GEOLOGICAL SURVEY CIRCULAR 820 

A Study of Reservoir 

Characteristics of the 

Nanushuk and Colville Groups, 

Umiat Test Well 11, 

National Petroleum Reserve in Alaska 

A Study of Reservoir 

Characteristics of the 

Nanushuk and Colville Groups, 

Umiat Test Well 11, 

National Petroleum Reserve in Ala!~ka 

By J. E. Fox, P. W. Lambert, J. K. Pitman, and C. H. Wu 

GEOLOGICAL SURVEY CIRCULAR 820 

1979 
United States Department of the Interior 

CECIL D. ANDRUS, Secretary 

Geological Survey 

H. William Menard, Director 

Free on application to Branch of Distribution, U.S. Geological Survey, 1200 South Eads Street, Arlington, VA 22202 
CONTENTS 

Page 

Abstract--------------------------------------------------------- 1 

Introduction----------------------------------------------------- 2 

Location---------------------------------------------------------- 2 

Drilling history----------------------------------------------- 4 

Umiat test well 11--------------------------------------------- 4 

Objectives and procedures---------------------------------------- 4 

Paleogeographic setting------------------------------------------ 4 

Age-------------------------------------------------------------- 9 

Core analysis---------------------------------------------------- 10 

Introduction--------------------------------------------------- 10 

Stratigraphy and depositional environn1ents--Nanushuk Group----- 10 

Tuktu and Grandstand Formations------------------------------ 10 

Killik Tongue of the Chandler Formation---------------------- 14 

Ninuluk Formation-------------------------------------------- 15 

Stratigraphy and depositional environments--Colville Group----- 17 

Seabee Formation--------------------------------------------- 17 

Tuluvak Tongue of the Prince Creek Formation----------------- 18 

Petrography------------------------------------------------------ 21 

Nanushuk Group-------------------------------------------------- 25 

Grandstand Formation and Killik Tongue of the Chandler 

Formation-------------------------------------------------- 25 

Detrital grains------------------------------------------ 25 

}fatrix--------------------------------------------------- 29 

Authigenic minerals-------------------------------------- 29 

Porosity------------------------------------------------- 30 

Ninuluk Formation-------------------------------------------- 30 

Detrital grains------------------------------------------ 30 

Matrix--------------------------------------------------- 31 

Authigenic minerals-------------------------------------- 31 

Porosity------------------------------------------------- 31 

Colville Group------------------------------------------------- 31 

Seabee Formation and Tuluvak Tongue of the Prince Creek 

Formation-------------------------------------------------- 31 

Detrital grains------------------------------------------ 32 

¥4trix and authigenic minerals--------------------------- 33 

Porosity------------------------------------------------- 34 

Factors affecting porosity and permeability---------------------- 35 

Core and well-log analyses--------------------------------------- 38 

Average porosity of each formation----------------------------- 39 

Average permeability of each formation------------------------- 40 

Formation-water resistivity------------------------------------ 43 

Results of porosity and permeability analyses------------------ 44 

Summary---------------------------------------------------------- 45 

References cited------------------------------------------------- 46 

ILLUSTRATIONS 

Figure 1. Index map of northern Alaska outlining location of 

National Petroleum Reserve in Alaska and showing 

Page 

Umiat Anticline-------------------------------------- 2 

2. Structure contour map of the top of the Grandstand 

Formation and cross section of Umiat Anticline------- 3 

III 
ILLUSTRATIONS (Continued) 

Page 

3. Stratigraphic section of Umiat test well 11------------ 5 

4. Cross section showing stratigraphic relationships of 

Lower Cretaceous deltaic facies, Umiat area, Alaska-- 9 

5. Index map of Umiat-Maybe Creek region, northern Alaska, 

including line of section----------------------------11 

6-12. Lithology, sedimentary structures, texture, inferred 

environment of deposition, and reservoir properties, 

Umiat test well 11 

6. Core 60 (911.0-915.6 m), Grandstand Formation----12 

7. Cores 56-58 (856.5-868.7 m), Grandstand 

Formation--------------------------------------13 

8. Cores 52 and 53 (744.9-749.8 m), Grandstand 

Formation--------------------------------------14 

9. Core 49 (723.6-729.4 m), Killik Tongue of the 

Chandler Formation-----------------------------15 

10. Cores 35-38 (623.9-639.2 m), Ninuluk Formation---16 

11. Cores 21-25 (402.9-419.7 m), Shale Wall Member 

of the Seabee Formation------------------------18 

12. Cores 15 and 16 (227.1-239.3 m), Ayiyak Member 

of the Seabee Formation------------------------19 

13. Lithology, sedimentary structures, texture, and 

inferred environment of deposition, cores 11 and 12 

(157.0-167.6 m), Tuluvak Tongue of the Prince Creek 

Formation--------------------------------------------20 

14. Lithology, sedimentary structures, texture, inferred 

environment of deposition, and reservoir properties, 

cores 1 and 2, (35.1-47.2 m), Tuluvak Tongue of 

the Prince Creek Formation---------------------------21 

15. Primary arenite triangle showing composition of 

samples listed in table 2----------------------------25 

16. Litharenite triangle showing composition of samples 

listed in table 2------------------------------------26 

17-20. Photomicrographs: 

17. Grandstand Formation, 860.8 m (2824 ft). 

Chert arenite showing excellent porosity 

and permeability------------------------------ 27 

18. Grandstand Formation, 860.8 m (2824 ft). Chert 

arenite showing excellent porosity and 

permeability----------------------------------27 

19. Grandstand Formation, 913.5 m (2997 ft). 

Phyllarenite with poor porosity and 

permeability---------------------------------- 27 

20. Grandstand Formation, 868.4 m (2849 ft)---------27 

21. Scanning electron micrograph of Grandstand Formation 

868.4 m (2849 ft)------------------------------------28 

22. Photomicrograph of Killik Tongue of the Chandler 

Formation, 700.4 m (2298 ft)-------------------------28 

23. Scanning electron micrograph of Killik Tongue of the 

Chandler Formation, 700.4 m (2298 ft)----------------28 

24. Photomicrograph of Grandstand Formation, 868.4 m 

(2849 ft)--------------------------------------------28 

25. Scanning electron micrograph of Grandstand Formation, 

745.2 m (2445 ft). Deformation of compressible 

grain by noncompressible grain-----------------------29 

26-30. Photomicrographs: 

26. Killik Tongue of the Chandler Formation, 670.6 m 

(2200 ft). Sparry anhedral to euhedral 

calcite crystals------------------------------30 

27. Ninuluk Formation, 637.9 m (2093 ft). Very 

tightly packed phyllarenite-------------------30 

IV 
ILLUSTRATIONS (Continued) 

28. Seabee Formation, 409.3 m (1343 ft). Tightly 

packed phyllarenite with authigenic chlorite 

Page 

matrix---------------------------------------- 31 

29. Seabee Formation, 409.3 m (1343 ft). Typical 

volcanic rock fragment------------------------ 32 

30. Seabee Formation, 235.0 m (771 ft). 

Phyllarenite with authigenic smectite matrix-- 33 

31. Scanning electron micrograph of Seabee Formation, 

409.3 m (1343 ft). Mass of intergrown flakes of 

authigenic phyllosilicate, presumably chlorite, 

filling an intergranular pore------------------------ 33 

32. Photomicrograph of Seabee Formation, 409.3 m (1343 ft). 

Chlorite-filled pore--------------------------------- 33 

33. Photomicrograph of Tuluvak Tongue of the Prince Creek 

Formation, 156.7 m (514ft). Phyllarenite with 

authigenic smectite matrix--------------------------- 34 

34. Scanning electron micrograph of Tuluvak Tongue of the 

Prince Creek Formation, 156.7 m (514ft). Dense 

masses and coatings of smectite with bifurcating and 

anastomosing fractures------------------------------- 34 

35. Scanning electron micrograph of Seabee Formation, 

229.8 m (754ft). Dense masses and coatings of 

smectite with bifurcating and anastomosing fractures- 34 

36. Photomicrograph of Seabee Formation, 229.8 m (754 ft). 

Smectite coatings on detrital grains----------------- 35 

37-40. Charts: 

37. Effective porosity versus depth----------------- 35 

38. Air permeability versus depth------------------- 36 

39. Effective porosity versus modal grain size------ 36 

40. Air permeability versus modal grain size-------- 36 

41. Air permeability of samples listed in table 2 plotted 

on primary arenite triangle-------------------------- 37 

42. Air permeability of samples listed in table 2 plotted 

on litharenite triangle------------------------------ 38 

43-46. Charts: 

43. Effective porosity versus percent phyllite 

plus schist----------------------------------- 39 

44. Air permeability versus percent phyllite 

plus schist----------------------------------- 39 

45. Effective porosity versus percent matrix-------- 40 

46. Air permeability versus percent matrix---------- 40 

47. Correlation of core porosity and R64" for beds 

stratigraphically above 610 m (2000 ft)-------------- 41 

48. Correlation of core porosity and R64" for beds 

stratigraphically below 610 m (2000 ft)-------------- 41 

49. Correlation of core porosity and Rl6" for beds 

stratigraphically above 610 m (2000 ft)-------------- 42 

50. Correlation of core porosity and R16" for beds 

stratigraphically below 610 m (2000 ft)-------------- 42 

51. Correlation of core and microlog porosities------------ 42 

52. Core permeability and porosity correlation------------- 42 

TABLES 

Page 

Table 1. Summary of drilling and production history of Umiat 

Anticline-------------------------------------------- 4 

2. Petrography and reservoir properties of selected core 

samples from Umiat test well 11---------------------- 22 

v 
3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

TABLES (Continued) 

Page 

Core-analysis and well-log data------------------------ 41 

Weighted average porosity, Umiat test well 11---------- 43 

Core permeability and porosity data-------------------- 44 

Weighted average permeability-------------------------- 44 

Water analysis and formation-water resistivity from 

724 to 735 m----------------------------------------- 44 

Water analysis and formation-water resistivity from 

746 to 751 m----------------------------------------- 45 

Water analysis and formation-water resistivity from 

864 to 869 m----------------------------------------- 45 

Formation-water resistivity from well-log analyses 

using SP and R 11 ------------------------------------ 45 

Formation-water ~~sistivity from well-log analyses 

using R

16" and R64 11 ---------------------------------- 45 

Formation-water res1stivity from well-log analyses 

using core porosity and Rt method-------------------- 45 

VI 
A Study of Reservoir Characteristics of the 

Nanushuk and Colville Groups, Umiat Test Wellll, 

National Petroleum Reserve in Alaska 

By J. E. Fox, P. W. Lambert, J. K. Pitman, and C. H. Wu 

ABSTRACT 

Cretaceous sandstones in the Umiat 

Anticline contain the largest volume of oil 

discovered to date in the National Petroleum 

Reserve in Alaska. Umiat test well 11, 

although dry and abandoned, penetrated the 

most complete sequence of Cretaceous rocks in 

the Umiat area. Cretaceous formations cored 

(oldest to youngest) were the Grandstand, 

Chandler, and Ninuluk Formations of the 

Nanushuk Group and the Seabee and Prince Creek 

Formations of the Colville Group. Cores from 

sandstone beds in each of the formations 

penetrated were studied to identify the factors 

influencing porosity and permeability. 

Based on lithologic, textural, sedimentarystructural, faunal and floral, and regional 

paleogeographic evidence, the Cretaceous 

stratigraphic sequence in the Umiat area can 

be described as complexly interbedded deltafront and delta-plain facies (named the Umiat 

delta). The Grandstand Formation and Killik 

Tongue of the Chandler Formation represent one 

thick progradational sequence of delta-front 

and delta-plain facies, respectively. This 

sequence was followed by deposition of 

transgressive marine facies of the Ninuluk and 

Seabee Formations, which were in turn overlain 

by another progradational delta-plain facies, 

the Tuluvak Tongue of the Prince Creek 

Formation. 

The delta-front sandstone of the Grandstand 

Formation is well-sorted, fine-grained to very 

fine grained, angular to subangular chert 

arenite and phyllarenite. Authigenic cements 

include dolomite, calcite, siderite, quartz 

overgrowth, kaolinite, chert, pyrite, and 

possibly some small flakes of chlorite. The 

source terrane was southwest of Umiat and, on 

the basis of the aforementioned petrographic 

evidence, consisted of low-grade metamorphic 

rocks and possibly sandstone and cherty 

limestone. The weighted average porosity, 

based on well-log analyses, for the lower part 

of the Grandstand Formation is 15.1 percent 

1 

and for the upper part is 15.6 percent; th?. 

weighted average permeability is 58.6 md for 

the lower part and 167 md for the upper part. 

The average size of visible pores is about 50 

~m. A linear relationship was established 

between permeability and porosity for sandstone 

samples from depths less than 405 m and gr~ater 

than 644 m; the average permeability of th~se 

intervals can be estimated with reasonable 

accuracy not only for the Grandstand but also 

for the Tuluvak, Seabee, and Killik. 

The delta-front, delta-plain marginal 

facies of the Killik Tongue of the Chandler 

Formation includes sandstone, siltstone, 

shale, and coal. Sandstone samples studied 

petrographically are similar to those of the 

Grandstand Formation; the delta prograded 

northeasterly across the Umiat area and th~ 

source terrane for the sediments remained the 

same. Well-log analyses indicate that the 

weighted average porosity for the Killik 

Tongue is 16.4 percent and the weighted av,~rage 

permeability is 96.2 md. 

The delta-front sandstone of the Ninuluk 

Formation is similar to that of the Grandstand 

and Killik, but is moderately sorted and 

contains less detrital quartz and significantly 

more metamorphic rock fragments than chert 

fragments. Sandstone in the upper part of the 

formation contains a considerable amount of 

calcite. Visible pores average about 35 ~m in 

size. The weighted average porosity for the 

Ninuluk Formation, based on well-log analyses, 

is 12.6 percent; the weighted average 

permeability is 10.7 md. 

The Seabee Formation is primarily shale 

deposited in an open-marine environment; 

sandstone units in the Seabee overlie and are 

overlain by black marine shale. The mineralogy 

of these sandstone units differs markedly from 

that of the older formations. The sandsto~es 

are characterized by an abundance of volcanic 

rock fragments, high content of volcanic 

plagioclase feldspar, and low content of 

detrital quartz. Quartz, chert, phyllite, and 

metaquartzite all appear to be the same 
petrographically as in the Nanushuk Group. 

Abundant chlorite and smectite reduce 

permeability and make sandstones of the Seabee 

inadequate reservoir rocks. Well-log analyses 

indicate that the weighted average porosity of 

the Seabee Formation is 11.5 percent; the 

weighted average permeability is 3.1 md. 

The Tuluvak Tongue of the Prince Creek 

Formation in the Umiat area is composed of 

predominantly delta-plain sandstone, siltstone, 

shale, bentonite, and coal. The source terrane 

was to the southwest and the marine shoreline 

was to the northeast of the Umiat area. 

Sandstone samples studied petrographically 

have a composition similar to those of the 

Seabee Formation except for a slightly higher 

content of quartz and slightly fewer volcanic 

and metamorphic rock fragments. Abundant 

authigenic smectite in these sandstones reduces 

permeability to very low values. Well-log 

analyses indicate that the weighted average 

porosity is 14.6 percent; the weighted average 

permeability is 3.9 md. 

Modal grain size is a minor factor 

affecting porosity and permeability; in all 

formations, porosity and permeability tend to 

increase with increasing grain size. A minimum 

grain size of about 175 ~m is necessary for 

good (>50 md) permeability. Composition of 

the rock has a major effect on porosity and 

permeability; rocks that have a higher content 

of compressible grains (phyllite, schist, 

mica, and, rarely, chert and micaceous 

metaquartzite) and rocks that have greater 

matrix and cement content generally have lower 

porosity and permeability. In general, rocks 

having the best permeability are chert arenites, 

and those with the poorest permeability are 

phyllarenites. Phyllite and matrix abundance 

are related to the mineralogy of the source 

terrane and to energy conditions at the site 

of deposition. Porous and permeable reservoirs 

in the Grandstand Formation and Killik Tongue 

should exist in those depositional areas that 

received only sparse amounts of metamorphic 

rock debris and in areas where energy conditions 

at the site of deposition facilitated sorting 

and winnowing of the sediment. 

In general, a large amount of expandable 

clay matrix has an adverse effect on effective 

porosity and permeability of reservoir rocks. 

Expandable clays are essentially absent in the 

Grandstand Formation, Killik Tongue of the 

Chandler Formation, and Ninuluk Formation; 

these units have good porosity and permeability. 

