasioned each cycle by leakage and some evaporation, but the loss is comparatively small.

The two mixing towers of absorbers are vertical cylindrical tower® about 30 feet high ate 8 or 7 feet in diameter, each containing about 13 baffle plates, through which the descending oil mixes with the ascending gas, forming the absorbant.

The compressor®, absorber towers ate pimp© are all housed in the same building, a® shown on the flow sheet.

The compressors are- a set of twin engines of Ooopexw

Bessemer type, (engine cylinder 16 by 30 inches\ sise of

Cylinder* § by 20 Inehesf 165 H.P.j ISO R.fMf,)♦ The ga® la taken in at 11 pound® ate compressed id 100#.

The oil ate water pumps are all made by the Worthington Company, The teller house contains 3 automatic tutelar

boll era, but only l boiler la now in use. It has a lopes water regulator. The capacity of the boiler is about lo3,000 cubic f oet per day. It is used to produce a team and hot water for the plant operation. The boiler houco also houses the light system which is a ICohler electric plant (1500 watt)# and run by dry gas. The remainder of the plant equipment, including

the heat exchanger, still, knock-out bob, reflux tower, gasoline condensing coils, and receiving house, have already

been discussed in the plant operation and are of the usual

type* BIHLXQOKAPHY

1. Max Bali, "One near Fort Collina,Colorado", A.A.P.G. Bull. Vol. 3, tlo.l, Jan.-Feb. 1934, pp.70-37.

¥ *. :uttUor,Gilluly and Lusk, "Geology and Oil and Gas Prospects of Northeastern Colorado? U.3.G.3. Bull,796-B, 1926.

3. N.W.Bass, "the Oil Possibilities of Western Kansas", Kansas Geol. 3urv. Bull• Ho* 11. 4* F,U. Van tuyl and Ben H. Barker, "Oil Possibilities in Eastern Colorado", Colo* School of ^ines Hag, Vol. 33, Ho.il, Oot-Hov. 1033. 5. J.A. Walds chmidt, "Characteristics of Older Cretaceous Formations of North Bast Colorado", A.A.P.O. Bull* Vol.17, No, 4, April 1?33, pp* 411-4: 1. 6. Charles H, Nankin Jr., "Study of Woll Sections in Northeast Colorado", A.A.F.G, Bull. Vol.17,No.4, April 1933, PP. 432. 7. Charles S. Laving ton, "Montana Group in Eastern Colorado", A.A.F.G. Bull. Vol.t?,No.4, April pp.3*7-410. c. Harry A. Aurand, "Present Development in Greaoewood. Area, Weld and Morgan Counties,Colorado", A.A.F.G. Bull, Vol.i?, No.4, April 1033, pp. 4S2-i;*»7, IV.t. Lee, "Continuity of some O n Bearing Sands of Colorado and Wyoming", U.3.G.S. Bull. 751, ir-ns, pp.

10. Junlud Henderson, "The Cret&ceoas Formations of North­ eastern Colorado", Colo. Geol. Durv. Bull. Ho. id, ifrrfO. 11. -toons, Cross,. Whitaker and SLdridge, "Geology of the Denver Basin", U.s.G.3. :iono. #?, 1396. 12. Robert W.Harrlson and Clifford R.Hom, "Report on Wellington Fort Collins Field, Colorado *

13. Lester Charles Uren, "Fetroloum Production Engineering" First Edit* 1024.

14. C.W, Hagee, "Handbook for Field Geologists", Third Ed. 1921, t$, "Structure of Typical American Oil Fields", A.A.F.G, Bymp. Vol. 2, 1CR3,

16. Walter A. Ver Wiebe, "Oil Fields in The United States" First m u . 1030. BIBLIOGRAPHY

Earnest Raymond Lilley, "The Geology of Petroleum and Natural Gas", ioj.2,

Robert Lesley Brown, "Valuation of Oil and Gas Lands", First Edit. 1984,

Frederic H. Lahee, "Field Geology”, Second Edit, 13j3,

Dorsey Hager, "Praotical Oil Geology", Fourth Edit* X'CDd* Dorsey Hager, "Oil Field Practice", First Edit. L92i.

G.H,Cox, 2,Ii.Dake and G. A. Hullenburg, "Field ilethods in Petroleum Geology", First Edit. 1331. F.M, Van Tuyl ana T.S. levering, "Physiographic Development of the Front Range, Colorado,” Sympos. of Abstracts of the Geological society of America, Dec.'2,1933# P. 7.

J. Harlan Johnson, "Geology of The Golden Area,Colorado", Colo, School of Mines Quarterly, Vol. #5, No, 3, JUly, i C 30 * Pp t &b"*is»9. TABLE U A GCTBRALI&1BD SECTION OF TM O O L O M B Q I T Z W W t * M A

Fo rmation Thioknes 0 Deaorlptioa

Quaternary 0 - 100* Gravel,sand and silt UNCONFORMITY ’ p#rtW<1 ~A *st Tertiarjj Eocene /Arlkaree 10-300* (Gravel , sand and 1 White River) clay) 5 unconformity Shale, sandstone Laramie £00-030* ahd coal Formation Sandstone and Foxhills 400=12000** . sandy shale Sandstone Shale with inier* Upper Pierre 5000- J '100 * bedded sandstone Cretaceous Shale Limestone and Mesozoic Niobrara •7)00-410* ' limy shale Li:aj atone Lark shale ^wifcii^ Benton 530-650* Interbedded sand­ * Shale i stone, limestone and bentonite

Dakota 170-473 Three sandstone Sandstone members with inteFbedded shale r !Comanche&n Morrison -00-3001 Variegated sari) ! Formation sandstone and limestone H JNCONPOR\lITY * Jurassic Sundance o-ioo* Massive sandstone Formation Red shale, and nn Trlassic or Lykino 400-80Q* sandstone with a Permian* Formation fee lime beds

Persian, Lyons 00— Cream colored , Sandstone sandstone Paleozoic Pennsylvanian Fountain 300-000* Variegated sand- Formation stono and UNCONFORMITY conglomerate Aroheozolo schist tad quart &i to 75. TABLE 2.

WELLS COMPLETED ^ DRILL I IB & ABANDONED BY COMPANIES & LEASES

COMPANIES LEASES .COMPLETED DRILLING ABANDONED

Union Oil Co. U.*S. Footer rs 0 0 of California « U.S. Bummer 1 0 0 n Buckeye - IT.P. 7 0 L » Mitchell . * 0 3 it Scott 5 '.) 1 «« Gault-PIatt 4 0 i Gault-Piatt-Puleston 1 0 0 n N.P. Stucheli •„> 0 0 *»■ N.P. BuOl)lOb Res. 1 0 I * * Dumont- Cook 1 0 0 »♦ Elder 1 0 0 it 0 ti Yoekey 1 0 Dkaent i» 0 0 tt Hess- I 0 1 it State 1 0 1 Thlmmig 1 0 i Continental Oil Fleming 1 0 0 Co. M Mitchell 1 0 1 If o CO 11 hr 0 ** If Elder 0 0

Roxana-Eeoughan- Buckeye -U.P. A 0 1 Hurst

Union Oil Go. Warren 1 V 1 of Colorado

YTyornl ng-1111 no i a Le Roy 1 0 1 Oil Co. - Great Northern Kitterman 1 0 I Oil Co. ^ n Howard 1 0 I Soverign Oil Co. Elder 1 0 1

TOTALS 41 0 13 76. TABLE 3.

WELLS COMPLETED, DRILLING it ABANDONED BY MONTHS.

1033 Completed Drilling Abandoned 1934 Compl, Drilling Aband#

Jan. 0 0 0 Jan. 0 0 0

Feb* 0 0 0 Feb. 0 i 0

Mar# 0 1 c Mar. 0 i 0

Apr. ) 1 0 Apr. vC 2 0

May. 0 1 0 May. mJ 2 0

June 0 1 0 Jun. 0 2 0

Jul. J 1 0 Jul. 1 2 0

Aug. 0 1 0 Aug. 0 1 0

Septi o 1 0 Sept. •o 0

Oct. 0 1 0 Oct. 0 3 0 > Nov. 1 1 Nov. 4 0 m Dec. 'V 0 Dec. 0 i 0

X925 Completed Drilling Abandoned 1 936 Coapl. Drilling Abai

Jan. 4 Jan. Wr*» 5 0 A, Feb. 0 Feb. v 0

Mar. o 4 0 am a r . %■ 8 0

Apr. 0 4 0 Apr. £: 8 0 o May. 4 J May. it1 9 0

Jun. Jw. 3 1 Jun. 3 7 0 o Jul. f>+ 4 1 J ul . 1 6 0

Aug. 0 3 0 Aug. 1 ? 1

Sept. p 4 0 Sept. 0 8 0

Oct. 1 4 0 Oct. 1 o 0 % Nov. 0 s*/ 0 Hov. k/ 0

Dec. 1 4 0 Dec. ? 0 7? TViTsTtt* %

WELLS COMPLETED, PRILLIN& AND ABANDONED BY MONTHS

192? Completed Drilling Abandoned 1926 Compl. Drilling Aband.

J £Ui • 0 3 0 Jan. 1 3 0

Feb. 1 4 0 Feb. 1 3 0

Mar. 1 3 0 Mar. 0 2 1

Apr. 1 2 0 Apr. 1 2 1

May. 0 1 0 May. 0 X 0

Jun. 1 1 0 Jun. 0 0

J ul • 0 0 0 Jul. 0 2 0

Aug. 0 *■> 0 Aug. 1 2 0 o 0 Sep b. 0 i,4 0 Sept. ■ 0 2 Oct. 0 O 0 Oct * 14* C\ 0

Nov. 0 0 Nov. 0 &o 1

Dec. 0 wx 0 Dec. i 0

1929 Completed Drilling Abandoned 1930 Compl. Drilling Aband.

Jan. • KJ 0 Jan. 0 1 0 Feb. 0 0 Feb. 0 l 0 <^ Mar. 1 0 Mar. 0 1 0

Apr. 0 1 Apr* o 1 o

May. 0 2 0 May. I 1 1 r> Jun. 1 t'J 1 Jun. o 0 0 Jul. 1 0 Jul • 0 0 1 Aug. 0 1 0

r> Sept. 0 1 \J Oct. 0 1 0

Nov. 0 1 0 Dec. 1 1 1 TABLE 3. 78.

WELLS rfrMPLBTRP, DRILLING AND ABANDONED BY MOHTHS

TOTALS BY YEARS

1923 1924 1925 1926 1927 1928 1929 1930

Completed 1 1 5 1 i w 4 t i . 4 1

Drilling 1 4 5 12 1 6 1

Abandoned 0 0 ** 1 0 3 3 2 TABLE 4.