The Seabee Formation and the Tuluvak Tongue of 

the Prince Creek Formation, however, have 

abundant smectite matrix; porosity in these 

sandstones is in large part fracture porosity 

in this matrix. These fractures may have been 

formed by swelling and shrinking of the smectite 

due to wetting and drying or by freezing and 

2 

thawing of ice crystals in the permafrost 

zone. When these sandstones come into contact 

with water, the clay matrix expands and chokes 

off the porosity and permeability. 

INTRODUCTION 

Cretaceous sandstones in the North Slope 

basin of Alaska have proven hydrocarbon 

accumulations. Umiat Anticline, dr~.lled and 

tested by the U.S. Navy between 1945 and 1952, 

contains the largest volume of oil discovered 

to date in the National Petroleum Reserve in 

Alaska (Brosge and Whittington, 1966). The 

quantity of recoverable reserves has been 

estimated to be as great as 122 million barrels 

of oil and an undetermined volume of gas 

(Espach, 1951). A large range in e9timates is 

due to the use of different recovery factors 

and reservoir parameters in calculating the 

recoverable reserves. Host of the oil and gas 

occurs in the Grandstand Formation of the 

Nanushuk Group. This study investigates the 

reservoir characteristics of Cretaceous 

sandstones in Umiat test well 11, located on 

Umiat Anticline. (All measurements in Umiat 

test well ll were made in the foot-pound 

system and have been converted to metric and 

rounded off to the nearest tenth of a unit in 

this report. No increase in the precision of 

the basic measurements is implied.) 

LOCATION 

Umiat Anticline is located near Umiat, 

Alaska, near the southeastern edge of NPRA, 

just north of the Colville River (fig. 1). 

The anticline is a west-trending structure 

that has a total structural closure of 

approximately 610 m (fig. 2) (Brosge and 

Whittington, 1966). Two maior west-trending, 

0 1 00 200 KILOMETERS 

0 100 200 M'LES 

Figure 1.--Index map of northern Alaska 

outlining location of National Petroleum 

Reserve in Alaska. 
152°30' 

69° 

25' 

A 

METERS 

2 

EXPLANATION 

* Projected well 

~ ~ ...... ~ Q:; Q:; ->c 

~ 

"'-l 5 ~ ~ 8 ~ 

~ 

680 

"0 

a ... * * ,..._ ... * <0 C\llOC'l"<t 

G) G) Q)Q)Q)Q) 5: 5: 5:5:5:5: 

., Ui (ii(i;(;;Cii 

2 2 2222 

1ii 1ii .E .E :::> :::> 

0 

A 

0 100 200 

0 100 

INDEX MAP 

!-

G) 

5: 

Ui 

2 

152°00' 151°55' 

EXPLANATION 

--- Structure contours on top 

of Grandstand Forrration 

- _l!_- Thrust fault--U, upthr·'lwn 

D side, D, downthrown side 

Dry hole 

well 

2 MILES 

KILOMETERS 

200 MILES 

A' 

Figure 2.--Structure contour map of the top of the Grandstand Formation and cross section of Umiat 

Anticline. Area of structure contour map is shown by crosshatching on index map. Modified 

from Brosge and Whittington (1966). 

3 
southward-dipping thrust faults bisect the 

anticline. Strata on the south limb have been 

upthrown at least 610 m relative to strata on 

the north limb; structural closure of about 

275 m exists on the south limb against the 

fault (Brosge and Whittington, 1966) (fig. 2). 

Drilling History 

Eleven test wells were drilled on Umiat 

Anticline during the period from 1945 to 1952 

(fig. 2); cores were cut during the drilling 

of all of the wells. The first 10 wells were 

drilled on the south flank (overthrust block) 

and test well 11 was drilled on the north 

flank (lower fault block). Test wells 1, 2, 

and 3 were drilled with rotary rigs using 

freshwater mud. Thin-section analysis of 

these cores by Krynine (1947, 1948) revealed 

expandable interstitial clays in several of 

the target Cretaceous sandstone beds. Krynine 

believed that these clays may have swelled 

upon contact with the mud filtrate and "choked 

off" the permeability. Beginning with test 

well 4, and for the remainder of the wells, 

cable drilling, using brine, or rotary drilling, 

using oil-base or oil-emulsion mud, was 

employed. Test wells 1, 2, 7, and 11 were 

dry; therefore, they were abandoned. Table 1 

presents a summary of production tests from 

each of the test wells. The oil in groductive 

wells has a gravity of 36.0° to 37.2 API, a 

pour point ranging from less than 15° to 

-32°C, and a sulfur content of less than 0.1 

percent; it contains about 35 percent gasoline 

and naphtha (Brosge and Whittington, 1966). 

The reader is referred to Collins (1958) for 

more detailed production information for each 

well. 

Table 1.--Summary of drilling and production 

history of Umiat Anticline 

Umiat 

test well 

[Modified from Brosge and Whittington (1966) I 

Drilling data 

Status Type of drill 

Total depth 

(meters) 

Dry and abandoned-------------- Rotary---------- 1,832 

--do--------------------------- --do------------ 1, 895 

Pumped 24 bbl oil per day; Rotary (core 174 

abandoned. test) 

Pumped 100 bbl oil per day; Cable tool------ 25b 

shut in. 

Pumped 400 bbl oil per day; --do------------ 328 

shut in. 

Pumped estimated SO bbl oil per --do------------ 252 

day; junked and abandoned. 

Dry and abandoned-------------- --do------------ 422 

Pumped 60-100 bbl oil per day; --do------------ 405 

gas estimated 169,923.5 cum 

(6 million cu ft) per day; 

shut in. 

Pumped average 217 bbl oil Rotary---------- 38J 

per day; abandoned. 

10 Bailed 222 bbl oil in 24 h; Cable tool------ 480 

plugged and abandoned. 

ll Dry and abandoned-------------- Rotary---------- l, 007 

4 

Umiat Test Well 11 

Umiat test well 11 was spudded on June 3, 

1952, and was subsequently drilled to a total 

depth of 1,007 m. Numerous shows of oil and 

gas were reported. In test well 11, water was 

found in the two sandstone beds of the 

Grandstand Formation that were the most oilproductive beds in other Umiat test wells. On 

August 29, 1952, well 11 was listed as dry and 

was abandoned. Although rocks of both Early 

and Late Cretaceous age are found in the 

subsurface throughout the Umiat area, well 11 

penetrated the most complete Cretaceous 

stratigraphic section because of its location 

on the lower block of the faulted anticline 

(fig. 2). For this reason, and because it is 

an unfaulted sequence, Umiat test well 11 was 

chosen for detailed study. (Refer to figure 3 

for the complete stratigraphic sequence for 

well 11; also note the shape of the electric 

log.) 

OBJECTIVES AND PROCEDUREf 

The major objective of this stcdy was to 

identify factors influencing porosity and 

permeability of Cretaceous sandstone units in 

Umiat test well 11. The informatior presented 

in this report should be useful in future 

reservoir studies of Cretaceous rocks throughout 

the area. 

A multiphase procedure was used in this 

study. One phase involved a sedimentologic 

study of selected cores from well 11. 

Sedimentologic information obtained from the 

cores was incorporated into the regional 

paleogeographic setting in order to make 

interpretations as to the environment in which 

sediment in each of the selected cored intervals 

was deposited. A second phase was a detailed 

petrographic study documenting the influence 

of texture and fabric properties and mineralogic 

and diagenetic factors on reservoir quality. 

Because of the abundance of swelling clays in 

this area and their demonstrated effects on 

drilling and recovery techniques, a third 

phase was implemented: identification, using 

X-ray diffraction, of the kinds of interstitial 

clay in the various sandstone units. The 

fourth phase of the study was the examination 

of electric logs to learn whether porosity of 

uncored zones could be determined from the 

available well logs and whether forreationwater salinity could be determined so that 

water saturation could be estimated from the 

logs. 

PALEOGEOGRAPHIC SETTING 

Cretaceous strata in the Umiat area of 

the North Slope consist of detrital clastic 

sediments derived from the ancestral Brooks 
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w 

a: 

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200 

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400 

500 

600 

700 

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a: 

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50 

100 

150 

200 

250 

SPONTANEOUS 

POTENTIAL 

(MILLIVOLTS) 

-20+ 

- -Ground level 

Sea level 

z 

0 

i= 

(jj 

0 

a. 

:::!: 

0 

() 

RESISTIVITY 

(OHMS m•!m) 

30 60 90 120 150 

Q) 

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5 

z 

X 

X 

X 

FOSSILS 

M 

A 

A 

X M M 

R R 

w 

z 

a: 

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EXPLANATION 

Gravel anc' sand 

Sandstcne 

Silty 

~ sand~tone 

Calcareous s::~ndstone 

IHHHI 

Siltstone 

Sandy siltstone 

Calcareous siltstone 

m 

Clay shale or 

claystore 

mBI 

Silty clay shale 

or claystJne 

Calcareous ~ clay 

shale or cl2ystone 

Clay 

~ ironstone 

Coalorcarboraceous 

~ 

material 

-

Limestone 

rm 

Bentonite 

ITJ 

Cored inte·val 

No sample rec:overed 

rn 

Core studied in 

this repo'i 

• Oil sho111 

A-Abundant 

M-Moderatel:' 

abundan• 

A-Rare (barren) 

X-Present 

Figure ].--Stratigraphic section of Umiat test well 11. Modified from Collins (1958). 

5 
FOSSILS 

Cl) 

w 

oc SPONTANEOUS w z Cl) 0 a: a: a.. i= w DEPTH POTENTIAL 0 :::> fD 0 <( 

~ a: ~ ~ (MILLIVOLTS) w (!' a: w 1- 0 ~ 

Cl) u. Cl) 

>- a: -20+ Cl) 1- w w 1-

~ w 

::!; 

~ ~ z .!!! .!!! 0 ·c: ·c: i= w .E .E c Ci5 RESISTIVITY a: ~ ~ 

0 0 .E ~ 0 Cl) 

a.. () .E a. (I) w ~ Cl) Ill .!!l "0 ~ z ::J 0 ::J "iii c oc Q) 0 0 Cl) al -;;; w <( () .J:J (I) (I) 0 Ill Ol () z al ~ (0HMSm3 /m) § al (a 10 ~ '5 oc z z c () Ol 0 <( 0 (I) til (I) a. c 0 30 60 90 120 150 ~ () ~ Cl) i5 ~ z 

+ 

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Figure 3.--Stratigraphic section of Umiat test well 11. Modified from Collins (1958)--Continued. 

6 
FOSSILS 

Cl) 

w SPONT AN EO US ~ ~ 

a: z ~ ~ 

w z 0 w "2 "2 Cl) a.. 0 a: POTENTIAL i= RESISTIVITY a: "§ .E c:: 

a: :::J i= w DEPTH Ci5 0 a:l ~ 

0 0 <( m 0 () .E :§ 0 (/) 

a: ::::!: ::::!: a.. c. Q) w ::::!: (MILLIVOLTS) (/) (/) !!! "0 j z (!) a: w ::::!: ::I w 0 ::::!: 0 0 ::I "iii c:: Q) a: ~ "' Q) 0 (/) a:l w LL (/) () Q) Cl <( Cl) a: .0 0 Co 0 (/) a:l z ::::!: >- w -20+ (OHMS m3 /m) § {II 1ii Q) 

Cl) 1- 'E a: 1- c:: 0 Cl 0 z w z ~ <( w w a; Q) c. c:: 0 u. ~ 30 60 90 120 150 <( () ::::!: Cl) i:5 ::::!: z 

1800 I 

I 

a: I w I m 550 I ::::!: I w w Cl) 

...J w ::::!: I :::J ...J ...J 1900 I 0 w 

> m ...J w I <( <( 

() ...J 

~ I 0 w <( Cl) 

~ () w I w ...J I a: <( 

() I I 2000 

Cl) 600 I a: I w 

a.. I a.. I :::J I 

2100 I 

' M \ ~ ) :::J 

...J I :::J ' z \ z ./ 

650 \ 

2200 M l 

\ 

X I ' / 

~ 

\ 

M I 

~ 2300 I ~ a: (!) / 

:::J w z Cl) \ ...J 0 I 0 :::J z ~ 700 \ 

0 Cl) <( ~ \ :::J I ::::i w z 0 ...J / 

() <( ~ { <( 

z 2400 \ ~ 

w I a: A M I () I 

a: r w X I 

~ I 2500 I 0 750 

...J 0 I z 

<( I ~ I Cl) 

0 I z I <( RUN 4 M a: I (!) 2600 I 

II 

I 

I 

I 

Figure ).--Stratigraphic section of Umiat test well 11. t1odified from Collins (1958)--Contjnued. 

7 
en 

w 

ii: 

w 

en Q. 

a: :::> 

0 0 

a: :::?i (!) w 

1-

en 

>- en 

::.:: 

:::> 

:X: en en :::> :::> 0 z w <( 

(.) z <( 

1-

w 

a: 

(.) 

a: 

w 

3: 

0 

...J 

Location 

Elevation 

z 

0 

i= 

<( 

:::?i 

a: 

0 

u. 

0 

z 

<( 

1-

en 

0 

z 

<( 

a: 

(!) 

::.:: 

0 

a: 

0 

1-

Total depth 

Status 

SPONTANEOUS 

z 

0 

a: POTENTIAL i= RESISTIVITY w DEPTH Ci5 lD 0 :::?i Q. w (MILLIVOLTS) :::?i :::?i 0 C/) 

a: (.) 

~ w -20+ (OHMS m"/m) w ~ 

~ w 

:::::. 30 60 90 120 

2700 

2800 

2900 

3000 

3100 

3200 

1000 ro.LJ 

3303 

Lat 69°24'29" N. Spudded June 3, 1952 

Long 152°05'58" W 

Completed August 29, 1952 

Kelly Bushing 481 feet 

Ground 464 feet Electric log by Schlumberger Well 

3303 feet 

Surveying Corporation 

All depths are measured from 

Dry and abandoned the top of the Kelly Bushing 

rn 

~ w ·c: a: ·e 0 ~ (.) .!2 

rn 

::I 

0 

~ <I> (J 

§ a::l 

c: z <I> 

150 ~ 

61 X 

FOSSILS 

~ 

~ 

·c: 

·e 

~ 

.!2 

rn .!!l. ::I "iii 0 rn <I> 0 a; 1ii (J Ol a; <I> (.) :::?i 

X 

c: 

..9:? 

0 rn c. <I> 

"0 

c: ~ (jj a::l Ol rn Jl! <I> 

0 0 c. c: 

en i5 

M 

M M 

M R 

A A 

M A 

w 

z 

ii: 

<( 

:::?i 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

w 

z 

ii: 

<( 

:::?i 

z 

0 

z 

Figure ).--Stratigraphic section of Umiat test well 11. Hodified from Collins (1958)--Continued. 

Range to the south. These sediments were 

deposited in continental alluvial fans and 

delta plains, and in nearshore- and offshoremarine environments. The sedimentary 

8 

environments generally prograded from southwest 

to northeast as the Cretaceous seas retreated 

from the area. Periodic transgressions of the 

sea caused a complex intertonguing of the 
nearshore-marine and continental facies (fig. 

3). Fisher and others (1969), basing their 

conclusions on work by Brosge and Whittington 

(1966), presented a deltaic interpretation of 

Lower Cretaceous rocks in the Umiat area, as 

shown on figure 4. They interpreted the 

Grandstand Formation as consisting of deltafront sands that overlie and intertongue with 

prodelta muds of the Torok Formation. The 

upper contact of these delta-front sands 

intertongues with the overlying Killik Tongue 

of the Chandler Formation, interpreted to be 

delta-plain deposits of mud and sand, rich in 

organic matter. As shown on figure 4, the 

delta-plain facies of the Killik Tongue thins 

to the east-northeast. Near Umiat, at the far 

east end of the section, very little of the 

delta-plain facies is present. This facies of 

Lower Cretaceous rocks eventually pinches out 

to the east and northeast of Umiat Anticline. 

z 

Transgression of the sea is indicated by 

deposits of sandstone of the Upper Cretaceous 

Ninuluk Formation (fig. 3). Continued 

transgression resulted in deposition of merine 

shale of the Seabee Formation. Near the end 

of Seabee deposition, the shoreline again 

prograded. Deposition was again deltaic; 

sands and silts grade vertically into nearshore 

marine-to-continental sands, silts, shale, and 

coal of the Tuluvak Tongue of the Prince Creek 

Formation. These facies relationships are 

similar to those of the Lower Cretaceous 

strata of this area. 

AGE 

The stratigraphic position of 

test well 11 is shown on figure 3. 

study of microfossils of the Umiat 

Bergquist (in Collins, 1958) noted 

fossilf' in 

In hif' 

area, 

that tl'~ 

z 

a: 0 £l. (/) UJ i= (/) £l. 0 a: 

i= UJ UJ :::> CD a: 0 <( 

~ UJ a: ~ UJ (/) C!J a: 

0 ~ 

LL 

(/) 

.><:§ 

1\ ::::J .... 0 

a.u 

cucu .2~ C.f.'ll ~E =>a; zo 

u u.. 

r-?-

Delta-plain organics, 

muds, and sands 

c: 

0 

~ Cl) 

E ::::J 

Ol 

a. 0 c: Cl) ::::J u.. 0 

0 ~ -c= f.'llCI) 

(/) (5 Q) ~ :03: ::::J '0 Cl) 

0 .><: c: ~ Cl) 

0 .c 

::::J 

.c 

I'll <( ~~ I'll (/) () N r-=- 0' a; ::::J Cl) 

u c: -c= I'll I'll Cl) z :03': Qj ~ Cii -

3: ·;:: 0 ::.:::2 -

_J 

.-::- 0' -

-

c::- 455' _- 1145' 

c: 

0 ··. -~ 

: 'V" E .. 0 ··: J: 1805' T.D. 

u.. :.:· 

'C . ::.:. c: 

I'll 

Cii -~ ·:·: "'0 

c: 

\ 1755'' 11. I'll 

(5 

c: 2V .><: 0 

e ~ 0 E ~ 0 

u.. 

..><: 

::::J 

]! 

;= 

0 

-~ 

a. ~-a; ..... 3: Cl) 

3:-

.92 

'-" 590' 

::-FAULT 

- -- =~v .:-::: 1335'=2092'1 

:: ~ ~ : \ ::- == ~ ::·. ~-:: -::1 --.:: 2800' .. ::."!FAULT 

f=-=v·l..;,.-~ ): ~12010'~2767' 1 

~~ ::~~; .)iv~~84~ ~ 2230' [;:. {:~ ~ FAULT ~ :.:,:':1 Delta ·: .. · :::.- ~ 3390'=3440'1 

. . .:·j,7Ctn'~~ 3910' ~ 

r.•.·.:IJ =~~~ ~~ ~ 3987' T.D. ~ t _/!= ~FAULT 

l

:·._.: 3800' § Prodelta muds ~ 4155'=4345'1 

·.··· t= ~ 

t= ~ I= ~ ~;;;;;;; 3760' T.D. ~ 

4020' T.D. ~ 

~ I= I= METERS FEET 

10:io 

500 

200 

300 1000 

~ ~;;:;;;;; 6005' T.D . 

1 Repeated interval 

has been 

removed 

CD 

~ 

UJ 

~ 

Cl) 

::::J 

Ol 

c: 

0 

~ 

~ 

~ 

:::> UJ <( 0 a: ~ a: UJ a: C!J (/) 

0 

LL 

(/) 

....:§ Qj 5 .2~ a.CU 

~E a.O :::>2:! zo Cl) 

u.. u a. ~?-

::::J 

.... c: e cuo 0 '0~ 

&i§ ..><: 

::::J .co .c Uu.. (/) 

::::J 

c: 

I'll 

z "'0 c:C: 

alO 

~~ c:E 

~~ 

(/) 

::::J 

0 

Cl) 

0 

I'll 

a; 

u 

Qj 

3: 

.9 c. 

c 

i! 

E 

c 

LJ. 

~ 

£ 

c 

t-· 

Figure 4.--Cross section showing stratigraphic relationships of Lower Cretaceous deltaic facies, 

Umiat area, Alaska. From Fisher and others (1969). Line of cross section is indicated on 

figure 5. 

9 
Grandstand Formation contains a number of beds 

having a fauna rich in arenaceous foraminifers 

of the Verneuilinoides borealis Zone. He 

reported that the microfauna! assemblage of 

this zone consists of about 60 species of 

forams mostly of the arenaceous type. He also 

reported the presence of a few calcareous 

foraminifers of the same species as those 

found in Albian beds of Europe. Some of the 

arenaceous species have also been described by 

Bergquist from Albian beds in western Canada. 

Bergquist reported that R. W. Imlay (oral 

commun., 1956) identified certain mollusks 

from beds of the Grandstand, Tuktu, and upper 

part of the Torok that are of middle Albian 

age. Dinoflagellates and acritarchs also 

suggest a middle to late Albian age for the 

Grandstand (May, in Ahlbrandt, 1979). 

The Killik Tongue contains a moderate to 

very rich flora of dinoflagellates, acritarchs, 

spores, and pollen (E. I. Robbins, oral commun., 

1976). This flora has been dated as middle 

Albian to early Cenomanian(?) (May, in 

Ahlbrandt, 1979). Shallow-marine beds occur 

in the lower part and contain a few arenaceous 

foraminifers that are part of the 

Verneuilinoides borealis Zone already described. 

The Ninuluk Formation is characterized by 

an abundance of arenaceous foraminifers, as 

identified by Bergquist (in Collins, 1958). 

He considered one of the species, Trochammina 

rutherfordia, to be indicative of a Cenomanian 

Age for the Ninuluk Formation. A moderately 

abundant assemblage of dinoflagellates was 

recovered from core 38 in the Ninuluk. These 

dinoflagellates were not datable, but they are 

similar to those of the underlying Killik 

Tongue (May, in Ahlbrandt, 1979). 

A small ammonite, Borissiakoceras sp., 

occurs in the shale beds of the Seabee 

Formation. Because of the presence of this 

ammonite, the age of the Seabee is considered 

to be Turonian (Gryc, in Payne and others, 

1951). 

CORE ANALYSIS 

Introduction 

Twenty-two cores, representative of 

sandstone units from the Nanushuk and Colville 

Groups and constituting 83.8 m of strata, were 

borrowed from the U.S. Geological Survey core 

storage facility in Fairbanks, Alaska. The 

stratigraphic position of each of the cores 

studied is shown on figure 3. A thin slice 

(1.25 em) was cut from each of these cores for 

detailed sedimentologic study. Sandstone beds 

make up a relatively small proportion of the 

overall lithotype of the total cored interval. 

Interbedded with the thin sandstone units are 

claystone, siltstone, and coal beds which were 

not studied. The following aspects were 

studied in the core analysis: visual porosity, 

lithology, color, grain size, bedding type, 

sedimentary structures, biologic constituents, 

10 

sorting, roundness, oil shows, and inferred 

environment of deposition. 

Data were gathered from the core specimens 

using a hand lens, binocular microscope, and 

black-light (fluorescence) apparatuE. 

Interpretation of depositional environments 

was primarily dependent upon the identification 

of sedimentary structures. Because of the 

fine-grained, homogeneous nature of most of 

the sediments and the abundance of interstitial 

clay, the sedimentary structures were difficult 

to see clearly. For this reason each of the 

thin slices of core was photographed using an 

X-radiography apparatus, and an X-ra~iograph 

photograph was printed to assist in 

interpretation. These prints revealed 

structures not otherwise clearly distinguished. 

A paleontologic study primarily concerned 

with foraminifers was made by Bergquist (in 

Collins, 1958). Fred May (U.S. Geological 

Survey, Denver, Colo.) and Eleanora Robbins 

(U.S. Geological Survey, Reston, Va.) examined 

slides prepared for identification of spores, 

pollen, and dinoflagellates. These 

paleontologic studies were used to assist in 

the interpretation of the ages and e"':'vironments 

of deposition. 

Although visual estimates of the grain 

size, sorting, roundness, and porosity were 

made from hand-specimen samples of the core, 

the reader is referred to the petrography 

section for detailed discussion of these 

aspects based on thin-section studies. 

Stratigraphy and Depositional 

Environments--Nanushuk Grouo 

Detterman (1956a) revised the n0menclature 

of formations of the Nanushuk Group, originally 

named the Nanushuk Series by Schrader (1902). 

Detterman divided predominantly marine rocks 

of the Nanushuk Group into three formations: 

Tuktu, Grandstand, and Ninuluk (fig. 3). The 

Tuktu is not distinguished from the Grandstand 

in the Umiat 11 test well. Predominantly 

nonmarine rocks were placed in the Killik 

Tongue of the Chandler Formation. 

TUKTU AND GRANDSTAND FORMATIONS 

Detterman (1956a) named the Grandstand 

Formation for a 518.2-m-thick sequence of 

predominantly marine rocks at Grandstand 

Anticline, approximately 56 km south of Umiat. 

In this area the Grandstand rests on the Tuktu 

Formation and interfingers with the Killik 

Tongue of the overlying Chandler Formation. 

Throughout the area of this study, the 

stratigraphic relationships between the 

Grandstand Formation and overlying and 

underlying formations are not completely 

established. According to Chapman and others 

(1964), the Grandstand at Knifeblade Ridge 

(fig. 5), just north of the Colville River 

about 105 km west-southwest of Umiat, is 

stratigraphically the same formation as the 
20 

I I 

30 MILES 

I 

0 

I 

50 1 oo 150 Mr_Es I I I I I 

0 

I 

10 

I 

20 

I 

30 40 KILOMETERS 0 100 200 KILOMETERS 

Figure 5.--Index map of Umiat-Maybe Creek region, northern Alaska, including line of section. 

Crosshatched area in small index map shows location of Umiat-Maybe Creek region within NPRA. 

Cross section shown in figure 4. 

Tuktu mapped just south of the Colville River 

in this same area. On the other hand, Brosge 

and \fuittington (1966) pointed out that the 

Grandstand Formation of the Umiat-Maybe Creek 

region (fig. 5) is probably considerably 

younger than the type Tuktu of Tuktu Bluff 

about 80 km south of Umiat. The reader is 

referred to Brosge and Hhittington (1966) for 

a discussion of stratigraphic problems of the 

Grandstand Formation. 

According to Brosge and Whittington 

11 

(1966), the Grandstand occurs throughout most 

of the Umiat-Maybe Creek area but thins to the 

north and east. It is absent in the well at 

Fish Creek, about 113 km north of Umiat 

(Robinson and Collins, 1959). At Wolf Cre~k 

Anticline, about 32 km west of Umiat (fig. 5), 

the Grandstand is about 378 m thick. At 

Umiat, the Grandstand is about 195 m thick, 

having thinned about 183 m in 32 km. 

Three lines of compositional and textural 

evidence are used to infer the depositional 
setting of the Grandstand Formation. First, 

in the Knifeblade and Titaluk wells, 80-97 km 

to the west of Umiat (fig. 5), thin coal beds 

are common throughout the Grandstand (Brosge 

and Whittington, 1966); at Umiat, on the other 

hand, coal streaks and partings are rare, 

suggestive of a more marine condition in the 

Umiat area during deposition. 

Second, sandstone beds in the Grandstand 

at Umiat Anticline are cleaner and better 

sorted than in the Wolf Creek and Square Lake 

wells to the west (fig. 5), possibly due to 

winnowing in the foreshore zone. Therefore, 

they have greater porosity and permeability 

than at other anticlines in the area (Brosge 

and Whittington, 1966). 

Third, the grain size of the sandstone 

decreases eastward, ranging from very fine to 

coarse at Knifeblade, very fine to medium at 

Titaluk, and very fine to fine at Wolf Creek 

and Square Lake (fig. 5). These regional 

compositional, textural, and thickness 

relationships suggest that the depocenter of 

the delta system, of which the Grandstand 

sandstones are a part, lay to the westsouthwest of the Umiat area. This delta was 

named the Umiat delta by Ahlbrandt (1979). 

Faunal evidence suggests a shallow-water 

nearshore-marine environment for deposition of 

the Grandstand sediments at Umiat. Nearly all 

shale beds and some of the sandstone beds 

contain abundant benthic arenaceous microfossils 

(Vernenilinoides borealis Zone), as identified 

by Bergquist (in Collins, 1958). Arenaceous 

foraminifers are commonly present in shallow 

nearshore-marine environments. A moderately 

rich assemblage of dinoflagellates, spores, 

and pollen also occurs throughout the Grandstand 

z I 0 ;;: J: >= DOMINANT GRAIN SIZE I "' "' w w 

0 "' 11. 

~ "" ~ w 

fu <( 11. 

z ~ ~ z z :E 8 z 0 <( u >= 0 

~ :.: ~ ~ ~ z u ~ ~ ::I 

~ ~ -c >--c ~ ~ ~ a1 0 " .. - u :E v; :E .. J:l 

Meters Feet > u.. u 11. 

TOP OF CORE 60 SBANGWELL ANG 

911.35- 2990 -; 

J- ~ I---- - I----

I----

912.88- 2995 f--

·~ I----

'"~~ ""' """ ~ == ~ ~ --

c----1-- I 'VV" 

"" ,~ := =~ I 3000 - -1--

vv '-"' == =r= - ""' 'Lor 'W" 

915.92- 3005 ""' 'W' 

EXPLANATION 

(May, in Ahlbrandt:, 1979; E. I. Robbins, oral 

commun., 1976), as would be expected in 

sediments deposited in a nearshore-marine 

environment. The dinoflagellate assemblage is 

of middle to late Albian age. Marin~ 

invertebrate megafossils (primarily mollusks) 

occur throughout the Grandstand sequ?.nce 

(Brosge and Whittington, 1966). 

At Umiat test well 11, the Grandstand 

Formation is characterized by a lower unit of 

very fine grained to fine-grained sandstone 

(approximately 92 m thick), separated from an 

upper unit of similar sandstone (31 m thick) 

by about 92 m consisting predominantly of 

shale (fig. 3). Cores 56-58 and 60 are from 

the lower sandstone unit, and cores 52 antl 53 

are from the upper sandstone unit. 

Cored interval 60 (911.0-915.6 m) is near 

the base of the Grandstand Formation and near 

the contact with marine shale of the underlying 

Torok Formation (:Eig. 3). The sandstone of 

this interval consists of medium-light-gray, 

very fine grained to fine-grained, wellsorted, subangular to angular quartz grains. 

Sedimentary structures include small-scale, 

thin, even-parallel, low-angle laminations; 

some interbedded homogeneous mottled units are 

especially prevalent in the lower half of the 

core (fig. 6). The sedimentary structures and 

lithologic and faunal evidence are interpreted 

as indicating delta-front sands depcsited in 

an upper shoreface (mottled, bioturtated beds) 

and foreshore--marine (lmv-angle, parallel, 

thinlv laminated) environment. 

~ored intervals 56-58 (856.5-868.7 m) 

(fig. 7) are near the top of the basal sandstone 

unit of the Grandstand. The fine-graineJ, 

well-sorted nature of the sandstone and the 

'"' 1- - N 

u ~ z z ~ ~ "' -~ -~ > ....J>~ 

i ~ w z ~ :::; <(o-,.... 0 <( 11. 

>= iii- ct!i:iO'- >= ~ ~ z X z 0 z 

~ ~ <" ::::1::::~-

~ g :.: >- ~ ~ 0< w E u <( x<~ < ~ > ::I u 2 ~- ~:E~ ~ u <( :E ~ 0 

Quartz (17) DELTA FRONT Chlorite Dolomite and 15 13.5 < 1 Immature 

Phyllarenite Kaolinite FORESHORE Illite siderite (1) 

Chlorite Quartz ( 1.5) UPPER SHOREFACE Phyllarenite Kaolinite Dolomite and 8.5 12.8 2.3 Immature FORESHORE Illite siderite (3.5) • UPP~~:~~~~ 

UPPER SHPREFACE 

FORESHORE 

UPPER SHOREFACE • Chlorite Dolomite and 10.2 0 Immature Phyllanerite Kaolinite 17.5 

Illite siderite (4.5) 

CJsandstane ~Tabular 

~ crossbedding 

~Even 

~ 

par~llel 

laminatoons I:::""--I Bioturbation 

1 As determined by x-ray diffraction ana1ysis. 

2As determined by X-ray diffraction ana1

ysis. 

3 As determined by core analysis 

Figure 6.--Lithology, sedimentary structures, texture, inferred environment of deposition, and 

reservoir properties, core 60 (911.0-915.6 m), Grandstand Formation, Umiat test well 11. 

See table 2 for more detailed information regarding mineralogy and reservoir prcoerties. 

12 
METERS FEET 

-

-

856.48- 2810 -=t 

858.01-

859.53-

- i 

186106-

I 

-

I 

ls62 sa- 2830 

-

I =t 

Q_ 

>-

1-

:.:: 

u 

2 

TOP OF CORE 

=--

1864.1012835-=I,-

~-= 

~ ~ 

WELL 

----1---

·-r---- WELL 

"' "' z 

0 

z 

::J 

2 

ANG· 

SBANG 

SB~NG 

ANGSBANG 

I 

! 

I DELTA FRONT 

I (FORESHORE) 

! 