BRIEF PRODUCT IOi! HISTORY OF SOME T O ^ m.l,s Qg FIELD

Bucke.ve No. 1 — It flowed from the time It was brought In, in 1PJ3, until Mar. 1927, through various slsed beans. Fro® Dec* 1927 until Feb. 1919, it flowed through a 5/id" bean. From FeB. 1029 until May 1920 it flowed intermittently and was shut down temporarily in May 1920. Sept. 1929 it was put on the pump and pumped until Aug. l?50, when it was shut down.

Buckeye No. 3 Brought in May 1026 and put on the pump in a

few days. It was pumped every third day and

produced a small amount of oil until April

when it was shut down.

goott No. t Brought in July ires* well flowed by heads

through *; 1/2" tubing until Oct. 31,19..3, when It was shot with V; quarts of r.itro; then

flowed through a 0 i / V casing through a 1 3/4** choke until June 1026. June 24-25 1925, tubing

and rods were pulled and a lead plug driven and plugged back fron 1-32C1 to 45121 • Shortly

after, pump rods were put in and well pumped until April 1928, when it was shut down.

Scott Ho* 2 — Brought in Nov. 12,1926. Nov. 30 it started

to flow and Dec* 5 it was deepened; Dec. 7 it

was shot with 40 quarts and started to flow

after it was shot. During 1927 it was swabbed

frequently and flowed until early in 1928 wher it was put on the pump. Seott No* 3 - Brought In Sept* 15,1928; It was shot with 40 quarts of nitro and after swabbing a short time was put on the pump*

Gaul t—Pia 11* Was completed Slay 20,1026; it flowed through a No. 1 1 3/1” bean cage until June 3* The size of the bean was gradually decreased to 1 1/4” on June 9f 1 i/o” on June 13, and 1/2” on Oct.7, The well' flowed until Dec.31,1'£6* Shortly after it was put on the pump*

Gaul t- ?ia 11— Brought in May 1996. -$*y 32 it was swabbed; June 6 Vo. ? It flowed through a 1 1/4” bean and it flowed through successively smaller beans of l”,3/i’' and 7/wf,” sizes until Jan. when it was put on the

pump and pumped until April i3.1:, when it was shut *io

G&uit-Pi&tt-- Brought in Deo. M,lr‘ C and flov.ad through the ITo. 3 casing until Dec.31; flowed through a i” Dean

until Jan. G 1027; through a 1/2” bean until June

14, and through a 5/"” bean until Aug. 13,1927,

after which it was pumped.

Mitchell 116.2- Brought in N o v 20,1926* It flowed until Mar.O

1S27. Gas lift was put in Oct. 1027, and it flowed by gas lift until April l?2£. May 1028 it was put on the pump*

Dumont-Gook-- Brought in Dec* 1025» flowed through 6 1/4” casing No.I and 1 1/4” choke,until June 1926;then put on pump* Poster No.l — Brought in Mar*29,1927, and flowed for several months with the production gradually decreasing# Aug. 1928 it was shot with 60 quarts of nitro, and

shortly after was put on the pump*

Fluiunor t!o .1— Brought in Mar. 192?. It flowed a short time and then a pump was put in and it flowed through the tubing part of the tiae ua.l was pumped part of the time until Nov.I.jO# At that tiae the tubing was

pulled and the well cleaned out, the pump rein­ stalled, and was pumped until Deo.1930, when it was shut down.

Yockey No.l — Brought in Oot.14,19:6, and began flowing under

a natural head and with occasional swabbing; a little later put on the pu-ip.

Bldor Ho.X — Brought in June 1926; flowed until Dec. 11)*J6, throu^.

a 3/4” bean. Swabbed Dec. 17,1'>26, then flowed a few days and put on pump the last of Dec. I X ’C*

Stuohell-Lake-^Beag^ht in May 18, iOSO; flowed through D i/2" No.l upset tubing until July 20,1986; then put on pump. 88. TABLE 5. (Note: Total Prod. 1923-24 from PROBUOTIOfT STATISTICS Buckeye # 1 = »555 bbls OIL, PRODUCTION BY YEARS — UNION OIL COMPANY 0? SALIPORNIA lvv • wj» Lease Wells 19-5 19-0 1927 1328 To 1929

Prod*wells x *4 4 5 Buckeye 5 %, 6 0 \ •30, 0 1 i *i 4 , .; i 0 .113, 030 . . . 34, 432 U.P. (On Lse.?) 1 1 !\r?r\ Av.Pd./woll M 30.070 4 fa t ^ — a100? Mitchell Prod, wells 1 1 1 0971 05,794 67,00? 173,672 (On Lee.3) tt Av.Pd./woll it tt tt 1 *4 b Ocoufc Prod, well s 7 4,0 :>3 0 0 ,6 :;:. 70,7 "0 43,605 1.05, 440 (On Lse.5) Av.Pd./well 30,30? ^ a fs * 14,535 Prod, wellb 1 A 1 ^ 1 . lXi no n L - 3, LJ 5 3 103,515 zii2 * J •• * w W «.y *V , *~ v<«-» «oi, *-.30 Cook (On Lse.i) Av.Pd./woll ,f »« It tf Prod, wells Poster — -- 16,61-4 00,071 54,688 U . S . (On Lse.i) Av.Pd./well tt 14.557 14. 1 Plummer Prod.wells -- «m» «m> mm i - • , ti .50 03,629 144,482 U.3. (On Lse.i) tt tt *y Prod.wells 3 4 Gaul t- w, ti o 4 £96,530 107,410 661,136 Piatt (On Lse.4} Av.Pd./well 70, •*63 ... vIm T?? 31, - 0 • - Prod.wells 1 1 1 M.P.Bubbles 5,060 I , 0 3 V v. » , V •»' •32,444 105,394 (On Lse.i) Av.Pd./well tf tl n 1 i D^nent Prod, wells-- — ~ — 16,177 10,761 04,538 (On Lse.) tt tt Av.Pd./well n, £ Prod.wells s "2...... St&o&ftll — - A 109,478 63,326 26,965 199,769

Av.Pd./well ’ 54,739 31,663 13,482 PROIXJ CTION 5TAPI3TICd

OIL PRODUCTION BY YLAR3 — CONTINENTAL OIL COMKBiy (1959)

Mo. or Lease Wells Production Buckeye Prod, wells U.P. 103,575 (On Lse.7) Av.Pd./Well 25.313 ^rod. wells 1 Mitchell 9,663 (On Lse.$) Av.Pd,/well tt Prod*wells 1 g Scott 20,227 (On Lse.5) Av.Pd./well 10.113 Prod, wells 1 Duoiont- 20,039 Cook (On Lse.i) Av.Pd./well tt n Prod.wells *•> Poster 17,160 U.S. (On Lse.5) Av.Pd./well 3,533. Prod- wells 1 Plummer 51,534 U.S. (On Lse.i) * Av.Pd. A/e H #rod.wella ■% Cault—' 131,623 Platt (On Lse.4) Av.Pd./well -•57 .. ?rbd*wells UJ Elder 115,008 (On Lae.5) Av.Pd./well 57 * 514 " Prod.*.veils 71 Stuchell l:;,D69 W.P. (On Lse.D) Ave.Pd./well 6,1-34 Prod.wells 1 G-ault- 6,756 riatt- (On Lee.I) Pulaston Av.Pd./well »t Prod, wells 1 Yockey 53,703 (On Lse.i) H Ave.Pd./weil Proi*wells I D ’ment 2,403 lOn'Lse.i) Av.Pd./well Tf Prod#wells I Fleming 4,310 . iQn Lse.i) well i t 84,

PRODUCTIOH STATISTICS OIL.QAS.ATO PROPPOTIOH BY XBARS — OOKTIMCHTiL Q X U 0 0 ,

No. or 1930 1931 Lease Wells Oil Gas Water Oil Gas Water j*; Buckeye Prod, wells 5 I 4 U.P. 77,434 750,636 109,947 | 47,880 330,306 10,827 (On Lse.7) ______Av.Pd./woIllS.49d 130.137 31.3391 U.970 -A,57q 4,7.07 Prod, wall 3 1 | 1 Mltcaall 10,422 323 38,222 | 6,013 1,213 48,483 {On Lae.3) ______Av.Pd./well____ ;______—"---- 1-, ______Is ] 2 Scott Prod.wells 9,024 13.324 3,116 5,137 3,3328,868 (On Lse.5) ______Av.Pd./well 4.313 0.912 4■057 3.593 . j.660 4.434 Prod.wells """ I I i Dumont- 10,253 23,772 51,170 | 3,o78 8,667 28,^78 Cook (On Lse*l) ______Av.Pd./well "______^______" 7 Prodweli's1™ 1 r~ :T 2 | a Poster 11,962 25,677 33,013 | 6,646 14,533 54,880 U.S. (On Lss.0) _____ AVaPdwell . S1900 j J.2..V35 lo>306 [ Oj,.Qf*3 i 7«*>59 17,440 Prod, wells ' n "’"l 111 r Pluaaor 6,6?i £,535 217,132 U.S. (On Lse«l) Av.Pd./well "______" " ' ' Prod.wells 3 ... "r ' '' I 3 Gault- 115,889 358,984 96,986 96,518 157,190 87,9** Piatt - (Etn L$e»4)' — ^ 429 I19T66I 323 3281 32.179" 52Y39rw;3?z Sider " 83,990 76,045 61*376 | 64^4 49,311 "'58 ,113* (On Lse.2) Av.Pd#/weli 41.995 36.022 30.688] 32.302 24, '29,17' *■roa.w.iiB■od.weili ~3 ~ T *5 stuch«ll 6,167 37,62 42,434 4,170 5.530 43,008 H.P. (On Lae.2) 3-^083 1,961 21.317 3,265 2.766 21, Prod, wells l 1 Gault- 12,005 5,661 74,410 I 5,354 3,426 80,3£5 Piatt- (On Lse.i) " ei.ee Prod.wells i .11 iockey 11,210 1,486 7,610 7,635 7,637 8,156 (On Lse.i) At . Pd.#/well Prod# wells D ’ment 4,528 2,225 J 2,784 ——— 370 (On Lse.i) ----- * Av.Pd./wlI " e Prod, wells i | % Fleming 18,228 469,824 175,056 14,471 36,365 73,24* (On Lse.i) I Av.Pd./well " " ■ i* * « L ii; kARY PRODUOTIOH STATISTICS PH., QAS.AMD WATER PRODUOTIOM BY X&ARS— GOUT INEMTAL OIL jJJ.