I 

(UPPER 

SHOREFACE) 

(FORESHORE) 

Chert arenite 

1-- Chert arenite 

1- Chert arenite 

N 

"' Q_ 

~ 

>-

~ u 

Chlorite 

Kaolinite 

Illite 

Chlorite 

Kool1nite 

Illite 

Chlorite j 

1-"' z 

~ u 

Quartz (1%) 

Calc1te (1%) 

Quartz (2~.) 

Kaolinite Quartz (2.5"1.) 

Illite 

16.4 100 I Immature 

17.4 158 Mature 

17.1 280 Mature 

ANGSBANG 

I:::::J ::::r ~ "'·"·· o~ ~- (UPPER 

Chlorite 

Kaolinite Quartz {1 %) 

Illite 

! Phyll arenite 14.7 T~~ ~~~tble Immature 

1

,

86868 288 ~~i'~----_l~~-~-v~~vv~~~r~~~ .. J]~~~~~=I~~~~S~H~O~R~VEF~A~C~E~)~--C-he-rt_a_r-en-'t_ej__Ka~l~~::~~-te_LQ_u_a-rt_z_(2_~_•)_j_3_j __ 1_9._21__4_0_0 __ l_M_a_t_ur_e_j 

- --1 f=r- - 1 As determined by petrographic analysis 

c=J Sandstone 

~~=-=1 Mudstone 

~ Even parallel laminations 

r_~f] Wavy parallel laminations 

r===--=:::1 Discontinuous wavy 

~~~~Ripple la.,ination 

I~------':! Bioturbation 

2 As determined by X-ray diffraction analysis 

3 As determined by core analysts 

~ Tabular crossbedding ~ nonparallel laminations 

~ Trough or lenticular crossbedding r;_~-- _J Curved parallel laminations 

Figure 7.--Lithology, sedimentary structures, texture, inferred environment of deposition, and 

reservoir properties, cores 56-58 (856.5-863.7 m), Grandstand Formation, Umiat test well 

11. See table 2 for more detailed information regarding mineralogy and reservoir properties. 

presence of a thin (0.6 m), homogeneous, 

bioturbated sandstone interval near the base, 

which is overlain by a thicker interbedded 

interval (4.0 m) containing low-angle parallel 

laminae and small-scale lenticular crossbed 

sets, support the theory of deposition as 

delta-front sands in a dominantly foreshore 

zone. This sequence grades upward into another 

bioturbated homogeneous sandstone unit, 

reflecting a slight marine incursion and 

deposition of delta-front sands in a shoreface 

zone. A thin (0.3 m) shale bed separates the 

aforementioned sandstone interval from the 

overlying sequence of sandstone, which is of 

approximately the same thickness. This upper 

sandstone unit differs from the lower by 

having more carbonaceous laminae, more abundant 

rippled laminae (asymmetric), and near absence 

13 

of bioturbation. Occasional flooding during 

deposition of this upper sandstone unit mc-.y 

have been responsible for the abundant 

carbonaceous detritus being carried so far 

offshore and for the formation of asymmetric 

ripples. These thin carbonaceous laminae may 

be time-equivalent to thicker coal stringers 

to the west. 

The sequence of predominantly nearshcremarine sandstone is overlain by a marine Ehale 

sequence (92 m), reflecting continued 

transgression of the sea. Abundant arenaceous 

and calcareous benthic foraminifera, abundant 

dinoflagellates, and some spores and pollen 

are present in the shale. This combination of 

fossils is commonly found in modern nearshoremarine environments. This shale sequence may 

have been deposited as prodelta muds. 
Cores 52 and 53 (744.9-749.8 m) (fig. 8) 

are from about 6 m below the top of the 

Grandstand Formation. This sandstone interval 

is similar to the lower 4.0-m interval just 

described from cores 56-58 and is also 

interpreted as a delta-front sand deposited in 

a foreshore environment. However, correlation 

with coal stringers to the west-southwest of 

Umiat is not obvious. The only evidence is 

black carbon grains evenly disseminated 

throughout the sandstone and concentrated in 

thin laminations on bedding surfaces. As was 

the ease with the foreshore sandstone of 

interval 60, the sandstone of this interval is 

also overlain by a transgressive shale. In 

this interval the shale is only 12.2 m thick 

and contains a rich fauna of arenaceous forams 

(Bergquist, in Collins, 1958). 

KILLIK TONGUE OF THE CHANDLER FORMATION 

The Chandler Formation is about 1,433 m 

thick at its type locality on the Chandler 

River and is predominantly nonmarine. It 

consists of two major tongues, the Killik 

Tongue and the Niakogon Tongue. The Niakogon 

Tongue is not differentiated from the Ninuluk 

Formation in the Umiat area (Brosge and 

~fuittington, 1966) (fig. 3). 

Detterman (1956a) named the Killik Tongue 

from exposures of strata approximately 854 m 

thick along the Killik River near its confluence 

with the Colville River, about 80 km southwest 

of Umiat (fig. 5). The Killik Tongue 

progressively thins to the northeast; at the 

.... 

z z > "" < z w 0 w z C( Cl ~ "' N 

~ 0 ~ "' 1<: w ::::> ~ :3 ;;; z z 8 u 0.. z tJ 0 >= < ~ 1il ~ ~ 0 

~ 0 

~ ~ "0 "0 "' "0 

~ li; "' >-"0 c: "0 "0 "' Cl> 

8~~ u.. "' Cl> c::;; Meters Feet > u.. ~ ~ 0.. 

<I) 

<I) 

w 

z 

0 

z 

::::> 

1il 

Knifeblade Anticline it is about 1,036 m 

thick, at Titaluk Anticline it is ab~ut 488 m, 

at Wolf Creek Anticline it is about 305 m 

thick, and at Umiat Anticline it is about 92 m 

thick. In the area to the southwest where the 

Killik Tongue is thick, Brosge and Whittington 

(1966) described it as consisting of streamchannel sandstone, siltstone, mudsto~e, and 

coal--a typical delta-plain facies. 

The Killik Tongue is essentially barren 

of megafossils. However, Brosge and Whittington 

(1966) reported the presence of marine 

assemblages near the top and bottom of the 

Killik Tongue in the Umiat-Maybe Cre~k area. 

Thin shallow-marine beds in the lower part of 

the Killik contain arenaceous forams of the 

Verneuilinoides borealis faunal zone. May (in 

Ahlbrandt, 1979) identified nearshore-marine 

assemblages containing abundant dinoflagellates 

and acritarchs from cores 41, 46, and 50 of 

the Killik Tongue at Umiat test well 11; an 

age of middle Albian to early Cenomanian(?) 

was established. Approximately 26 species 

were observed, most of which are new species. 

An abundant flora of spores and pollen was 

reported from core 50 (E. I. Robbins, oral 

eommun., 1976). 

The abundance of coal diminishes to the 

northeast, and only a few very thin (10 em) 

stringers are present near the top of the 

Killik Tongue at Umiat. This decrease in 

abundance of coal, the predominance of a 

nearshore-marine fauna and flora, an1 the 

general thinning of the Killik to th~ northeast 

suggest a facies change from well-developed 

.... 

z ~ z -~ "' u 1-~ 

~~ ~ ~ z ~~~ 0 w "' >= < 0.. 

~ .... 

~ ~ z 0 g z ~ z 

~: ::::> ::::>- 1il 1<: 

u > ~ ~ ~:c~ ~ > < 1il d ~ ::::> u ~~~ ~ 0 < 

~ = COl SBANG- DELTA FRONT 

745.43- 2445--

.::: - -

= 746.95- 2450 -

- = 

-

= 748.48- 2455 -

: 

: -

750.00- 2460 = 

-

-

c=J Sandstone 

... "' . 

~ 

~· . ·~ 

·.R=s 

~===== 

E;; 

~~ 

·,.:j· .. Y:;-: -C 

·,,, ~ 

~Tabular 

~ crossbedding 

-~ == ANG (FORESHORE) 

--

--

~= = WI:LL s~~-~G- 1----

1---- 1---

= t::::= 

==f= f= 

=f= f= -r-t--

=~ ~ 

=f= 1-- WELL· 

~ MOD. =f= WELL 

=f= ~ c-- ~ 

~Trough 

~ 

or lenticular~ Even parallel 

crossbedding ~ lammations 

~Discontinuous 

~ 

wavy 

nonparallel laminations 

Chlorite 

Chert arenite Kaolinite ! 1 7.6 Illite 

Chlorite Quartz( I%) 

Chert arenite Kaolinite Dolomite and 9.5 16.4 

Illite Siderite (0.5%) 

Chlorite Quortz(1%) 1211 .8 r Chert arenite Kaolinite Dolomite and 

Illite Siderite(3%) 

Chlorite Dolomite and Chert arenite Kaolinite Siderite(2.5%) Illite 

1 As determ1ned by petrograph1c analys1s 

2 As determined by x-ray diffraction analysio 

3 As determined by core analysis 

120 Mature 

Immature 

Immature 

27 Immature 

Figure 8.--Lithology, sedimentary structures, textures, inferred environment of deposition, and 

reservoir properties, cores 52 and 53 (744.9-749.8 m), Grandstand Formation, Umiat test 

well 11. See table 2 for more detailed information regarding mineralogy and reservoir 

properties. 

14 
delta-plain facies to the southwest to a 

dominantly nearshore-marine facies at Umiat. 

Core 49 (723.6-729.4 m) is from the 

Killik Tongue (fig. 3). The sandstone in this 

core is light gray and fine to very fine 

grained; it contains well-sorted, subangular 

to angular grains (fig. 9). Analysis of the 

core indicates two major kinds of sedimentary 

structures: small-scale, lenticular, crossbed 

sets of thin laminae interbedded with smallscale, low-angle, even-parallel sets of thin 

laminae. A few thin, ripple-laminated beds 

are present near the base of this core. These 

sediments are interpreted to be foreshore 

sediments; the well-developed delta-plain 

facies lies to the west. 

NINULUK FORMATION 

In the Umiat area the Ninuluk Formation 

is mapped as a single unit with the Niakogon 

Tongue of the Chandler Formation. To the 

south of Umiat, south of the Colville River, 

the Ninuluk Formation and Niakogon Tongue of 

the Chandler Formation are separately defined 

and mapped (Brosge and Whittington, 1966), 

The Ninuluk Formation contains abundant 

sandstone and is easily distinguished from the 

dominantly marine shale of the overlying 

Seabee Formation. 

The thickness of the Ninuluk varies from 

a maximum of about 280 m just south of Weasel 

Creek Anticline (fig. 5) to about 29 m on 

..... 

~ z z w <( z w z < w 0 l!l D.. 

~ "" N 

~ 0 ~ "' ~ ~ ~ (; v; z 

8 z ~ z :.: ~ u 0 0 <( ::E u 

~ 0 

~~~ ~ ~ ~ ~ ~ >-"C c: 

~ ~ ~ 0 ~ .!: L.L 

Meters Feet u ::E u; > if 

TOP OF CORE WELL f-f-

~ 

~ t-t- 723.90- 2375 

~ ff-~ 

- ~ f= ~ 

I= .r-~ ~ 

.:::::: !:=-' t-~ 

725.42- 2380 

~ r---- 1--

f--

~ t--~ 

726.94- 2385 

-

c---

728.47- 2390- ~-

~-- c--:= ~HI - r--~ 

"' "' w 

z 

0 

z 

::1 

~ 

Umiat Anticline, a distance of about 64 km to 

the northeast (Brosge and Whittington, 1966). 

This trend in direction of thinning is similar 

to that of the underlying rocks of the Narushuk 

Group. In contrast, the overlying marine 

sequence of the Upper Cretaceous Seabee 

Formation thickens to the northeast (Bros~e 

and Whittington, 1966). 

In the Maybe Creek area (fig. 5), 

approximately 64 km to the west of Umiat, the 

Ninuluk consists of complexly interbedded 

sediments containing nonmarine fossils anc 

coal interbedded with beds containing shallowmarine fossils (Brosge and Whittington, l~S6). 

Cores 35-38 (623.9-639.2 m) are from the 

Ninuluk Formation (fig. 3). These rocks are 

predominantly medium-light-gray, very fine 

grained to fine-grained, moderately well 

sorted to well-sorted, angular to subangular 

sandstone (fig. 10). About 1. 5 m above tl'~ 

base of the core is a 1.5-m-thick sandstor~ 

interval that is moderately well to poorly 

sorted, is angular to rounded, and contains 

coaly laminae. In this basal unit are thin 

beds of poorly sorted clay-pebble conglomerate 

(clay clasts as large as 2.5 em in diameter) 

in a clay matrix; these beds are interbedded 

with moderately well sorted, thin, very fine 

grained to fine-grained beds. Immediate!~· 

above this basal 1.5-m-thick unit, smallscale, curved-parallel and discontinuous, 

wavy, nonparallel coaly laminations are present. 

The lower part of this interval contains a 

"C ..... u w~ z z E 

~ "' ~ -'>-~ I ~ 0 D.. 

w z -~ >- E" <(t-r- ;::: <( 

~ z >< 6~ ::::; a::ii:ct- z 0 g z ~ ~ ::!=:~"": 

~ ~ ~ w"' iii .......... -" :.: >- <( u..O <( 

~ > u <( ::1 u ::E L.La: ~~! 

~ ~ 0 ~ d <( w2 

SBANG- DELTA FRONT 

ANG (FORESHORE) 

Chlorite Dolomite ond 

r-Chert arenite Kaolinite Siderite(0.5%) 7 19.6 102 Immature 

Illite 

Chlorite Quortz(0.5%) 

1- Chert oren ite Kaolinite Dolomite ond 16 16.8 10 Immature 

Illite Siderite( 1.5%) 

Kaolinite(0.5%) 

1 As determmed by petrograph1c analysos 

LJ Sandstone ~Tabular 

~ crossbedding 

~ 

~ 

Trough or lenticular ~ Even parallel 

crossbedding ~ laminations 

2As determined by x-ray diffraction analysis 

3As determined by core analysis 

~ Wavy parallel 

l=.:::::::J laminations 

D7/l Curved parallel 

~ laminations 

Figure 9.--Lithology, sedimentary structures, texture, inferred environment of deposition, and 

reservoir properties, core 49 (723.6-729.4 m), Killik Tongue of the Chandler Formaticn, 

Umiat test well 11. See table 2 for more detailed information regarding mineralogy End 

reservoir properties. 

15 
..... ..... l ~ ~ z 1:< z w w < z w "' z z ~ "' u 0 "' ~ ~~ ~ :r D.. 

~ "' z < N C) w i 0 w z -~ c ;:: "' ~ i= ~ ~ v; z z ;:: < D.. 