Ho .of 1932 1933 (To Sept* Lease Wells Oil Gas Water Oil Gaa Water Ksrsar:.: ^srsasasTssm&.'zm Buckeye Prod, well s 4 U.P. 31,036 151,026 25,368 (On Lae.7) 15,064 67,603 33,326 Av.Pd./well 7,771 37.981 6.342 3.766 16.001 8.081 ipro

(On Lse.3) tt Tt f» ______totXtbdttOl ______T 8oo tt Prod, well 3,116 663 4,788 1,602 224 8,767 (On Lse*5) Av.Pd./well____ "— Prod, wells Dumont- t*002 <*,638 38,404 4,636 4,363 £4,966 Oook (On Lse.i) i t n A ti «i . Av.Pd./well Prod. wells Foster 5,499 7,213 44,612 3,106 3,36? 36,799 _ U.S. (On Lse.2 ) ______AluZ&Jviik. & J M — 1.SS3 1.783 14,399 Prod, wells o Gault- 75,057 142,447 93,412 38,278 93,121 7 3 ,6 5 ^ Piatt (On Lse.4) ______Av.Pd./well 35.019 47.488 31.137 12,757 32,707 S7,_»$Z Prod.welia 3 Elder 59,400 44,933 63,675 33,231 27,919 44,03# (On Lee.2) Av.Pd./.all 30.745 S3.469 34.837 16.615 13,959 Qg,Qir Prod, wall a ' ' 2 Stuchell 2,047 1304 35,51.0 1072 255 25,816 IT.P. (On LBe.8) Av.Pd./well 1.473 832 17.753 336 127 12.008 rod, mil s i Gaul t- e,388 4,311 85,181 3,542 \fjf4 p S ^ € ^ 7 Platt- (On Lse.i) _ Pul.b ton Av.Pd./mil " n Prod* wells i Tookey 5,099 571 6,700 0,360 1,294 5,350 fOn Lse.i) n W , . > INI l l l t t M M M* H f l M M A ‘« * •» Prod# wells D iaent 8,096 -- 3,26c. 1,268 — 1,596 (On Lse.I) Av.Pd./wi «« Prod. |f 8 1 Fleming S T 14,800 39,353 74,193 9,592 35,073 46,039 (On Lae.l) Av.Pd./well w « n 86.

PRODUCTION STATXSTI03

HO. of Production to Sept.i. lg a Lease Wells o-as Wateer

Buckeye U.P. 7 559,271 1,308,522 186,468

Mitchell 3 £00,176 8,202 194,052

Scott 5 304,596 18,050 34,538

Dumont-Cook 1 525,737 46,066 110,313 o O cn Foster 8 99,000 * 141,304 U.S. >;• ' ) n Plummer 1 172,43? iuf p 9-/ 217,132 U.S.

Gault-Platt 4 1,218,902 750,742 351,021

N.P.Bubbles 1 7,733 -- --- Res.

Elder 2 610,704 198,213 227,428

N.P. Stuchell 2 220,704 11,351 146,668

Gault-Piatt- 1 97,031 17,358 839,971 Puleston

Yo ckey I 200,550 10,983 27,706

D'ment I 56,017 -- S, 459

Fleming 1 01,811 631,115 368,537

Totals 4,196,290 3,000,089 2,893,68?

Hotel total Oil Produetion Given* Gas and Water production from Janu 1*1030, only.

HO-tjgti Oil and Water Production given in Barrels. Gas Production given in Thousands of cubic feet, 8?.

WELL LOg

UNION O IL GO. OF CALIFORNIA

Wellington ?1 or (BUCKEYE .?i) Blev. 5470* 2270* S. & 376* E. of N.W. cor# seo. 31-10-68 T.D. 4205• Wellington Field, Larimer County, Colo. Comm. 3/20/1023

Comp. 1 1 /1 2 /2 3

Formation From To Form ation From To

Soft brown gumbo 0 3 C ray sh ale 1075 1095

White quick sand 8 2 0 (e a te r ) Or. sandy sh. 1095 1120 Coarse br. sand 20 30 Cray sh. U20 1248fmaking some water, cemented 1178* of B r. sh* 35- 12 l/2 M casing)

Coarse br. sh. 35 Uard I s . w ith s h e lls 124.0 1253 Soft yellow day 38 4 5 (show w ate r)co arse lim e y g r . ah. 1253 1350

Hard blue oh. 13 65 Hard shelly Is. 1352 1057 Fine s^ndy gr.sh. 05 170 •uiney gr. sh- 1357 1400

Fine gr. sh. 170 320 Cray sh. 1460 t ‘3?C Soft gr. 3h* 320 455 Gr.ah.& shells 1570 1780 Fine sandy c.h. 455 475 Sof t g r • sh* ( cr.vinrr ) 1720 12 -0

Cray 3h. 475 540 C ray sh- 1840 tOSCf 1 10” oasin g at 1230#) Coarse gr. 3’.ady sh.5 570 Limy gr. sh- 1050 2255 Sandy for’4* 570 535 , . S o ft g r.s h a le 2255 2400 Hard gray sh. 5?5 705 ( she?/ o f w atS r, (no o il or gas; e< ite d . ran 841* of 15 1 /3 ” . i Sandy gr# sh. 2400 2415 S o ft g ray sh# 705 765 Soft gr* sh* 2415 2440 Cray sh. 765 875 Sticky sandy sh. 2440 3530 Fine gr# sd. 375 96?(a little water a t 9 3 0 *, sm all show o f b la c k o i l a t 0 5 0 *. Ran 12 1 /2 " . Soft br. sandy sh.3530 8555 Oray sh. 967 1015 Oray ah. 2555 3568 Sandy gr* ah. 1015 1075 Coarse ftp. sh* 3568 3566 WELL LOQ ( c o n tin u e d ) UNION OIL CO* OF CALIFORNIA

WELLINGTON * 1 o r {BUCKETS ?l) Slav. 5470• 2270* S. A 876f E* of N.W. cor. sec. 31-10-68 T.B. 4295*

Wellington Field, Larimer County, Colo* Com* 3/20/83 Comp* 1 1 /1 2 /2 3

Formation From To Form ation From To—

Bark hard shells 3566 3574 Hard gr* sh.&shells 4225 4235 Hard gr.sh. 574 2600 Cray sh. 4235 4285

Sticky sandy gr*ah*2600 3030 Sand(^uddy) • 428b 4296 (82 If feet gaa at 4285J Hard gr* sh. 3030 3060 (s m a ll show o f o i l a t 4122% Sandy gr*ah- 3060 3220 Hole earing, 8 1/4" casing run 4231 % Fine gr.sh. 3220 3230

Sandy gr*sh< 3230 3260 Casing>ng Record Feet of Casing Dimensions Soft gr. ah. 3260 3340 (hole caving, ran 3320* of 8 1/4* casing) 90.. (plain shoe; top of Cray sh. 3340 3445 drive pipe driven into Hard gr. sh* A shells 3445 3570 blue ah* and cemented.) 641f ' 70./ 15 1/2* Limy gr. shale 3570 3730 (plain shoe* )

Sharp gr*sd*(Frontier) 3730 3733 U78* 50# 12 1/8* Sandy gr*sh* 3733 3775 (cemented with 25 sacks concrete brand cement Cr«sh* A shells 3775 3855 A 5 1/2 gal* Konset)

Coarse dark sh* 3855 3875 2554* 45# 10"

Soft dark gr*ah* 3875 4010 (hole caving) (Baker shee)

Bard gray shale 4010 4040(d rilling with/4231» Under reamer)! 36# 8 1 /4 * (plain shoe). Soft gr* sh. 4040 41£0( oaving) Shot Record Sofjt dark gray Sh. 4120 4165( small show of oil at 4066. No shots used* C ray sh* 4165 42<£5 UWIOH OIL 00. OF CALIFORNIA

BUCKKXE U.F* #2 Kiev. 5453*

1073• S. A 1071* W. o f N .B . c o r.. see. 31-10-68 T.D* 4313*

Wellington Field,, L a rim e r County, C o lo . Comm* 1 1 /1 2 /8 4

Comp* 1 0 /3 0 /8 6

Form ation From TO mHs F orm ation From To Gray gravel 0 17 Hard gr* sh. 1110 1153 Brown gravel 17 40(w a te r) Sandy gr. sh* 1153 1175 Coarse br* sand 40 45 Dark gr* shale 1175 1206 G r* sand 45 60 Fine gray shale 1208 1840 Gray .shale eo 63 Gray shale 1840 2115 Bard gray sand 63 78 Hard gray shale 2115 **500 G ray sh ale 7Q 880 G ritty gr*sh. 2500 2600 Bard gr* shale 280 555 G ray sh ale 2600 2635 G• 4 ritty shale 535 360 Hard gr*sandy sh.2635 8740 Bard gr.sh* 560 570 G ray sh ale 2740 8795 Gr. sandy sh. 570 62,5 ($ho# v/ato r)

G ray sand 623 632 Sandy gr.sh* 2705 2930 Sandy sh* 532 680 Hard shells 2930 2935

G ray sh a le 650 705 Gray sandy sh. 2935 3400 Hard gray shale 703 742 G r . s h . A s h e lls 3400 5410

G ray sh ale 742 895 Gr* sandy sh. 3410 3490 Sandy gr*sh. 895 953 ishow iron pyrites)

G ray sand 953 995 (continued)

W ater sand 905 1020

Bard gr* sh. 1020 1090

Sharp gray sh* 1090 1110 WELL LOQ

UNION OIL 00. 07 CALIFORNIA

BUCKETS U .P . #2 EL«v. 5433' 1273* 3. * 1371' W. of N.B. cor.see. 31-10-68 *.D. 4313* Wellington Field, Larimer County, Colo. Comm. 11/12/24 Comp. 1 0 /3 0 /2 3

fo rm a tio n from 12. Casing Record Light gray she 340C 3520 Feet of casing Dimensions Hard gray ah* 3520 3620 59 20** d ra y sh ale 3620 3680 700 15 1/2" fine gr* shale 3680 3700 1C12 12 l/2"(oeaented with 100 sacks oea.) Light gray shale 3700 3765 2394 10" Sand( Frontier) 3765 3770 3900 P. 1 /4 " d ra y l i n y she 3770 3865 4.^94 6 1 /4 " ( cemented fine gr.sh. 3865 • 3200 with 400 saek§ oca.) d ra y sh a le 3000 41^5 Shot Record Hard gr.sh. 4185 4211 » Mo shots used* Dark gr* sandy sh* 4211 'L.&OC show o f ir o n p y r ite s ) d ra y s h a le 4250 4290 Shale & bentonite4#.' it? 0 4303 Hard fine sand 4303 4313 (Blew in gas well, approx. 6 M.G.P.) (Huddy) • H i .. UHION OIL 00. OF CALIFORNIA

BUCKETS U .P . #3 El97. 5491*

1020* S. 4 210* S. Of N.W. OOr. 9*0. 31-10-68 T.D. 4538 ’ Wellington Field, Larimer County, Colo. Com. 12/17/23

Ooap. 4/16/26

Form ation F ro a M Fgyaa.tjgt Pisa la S u rfac e 3 23 Hard gray lime 3682 3894*

G ra v e l 33 29 G r* sd# ( F r o n tie r ) 3894 3900

Zellow sand 32* 46 Dark sandy sh* 3900 3940 Blue sandy sh* 16 80 Black sh* 3940 4410

G ray sand 80 135 Gray shale 4410 4469 B lue sh* 133 100 Fine gr*s&* (Mudd^J4469 455*(oil) Brown sh. 190 260 (aand contained water, plugged with cement , Gr# sandy ah* 360 275 U/17/26). Brown shale 3?5 635 Gr* sandy sh* 656 723(show of water) G ray s h a le 733 1020 Dark sandy sh* 1030 I040(little water)

Gray sand 1040 1082 °M&BS-S222& G ray sh* 1062 1150 Feet of oasln^ Dimensions

Sand 1150 1160 36 20" 725 16 i/a» Gr* sandy sh* 1160 1255 12S4 is 1/2'' (assented 2560 io " Slick shale 1255 1234 3606 8 1/4" 4451 • 6 l/4"(pull#a} G ray sh ale 1284 2510 4468 fi l/4"Cp*.fua 6 Joints of this pall Gray sandy sh* 2510 3200 5200 3475 G ray s h a le ffnr** Black shale 3475 3633(show Of O il) Bo shots used

Light shale 3638 3582 W u l i 9 f t OHXOH O IL 0 0 . OF CALIFORNIA BUCKETS U.P. «4 Kiev. 5456'

58?' E. A 858* H. Of S.W. oop.eeo. 31-10-88 T.D. 4581' Wellington Field, Larimer County, Colo. Comm. 1/7/86 Comp. 8 /8 6 /3 8

Formation From l a Form ation From to

Brown guiabo 0 14 Gray sandy form. 1142 1160

Gravel « quicksand 14 23 Gray_.ah^ ___ 1160 -4305

Y e llo w d a y 23 50 Gr* sandy sh. 1305 13 40

Gray sandy sh# 50 53 Gr.limy sh. 1340 1335

Hard b r* sh. 35 60 G r. sh ale 1635 2153

Blue gr*sandstone 00 120 Soft caving sh. 2J.50 2210

Hard gray ah. 120 170 G ray sh# 2210 2550 Sandy ah* 170 195 Gr* sandy sh. 2850 3355

Hard fine gr*sh. 133 340 Soft gr* sh. 3355 3476

Soft gr.eh. 540 570 Gr.sh. & sheila 3475 3486 570 Gray sandy sh. 390 Bark caving sh. 3435 ODO^J

Bard gr. sh* 590 605 Bight gray sh. 3530 3720 Gr# sandy ah. 605 650 Gray Hay sh. 3780 3830

G ray sand 650 630(show water)i>arfc ^ 3380 3920

Hard gr.sh* 680 870 Biay eh. * shells 3920 3950 940 S o ft sh. 870 Bight shelly Is* 3050 3290 950 Gr* sandy sh. 940 Hard shells 3990 4002 950 1006 G r.e h . Gray sd.(frontier)4002 4030 Soft gr.sd.(Hyg*> 1005 . 1082(little water)

Gr*sandy sh* 1080 1005 Bard gr*ah*4 shells 4030 4100

G ray s h a le 1095 1140 Soft ah** hard sheliseioo 4150 WELL LOG (continued) UNION O IL CO. OF CALIFORNIA

BUCKEYE U .P . H Kiev. 54569 537* S. A 653* N. of S.W. cor.sec. 31-10-63 T .D . 45819

'.Tollington Field, Larimer County, Colo. Comm, 1 /7 /2 6 Coop. 8/26/26

Fo ra n t Io n F ro i| To

S o ft d ark muddy sh. 4150 4230 Hard dark sh.* shells 4230 4200 Shale arid shells 4290 4576

Gray sand (.Muddy) 4576 4677(water * trace of o il)

Hard shell 4577 4579(water * verylittle oil) Hard sandstone 4673 4531.

Feet of casing Dimensions

38 20” (90/) ~ . - 608 15 l/S" C?V') pulled

1 2 5 6 .12 1/0" (50 ) cemented.

£373 10" ( 45;?) 3661 8 1/4" (36#) 4581 6 1/4" (£6#)

8 5 S O S S 2 E & Ho shots used. • ^ L L i C UNION O IL CO, OF CALIFORNIA

HUOKEYE U.?. #5 Kiev. J5414f

6 6 3 ‘Si* * ’8;) *W. of

V eil lag ton Field, Larimer County, Colo* C o m # 2 / 4 j/i •t«#7 Comp* C./l7/tw27

£ojgaaUon From To_ Casing Record

G ra v e l 0 66 ^ee t of Casino Pi men al one B lue shale 65 125 66 A**> / Sandy gray shale 125 135 B lu e sh ale 185 255 13 00 as l/3"Cceaant«d Gray shale 255 600 ^ 480 1 0 " Gray sandy sh. 600 1075 *011 3 1/4" 1075 1125 G ray sand 6 i / 4 " Gr,sandy sh# J125 .M 3 5 Shot Record G ray sand 1loo 1160 Shot w ith 30 q u a rts Sandy shale 1150 1 130

G ray sh a le a 130 1.J15

Gr.sandy ah* 1«*15 1325

G ray s h a le 1.-.25 1310 » Gray sandy shale 13.10 1425

G ray sh a le 1425 2605

Gr. sandy shale :eo5 o;';ao G ray sh ^le 3 *0 0 ;.,J83 G ray lim e 3085 # 5 *-12

Gray sand;Frontier 3043 335;* 395:' 4040 • Gray sandy sh* • G ray eh« 4040 4507 Gr.sd.(Muddy) 4 307 4.546 ( o i l ) usias_oa co. of taijrowriA

BUCKKYH U .B , ,fd BlOV. 5442 840*8. H 1943' .7. of H.S, COP. Soft. 31-10-88 T.D, -441R W oXllngton F I aid , L a rim e r County, C o lo. doom.

Comp. */u/x:!33

formation from Jo Saalnn Record Gravel 0 48 goat of caelaa D^a&lffia

Grey sandy shale 45 85 33' so" Hard gray sand 35 1-17 t71 15 i/: "(pulled) -Bard ^ray-shaitr 147-- 5S5 " 1 2 3 3 ...... 1- (cemented

Or. sandy shale 5^5 630 2313 13"

Oray shale 650, 646 S 5 4 1 a 1/ 4 " (oeaented * Oray sandy sh* 645 725 4 3 .; 2 C i/4 " Oray shale 7S5 "60 Shot Record Or# sandy sh. 660 tot .*> * shot with 30 quarts, Or. ad. (Hygiene)1010 100 > Oray shale 1080 1147 Or. erndy sh. 1147 1165 Oray shale 1163 £350 Or.sandy styaic v$ 5o 3310 Oray s h a le 5310. * 3760 O ray Itae 3 7 6 0 . 3075

O rf ad.(Frontier 3323 3335 Orey s h a le . 35*35 4371 Or.ad.(Muddy) 438t 4413 (oil) 'THT-Jj 1 0 0

UNION OIL CO. 0? CALIFORNIA

BUCKEYE U .F . <}? Kiev. 541? . • / 1560’N. of 3.B. cor. 3eo. 31-10-60 T.D. 45:-'3

Wellington Field, Larimer County, Colo. , Coosa, 1/3 i/i'-ss

Comp. f t / t V 14’” *'

Formation . F r o m t o d&sintf Reoord

G t ^ v ' 1 0 5 3 Feet of Casing D i m e n s i o n s

B l u e s h a l e 5 0 1 0 0 5 7 s o * < d r a y s a n d ______1 5 0 . V» .. . 6 0 0 . . ______l a l/-"-(-pulle

Oray sandy shale 1 5 0 1 5 0 1 2 6 0 is i/8"(oeffieat«4

B l u e s h a l e 1 - 0 6 1 0 3 3 5 3 1 0 * '

Gray s;%ndy ahale 0 1 0 7 3 0 2 6 1 4 a l/4*(cemented,

w i t h r . Q s a c k s ) d r a y s h a l e 7 5 x 1 1 0 3 4

4 4 7 5 6 1 / 4 ” G r a y s a n d 1 0 5 4 1 0 0 5

dr* e&ndy shale jU > - ’ 6 i 1 i' O . Shot Record

d r a y s h a l e U r , 5 1 1 9 0 S h o t w i t h 1 0 , 2 0 and 40 quarts.

- Or. sandy shale i i o o 1 2 0 5

dray shale 1X06 £ 0 1 0

dr* sandy shale £ - 1 0 L 2 0 O

d r a y s h a l e : I 2 0 0 2 3 5 0

dr*sandy shale 2 5 5 0 . £ 4 0 0

d r a y s h a l e 0 4 0 0 ; 5 0 J

dr*sandy shale . 5 0 0 4 > » w 5

d r a y s h a l e 3 4 * 5 3 6 5 0

d r a y l i m e 3 5 5 0 3 2 1 5

dr. sd* {Frontier) 3 9 1 5 3 9 3 5

d r * s h a l e 5 9 2 5 4 4 7 5

Band (Muddy) 4 ' 7 3 4 5 3 5 ( o i l ) a s u , XXXI

UNION OIL 00. 07 CALIFORNIA

SCOTT ,?X 51«T. 3403 * 1743’E. * 3or; • N. of 3.W. oop. eeo. <5-7-03 T.D. 8100* Welllngon Field, Earimer County,Colorado. Coia.a. 4 /1 0 /3 4 Comp. 7 /8 1 /8 3

F orm ation From 2st formation From 2&

Sancl and g ra v e l 0 29 Gray shale 4100 4424

S h e ll and sandy sh • 39 105 Sandy shale 4424 4439 d ra y 3and 1^5 132 White sd.(:

Sandy shale 105 517 Sandy shale 4560 4000 Hard sand 517 522 Gray sand 4600 4708 Sandy shale 5 S3 805 Gray sandy shale 4708 4790 B lu e sh ale 305 333 White sand 4790 4794 Sandy shale S33 1008 Red & g r. sandy sh* 47**4 4220 dray saniltHygiene) 1003 1074 Dark: sandy s h a le 432; 4311 Sandy shale 1074 1533 Red and gr. sandy sh* 4841 5090

Lime 1533 1540 Gray sand 5090 5 1 0 0 (w a te r Sandy shale 1540 1823 i ii ii nun m m Casino Record S h e ll 1833 1324 Sandy shale 1824 2 8 3 8 (show g a s )F e e t o f c a s in * Dimensions

Oray shale 8383 3235 29 * - 2 ”(stovepipe (drilled with Rotary to 3290') 1354' 15 1/8" Blue shale 3305 3300(ahow gas) 8758* 10”( cemented Blue and gr.shale 3300 3305 3432* 2 1 /4 " " Line 3395 3925 Gray sand(Frontier)3925 3040 Shot Record

Light sh.A sheila 3040 4000 Shot w ith 12 q u a rts .