~ < ..... ,... 

fu < 8 z z z ~ z "';;;: o- z :.: u 0 ;:: c ~ 0 g .......... < ~ ~ i= :E ~ 

~ ~ z 

I 

:.: ~ ~ ~ u- .>i c u c w"' 

~ ~ ~ ~ ~ "0 ::I 

~ > u 

>-"O ~ "0 "' ~ < tt~ ~ ~ ~ ~ as c ~ u ::I u w2 c ::. ~ c: G> G> f < 

~ LL c: Meters Feet u :E c;; > LL :E ~ 

-

- ~~~- s:~~G - -= TOP OF CORE 

DELTA FRONT Chlorite Dolomite and 

2050 = ... ~ "7' - Phyllarenite Kaolinite Siderite(4.5%) .5 10.6 0 Immature 

624.84- . ~ Illite Calcite(21.5%) 

- ~~' 

-

626.36- 2055 .:.-. ---

- ' '~~· 

·~ == = I 

- == f= I Dolomite and Chlorite Siderite(0.5%) 627.88- 2060 Phyllarenite Kaolinite 8.5 11.8 0 Immature 

t Illite Calcite(23.5%) 

~ ~ ~ 

Kaolinite(!%) 

- I -

629.41- 2065 -

-. -~~ . 1--f.---- f.---- Chlorite Dolomite and 

-

=· 

- Phyllarenite Kaolinite Siderite(4.5%) 13.3 0 Mature f= = = Illite Calcite(8%) 

2070- ~ ==-== Kaolinite(!%) 

630.93- _L f= == == = ~· ~ ~ ~ ~ 

- f= = = -;. 

= = = -

== 632.46- 2075- .- ~ 

~ ~ • ~c • 

- s:~~G I WELL -

Chlorite Dolomite and 

633.98- 2080 = Metarenite Kaolinite Siderite(1.5%) 7.4 0 Mature MOD. 

;~~~~G· Illite Calcite(56%) 

f= r= WELL 

= .~ ~ r-r- WELL -

f= f= : t= Chlorite Dolomite and 

635.50- 2085 ~~~~~ ~· ~ ~ - Phyllarenite Kaolinite Siderite(4%) 11.6 0 Immature 

: ~ i ~Q_D. ~~lg- IN Illite Calcite(6.5%) 

: ~<> POOR (FLUVIAL?) Kaolinite(3.5%) 

- -

= ..... ~.: -- = ""~ ~- iii 637.03- 2090 [o '"~ ·~ -I - . ---- ~~~-

s:f~G DELTAFRO_~T 

- - ~ ;.,::..c:-e:::_ - Illite - Phyllarenite 1 0 Immature Chlorite 10.4 

: ~~ ~ e-- 638.55- 2095 -_-=-

-

-

!: .,. :--J Conglomerate 

~~ -: · :~:~ .. ~~ Sandstone 

f= =i Claystone 

~Coal 

~ Tabular crossbedding r=:::l Discontinous wavy 1

As determined by petrographic analysi' 

t::....::::::.. nonparallel laminations 2As determined by x-ray diffraction ana'ysis 

~ Trough or lenticular crossbedding ~ Cu

1 ~ ~ rv~d P?rallel amonatoons 3As determined by core analysis 

~ Even parallel laminations 

~ Wavy parallel laminations 

~ Microcross-lamination 

Figure 10.--Lithology, sedimentary structures, texture, inferred environment of deposition, and 

reservoir properties, cores 35-38 (623.9-639.2 m), Ninuluk Formation, Umiat test well 11. 

See table 2 for more detailed information regarding mineralogy and reservoir prope~ties. 

moderately abundant assemblage of 

dinoflagellates (F. E. Hay, oral commun., 

1973). These were not datable, but they are 

similar to those of the underlying Killik 

Tongue (middle Albian to early Cenomanian(?)) 

(May, in Ahlbrandt, 1979). In turn, above 

that interval are small-scale, low-angle, 

parallel laminae of sandstone interbedded with 

homogeneous unstructured sandstone overlain by 

a few thin (15 em) sandstone beds having 

16 

lenticular crossbeds. Also, small-scale, 

curved-parallel and discontinuous, WEvy, 

nonparallel coaly laminations are present. 

The upper part of the cored interval was 

barren of fossils. 

On the basis of sedimentary structures, 

fossils, and thickness trends the N~_nuluk in 

the Umiat area was deposited, in large part, 

as delta-front sands in a shallow-marine 

foreshore environment, seaward from the typical 
delta-plain facies of the Ninuluk at the Maybe 

Creek area to the west. 

Stratigraphy and Depositional 

Environments--Colville Group 

The name Colville "Series" was first used 

by Schrader (1902) for rocks exposed along the 

Colville River below the mouth of the Anaktuvuk 

River (fig. 5). Later studies by Gryc and 

others (1951) resulted in the application of 

the name Colville Group to these rocks. They 

also included approximately 915 m of other 

Upper Cretaceous rocks underlying the originally 

defined Colville "Series" and overlying the 

Nanushuk Group. 

In the Umiat area, the Colville Group is 

about 1,678 m thick and includes three 

formations: the marine Seabee, the overlying 

nonmarine Prince Creek, and the overlying 

marine Schrader Bluff (Brosge and Whittington, 

1966). Umiat test well 11 spudded in the 

upper part (Tuluvak Tongue) of the Prince 

Creek (fig. 3). 

SEABEE FORHATION 

The Seabee Formation of the Colville 

Group thickens eastward from about 250 m at 

Wolf Creek to about 458 m at Umiat test well 11 

(fig. 5). 

The Seabee was originally named for 

Seabee Creek by Gryc and others (1951) and was 

included as a member of the Schrader Bluff 

Formation. Later it was redefined as the 

Seabee Formation by Whittington (1956) to 

include all the dominantly marine strata of 

the Colville Group that underlie the Tuluvak 

Tongue of the Prince Creek Formation. The 

type Seabee is in Umiat test well 11; strata 

lie between 166.1 m and 621.8 min this well. 

The Seabee has a very widespread distribution, 

extending from the Arctic coast to about 80 km 

south of the latitude of Umiat (Brosge and 

1.Jhittington, 1966). 

The Seabee Formation has been subdivided 

into two members: The upper member is the 

Ayiyak Hember (Detterman, 1956b); it is composed 

of about 92 m of greenish-gray siltstone and 

silty shale and light-tan to light-chocolatebrown sandstone. Detterman and others (1963) 

named the Seabee below the Ayiyak Member as 

the Shale Hall Hember, consisting dominantly 

of shale. 

Brosge and ~~ittington (1966) recognized 

four distinct sandstone beds in the Seabee on 

the west part of the Titaluk Anticline near 

Titaluk test well 1 (fig. 5). These sandstone 

beds pinch out to the east, with younger ones 

extending progressively farther east; they all 

pinch out at about the area of Fry Creek and 

Banshee Creek, approximately 80 km west of 

Umiat. Brosge and Hhittington (1966) pointed 

out that the distribution of these sandstone 

beds suggests that they were deposited in a 

17 

nearshore-marine environment by a generally 

eastward-regressing sea. The shoreline 

configuration was probably northwest. 

Cores 21-25 (402.9-419.7 m), from near 

the middle of the Shale Wall Member, consist 

of moderately well sorted, very fine grained 

to fine-grained, subangular to angular sandstone 

with some grading, especially near the top 

(fig. 11). This entire interval is dominated 

by homogeneous, generally structureless 

sandstone, indicating rapid deposition without 

development of laminae. Randomly distributed 

throughout the interval are thin (15-30 em) 

stringers of sandstone exhibiting low-angle, 

even-parallel bedding. Ripple-laminated beds 

are rare. Two mudstone beds are present at 

the base of the cored sandstone interval; 

mudstone clasts and contorted mudstone 

laminations are present. This is the first 

(oldest) cored interval in which trace amounts 

of bentonitic clay matrix were observed. This 

sandstone interval is overlain and underlain 

by dark marine shale and includes mudstone 

clasts at the base, graded bedding, and 

occasional ripple laminae. These features 

suggest marine turbidite deposition. The 

sediment may have come from a delta to the 

west. 

In shale beds approximately 23 m above 

and 15 m below the cored interval, Bergquist 

(in Collins, 1958) reported the occurrence of 

the Turonian ammonite Borissiakoceras. 

Approximately 46 m below the lower 

Borissiakoceras, Bergquist noted a shale 

interval that contains abundant radiolarians. 

Other marine invertebrates reported in the 

Seabee shales include the ammonite genera 

Scaplites and Watenoceras and the bivalve 

mollusk Inoceramus labiatus (Brosge and 

Whittington, 1966). The marine fauna of the 

Seabee Formation shales at Umiat test well 11 

is less diverse and typically more open marine 

than the Seabee Formation 64 km to the we~t at 

Maybe Creek (fig. 5). At Maybe Creek a very 

abundant and diverse mollusk assemblage is 

present (Brosge and Whittington, 1966), 

indicating shallower marine conditions in this 

area than at Umiat during Seabee deposition. 

Cores 15-16 (227.1-239.3 m) are from the 

Ayiyak Member of the Seabee Formation (fig. 

3). Sedimentologic evidence (fig. 12) suggests 

that this very fine grained to fine-grained 

sandstone with a bentonitic clay matrix was 

probably deposited in a nearshore-marine 

(foreshore) environment. The abundance of 

low-angle, even-parallel laminae of finegrained to very fine grained, moderately well 

sorted to well-sorted sandstone and the moderate 

abundance of tabular, small- to medium-scale 

crossbed sets with tangential lower contacts 

give rise to the above interpretation. 

Whether these sandstones (cores 15-16) 

were deposited in a delta-front environment is 

difficult to ascertain. Broken fragments of 

pollen and spores have been identified 
Meters Feet 

-

403.86- 1325-: 

w 

~ "' 

u 

~ 

MOD 

r---- MOD 

"' "' w 

z 

0 

z 

::I 

~ 

SBANG· 

ANG I SBANGAN!3 

1-

z z :E 0 

Q 0 ;:: 

5 g ~ 0 

TURBIDITE ?_ 

Smectite 

- _, __ .. 

·: 

f== f== --+1----1;=:-+---+-+--f-+--+------j_r- liyh~~~~\~e 

f= 

Illite 

Kaolinite 

Chlorite 

Smectite 

Calcite(0.5"1o) 21.5 18.4 127 Immature 

405.38- 1330-:: 

- -

406.90-

-

c-' -- 1--1--

I- Volcanic 

litharenite Illite 

Chlorite 

Colcite(41.5"1o) 0 0.6 0 Mature 

408.43- 1340-

- - < ~- --+~---1~-+--+-+-----ii--+--t----il- Phyllorenite 

< 1--- ~== 

Smectite 

Illite 

Chlorite 

Calcite(1.5"1o) 30 6.5 Immature 

1345 -f-: :. :. 1--- --+r------1_-+--+-+-----i-+--t-----j 

"~~[5< ~= 

409.95-

-

411.48-

-

1355-:: 

~ 

- ' bM:,D s·BANG 413.00-

- ~- ':'· 

.... _,~~~~~---~1--81-± 

t-r--- M DD SBAlG. f-fl=---lf=-~:.:.:;:_::__+-"-A7-:"N-==-G-+---t----1r-liyh~~~~\~e 

l=f= 

- Smectite 

Illite 

Chlorite 

Calcite(1.5"1o) 33.5 7.0 Immature 

414.52- 1360-

- - =f=== ~= 

~= 

416.05- 1365-: 

~= 

+~--+~-1---+-+--+-+-----11----+-liYh~~~~\~e 

~~ 

Smectite 

Illite 

Chlorite 

Mixed layer 

Calcite(0.5"1o) 35 10.1 0 Immature 

- -

417.57- 1370-:: 

- M~D 

r""-~~l Conglomerate 

L _: _'' =:-] Sandstone 

j.;_-gj Siltstone 

1.::::..:-.:] Mudstone 

I =-:::=.1 Claystone 

~ Even parallel laminations 

1...::::-~1 Discontinuous wavy nonparallel laminations 

Bill Discontinuous curved parallel laminations 

1

As determined by petrographic analysis 

2As determined by x-ray diffraction analy$iS 

3 As determined by core analysis 

~Wavy parallel laminations ISVVV\.1 Contorted lamination 

Figure 11.--Lithology, sedimentary structures, texture, inferred environment of deposition, and 

reservoir properties, cores 21-25 (402.9-419.7 m), Shale Wall ~1ember of the Seabee Formation, 

Umiat test well 11. See table 2 for more detailed information regarding mineralogy and 

reservoir properties. 

(E. I. Robbins, oral commun., 1976) and may have 

been carried into the area by distributaries of 

a delta plain. Core number 17 (245.4-248.4 m), 

from a shale bed approximately 6 m below the 

base of core 16, contains abundant dinoflagellates and some spores suggestive of 

a setting close to a marine shoreline. Abundant 

bentonitic clay matrix is present in these and 

younger strata. 

18 

TULUVAK TONGUE OF THE PRINCE CREEK FORMATION 

Gryc and others (1951) named the Tuluvak 

Tongue for outcrops east of Umiat on the 

Chandler River (fig. 5). Here coal and 

conglomerate occur in abundance; they may 

represent a lobe of delta-plain sediments 

similar to lobes of equivalent age at Wolf 

Creek and Maybe Creek to the west of Umiat. 
z 

0 

~w ~ ~ en 

c c( ~ 8 

2 Meters Feet 

TOP OF CORE 

"' 

w "'

z 

c 

z 

::J 

~ 

"' w 

D.. 

~ 

>-

c( 

d 

227.07- 745 -==1=-=1=-=t-'M-'-'OrDisAaNtjGNG-~D:..:ECFLTfCA~FRstOKNlFTtel---j Smectite Dolomite and === SBANG _ Feldspatic Illite Siderite(0.5%) 14.5 18.2 .1 Immature ~ ~ 

~ ~ . :~ ~· -:~ 7--' f:::== phyllarenite ~h~~~~~ Calcite(2%) - . ~~ 

'~ - 228.6 - 750 

!-----

~== 

- . '·;~'· -

o~·- =~ = Smectite Dolomite and 

=~= - Phyllarenite Ka~l:~~te Siderite(2%) 35.5 '1' .7 7.0 Immature 

230.12- 755 _. ~ . ~ ~ =--1~--11-=--+--f---+-+---11-----1-------1 Chlorite Calcite(2%) 

-1--1----=~= MOD- AtiG- - ~ . WELL SBANG 

231.64- 760 MOD 

-

233.17- 765 

,, -

234.69- 770 

-

Smectite Dolomite and 

- Metarenite Illite Siderite(1.5%) 17.0 12.7 Immature 

Chlorite Calcite(14%) 

Smectite 

1- Phyllarenite K~~:r~ite 

Chlorite 

Calcite( I%) 15.0 20.6 48 Immature 

t;~.;~}'j Conglomerate 

f;:::;~,}:\J Sandstone 

~Trough crossbedding 

~ Even parallel laminations 

~ Curved parallel laminations 

~ 

~ Discontinuous curved parallel 

laminations 

1

As determined by petrographic analysis 

2As determined by x-ray diffraction analysis 

3As determined by core analysis 

I ~ I Bentonite f$$j Wavy parallel laminations ~ Microcrass-lamination 

~ Tabular crossbedding 

Figure 12.--Lithology, sedimentary structures, texture, inferred environment of deposition, and 

reservoir properties, cores 15 and 16 (227.1-239.3 m), Ayiyak Member of the Seabee Form£tion, 

Umiat test well 11. See table 2 for more detailed information regarding mineralogy and 

reservoir properties. 

There previous workers (Brosge and Whittington, 

1966) noted the presence of conglomerate and 

conglomeratic sandstone units in the Tuluvak 

Tongue. These conglomeratic units grade 

eastward into sandstone, pinching out somewhere 

between Wolf Creek and Umiat test well 11, a 

distance of approximately 48 km (fig. 5). At 

Wolf Creek, the Tuluvak Tongue is about 171 m 

thick and contains at least three units of 

conglomerate and conglomeratic sandstone 

separated by finer grained clastics. Bentonite 

beds are also present. At Umiat test well 11, 

160 m of Tuluvak is present; it is exposed at 

the surface and some of the upper part is 

missing due to erosion. At Umiat the Tuluvak 

Tongue consists of interbedded very fine 

grained sandstone, shale, and siltstone (all 

quite bentonitic) and thin coal beds (fig. 3). 

In the Vlolf Creek-Haybe Creek area west 

of Umiat, the Tuluvak Tongue was building 

northward (Brosge and ~fuittington, 1966). 

This is indicated by finer grained sandstone 

found in the lower strata and by successively 

19 

younger and coarser clastics being deposited 

farther north; gravel and plant material 

become increasingly more abundant. The eastward 

decrease in grain size from fluvial conglo~erate 

to fine-grained sandstone suggests an increasing 

distance from the source, which was to the 

west-southwest, and a change in depositional 

environment from high energy fluvial to th~ 

west to lower energy fluvial, possibly deltaplain deposits, to the east. The number of 

coal beds and the abundant floras of spores 

and pollen suggest abundant plant life. A 

complexly interbedded, very nearshore marine 

to continental depositional environment 

existed in the Umiat area during depositio~ of 

the Tuluvak Tongue. This interpretation is 

supported by numerous spores, pollen, and 

dinoflagellates in the upper part of the 

Seabee and throughout the Tuluvak Tongue, by 

beds with many arenaceous foraminifers, ani by 

abundant coal-rich beds interbedded with thin 

sandstone, siltstone, and organic-rich shale 

beds. 
Cores 11-12 (157.0-167.6 m) contain 

strata from the base of the Tuluvak Tongue, 

very near but just above its contact with the 

underlying Ayiyak Member of the Seabee Formation 

(fig. 3). The lower 3.7 m of this cored 

sequence contains predominantly fine grained 

sandstone with a bentonitic clay matrix. Lowangle parallel laminations and tabular and 

wedge-planar crossbed sets are present (fig. 

13). Beds with these characteristics may 

reflect deposition of delta-front sands in a 

foreshore environment. A moderately rich 

assemblage of spores, pollen, and 

I-

>- z 

z a=: w <( 

0 <( a=: z 

:I: ~ ~ j:: V) ~ 1- 1- c a.. u w z 1- a.. 

w z <( 0 0 a.. w u 0 

c <( ~ 1- a=: >- ~ c 1- ~ a=: a=: c 1- 0 w V) 

LL >-"'0 V) 0 :l 

METERS FEET u~ 

158.5 

160.1 

c;; -

dinoflagellates occurs in this interval (E. I. 

Robbins, oral commun., 1976), attesting to the 

marginal-marine environment of depoeition. 

The upper 4.3 m of the core cortains very 

fine grained to medium-grained sand~tone 

having a bentonitic clay matrix. Th~ dominant 

sedimentary structures are small-scc.le 

lenticular crossbed sets, interbedded with a 

few climbing ripple laminae and small-scale 

tabular and wedge-planar crossbed sets. Some 

coaly and partially oxidized plant fragments 

are also present. The upper part of the core 

represents more fluvial conditions cf deposition 

z V) 1-

<( w V) z N C) w c w z a=: c;; z z w ~ 0 C) j:: c a=: z j:: a=: LL a=: z w 0 0 c;; 

0 ~ LL a=: 0 "'0 "'0 "'0 V) 0 z > a.. V) V) "'0 "'0 V) a=: z w c: V) Q) c LL c: Q) Ill :::0 w 

> LL ~ u a.. 

ANG- DPTA PLAIN 

SBANG (FLUVIAL?) 