Dark shale 4090 4190 '.TELL LOO

ONION OIL CO. OF CALIFORNIA SCOTT !‘2 EL«y. 5377' 966’ W. & 650* N. of S.E. cor.eec. 6-9-6U T.D. 4456* Wellingion Field, Larimer County, Colo. Comm. 7/30/1926 Comp. n/S/1920

Formation From I»-3 Jo Casing Record Gravel 0 80 Feet of Casing Dimensions Blue shale 00 115 83 20” Gray sand £15 160 800 15 1/211 (pulled Blue shale 160 400 1270 12 i/i,” (cement Gr. shale 400 075 2435 10” Sandy gr«sh. 675 1020 3650 8 1/4” Sand (Hygiene) 1020 105o(water sand) , „ / *» 44o* 6 l/4 Shale 1055 1075

Sand 1075 1105 Shot Record Shale 1105 1130 Shot with 40 quarts of nitre. Sandy shale 1130 1200

Gray shale 1200 2585

Gray sandy sh* £535 3295

Gray sh* 5205 3600

Gray limy sh* 5600 3800

Gray lime 3800 3875 Sand (Frontier) 3875 3900

Black shale 3900 4432

Gray sand (Muddy) 4432 4456 (Oil) WELL LOG UHION OIL 00, OF CALIFORNIA

SCOTT #3 Elev. 5391*

2350* W. & 675 * H. of S.S. cor. Bee. 6-9-68 T.D. 4345*

Wellington Field, ^ariaer County, Colo. Comm. 6/24/28 Comp. 10/9/28

Formation from To Formation From To

Soil 0 3 Dark sandy shale 3425 3525

Oray sand 3 no Oray shale 3525 3675 Xellow sand muck M t-> 47 Light gr. lime 3675 3735

Oray sandy shale 47 72 Or. sand(Frontier 3735 3750

Sand 73 76 Oray shale 3750 4250

Oray shale 76 535 Oray sandy sh. 4250 4276

Oray sandy sh. 585 600 Gr. henton!te 4276 4290

Oray sand 6pp 305 Oray sand(Iuuday) 4290 43 45 (Oil) Oray 3hale 605 P12 Oray sd.(Hygiene) 012 943 CaslnK Record Oray shale 043 960 Feet of Casino Dimensions Oray sand 960 974 87 20tt Oray sandy shale 074 1000 815 15 Oray shale 1000 1210 1/2 w (pulled 1150 12 1/2 w (cement Oray sandy :*hale 1610 1290 2700 10N Oray shale 1290 2330 4290 8 i/4" Dark gray shale 2230 2 105

Oray sandy shale 2405 3055 Shot Record CM o to 3290 o Oray shale 3055 Shot with 13, % and 40 Dark gray shale 3290 3425 quarts of nitro. WELL LOG

CONTINENTAL OIL COMPANY

SCOTT H Elev. 5300* 193?fN# # 1319* W# of the S*E# oor# eeo.6-9-68 T.D# 4410*

Wellington Field, Larimer County, Colorado# Comm# 7/23/1329 COmp# 12/13/1929

Formation fJKUft.. To Casing Record

Gravel 0 65 Fee iaslng Dimensions Sandstone 65 105 02 90/ d o * (plain Shale 105 575 790 70# 15 1/2" Sand (Hygiene) 975 1060 (stater) 1205 45/ 12 1/2** (plain Shale 1060 2450 2192 45/ 10*(10 thd#Nat Sandy shale 2450 3845 (Cemented with 41 sacks) Dark gray shale 3245 3550 2794 36/ 8 l/4* (DBX) Lime sh# shells 3550 3745 4375 ‘6 v 6 l/4M (DBX) Hard gray lime 3745 . 3828 Hard sand(Frontier) 5328 3345 Shot Record Shale 3845 4302 Ho rdcord Sh# <1 bentonite 4302 4316

Gr# shale 431C 4366 Hard sand 4366 4367 (little

Black shale 4307 4369 3h. & sandy sh# 4369 4371

Sand (Muddy) 4371 441o(show of CONTINENTAL OIL COMPAKT SCOTT #5 Eler. 34101

N.E. 1/4 of -£*W* 1/4, amotion 6-9-68 T.D* 4315# Wellington Field, Larimer County, Colo* Com;* Comp.

Formation !?B To Oravel 0 45 Oray shale 45 930(water)

Sand (Hygiene) 920 935 (water)

Oray shale 935 3240

Oray sandy shale ^2 40 3220

Oray shale 3230 3413 (show gas at 3403;oil 25 bbls*)

Oray limey shale 3415 3510

Oray lime 3510 3750

Sand(Frontier) , 3750 3770 (slight sho* of oil)

Oray sandy shale 3770 • 3795 Oray shale 3795 4300 Sand (Muddy) 4300 4315 (oil.and water)

Casing Record

Feet of Casing Dimensions

35 20” 788 15 1/2" (pulled) 1162 12 l/2w( cementedwith 125 sacks cement)* 2310 10" 3456 8 1/4” (cemented with wsacks cement) • 4291 6 1/4" w k j k aa W l O X OIL CO. OF CALIFORNIA MITCHELL #1 Kiev. 540* * 8906 • E* A 37351 N. of S.W. cor. 800* 6-9-68 f*D* 4216 f Wellington Field, Larimer County, Colo. Comm* 8/19/84 Comp. 7 /1 9 /8 4

Form atio n From To Form ation From ®SL*» C ra v e l o 10 Caving gr.sh* I8 6 0 1785

B r. gumbo 10 14 Hard gr* sh* .1785 1930 Br# sandstone 14 37 Limy gr*sh* 1930 *140 (hole oavlng) Sandy br* shale 37 46 Sandy gr.sh* 8140 8210 BlulSh gr* sh* 45 60 O r. ah* 8210 2340 Sandy gr*ah* 60 170 Sandy gr««*h* 234C 2960 C ray sh ale 170 540 C ray sh* 2960 2995 Sandy gr* ah. 540 5 6 0 (show w a te r) Sandy gr.sh* 2995 3040 Fine gr*sh* 560 810 B lue sh ale 3040 3140 Sandy gr. sh. 810 845 Soft br»sh* 3140 3255 Cray sandstone 845 930(water) (hole caving) (H y g ien e ) Fine gr*sh« 3 *5 5 3335 Cr« sandy sh. 930 945 Bark sh* 3335 3370 O r*s h a le 945 970(show water) O r* sh a le 3370 3415 Fine gr«sh« 970 1005 # Light gr«sh« 3415 3600 Soft sandy fox42 1005 10S5(little water) Liny gr*sh* 3600 3640 C ray sh* 1085 1070 Hard shelly Is* 3640 3660 8andy gr.sh, 1070 1095 C r « ad* (Frontier}3660 3690 C ray s h a le 1095 1808 (small show o f oil)

Sard s h e ll 1308 1805 Bark gr* ah# 3690 3960

Limy gr*sh* (caving) 1805 1430 Soft dark sh* 3960 4106 (oaring) Soft gr* A * (caving) 1430 1660 (continued) TTELr, T,nn-

UNION OIL CO. 05* C/XIPOHNIA

MITCHELL .?! Kiev. 5405* 2006* S. & 37351 N. of S.W. cor. see. 6-9-68 T.D. 42161 Ytellington Field, Larimer County, Colo. Coma. L/19/84 Comp* 7/XS/34

Formation From 2 a Oray 3h. 4105 4135 Hard gr.sh. 4135 4171 (show of gas) Sandy i;h. '* 8and 4171 41.75 It w »

T ig h t gray -and 4175 m e Oas sand (MuddyJ 4216 4215 (Came in a large gasser, July 19, 1924, Blew 4200' of water out of hole). {Caught fire fro.i static electricity mile trying to cap, 7/23/i024.)

Casing Record

Feet of Casing Dimensions

37 ;0"*90.-' D.B.X. plain shoe drive pipe)* cemented with M each of cement* -

lioi 12 l/2M (&o# D.B.X., plain ahoe) cemented with 50 sacks of oenent 26 f gal. of Xonset. 32031 10* (46# D.B.X., Baker shoe), set on elanps).

4134* 8 1/4* (D.B.X.,Baker shoe), (frozen).

59 f 6 1/4" (26/, plain shoe, liner) (adapter on top, Bottom set at 4195*)•

Shot Record — No shots used. x h u a h UNION O IL 0 0 , OF CALIFORNIA

MITCHELL #2 Blew* 5407* 963* W. & 633* S. of N,B, cor, sec. 6-9*68 T.D. 4472*

Wellington Field, Larimer County, Colo, Comm, e /6 /1 9 2 6 • • Comp, 1 1 /2 3 /1 0 2 6

F o rm atio n Fp*m To Casing Keoopa O ra v e l • w 65 Feet of Casing Dimensions. B lu e sh a le 65 100 67 20* Oray sand 103 165 300 15 l/2 B (pulled O ray sh a le 165 670 1275 12 t / a B( cemented Or. sandy shale 670 1040 2435 10* 0r#sd*(Hygiene) 1040 1130 (show o f w a te r)

O ray sh ale 1130 25 H5 3600 8 1 /4 * O ray sandy sh a le 25*15 3300 4455 6 1 /4 " O ray s h a le 3300 3585 Record Light gr# sh. 3585 3850 phot

Or.sd, & lime 3830 3905 No shots used Oray sand(Frontier) 3205 3220

O ray s h a le 3920 4455 Or,sand (Muddy) 4455 4472 (o il and gas) CONTINENTAL O IL OOHPANT MITCHELL* #3 K ie v , 5399

1909* S* & 1212* W, Of N«E, oor* Sec, 6*9*68 T*D, 4410* Wellington Field, Larimer County, Colo, Com, Comp,

Formation From Casing Record Oravel 0 loo Feet of Casing Dimensions

Oray sandy shale too 100 80 20 * Oray shale 120 275 800 15 l/£" Oray sandy shale 975 235 1233 12 1/2:“(cemented with 125 sacks) Oray saad(Hygiene) 985 1030 (little water)

Oray shale 1030 1033 2435 10“

Oray sand 1038 1072 3600 3 1/4” Oray shale 1072 3555 4362 6 l/4M. Light gray liiae 3535 3370 Shot Record Sh,with iiae shells 3370 3630 No re co rd Hard gray lime 3600 3795 Hard shite il.ue 3705 3813

Or* sd* (Frontier) 3810 3832

Limey shale 3832 4000 Dark gray shale 1000 4340

Blaok shale 4340 4362

Sand(Kuddy) 4362 4410 (o il a water) WELL LOG

UNION OIL CO. OF CALIFORNIA GAULT-PIATT #1 KL ev. 540 I V 2350* E. & 432' S. of N.?.1. cop. sac. 7-9-63 T.D, 4437*

Wellington Field, Larimer County, Colo. Comm. 1 /1 5 /1 9 2 6

Comp, 5/29/1226

Formation From To Casing Record Gravel Feet of easing Dimensions Sand 21 50 60 20” Soft blue shale 60 9Q 900 15 1/2” 3oft gray sand 00 120 12 50 1° l/o**(cement Hard blue 3d, shell 120 !:;? 2370 10” Soft gray shale 127 228 3 570 ft 1 /4 " Blue sandy shale 223 250 A A V\ /4 ° Blue shale 150 992

Or# sand (Hygiene) 193 1 0 0 ' water) Shot Record

Oray shale 1000 1143 ho siots used

Oray sandy shale - 1142 1020

Oray shale 1230 3305

White lias 3805 5375 Sand (Frontier) 3875 3890

Oray shale 3890 4260

Dark gray shale 4340

Light gr. sandy sh. 43 40 4400

Sand (Muddy) 4 4 0 0 4422 (oil)

Sand & bentonite 4422 4424 "

Sand 4424 443/ ” W8LL LOft

TJNXON OIL CO. OP CALIFORNIA

GAULT-PIAT Elev. 53311

SOI?* N. & 3052* .7. of &.S. cor.sec. 7-9-03 f4D. 44331

Wellington Field, Larimer County, Colo. Comm. 8/21/25 Comp. 6/7/26

Formation From To Formation From To o o Cellar 20 Cray shale 3C56 38 >0(snow

:* of oil w>t 3 669, gas at 5663, Crave! *••4 and water).

Sand 24 49 Cr.3h.% lime ahells 3800 3735 Yellow clay 4r 50 Sand(Frontier) 3785 3995 o9 70 Cray sand Cray sandy sli. 3JP5 3930 7> 0 Cray shale Cray ..hale 3 ^ 0 *307 Dark shale 00 105 ftr.sh.A shall s 1387 — KV. Cray shale 105 114 SaadOYuddyJ 4408 4483(oil) Cray sand 114 175 175 133 Cr.sandy shale Casing. Record Dark gr*sh. 183 283 # Feet of casino Dimensions Sandy gr.sh. 283 305 87 80" Cray shale 305 600 790 15 1/2”(pulled) Sandy gr«sh. 600 895 1284 12 1/3 w(cemented Cray sh. 895 990 2370 10" Sandy gr.sh. 990 1034 3740 8 l/4n( cemented) Cr*sd.(Hygiene) 1034 1120 4418 6 1/4" Cray sandy sh. 1120 1170

Cray sand 1170 1187 Shot Record

Cray sandy sh. 1187 1267 No shots used.

Cray shale 1267 2710

Cray sandy sh. 2710 3255( show Of O U ) TOJ,

UNION O IL CO. OP CALIFORNIA

OAULT-PIATT fiS Kiev. 5380*'

8015* 7T. A 3017* 3. of N.B. oor.aoo. 7-0-68 T.D. 4408’

Wellington Field, Larimer County, Colo. Comm. 9/. 2/26 Coup. i.2/2 *//2 C

Form ation From 2a Casing Record Sand 0 60 Feet of Casing Dimensions

Blue sandy sh. 60 85 85’ *0" S hale 85 95 770 15 1/2** (pulled

G ray sand $5 163 1245 12 1 / 2 n( cemented

Dark gr* eh* 163 470 2015 10" O ray sh ale 470 695 3530 8 1 /4 *

Or* sandy lime 69 5 704 4390 6 1 /4 * O r. sh a le 704 995

Gr.sd. (Hygiene) 9 9 6 1045 Shot Record

O ray sh a le 1045 1055 Wo shots used. Oray sand 1055 1087

O ray s h a le 1087 2640 Or. sandy sh. 2640 3650

White shale 3650 3320 W hite l i n e 38130 3870

Or* sd. (Frontier) 3870 3880

Or.sh. & shells 3880 4397

Band (Muddy) 4307 4402 ( O il ) w & - . m CONTINENTAL OIL COMPANX GAULT-PIATT H 321 ey. 53091 673# S. & 2003 * of H.E. cor. sea. 7-0-60 T.D . 4372* Wellington Field, Larimer County, Colo. CoaiB. 9/10/1928 Comp. 13/30/1928

Form ation Z E 2E . To Casing Record O ray sh a le 0 35 Feet of Casing Dimensions Oray sandy sh. 35 100 105 20* O ray sh a le 100 970 655 15 1/9*(p u lle d Oray sd* (Hygiene) 970 1060 1200 13 3/3*(cement

O ray sh a le 1060 2560 * o 2380 H Oray sandy sh* 2560 3160 4337 8 1/4" O ray s h a le 3160 3520

O ray lim e 3530 3340 Shot Record

Oray sand( Frontier) 3340 3347 No shots used. O ray s h a le 3347 4315 Oray bentonite 4515 4320 O ray sh a le 4320 4360 Oray sand (Muddy) 4360 4372 ( O U ) OHIOH OIL CO. OF CALIFORNIA N.P. STUCHELL LAKE r?i Kiev. 3366* •60S' W. <% 6 j2* N. Of S.E. oor. sec. ?j£0-68 T.D. 4643' Wellinston Field, Larimer County, Colo. Comm. 3/3/1936 Comp. 6/11/36

Po ra a tio n P ro a To Form ation From * $ U C e lla r 0 21 Bark shale 3913 4040

Brown sand 31 73 (w a te r) Lim e s h e ll 1040 4051

B ark sh ale 73 300 Lime and shale. *051 4104 L ig h t sand *01 Cr.sd.(Frontier)4104 4135

Light shale *.)! 0 Cray sh ale 4135 4160 Dark sh ale 330 070 Bark sh ale 4 io J 457 c

L ig h t sh ile 370 L i vht shell 4aO/ 3 457V L ig h t sand C 00 346(little water)

Light shale* 54© 300 .•hits oezitouite 4077 4otw D ark sh ale 560 73:,(little w ater)

Hard hr. shell 7/VS ?*»0 Hard dark shale 4i>w-> 4640 Light sandy shale 703 £-‘? Cray Su.nd(.,iuddy) 4C40 4642 G ray sh ale 800 i.133 iPH)

Cray sandy shale 1133 X215 (Hygiene) CafelngRecord 1013 1060 W hite sand F e e tof Casino Dimensions 1360 1450 C ray sh ale 00 BO" 1450 .1460 Cray sandy shale <300 15 i/s"(pulled 1460 2583 Brown shale 1435 IB l/2"(oeaenlEV 3535 37: o Br*sandy shale 2430 10" 33 30 B ark sh a le 3700 3710-' 3 1/4" Light sandy oh. 3S50 3 15 4040 6 1/4" 4606 2 1/2" (tubing Shot Record -Bo shots UHIOH OIL CO. OF CALIFORNIA

U.F. STUCHELL ,f0 SLev. 5373*

848* W. & 3334* S* of N#E* cor. sec* 7«*C— 08 T*D* 4503*

Wellington Field, Larimer County, Colo. Comm* 6/23/1936

Comp. 1 1 /2 9 /1 9 2 6

v & m a & s s From To o&Jim Record Brown sand 0 40 F e e tM easing Dlagsslogs C ray sand 40 75 30 30"

B lue shale <*♦f <>r* 110 800 15 1/2" (pulled) B ark g r . shale n o 125 13S5 U 1/2" (cemented Oray sandy sh* i2b 190 2405 10" O ray shale I'C noft 36: 5 8 i/4"

Oray candy shale 225 300 437^ 6 1/4" O ray sh ale 300 1135 Shot RocorCf Oray sand(Hygiene ) 1135 U05( water) Shot with 30 and 40 q u a rts . O ray chalo 1135 1010 O ray sand 1213 1035 O ray sh ale 1235 2800

Or*sandy sh* 2800 3130

O ray sh a le 3130 3640

Dark gr* sh. 3640 3670

Light gr.sh. 3670 3855

Oray lime shells 3355 4032 Oray sand(Frontier)4332 4043

Light gr* shale 4045 4010 Dark shale 4010 4570 Oray sand (Muddy) 4570 45^3 ( o i l ) UNION O IL 0 0 . 07 CALIFORNIA

U .S . PLUMMER !fl 31«V. 5 (4 9 ' 841’ B. .% 1943’ W. of S.E. eor. aeo. 3 0 -1 0 -6 8 T.D. 4368’

Wellington Field, L&rimer County, Colo. Coma, o/lfl/as

Comp. 3/iJS /av

[form ation From Sa Form ation Froia To

S o il 0 5 Baric gr«sh. 5430 3610 t r a v e l 5 41 (little water) Jjlsht &P. ah, , 3610 3w50

Hard gray aand 4 ; 55 Gray sh ale 3050 5860 Oray sandy sh. 53 125 3 h lte lim e 3600 3 3 *0

G ray sand 3tone 125 131 dr.sd.(Frontier 3920 3940

dray sandy ah. 131 164 Bl;j cfc shale 3040 40 OC

Hard sandstone 104 0 W* \ ** Br.gh*& lim e 1000 4055 Sandy gray shale 230 248 Gray sh. 4055 1468 Hard b lu e 3hale 24 S 270 Gr. aand(Hygicno 4463 1533 d ra y sh ale 270 284 Gray shale 4533 4502 (o il and water) Shale 234 305 Shot Record -no shots* Sandy br* shale 305 50G Casing Record d ra y sh a le 506 740 o f caein g Dimensions Sandy gray shale 740 775 SftSfe. 20 24" B lu e sh a le 775 790 238 00" d ra y lim e 700 803 . 806 15 1/2"(pulled d ra y sh a le 303 1075 «4 i § £ 1 1325 12 1/2"( cemented 1075 11?0(water) 3450 10" d ra y sh a le 1170 1290 3660 8 1 /4 " ( cemented Hard sand 1200 1300 4168 6 1 /4 " dray sandy sh* 1300 3430 4479 4 3/4“(cemented) WELL LOG