~~~~~i~i~~~~~~ DELTA FRONT 

--i--i--i,___t--+--+--+--+- (FCQESHORE) 

161.6 530 

h~:~#(] Conglomerate 

[UJ/}:\?!) Sandstone 

~Coal 

~~Tabular 

~ crossbedding 

~ 

~Trough 

crossbedding 

~ 

~ Even parallel 

laminations 

~ 

~ Discontinous wavy 

nC'nparallel 

la'11inations 

~ 

~ 

Cun·~d parallel 

lcminations 

Figure 13.--Lithology, sedimentary structures, texture, and inferred environment of derosition, 

cores 11 and 12 (157.0-167.6 m), Tuluvak Tongue of the Prince Creek Formation, Umiat test 

well 11. 

20 
than the lower part. It probably represents 

an intertonguing of deltaic-marine-shoreline 

and fluvial deposits. 

Cores 1-2 (35.1-47.2 m) (fig. 3) consist 

of very fine grained sandstone with a bentonitic 

clay matrix (fig. 14). Very low angle, 

parallel-laminated sets are interbedded with 

small-scale (5 em thick) lenticular crossbed 

sets throughout the core. Bioturbation is 

common in silty to very fine grained sandstone 

beds containing coaly laminations near the 

base of the core. Ripple laminations occur in 

a few thin beds. These sands are interpreted 

as representing a low-energy, fluvial floodplain system in a delta-plain environment. 

The interval between cores 2 and 11 is 

composed of interbedded bentonite, sandstone, 

siltstone, shale, and coal. A very rich 

assemblage of spores and pollen was reported 

in several samples from this interval (E. I. 

Robbins, oral commun., 1976), supporting a 

continental setting for these sediments. 

Summary.--The following summary of 

characteristics of the sandstone cores studied 

includes some data from table 2: 

~ 

z 

;:::: 

~ 

~ 1-

z z w <( z 0 ~ or:: z ~ w 

~ 0 ;:::: "' :.: w ~ N 

z <( .... u .... z :E v; 

<( ~ e ~ ~ ~ u 0 ~ 

0 

~ 0 ..., 

f2 ~ ~ ,....., ~ "' ~ c: ..., a :> - u.. c: II> ~ Meters Feet u ~ iii > u.. ~ u if 

"' "' w 

z 

0 

z 

::I 

~ 

ANG· 

=~ 

=~ 

=~ 

=~ 

--'-----

=== 

--- === 

==~ 

==~ 

=== === 

=== 

MOD. 

WELL 

SBANG 

Characteristics Nanushuk Group 

Environment--------------- Predominantly 

foreshore and 

shoreface sands 

deposited in a 

delta-front----

Volcanic rock fragments--- Not abundant-----

Metamorphic rock fragments Abundant---------

Smectite------------------ Absent-----------

Quartz grains------------- Abundant---------

Feldspar------------------ Not abundant-----

Biotite------------------- Not abundant-----

Detrital chert------------ Abundant---------

Organic material---------- Not abundant-----

Quartz overgrowths-------- Abundant---------

Calcite cement------------ Not abundant-----

Matrix material----------- Not abundant-----

Reservoir quality--------- Good-------------

PETROGRAPHY 

Col ville Group 

Variety of environments rep-:--esented 

including turbidite, 

foreshore, and 

fluvial. 

Abundant. 

Not abundant. 

Abundant. 

Not abundant. 

Abundant. 

Abundant. 

Not abundant. 

Abundant. 

Not abundant. 

Abundant. 

Abundant. 

Poor. 

Forty-five core samples ("perm plugs") 

previously used for porosity and permeability 

analyses (Collins, 1958, p. 192) were thinsectioned and studied petrographically in an 

effort to identify the factors affecting 

porosity and permeability. Except for one 

sample of siltstone, all samples are sandstone. 

X-ray diffraction analysis was used to identify 

clay and major mineral constituents in samples 

taken as closely as possible to 35 of the 

1-

~ z } z ~ "' u 

i ~ 0 w z -~ 

~E ~ ~ ~ <( .... z ~ 0 ;:::: z ~ ~ z I ~ ii1 

~ g ~ ~~ ::I :.: >- ~ < ..>i. 

~ > u 

~ <( ::I u ~ ~ ~ ai 0 0 <( 

DELTA PLAIN 

Smectite Dolomite and 

Feldspathic llli.te. Siderite(l.5%) 26.5 10.2 

- phyllarenite Kaolon.'te Calcite(7.5%) Chlonte 

Immature 

c=J Sandstone (: -1 Coal ~ 

~ 

Even parallel 

laminations 

r::::::::::-::: Discontinuous wavy 

t::::....:::::: nonparallel laminations 

1 As determined by petrographic analysis 

2As determined by x·ray diffraction analy$iS 

3As determined by core analysis ~Breccia ~ 

~Trough 

~ crossbedding 

c=::::::::l 

~ 

Wavy parallel 

laminations ~Curved parallel laminations 

Figure 14.--Lithology, sedimentary structures, texture, inferred environment of ~eposition, and 

reservoir properties, cores 1 and 2 (35.1-47.2 m), Tuluvak Tongue of the Pr1nce Creek 

Formation, Umiat test well 11. See table 2 for more detailed information regarding mineralogy 

and reservoir properties. 

21 
Table 2.--Petrography and reservoir properties 

[Mod., modal; Max, maximum; Qm, monocrystalline quartz; Pq, polycrystalline quartz; P, plagioclase feldspar; K, alkalic feldspar; Mu, muscovite; B, biotite; 

metaquartzite; Cl, chlorite; Ph, phosphatic(?) nodules; Or, organic material; Qg, quartz overgrowths; Ch, chert; Ka, kaolinite; D, dolomite and siderite; 

smectite; Ml, mixed layer; Ap, Air permeability; Ep, effective porosity; Vp, visible porosity; V po, modal size of visible pores; PWC, pore-wall coatings; 

1 

Color 

Mod. Max. 

grain grain 

size size SortOptical mineralogy• 

Detrital rains 

Sample 

No. 

Depth 

m(ft) Dry Wet (Jlm) (Jlm) ing' Stain' Qm Pq p• K Mu Og G Z T Lv Ch Mp Mq Cl Ph 

118 

128 

140 

233 

33L 

514 

519 

532 

Mean 

Stan. 

dev. 

36.0(118) 

39.0(128) 

42. 7(140) 

71.0(233) 

100. 9(331) 

156. 7(514) 

158. 7(519) 

162. 2(532) 

N7 

na 

N7-N8 

N7 

N7 

545 166.1 ( 545) N7-N8 

746 227,4( 746) NS 

754 229,8( 754) N7 

763 232. 6( 763) N7 

771 235.0( 771) N6 

1328 404. 8(1328) N7 

1331 405. 7(1331) N6-N7 

1343 409. 4(1343) N6-N7 

1358 413. 9(1358) N7 

1365 416.1(1365) N6 

1824 556.0(1824) N6 

Mean 

Stan. 

dev. 

SY4/l 90 

na na 

SY4/1 225 

N4 90 

SY4/1 80 

570 

na 

722 

494 

456 

121.3 560.5 

69.3 117.6 

SYS/1 230 722 

5Y4 /1 150 608 

5Y3/1 95 532 

SY4/l 120 456 

5Y4/1 260 608 

5Y4/1 133 494 

5Y4/1 190 760 

5Y3/1 150 418 

5Y4/1 150 646 

5Y4/1 135 608 

5Y4/1 75 494 

153.5 576.9 

54.8 100.6 

N4-

2049 624. 5(2049) N6-N7 SY4/l 85 228 

2060 627.9(2060) N6 SY4/l 150 418 

2068 630. 3(2068) N7 5Y4/1 160 342 

2075 632.5(2075) na 

N3-

2080 634. 0(2080) N6-N7 SY3/1 120 304 

2085 635,5(2085) N6-N7 5Y3/1 ll5 760 

2093 638, 0(2093) N6 N3 95 684 

2110 643.1(2110) N6-N7 N3 190 1026 

N4-

2117 645. 3(2117) N6 5Y4/l 228 1406 

2120 646.2(2120) N6-N7 NS 228 1786 

N4-

2128 648.6(2128) N7 5Y4/l 190 570 

156.1 752.4 

vps 

ps 

ps 

ps 

ps 

Mean 

Stan. 

dev. 52.1 512.6 --

2200 670,6(2200) N7 

2235 681. 2(2235) N6 

2298 700.4(2298) N6-N7 

2305 702. 6(2305) N7 

2378 724.8(2378) N7 

2386 727.3(2386) N7 

Mean 

Stan. 

dev. 

2445 745.2(2445) N6-N7 

2450 746.8(2450) N6-N7 

2453 747. 6(2453) N6-N7 

2460 749.8(2460) N6-N7 

2532 771,8(2532) SY7/l 

2813 857. 4(2813) N7 

2824 860.8(2824) N7 

2832 863. 2(2832) N6-N7 

2841 865. 9(2841) N7 

2849 868.4(2849) N7-N5 

2925 891.5(2925) N7 

2990 911.4(2990) N7 

2997 913. 5(2997) N7 

3005 915.9(3005) N6-N7 

Mean 

Stan. 

dev. 

All samples 

Mean 

Stan. 

dev. 

SYS/1 100 

N4-

SY4/l 190 

NS 190 

5Y4/1 70 

N4-

5Y4/l 175 

5Y4/1 57 

266 

532 

798 

190 

456 

304 

130.3 424.3 

61.7 222.1 

5Y4/1 150 1064 

5Y4/l 133 646 

N4-

6Y4/1 114 532 

5Y4/1 150 722 

SY4/1-

10Y4/2 270 836 

N4-

SY4/1 190 608 

SY4/l 228 570 

SYS/1 228 608 

N4-

SY4/1 150 381 

SY5/1 209 608 

SY4/l 80 304 

SY4/1 165 320 

SY4/l ISO 380 

SY3/1 116 228 

166.6 557.6 

52.4 226.9 

152.2 588.1 

55.1 297.3 

s 

A 

s 

A 

s 

A 

Tuluvak Tongue of the Prince Creek Formation 

22.0 

na 

15.0 

12.0 

7.5 

1.5 10.0 

na na 

6.0 9.0 

3.0 6.5 

1.0 3.0 

1.5 

1 na 

1 na 

1 na 

tr 

na 

tr 

tr 

0 

3.5 

na 

.5 

tr 

8.0 

tr 

na 

tr 

tr 

tr 

na 

0 

0 

0 

na 

0 

0 

0 

na 

0 

0 

0 

1.5 

na na 

0 15.0 

0 10.5 

0 s.o 

11.0 

na 

12.5 

13.0 

4.5 

8.5 

na 

7.5 

8.5 

3.5 

3.0 

na 

5.5 

7.0 

3.0 

tr 

na 

na 

tr 

0 

0 

na 

0 

0 

0 

14.13 2. 88 7.13 0.08 3.03 0.1 o.o o.o o.o o.o 8.00 10.25 4.0 4.63 o.os o.o 

6.09 2.25 3.12 .05 3.65 .o .o 

Seabee Formation 

12.5 4.5 4.0 2.5 tr tr 

10.0 6,5 11.5 6.0 tr 1.5 tr tr 

15.0 2.5 6.0 2.5 .5 1.5 tr tr 

16.5 5,0 8.0 1 na tr 1.0 tr 0 

8.5 8.5 9.0 .s tr .5 tr 0 

8.0 1.0 7.0 2.0 tr 1.0 tr 0 

6.0 .5 9.0 .5 tr .5 tr 0 

10.5 3.5 9.0 tr tr 1.0 tr tr 

9.0 tr 9.0 1.5 0 2.0 tr 0 

8.0 1.0 12.5 1.0 tr 1.0 tr tr 

29.5 8.0 2.0 .s .s • 5 tr tr 

12.14 3.74 7.91 1.71 0.15 0.96 0.1 o.s 

6.57 3.02 3.06 1.74 .18 .ss .o .5 

Ninu1uk Formation 

.o 

tr 

0 

0 

tr 

.o 

0.02 o.o 

.04 .o 

.o s. 96 3. 93 2. 3.~ 1. 97 .06 .o 

n.o 

7 .s 

2.0 

2.0 

5.5 

28.5 

22.5 

16.5 

22.0 

21.0 

0 

o.o 12.59 

22.5 11.0 11.5 tr 

7.0 14.0 9.0 1.5 

10.5 14.5 4.5 tr 

10.5 11.0 12.5 tr 

14.0 19.5 10.5 tr 

6.0 11.5 12.0 tr 

4.5 8.0 s.s 1.5 

6.0 11.5 9.5 .5 

5.5 14.0 2.0 tr 

5.0 9.0 5.0 tr 

s.o 10.5 6.5 .5 

8.77 12.23 8.05 0.43 o.o 

.o 9.94 5.46 3.16 3.52 .55 .o 

A 20,0 5.0 0.5 0.5 tr tr 

tr 

,5 

tr tr tr 7.0 18.0 13.5 o.s 

A 17.0 3.5 1.5 1.5 tr 

A 22.5 6,0 1.0 tr 1.0 

s 10,5 3.0 .5 3.5 tr 

A 9.5 3.5 1.0 1.0 tr 

32,5 6,0 .5 .s tr 

47.5 8.5 tr tr tr 

43.0 10.5 tr tr tr 

41.5 6.0 .s .s tr 

41,5 8.0 1.0 tr tr 

tr 

tr 

.5 

0 

tr 

0 

tr 0 0 

tr 0 tr 

tr tr 

tr tr 

tr tr tr 

tr 0 0 

tr tr 

tr 0 

tr tr 

tr 

tr 

tr 

0 

tr 

tr 

13.5 16.0 12.5 tr 

15.0 18.0 16.5 tr 

6.0 9.5 9.5 tr 

tr 23.0 24.5 12.5 tr 

0 8.5 21.5 10.5 4.5 

0 13.0 8.5 10.5 1.0 

17.0 8,0 12.5 1.0 

17.5 7.5 19.0 1.0 

tr 12,0 9.0 18.5 .5 

28.55 6.00 0.67 0.79 0.19 0.15 0.1 0.02 0,07 0.05 0.0 0.02 13.25 14.C5 13.55 0.89 0.0 

A 

s 

A 

s 

A 

14.34 2.43 .44 1.06 .28 .19 .o .04 .os .os .o 

Killik Tongue of the <:handler Format!<>n 

29.0 

48.0 

50.5 

39.5 

31.0 

44.5 

6.5 

6.5 

6.0 

10.0 

8.0 

4.0 

1.5 

1.5 

tr 

2.0 

3.0 

2.5 

2.5 

.s 

tr 

3.0 

s.s 

1.0 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr tr 

tr tr 

tr tr 

tr 0 

tr tr 

tr .5 

tr 

tr 

tr 

0 

tr 

tr tr 

,04 5.23 6.29 3.35 1.33 o.o 

tr 

.s 

0 

0 

tr 

0 

9.0 10.0 

16.0 7 .o 

14.5 2.5 

13.0 6.0 

22.5 6.5 

14.0 7.5 

1.5 

7.5 

9.0 

5.0 

8.5 

4.0 

2.0 

.5 

tr 

tr 

tr 

1.0 

40.42 6.83 1.77 2.10 0.10 o.o8 0.1 o.1s o.o3 o.os 0.2 0.12 14.83 6.sq s.92 o.63 o.o 