UNION O IL CO* OF CALIFORNIA

YOCICEX 111 E le v , 5362 *

Canter of -IfrB. 1/4 of H*E. 1/4 of sec. 7-9-68 T.D. 4 5 3 1 1

W ellington Fiel d, Larimer County, < Colo. Comm. 6 /1 1 /1 9 2 6

Comp. 1 0 /5 /1 9 2 6

F o rm a tio n From To Casing Record

Sandy c la y 0 45 F e e t o f C a s in g D im e n s io n s

G ra y s h a le 45 85 67 2 0 ” G ra y sand 65 105 300 15 1/2” (pulled

G ra y s h a le 105 1120 1370 12 i/2”(cement

Sand (Hygiene) 1X20 1200 2440 10rl

•; o Sandy shale X tit wv 1200 3760 8 1 / 4 ” Sand 12 30 1290 4515 6 1 /4 ” G ra y s h a le 1390 378 5

Gr. sandy sh. 1 lim e 3 72 5 3 ^7 5 Shot Record

Sand (Frontier) 3075 4105 11 c\r* No s h o ts vi iw*a VNfc* Dark gr* sh. 4005 4330

G ra y s h , 40 00 4515

Sand (Tffuddy) 4515 4531 ( o i l ) UNION O il. GO. OF CALIFOHNIA U .8 . POATSR n. El07. 3460* ?30* S.' <% of $.E. Cor. 8* 0 .3 0 -1 0 -6 ;* T .D . 1 4 3 0 ’ WWllngton Fiold, Lari;a»r County, Colo. Coma. 3 /S C /lt* 3 Oaap. 4/i?/i n.-j? ffenaatton . From. 22 casing, Sell mid gruvsl o 7 Qt Casing immaXon*

G ra v e l 7 *2. 21 24"

S o ft sandy ..sh ale . _ j3S__ 54 . jL&? 20*^_ _ ,_ 3andy shale 04 46 716 15 i/s^fpulie

Soft Coarse sand 46 65 (eater) 1243 ta i/x"(#mu Bard gray sand 56 77 3360 to"" *

Dark sandy shale 77 33 3530 C 1/4"

Bard gray sand 130 (water) 437S 6 1/4 .

Blueshale 159 51* Mhot Rooord

Grey shea© . 314 1013 Shot w ith C, 1J,3C,£,0 coMl G r a y s a n d 1 0 1 C 1086(w a te r). 40 q u a r t* . Gray sandy shale 1 0 . 5 3500

Hard gr. limy shale 5500 3 C3~ ‘

Grey sand . 5 3 3 2 - 3860

Dark sandy shale * 3000 3330.

Dark s h a l e 3 3 3 9 4373

Band (Buddy) 437a 44Sar (S U ) UNION o n . CO. OF CALIFORNIA u.s. RosTan #» si«*. &i?o l«»i' lU A .as'• tf. Of 3.S. cor. 3eo. 30-lQ-C«i. T.D.' 4530

W«llln«ton Meld. Larimer County, Colo* C o m * 1 Comp« i/i i/ '• formation Front fo Caainp: Record

¥#119* aand 0 ?? Feet of Casing 'Plaenslona Blue sand ?? 135 61 so* Blue shale 135 -160 285 15 l/^tputt Blue shale *Ovi aft _ --S30T...... 1340 13 3/fc*(Ckwu Klray sand .*30 333 <*139 1 0 ’’ Blue shale aio «86 3630 : 1/4* (Ceau Gray Band aio -.05 4430 S l/' , Gray shale c>35 1115

Bray »and 1a 15 U60L No shots used* Bray slmle ,1160 3560 H Light gr* 11..ie C.-660 3 6 5

Frontier *^c;& 3U)3 30055

Bray shale 3 W 4450 ' Bend 4400 4330 (oil) MSI, LOO mttoK oil oo. or California DUMONT-OOOK /fl Bier. 8370'

2045* W. <5b 573# N. of* S*E* oor.seo *7«*9~68 T.D* ^4467# Wellington Field, Larimer County, Colo* Conun* 6 / l / l 925 (knap* 1 2 /1 9 2 6 ♦

Form atio n From F orm ation From 2 a C e lla r 0 23 • Broun shale 2930 2940 Sard sand 25 30 Hard brown sh* 2940 2990 Hard brown sd* 30 50 C ray sh* 2990 3060 Hard yellow ad* 30 60 B ark sh* 3060 3120 Hard gray sand , 60 6 l ( w a te r) C ray sh* 3120 3375 Fine gray sand 55 80 Brown sh. 3375 3530 H ard gray sand 30 35 B ark sh* 3530 3560 C ray sandy sh* 85 85 C ray sh* 3560 3575 B lu e sh ale 95 135 B ark ah* 3575 36^5 C ray sand 135 205 Brown sh* 36.^5 3810 Blue shale 205 5*>0 n h lte sh* 3810 3840 Hard blue eh* 500 350 Lim e St white sh* 3840 3885(show Soft blue ah* 850 990 o f g as) Cray sandy sh* 090 1010 Fine gray sand 3885 391C (N io b ra ra ) C ray sh a le 1010 1060 B lac k sh* 3912 3947 Cray sand(Hyg*) 1060 1150(water) Soft dark sh* ' 3947 4030 B lu e sh* 1150 1160 C ray sh* 4030 4000 Sandy blue sh. 1160 1165 S o ft sh* St bentonite 40904112 B lu e sh a le 1165 2135 B a rk sh* St s h e lls 4112 4160 C ray s h a le 2X33 2425 Brown sh* 4160 4300 Cray sandy sh* 2435 2000 Blaok shale 4300 4437 C ray si}* 2600 2930 Sand (Muddy) 4437 4 4 6 7 (0 1 1 ) wsr^ t.qa (continued) UNION OIL CO* OF CALIFORNIA

DUTIONT-COOK U }&ev. 5370*

2045* T. * 6 7 2 1 N. Of S.fi* oor. see. 7 - 0 - 6 3 T .D . 4467*

Wellington Field, Larimer County, Colo. CoiB&u 6 / i / 1152 5 Comp. 1 2 /l w2 5

Carina Record Feet of casing Dlmenalona s

76 00# O

350 70? 15 1/3"(pulled) 1310 50.: 12 i/2"( oemented

0130 •15. ‘ to" 3042 36# 3 1/4" ( cemented) 1-.H7 36,- 6 1 /4 ”

Shot Record No shots used IKLL LOS

UNION OIL CO. OP CALIFORNIA

B*ment !?\ ELev. 5369* 8.Q5* W. & 677* S. of N.E. cor. sec. 7-9-08 T.D* 4598'

Wellington Field, Larimer County, Colo. Comm. 19/21/1926 Comp. Mar. 23/1927

Formation From To Casing Record Gravel 0 45 Feet of casing Dimensions Sand 45 75 52 20*’ G ra y s h a le 75 150 220 15 1 /2 ” (pulled Sandy s h a le 150 205 1340 12 1 / 2 ” (cement Gray s h a le 205 1090 2352 1 0” Sand (Hygiene) 1090 1165 3700 3 1/4” Gray s h a le 1105 3965 4540 a i/4” Gr.sandy sh.{Frontier 3903 3 9 wO

Light g r . s h . 5980 4532 3hot Record

Gray sand (Muddy) 4 OO Ac 4 3 o ■ \ o i j .) Lho ti w ith 30 quarts

. Bentonite 4553 4555 Ox xxx Ci ru .

G ra y sand (M uddy) •1535 4596 •,sll r,oa UNION OIL CO. OF CALIFORNIA GAUI.iT-PIATT-PULKSTOI! ,'l Kiev. 537U’

2681*3. 26»5* W. of U.K. cor, sec. 7-9-68 T.D. 4463*

¥/ellington Field, Larimer County, Colo, Coma* 12/17/27

Corap. 4/23/28

Formation From Fo rma tic n F roia To

Cellar 0 15 Gray limey sh* 3600 3603

Brown sand 15 40 Ctr. sd. (Frontier 3893 0020

Gray sand 1-0 80 Dark gray sh. 3320 4435

Gray shale 80 1 18 Cr ray oc.rr.ly sn# 4 io 0 vlod

Gray sand 113 118 Gray sand(Muddy) 4438 4453(oil) Gray sandy sh. US 135

Light gr* sand 185 158 Casing Record

Dark gr.shale XGO 270 Feot of easing Dimensions

Brown shale 355 1•i. - • 4W \J

Gray shale 355 CG2 C 3 0 15 1 /a” (pul 1 ©d Light gr* sandy eh • QtP 67 5 15 56 -13 8/8 "(cement

Gray sandy oh. c?5 710 22 55 10” 200 Gray shale 710 5 567 8 1/4” 1033 Hard light shale 890 4438 6 i/4" Gray sand(Hyg1ene ).1033 1068

Gray sandy sh. 1068 1130 Shot Record

Gray sh. 1130 1195 No shots used

Gray sandy sh* 1105 12 40

j£ray sh. 1240 2600

Gr, sandy sh# 3500 3930

Dark gr*sh* 3230 3600 WELL LOG

OBION OIL CO, OF CALIFORNIA

ELDER gi ELey. 6360*

1364* W. &672' S. of U.K. eor* sec, 13-9-68 T«D« 45221

Wellington Field, Larimer County, Colo* Comm. 2/9/192©

Comp, 6/20/1936

Formation Frqm 12 Casino Record Sandy shale 0 25 Feet of easing Dimensions Xellow sandy shale 25 45 05 20" dray sandy shale 45 155 665 13 1/2" (pulled Hard gray shale 155 rso 1383 12 i/2*{cement dray shale MOOd Kl w 325 2400 10" dray sand 225 27C 3667 3 1/4" Blue shale 2?Q 300 4511 6 i/4"

Brown shale 300 370 Shot Record Blue shale 370 1025 Ho shots used Sandy gray shale 1035 1095

Blue shale 1095 1133 dray sand (Hygiene) 1133 ' 1222 Blue shale 1302 2755

Sandy gray shale 2755 3330

Blacli shale 3330 3650 dray shale(limey) 3650 3966

Sand (Frontier) 3966

Shale 3983 3986 dray sandy sh.& shells 3036 4100

Dark shale 41 "*0 4 4 6 5 dray shale 4465 4514 Sand (Muddy) 4514 4522 (oil) WELL LOG

CONTINENTAL OIL COMPANY

ELDER ELev. §353*

167S* 3. k 1564* W. of U.S. cor. sec• 18-0-68 T*D. 4504*

Wellington Field, Larimer County, Colo. Comm* 11/5/1908

Comp. 3/9/1929

Formation From To Casing Record Cellar 0 15 Feet of Casing Dimensions Brora gravel 1 5 ***c,:'> •>>?' 40 20“ Gray sand 50 60 600 15 1/2"(pulled) Gray sandy shale 61 135 1355 12 i/3” (cemented id .165 Gray sand with 155 sack* c* o Gray sandy sh. 1 0 5 • » .. .• 3155 10”

Gray sand 330 975 3067 8 1/4" Gray shale b 7 5 6*5 44fe6, 6 1/4" G r • s c,.i i c ly ijfi • s,Jr, .ohO ‘A 73 5 Shot Record Gray shale 77 D 1115 No record. Gray cand {Hygiene 1110 1170