8.90 2.02 1.00 2.01 .o .04 .0 .18 .OS .OS ,4 

Grandstand Formation 

41.5 14.0 

34.5 7. 5 

37.5 4.5 

42.5 s.s 

32,0 8.5 

33.0 9.5 

29.5 12.0 

so.o 10.5 

31.5 8.5 

44.0 5.5 

42.5 4.0 

29.0 7.0 

33.0 6.5 

35.0 6.0 

36.82 7.82 

1.5 

1.0 

.s 

tr 

.s 

1.0 

1.5 

.s 

.5 

1.5 

3.5 

2.5 

2.5 

3.5 

1.47 

0.5 

.5 

•na 

tr 

1.0 

1.0 

1.0 

1.0 

3.0 

1.0 

2.5 

6.0 

2.5 

2.5 

• 74 

tr 

.s 

tr 

tr 

tr 

tr 

tr 

• 5 

0 

tr 

tr 

tr 

tr 

0.14 

6.30 2.89 1.12 1.58 .16 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr 

tr tr 

tr tr tr 

tr 

tr 

tr 0 0 tr 

tr tr 0 

tr tr 0 

tr tr 0.5 

tr tr tr 

tr tr 0 

tr 0 

tr 

tr 

0 

0 

0 

0.04 0.1 o.os 0.05 0.04 o.o 

.05 .o .os .13 .05 .o 

.19 4.43 2.4~ 2.92 .76 .o 

tr 

tr 

.s 

0 

tr 

tr 

0 

tr 

0 

0 

.s 

0 

tr 

0.11 

23,0 6.0 4.5 tr 

19.5 10.0 6.5 1.0 

19.5 7.5 7.5 

20.0 8.5 4.0 

39.5 1.0 2.5 

.s 

tr 

27.5 s.o 5.0 tr 

27.5 4.5 3.5 tr 

14.5 1.0 s.s 0 

18.5 11.5 8.5 

20.0 4.0 8.0 

8.0 11.5 1.0 

12.0 16.0 4.0 

11.0 19.0 5.5 

10.0 16.5 3.5 

.5 

0 

tr 

.5 

.5 

.5 

tr 

0 

0 

0 

0 

0 

0 

19.32 8.71 4.96 0.29 0.01 

.17 8.40 5.67 2.13 .30 .03 

27.41 5.85 3.41 1.54 0.14 0.56 0.1 0.05 0.04 0.03 o.o 3.84 13.99 10.32 7.72 0.48 o.o 