Gr * ct.nu,/ »n • 1170 1100

Gray sand i 100 i. ►-* > .7

Gray shale 1005 saao

Gray sandy shale <^0O 7-1 0/F w^ V*

Gray shale 63^0 3740

Gray lime 3740 3700

Gray g^. 3760 3 9 mo

Gray lime 3900 3050

Gray sand(Frontier 3950 3 9oQ

Gray shale 3960 440 i •

Gray sand (Muddy) 4492. 450i (oil) i K U j j j o a

CONTINENTAL OIL COMPANY FLEMING- H. Elev. 54S3*

1948’ S. 4 3468* V. Of N.E. oor. Soo. 6 - 9 - 6 8 T.D, 4241* Wellington Field, Larimer County, Colo. Comm. 4 / 6 / 1 2 2 9 Comp. 7/16/1929

F o i m U o n From To Casing Record dray shale 0 380 Feet of casing Dimensions

Sandy shale 380 705 61 20* Shale 70S 880 780 15 i/2”

Sand( water) Hygiene 880 900 1.120 12 l/2” (oemente

Sandy shale 000 1050 with 125 s&ofc dray shale 1280 2 3 8 0 2375 10* dr* ah. & sandy ah* 9330 3390 3500 3 1/4"

Limey shale 3300 3G90 4215 6 1/4* Sand( Frontier) 3 6 9 0 3695 Shot Record Light gr* sh. $L»s. 3695 3790 Ho record Shale 3790 4210 Sand(riuddy) 4210 4*4^ i (gas, oil and water) YfBUb LOa UHION OIL, 30. 0? CALIFORNIA

N.P, BtJBBLSS ,''i Kiev. 5300*

1585* 15. Y .'JOS' S. of N.TT. oor. sec. 7-9-80 1.0. io'O1 Wellington Si old, Larliaot' County, Colo. Coaa, 1/23/1P06 Coap. ?/. l/lPfc'6

Formation From To Formation From To Collar 0 IB Dark gray shale 1515 -550 Bro??n sand 40 Gray sandy sh. 2550 3550 Harcl gr. sand 40 0 ) Dark gray shale 3550 3745 Blue shalo 35 \ *' Light gr.li y 3ih. 3745 4 617 Dark gr. shale r? if+. Sand{F ron t i e r J 4017 4 MO Blue shale •a > 115 Lime and sand ■MO VV55 Hard dark sh* :.!5 1. '8 Dark gray shale 406 5 4 *>80 G-ray sand 155 17 5 vrray sanaimuddyJ 4580 4586101/; G-ray sandy sh. 175 000

Hard gr.sd. 000 8 5 5 Casing Record Dark gray sh. 0.15 560 Feet of Casinr. Dimensions Light gr. sh. 560 5~40 58 *0ti Gray sandy sh. 500 605 8 an 15 1/2”(pulled Light gray shale 605 1034 1335 12 !/.-'* (cemented Gray sand(Hyg1e ne) 1084 U ? 2 2405 ID* Gray sandy shale 1172 1810 . 3600 0 1/4" Hard gray sand 1210 1220 A g q n 6 X/4" Gray sandy sh. 1230 4579 2 i/o”(tubing Gray sand 1830 1243

Gray sandy sh. 1245 • IT DO Shot Record Light sandy shale 1300 1315 Ho shots used. WELL LOG

UNION OIL 00. OP CALIFORNIA

HESS jt 1 Elev. 5414 *

660* N. & 310* E. of 3.W. cor* sec. 32-10-63 3.15, 4925*

Wellington Field, Larimer County, Colo. Coiam* 9/12 / 1 2 2 4

Formation ? roa To_ Fo ma t ion From lo

Cellar 3 11.} Gray sandy shale 2720 3670

lello v* sc» i'iC to no 1 ^ 3 5 Brown shale 3070 3025

G-ray sandy shale 35 C5 3 5 Gray shale 3 0 2 5 4135

Blue shale 23 5 o?0 Limy shale and 413 5 4220 shells(Niobrara) Shells 6 7 3 705 Gray sand( Niobrara 1020 Liao Gray sandy shale 705 1040 ( shov; oil)

Shells 1040 1050 Bandy shale 422 0 4244 (Benton-Carlisle) Gray sandy eh&le i» 0 50 1195 Gray shale 4244 4747 Gray shale 1195 1300 Gray sandy shale 4747 47 32 Gray sand (Hygiene) 1300 13 75 (show gas at 4G 70*}

Gray sandy shale 1375 1400 Gray sand 4792 4932 i water and some gas) Dark sand 1400 1405 Gray sandy shale 49 22 4225 Sandy shale 1405 1415 {3260* of fluid-oil and *' * 1 1450 Gray shale water, in hole)- 1 2 /3 /2 5

Bluish gray sandy 1450 1515 Well abandoned. shale

Gray shale 1515 1343 Casing Record Blue shale 1545 1560 No record. Gray shale 1560 1590

Gray sandy shale 1530 1705 Shot Record

Gray shale 1705 2? 15 No shots used. Gray lime 2715 -MO *f * «2>< I 'J WELL LOG

UNION OIL GO. OF CALIFORNIA

STATU H Elev. 5470*

1080* S. 4. 660* V of N.S . oor. sec. 38-10-69 T.D. 3314*

Wellington Field, Larimer County, Colo. Comm. iO/7/192

m ^ Formation From To Formation From

Cellar 0 15 G-ray shale and 4310 157G shells Brown sand;>tone 15 35 Hard gr. sand 4373 4404 Gray sandy ahale 35 115 (Frontier)

Hard sand 115 120 Soft brown sh. A 494 -6 90*

Gray sandy shale 180 135 Soft gray hentoni f ,1 0 4700 < Hard sand 135 150 Brown shale t i \ 1 . 7 •

Sandy gray' shal e 150 235 Hard fine sand /.1 r-.- io -1* n, • 4904 (show oil <1 g< White sand 235 260 Hard dark sand 4994 500? Sandy gr* shale ‘-‘60 915 Gray shale 5007 5010 Hard Dlua shale 915 223 Gray sand 5012 5 281 (krgy shale 902 1230 Dark shale 30C1 3080 Gray sd *{Hyg i ene) 1 r 30 13i0(water)

Blue shale 15 i 0 1335 Light sandy lime 5930 3 . ■■ o

Sandy gr.shale 1325 138? Dark sandy shale «.J -.•* 5118

Brown sand 1337 1409 Light shale 5156 51.04

Gray shale 1409 2930 Dark hard shale 5194 5205

Sandy gr* shale 2 930 3745 Hard lime 5205 621,..

Gray shale 3745 4085 Dark shale 5212 511?

Black shale 4035 4065 Gray sand 5.217 5243

Gray shale 4265 4305 Dark sandy sh. 3 '1:0 5244

Hard light lime 4305 4320 Li gilt sand 0344 5253 (Dakota) (show oil) (continued) WELL LOG

UNION OIL CO. OF CALIFORNIA

STATE #1 Elev, 54701

1980* 3. 3 660’ W. of N.E. cor* sec. 36-10-6© T.D. 5314*

Wellington Field, Larimer County, Colo. Comm* i0/7/1924

Formation From To

Light pinkish shale 5253 5279

Light sandy fchell 5279 5281

Dark sandy shale 5231 5292

Light sand{Lakota) 5292 5314

.Bwwora. No record.

Shot Record

No shots us^d. m & . j o t UNION Oil, GO. OF COLORADO

WARREN FAR!! .''i Elev. 5352‘

S.V7. 1/4 Of U.S. i/4 Of sec. 8-2-68 T.D. 5320’ East of Hellington Field, Larimer Uonfcy, Oolo.

£ o g » M 9 . n From TO Formation From To Clay 0 8 Brown and gray 3066 2730 shale Quick sand 8 i n Blaok shale 2730 2330 Blue shale loo 453 Brown sandy sh. 2930 3375 Hard sand 455 485 Light sandy ahale5375 3875 Sandy shale 485 735 Bark shale 3375 4125 White sand 735 745 Gray sh*& sheila 4125 4450 Sandy shale 745 798 White lime shells 4450 4510 Gray sand 703 800 Lime and shells 4510 4715 Brown shale 300 885 White sand 4715 4733 Gray sand 835 920 (Frontier)

Gray shale 020 1060 Gray sandy sh* 4733 4945

Gray sandy shale 1060 1450 Blaok shale 4940 4070 Sd.(Hygiene) 1450 1540 Brown 3hale 4970 4 9 9 0 Grey sandy shale 1540 1703 Gray shale 4290 5020 White sand 1798 1323

Sandy shale 1328 1910 Well Abandoned Gray sand 1910 1920 Casing Record Blue shale 1920 1934 No Record* White sand 1934 1940

Brown shale 1940 1968 Shot Record

White sand 1968 1986 No Record* Broken sand 1986 2 0 6 6 £

/r»p N

^ U ' — — • 1— I

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o o o o o o o lo o n N M oixvy nes/jid SKETCH OF TYPICAL FLOW LINE HOOK UP FOR OIL AND G-A5 V/ELLS.'IN THE WELLINGTON COLORADO FIELD

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PLATE Z SKETCH OF TYPIC<*L ?J2?RHoSO HII:Gr HOOK UP FOE RKPKE^SURIUG Y/FLLS, IN THE Y/SIYblESTOK COLORADO FIELD

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PLATE 3 SKETCH OF NORTH CENTRAL GATHLRTNG SYSTEM

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PLATE 4 SKETCH OF SOUTH CENTRAL GATHERING SYSTEM

WFiLINGTON OfL FT ELD.j COLORADO t^OlC ImeS from U/ells f l£ o b b/. Haif Tank —^ line To O—o i Jasa/tnc plan! Joo bbi. Haa TanK-y o V - 'ft ot L Line> |2

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PLATE. 5 F L O W S H E E T

OF CONTINENTAL OIL COMPANY ABSORPTION GASOLINE PLANT

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LE03ND f fi > 0 1 »11 '(I) . Crfxa meter \T i • Oulli Gasoline \2) , Zozxo rca aova Knock-out box f • storage tanka ' 3; . Ahsorbin-l to*7e 3 Tie flax tower .{ 1 b).Boi 1 er houa o .4). Abs^rbate pumps. ■! 9) • Cond?Bsln& coil \ { 13}.Reflux { 5) . FI sat BU chans era. , ~ - 1 Receiving.house absorbate pump (11).Cool ins coils ( 15; . 'lathi’* pu..ips.

Gas lines ---- Gasoline vapor lines— waUr Lines - 'ilneral oil lines — Gasoline lines ------PLATE 6 UJ Thouttrtdt o -f- Cubic FccT oj- Gas

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