14.18 3.14 3.59 1.57 .18 1.32 .o .08 .08 .05 .01 7.43 7.34 5.36 4.38 .77 .01 

~~~:~~~t~:! ~=~=~s~n !~~;1 analysis of 200 points; 

vws, very well sorted; ws, well sorted; 

mws, moderately well sorted; ps, poorly sorted; 

values for all constituents are in percent. vps, very poorly sorted. 

22 
of selected core samples from Umiat test well 11 

Og, gray opaque mineral; G, garnet, Z, zircon; T, tourmaline; R, rutile; Lv, volcanic rock fragments; Ch, chert; Mp, phyllite and (or) schist; Me>, 

Oy, yellow opaque mineral; Det., detrital; grns., grains; aut., authigenic; min., minerals; C, calcite; Mx, matrix; Q, quartz; Dd, dolomite; I, illite; S, 

na, not analyzed; tr, trace; leaders ( ---), not applicable; np, not present; Stan. dev., Standard deviation; pet., percent; md., millidarcy] 

Det. 

grns. 

and X-ray mineralogy 

-----:-Au-t""'"h-:-i-ge-n-=-i-c -m-:-i-ne_r_a=-ls-- :~~:·----,Mx;-----~Ro:-c-:k-na_m_e ____ Who~;::~c~e~;~~~ion g~:k f~=~~~~) 

Reservoir properties 

OrQgCh KaD 0y C KPCDdClKai S Ml Ap Ep Vp V po PWC Sample 

(md) ( ct.) ( ct.) (~m) (:ct.) No. 

Tuluvak Tongue of the Prince Creek Formation 

tr 

na 

0 

.s 

tr 

na 

0 

0 

0 

na 

0 

0 

0 

0 1.5 

na na 

0 s.o tr 1.0 

0 1.0 

na 

tr 

tr 

0 

7.5 

na 

0 

5.0 

2.0 

26.5 Feldspathic phyllarenite- 46 130 130 np np 

na---------------------- 43 44 38 np np 

na na----------------------- 38 87 52 17 25 

23.0 Volcanic litharenite---- na 

33.0 Phyllarenite------------- na 

57. 5 -----do----------------- na na na na 

na----------------------- 42 23 82 7 27 

na---------------------- 39 63 37 34 38 

0.18 o.o o.o 0.03 2.13 0.05 3.63 35.0 

.22 .o .o 

0 

1.5 

tr 

tr 

.5 

tr 

0 

.5 

tr 

1.0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

.05 1. 93 .06 3. 30 15.56 

1.0 

.s 

2.0 

1.5 

tr 

0 

tr 

0 

0 

0 

4.0 

tr 10.0 

tr 2.0 

tr 2.0 

tr 14.0 

tr 1.0 

tr .s tr 41.5 

tr 1.5 

tr 1.5 

tr .5 

tr 16.5 

Seabee Formation 

7.0 Phyllarenite------------- na na na na 

14.5 Feldspathic phyllarenite- 40 12 62 np 31 

35.5 Phy11arenite------------- 33 85 48 np 33 

17.0 Metarenite-------------- 32 29 32 17 17 

15.0 Phy11arenite------------- 37 35 54 7 7 

21.5 Volcanic litharenite---- 17 31 32 10 5 

.o -----do------------------ 12 32 45 103 6 

30.0 Phy11arenite------------ 22 50 85 np np 

33.5 Volcanic litharenite----- 14 49 39 np np 

35.0 -----do----------------- 28 61 90 np np 

15.5 Phy11arenite------------- na 

0.35 o.o o.o o.o 0.84 0.1 8.27 20.41 

.49 .o .o 

tr 

tr 

0 

0 

tr 

tr 

tr 

tr 

0 

.5 

tr 

tr 

tr 

.o 1. 26 .o 12.46 11.84 

0 4.5 

1.0 .5 

1.0 4. 5 

0 1.5 

3.5 4.0 

0 tr 

0 tr 

0 1.0 

tr tr 

0 1.0 

tr 21.5 

tr 23.5 

tr 8.0 

tr 56.0 

tr 6.5 

tr tr 

tr 0 

tr 

tr 

tr 

Ninuluk Formation 

8.5 

8.5 

s.o 

Phyllareni te------------ 39 

----do------------------ 42 

-----do----------------- 61 

na----------------------- 59 

tr Metarenite-------------- 30 

11.0 Phy11arenite------------- 63 

15.0 -----do----------------- 39 

4.0 Metarenite--------------- na 

5.0 -----do----------------- na 

4.0 ----do------------------ na 

3.0 -----do----------------- na 

8 28 31 23 

11 26 29 39 

48 28 19 26 

6 32 20 34 

33 134 57 

34 19 16 

13 np np 

0.02 0.12 o.o 0.56 1.73 0.1 11.56 6.41 

19 

20 

12 

17 

14 

33 

17 

np 

np 

31 

na na 

17 12 

30 12 

21 np 

12 5 

13 9 

4 np 

13 np 

19 np 

8 np 

14 

17 

13 

23 

16 

20 

11 

28 

13 17 

8 8 

20 np 

45 

51 

28 

na 

29 

26 

na 

46 

41 

71 

27 

11 

14 

18 

14 

10 

47 

37 

20 

53 

9 

12 

26 

na 

9 

5 

na 

3 

7 

3 

2 

tr 

tr 

3 

tr 

tr 

np 

np 

np 

np 

34 np 

24 np 

48 np 

np na 

np 21 

np 6. 21 

(1 

np 

np 

0 

0 

10.2 

13.1 

5.4 

17.85 

13.94 

15.9 

16.8 

2.0 100 

na na 

1.0 50 

tr 20 

4.0 100 

95 

na 

95 

95 

100 

0.03 14.47 1. 78 67 .so 96.25 

.05 3.27 1.67 39.48 2.50 

<1 np 5.1 

np 7.0 

np .0 

np 48 

np 27 

np 0 

tr 0 

np 0 

11 0 

0 

14.9 

18.25 

17.7 

12.7 

20.64 

18.4 

.55 

6.46 

7.03 

10.1 

9.66 

2.5 

7 .o 

1.0 

1.0 

7 .o 

1.0 

0 

0 

0 

0 

.5 

50 

70 

40 

40 

20 

60 

0 

0 

0 

0 

15 

95 

95 

95 

95 

95 

75 

0 

0 

0 

0 

75 

7.93 12.40 1.82 26.82 56.82 

15.55 6.24 2.67 26.29 45.68 

np 

np 

np 

np 

np 0 

np 0 

np 0 

29 

14 

28 

na 56 

10.58 

11.79 

13.32 

7.39 

11.55 

10.41 

14.50 

0.5 

1.0 

1.0 

tr 

tr 

6.5 

23 

20 

40 

0 

30 

20 

80 

13.45 2.0 40 

13.40 2. 5 25 

15.65 5.5 70 

0 

25 

0 

50 

60 

15 

20 

60 

40 

12.70 12.20 1.92 34.80 24.0 

118 

128 

140 

233 

331 

514 

519 

532 

545 

746 

754 

763 

771 

1328 

1331 

1343 

1358 

1365 

1824 

2049 

2060 

2068 

2075 

2080 

2085 

2093 

2110 

2117 

2120 

2128 

.04 .14 .o 1.11 1.86 .o 18.01 4.35 19.28 2.38 2.31 24.14 24.24 --

tr 

1.0 

1.0 

.5 

tr 

.5 tr 

tr 1.0 

tr 

tr 

tr 1.0 

0 .5 

.5 1.5 

tr 31.0 

tr· tr 

tr tr 

tr 0 

Killik Tongue of the Chandler Formation 

5. 5 Phyllareni te------------- na 

3.5 Chert arenite----------- na 

3. 0 ----do------------------ na 

9.5 -----do----------------- na 

na 

na na 

na 

na 125 

na 550 

na 13 

tr 7.0 ----do------------------121 8 23 np np 6 18 np np 102 

tr tr 16.0 -----do----------------- 95 21 95 np np 18 33 22 np np 10 

12.4 0.5 

15.65 7.5 80 

19.80 13.5 80 

16.15 10.5 40 

19.6 7. 5 50 

16.78 2.5 40 

60 

10 

(10 

40 

40 

40 

o.o 0.53 0.02 .12 0.70 0.1 5.22 7.42 133.33 16.73 7.0 49.50 33.33 

.o .40 .04 .19 .56 .o 12.63 4.83 210.78 2.75 4.85 27.74 19.66 

tr tr 

tr 1.0 

tr 

.s tr tr 

tr 

0 

Grandstand Formation 

3.0 Chert arenite------------107 5 12 np np 

9.5 -----do------------------127 np 56 np np 

12 np np 120 

11 np np 81 

12.0 ----do------------------ 88 17 np np 10 6 15 np np 18 tr 1.0 

0 tr 

tr 3.0 0 

tr 2.5 1.0 tr 11.0 -----do------------------121 20 np np 13 13 25 np np 27 

0 1.0 tr 

1.0 tr .5 tr 

2.0 tr 2.5 tr 

2. 5 0 tr tr 

1.0 1.0 

0 2.0 

0 tr 

0 1.0 

0 1. 5 

tr 

0 tr 

• 5 tr 

0 3. 5 

.5 1.0 

.5 3.5 

0 4.5 

.5 tr 

.5 0 

.5 1.0 

tr 0 

tr 

0 

0 

tr 

0 

tr 

0 

0 

0 

0 

0 

1. 5 ----do------------------ na 

8.0 -----do------------------115 np 28 np np 

3.0 ----do------------------123 7 24 np np 

3.0 -----do------------------150 6 30 np np 

11.0 Phy11arenite-------------164 18 np np 

3.0 Chert arenite------------133 13 np np 

19.5 Phy11arenite------------- na na 

15.0 -----do----------------- 68 10 47 np np 

8. 5 ----do------------------ 74 25 44 np np 

17.5 -----do----------------- 55 20 43 np 11 

na 

11 

13 

17 

235 

np np 100 

np np 158 

np np 280 

na na 

np 

np 

6 23 np 

10 26 np 

8 30 np 

np 7 na 

np 400 

0 

np <1 np 2.3 

np 0 

17.60 6.0 

16.45 8.0 

14.83 6.0 

14.95 s.o 

60 

40 

50 

50 

18.96 12.0 100 

16.35 8.0 60 

17.35 u.s 75 

17.1 11.5 120 

14.71 4.0 

19.25 10.5 

11.96 3.5 

13.5 5.0 

12.85 5.5 

10.2 .5 

40 

100 

12 

30 

50 

17 

25 

25 

25 

50 

<5 

30 

<1 

<1 

.75 

<1 

55 

25 

25 

40 

2200 

2235 

2298 

2305 

2378 

2386 

2445 

2450 

2453 

2460 

2532 

2813 

2824 

2832 

2841 

2849 

2925 

2990 

2997 

3005 

0.09 1.03 0.02 0.34 1.36 0.21 0.10 8.96 101.53 15.43 6.93 57.43 27.16 ---

.26 .77 .04 .66 1.65 .30 .26 5.80 

0.14 0.42 0.01 0.25 1.30 0.13 5.64 13.30 

.31 .63 .03 .66 1.54 .17 11.85 11.91 

4A, alizarin red; s, sodium cobaltinitrite. 

5Includes some alkalic feldspar in some samples • 

125.97 2.65 3.46 31.73 22.31 --

54.13 14.06 4.12 44.76 40.67 --

na 112.37 4.09 3.96 31.17 35.50 ---

6unsuccessful stain; counted with plagioclase. 

7 Sample too friable to test. 

23 
perm-plug sample locations. No previous 

petrographic study of rocks from Umiat test 

well 11 exists, but Krynine (1947, 1948) and 

Krynine and Ferro (1952) studied rocks that are 

stratigraphically equivalent in other test 

wells in NPRA, including other Umiat wells. 

Sample depth, stratigraphic position (using 

the boundaries assigned by Collins, 1958), 

petrography, and reservoir properties of all 

samples are shown in table 2. 

Two disc-shaped slices 20 mm in diameter 

were cut from the end of each perm plug and 

used to make one standard petrographic thin 

section per sample. Thin sections of samples 

with high contents of smectite were cut and 

ground in oil. The thin sections were 

impregnated with blue dye to show porosity. 

Thin sections of samples with high contents of 

carbonate minerals were stained with alizarin 

red dye; the remainder were stained with 

sodium cobaltinitrite for feldspar 

identification. Two hundred points per thin 

section were counted for modal analysis. 

Hodal grain size of the sand fraction only was 

estimated using an ocular micrometer; and, 

similarly, sorting of the sand fraction only 

was estimated using the reference photographs 

of Beard and Weyl (1973). The rocks are named 

according to the classification of Folk and 

others (1970), with the addition of the term 

"metarenite" to describe a litharenite composed 

mainly of metamorphic rock fragments other 

than phyllite. 

For each sample studied by X-ray 

diffraction techniques, the fraction that is 

less than 2 ~m (micrometers) was used to 

prepare an oriented clay moun5 which was 

subsequently glycolated at 60 C for 24 hours 

and heated to 300°C and 500°C respectively for 

1 hour. X-ray diffraction patterns were run 

after each of these steps. In addition to 

analysis of the fraction that is less than 

2 ~m, each sample was analyzed on a whole-rock 

basis in order to identify the major mineral 

assemblages. For each mineral identified, the 

height of a specified peak above background 

was measured in order to determine a peak 

height intensity. Table 2 shows the relative 

proportions according to peak height intensity 

between the identified clay minerals for each 

of the samples studied. Each X-ray diffraction 

trace was run at 2° 28 per minute with nickelfiltered CuKa radiation. Instrument conditions 

were 34 kilovolts, 18 milliamperes, and a 

counting rate of 3,000 counts per second. 

Criteria used for clay-mineral 

identification are as follows: Kaolinite 

displays a sharp basal (001) peak at 7.13 A 

and a (002) peak at 3.58 A. The kaolinite was 

unaffected by glycol and0 collapsed after being 

heated for 1 hour at 550 C. Because all of 

the samples studied contained considerable 

amounts of well-crystallized chlorite, the 

(001) kaolinite peak could not be distinguished 

from the (002) peak of chlorite. Therefore, 

24 

resolution of the 3.54-A chlorite peak from 

the 3.58-A kaolinite reflection was used 

for positive kaolinite identificatio~ and 

measurement of peak intensity. 

Chlorite gives a sharp (001) basal spacing 

at 14.2 A. The intensity of this peak is 

unchan§ed upon glycolation or heat treatment 

at 550 C for 1 hour. A sharp, well-1eveloped 

(002) reflection is present at 7.0 A and is 

consistently more intense than the (001) peak; 

however, it interferes with the (001) kaolinite 

peak. Positive chlorite identification was 

based on the presence of a sharp (004) peak at 

3.54 A. Both the (002) and ~004) reflections 

collapse upon heating at 550 C for 1 hour. 

Illite is identified by a strong, wellordered (001) reflection at 10.0 A that is not 

affected by glycolation. Heat treatments to 

500°C for 1 hour cause a sharpening of basal 

reflections. 

Smectite shows a broad basal (001) 

reflection at 12.6 A, which expands to 17.3 A 

upon glycolation at 60°C for 24 hours. Because 

the smectite contains between 80 and 100 

percent expandable layers, the (003) glycolated 

reflection at 5.68 A was used to measure pe~k 

height intensity. Heat treatment above 300 C 

caused the smectite to collapse. A measure of 

crystallinity following the methods of Biscaye 

(1965) indicates that, in almost all of the 

samples studied, the smectite is well 

crystallized. 

Interstratified minerals are recognized 

in only two of the samples studied. Glycolation 

and heat treatments indicate that the mixed 

layering is predominantly chlorite-snectite. 

Its presence is indicated by an inconplete 

collapse of the smectite peak upon heating at 

550°C for 1 hour. 

The following criteria were used to 

identify the major minerals in the whole-rock 

fraction. Quartz identification was based on 

the presence of the 4.27-A reflection. The 

strongest (101) quartz peak, at 3.35 A, 

interferes with the (003) peak of illite at 

3.33 A and therefore was not used for measuring 

peak height intensity. 

Both alkalic feldspar and plagioclase 

feldspar were recognized in all of tl'~ samples 

studied. The peak position used to identify 

alkalic feldspar ranged fr~m 3.20 A to 3.25 A, 

and the plagioclase reflection rangec from 

3.18 A to 3.19 A. 

Calcite and dolomite were identified in 

samples from the Tuluvak Tongue of tl'~ Prince 

Creek Formation and from the Seabee and Ninuluk 

Formations. Calcite was identified l'Y a 

strong sharp peak at 3.03 A and dolomite by a 

sharp symmetrical peak at 2.89 A. Siderite 

was tentatively iuentified in some samples by 

a reflection near 2. 79 A; however, its presence 

was somewhat uncertain. Neither magr~sian 

calcite nor ankerite was recognized in any of 

the samples studied. 
Nanushuk Group 

GRANDSTAND FORMATION AND KILLIK TONGUE OF THE 

CHANDLER FORMATION 

Rock samples analyzed from the Grandstand 

Formation and Killik Tongue are petrographically 

similar. They are light-gray, well-sorted, 

very fine grained to fine-grained chert arenites 

and phyllarenites relatively poor in quartz 

and rich in lithic fragments such as chert, 

phyllite, and metaquartzite (figs. 15-19). 

Detrital grains are mainly angular to 

subangular. The amount of matrix is highly 

variable, and, except in sample No. 2200, 

carbonate is present in small amounts. Many 

of the samples from the Grandstand Formation 

and Killik Tongue have excellent porosity and 

permeability (figs. 20-23). 

Detrital Grains 

Quartz grains are generally strained and 

quartz individuals in polycrystalline quartz 

grains generally have slightly sutured 

boundaries. Most plagioclase grains exhibit 

albite twinning and appear to be sadie 

plagioclase. The plagioclase is unzoned and 

generally unaltered. Grains of alkalic feldspar 

are blocky and mostly unaltered. The feldspar 

is generally untwinned, although a few grains 

exhibit grid twinning. Some grains are 

perthitic. X-ray diffraction analysis indicates 

that alkalic feldspar is significantly le~s 

abundant in the Nanushuk Group than it is in 

the Colville Group. 

Detrital chert is dominantly 

microcrystalline, with the individual crystals 

averaging about 3-12 ~m in diameter. The 

QUARTZ 

LITHIC 

FELDSARENITE 

FELDSPATHIC 

LITHARENITE 

EXPLANATION 

6. Tuluvak Tongue of Prince Creek FormE'tion 

Seabee Formation 

1!!1 Ninuluk Formation 

o Killik Tongue of Chandler Formation 

X Grandstand Formation 

6. 

1!!1 1!!1 

. . 

FELDSPARL-----------------~------------------~~----------------~----------------~ ROCK 

50% FR.AGMENTS 

(including chert) 

Figure 15.--Primary arenite triangle (Folk and others, 1970) showing composition of samples listed 

in table 2. Each symbol indicates the formation from which the sample came. 

25 
METAMORPHIC 

ROCK FRAGMENTS 

\ 

\ 

\ 

\ 

EXPLANATION 

6 Tuluvak Tongue of Prince Creek Formation 

• Seabee Formation 

181 Ninuluk Formation 

o Killik Tongue of Chandler Format'on 

x Grandstand Formation 

PHYLLARENITE 

X\ \ 

0 

VOLCANIC LITHARENITE 

0 0 

0 

x\ 

\ 

~ 

\ 

~ 

\ 

SEDIMENTARY LITHARENITE \ X 

IGNEOUS SEDIMENTARY 

ROCKL-----------------------------------~~--------------------------------~ ROCK 

FRAGMENTS 50% FRAGMENTS 

Figure 16.--Litharenite triangle (Folk and others, 1970) showing composition of samples listed in 

table 2. Each symbol indicates the formation from which the sample came. 

chert grains are colorless to yellow to dark 

brown, and some grains are highly charged with 

inclusions, including clay(?) and euhedral 

crystals of pyrite and dolomite. Patches of 

chalcedonic chert, both length-slow and lengthfast varieties, occur in a few microcrystalline 

chert grains; a very few grains are wholly 

chalcedonic chert. In rare cases chert grains 

are slightly deformed, but in general they 

behave as noncompressible (nonductile) detrital 

grains. Some grains that otherwise appear to 

be chert contain abundant and, in some cases, 

subparallel flakes of sericite. These grains 

of "sericitized chert" may represent altered 

or even slightly metamorphosed chert, or they 

may actually be grains of a low-grade 

metamorphic rock such as slate. 

Metamorphic rock fragments include both 

phyllite and metaquartzite. The phyllite is 

characteristically composed of subparallel 

flakes (average size 3xl5 ~m) of sericite and, 

26 

more rarely, chlorite, and equant to slightly 

elongate anhedral crystals of quartz. Similar 

fragments with mica flakes larger than 140 ~m 

are extremely rare and are classified as 

schist in this report. In sample Nos. 2298, 

2305, 2445, 2450, and 2453, some phyllite 

fragments contain small prismatic crystals of 

what appears to be clinozoisite. In general, 

the phyllite grains are highly compressible 

(ductile) and are mashed and stretche1 between 

noncompressible detrital grains (figs. 24, 

25). Grains composed of foliated quartz 

individuals have been classified as 

metaquartzite in this report, whereas grains 

composed of unfoliated quartz individuals have 

been classified as polycrystalline quartz 

grains. The metaquartzite is similar to the 

phyllite, except that the metaquartzite contains 

greater than 50 percent quartz and the quartz 

individuals are generally larger and nore 

definitely stretched. Most metaquartzite 
Figure 17.--Grandstand Formation, 860.8 m 

(2824 ft). Chert arenite showing 

excellent porosity and permeability. 

Note variety of detrital grains and 

mashed phyllite grain. Ch, chert; K, 

alkalic feldspar; G, garnet; Mp, 

phyllite or schist; Mq, metaquartzite; 

Po, pore; Qm, monocrystalline quartz; 

Pq, polycrystalline quartz. 

Photomicrograph, plane polarized 

light. 

Figure 18.--Grandstand Formation, 860.8 m 

(2824 ft). Chert arenite showing 

excellent porosity and permeability. 

Note variety of detrital grains and 

mashed phyllite grain. Photomicrograph 

same as figure 17 but with crossed 

nicols. 

grains contain a considerable amount of sericite 

as thin undulating laminae or as flakes bent 

around quartz crystals, but some grains are 

nearly pure quartz. A few grains of graphitic 

metaquartzite occur in almost every sample. 

27 

Figure 19.--Grandstand Formation, 913.5 m 

(2997 ft). Phyllarenite with poor 

porosity and permeability. Note 

variety of detrital grains, mashed 

phyllite, and slightly deformed 

metaquartzite (near center). C, 

calcite; Ch, chert; P, plagioclase 

feldspar; Mp, phyllite or schist; Mq, 

metaquartzite; 0, opaque mineral; Po, 

pore; Qm, monocrystalline quartz; Pq, 

polycrystalline quartz; Qg, quartz 

overgrowth. Photomicrograph, plane 

polarized light. 

Figure 20.--Grandstand Formation, 868.4 m 

(2849 ft). Note numerous intergranular 

pores, a few of which are bounded by 

quartz overgroHths. Ch, chert; Ep, 

euhedral pyrite; P, plagioclase 

feldspar; Ka, kaolinite; Mq, 

metaquartzite; Ot, open throat; Po, 

pore; Qm, monocrystalline quartz; Pq, 

polycrystalline quartz; Qg, quartz 

overgrowth. Photomicrograph, plane 

polarized light. 
Figure 21.--Grandstand Formation, 868.4 m 

(2849 ft). Note excellent intergranular 

porosity. Scanning electron micrograph. 

Figure 22.--Killik Tongue of the Chandler 

Formation, 700.4 m (2298 ft). 

Note intergranular pores, many of 

which are bounded by quartz overgrowths. 

Deformed chert and phyllite plug 

intergranular pores at lower left. 

Ch, chert; Mp, phyllite; Po, pore; Qm, 

monocrystalline quartz; Pq, 

polycrystalline quartz; Qg, quartz 

overgrowth. Photomicrograph, plane 

polarized light. 

Most metaquartzite grains behave as 

noncompressible grains, but some that have a 

high content of sericite are slightly 

compressible. 

Volcanic rock fragments are present in 

trace amounts in several samples; they consist 

of plagioclase microlites (average 20x60 ~m) 

in a random or subparallel arrangement set in 

a chloritic groundmass. The groundmass is 

more abundant than plagioclase in some fragments 

28 

Figure 23.--Killik Tongue of the Chandler 

Formation, 700.4 m (2298 ft). Note 

intergranular pores and quartz grains 

with quartz overgrowths. The pillowshaped grain at left center may be a 

phyllite grain. Scanning electron 

micrograph. 

Figure 24.--Grandstand Formation, 868.4 m 

(2849 ft). Phyllite grain partially 

squeezed into intergranular pore. 

Quartz overgrowth also partially fills 

pore. Sericite of phyllite grain 

appears to slightly etch quartz grains, 

suggesting some recrystallization of 

sericite. Mp, phyllite; Po, pore; Qm, 

monocrystalline quartz; Pq, 

polycrystalline quartz; Qg, quartz 

overgrowth. Photomicrograph, plane 

polarized light. 

and less abundant in others. Biotite is 

present as pleochroic pale-brown to dark-brown 

flakes (100 to 400 ~m long) with frayed ends; 

some are partially altered to chlorite. What 

appears to be detrital chlorite occurs as 
Figure 25.--Grandstand Formation, 745.2 m 

(2445 ft). Deformation of compressible 

grain, possibly phyllite, by 

noncompressible grain. Scanning 

electron micrograph. 

flakes composed of a single crystal and as 

flakes composed of a scaley mass of almost 

cryptocrystalline crystals; optical properties 

indicate that at least some of the chlorite is 

penninite. 

Organic matter occurs as highly deformed 

masses and stringers as much as 4 mm long that 

totally lack cellular form. As seen in thin 

section the material is nearly opaque, but 

very thin edges are deep orange. Other detrital 

components occur in small amounts in the 

samples and are shown in table 2. 

Matrix 

As seen in thin section, matrix (material 

smaller than 30 ~m) consists mainly of randomly 

oriented to subparallel flakes of sericite and 

some chlorite, and tiny grains of quartz. 

Much of this material appears to be detrital 

and probably represents "hash" resulting from 

the abrasion and disintegration of phyllite 

and metaquartzite fragments. However, many 

detrital grains are etched and slightly embayed 

by the matrix, indicating that at least some 

of the matrix phyllosilicates are authigenic. 

In addition, coatings as much as 10 ~m thick 

of subparallel flakes of authigenic(?) sericite, 

chlorite, and (or) illite occur locally along 

some detrital grain contacts. 

X-ray diffraction analysis indicates the 

presence of illite, chlorite, and kaolinite in 

the fraction that is less than 2 ~m in size; 

however, they appear to be less abundant than 

in the overlying formations. No smectite was 

detected. Clay material identified as illite 

in all samples from Umiat test well 11 has a 

sharp, well-ordered 10-A peak, suggesting that 

much of this material may be detrital sericite 

rather than authigenic illite. Similarly, 

29 

material identified as chlorite in all the 

samples has a sharp, well-ordered peak 

suggesting that at least some of the chlorite 

is detrital metamorphic rather than sedimentary 

in origin. 

Authigenic Minerals 

Quartz overgrowths on free surfaces of 

detrital quartz grains are a ubiquitous but 

minor authigenic mineral (figs. 22, 23). They 

are as much as 15 ~m thick and, as seen in 

thin section, have straight or sawtooth edges. 

Locally the contact between the overgrowth and 

the detrital grain is marked by opaque dust or 

authigenic(?) illite. Some overgrowths are 

etched by matrix phyllosilicates. The 

overgrowths project into, but rarely completely 

fill, intergranular pores. Other authigenic 

minerals that occur in small amounts include 

kaolinite, which occurs as intergrown masses 

of vermicular crystals (5-15 ~m in length) 

that completely fill some pores; chert; pyrite; 

and possibly some smaller flakes of chlorite. 

Several kinds of carbonate minerals occur 

in the samples. Sparry colorless carbonate 

crystals (100-150 ~m in diameter) and clusters 

of two to four such crystals, in sample Nos. 

2925, 2990, 2997, and 3005, are unstained by 

alizarin red and are apparently dolomite. The 

crystals have shapes suggestive of rhombs, but 

the edges of the crystals are irregular and 

replace adjacent detrital silicate grains. 

Tiny (1-20 ~m in diameter) yellow authigenic 

crystals of another carbonate unstained by 

alizarin red are very common in these and 

other samples from the Grandstand Formation 

and Killik Tongue; they appear to be siderite. 

These crystals are generally subhedral to 

euhedral and occur as single crystals scattered 

evenly through the rock or as equidimensional 

clusters as much as 250 ~m across. The 

single crystals occur along grain boundaries 

and pore walls, and, locally, replace quartz, 

chert, and phyllite; in deeper samples from 

the Grandstand Formation, they coat dolomite 

crystals. In sample No. 2925 siderite 

individuals smaller than 7 ~m in diameter are 

spherical and composed of radiating crystals. 

Calcite occurs mainly as sparry anhedral 

to rhomb-shaped individuals (50-150 ~m in 

diameter) that may represent recrystallized 

detrital carbonate grains (fig. 26). The 

grains are .composed of one crystal or as many 

as 15-20 small anhedral crystals. Many of the 

grains exhibit twinning. The twin lamellae 

are unbent, suggesting that recrystallization 

of the original carbonate occurred after 

compaction. Calcite is less common as large 

optically continuous (poikilotopic) crystals 

as much as 800 ~m across that slightly replace 

detrital silicates. 

Both types of calcite are present in 

sample No. 2200, but the detrital variety is 

more abundant. With the exception of sample 

No. 3005, no carbonates were detected by X-ray 
Figure 26.--Killik Tongue of the Chandler 

Formation, 670.6 m (2200 ft). Sparry 

anhedral to euhedral calcite crystals 

that may represent recrystallized 

detrital carbonate grains. Authigenic 

calcite fills intergranular pores and 

partially replaces detrital silicate 

grains in lower left-hand corner. Ca, 

authigenic calcite; Cd, recrystallized 

detrital calcite; Ch, chert; Mp, 

phyllite; Po, pore; Qg, quartz 

overgrowth. Photomicrograph, plane 

polarized light. 

diffraction analysis, possibly due to their 

presence in very small amounts or their somewhat 

erratic distribution; sample No. 2200 was not 

analyzed. 

Porosity 

Porosity and permeability values are high 

for the Grandstand and Killik samples studied 

(table 2). Most porosity is primary and 

intergranular; secondary porosity due to 

leaching of feldspar grains is minor. Partial 

leaching of feldspar grains was noted in 

sample No. 2841. Visible pores (pores visible 

at magnifications to about 800x) have an 

average size of about 50 ~m. They are mainly 

triangular, equant, or crescent-shaped spaces 

between noncompressible grains such as quartz, 

feldspar, and chert. }~ny pore walls are 

formed of straight-edged quartz overgrowths, 

and these are generally free of phyllosilicate 

coatings. Less than 50 percent of the length 

of most other pore walls is coated with 

phyllosilicate coatings. 

NINULUK FORMATION 

The sandstone samples studied from the 

Ninuluk Formation are similar to those from 

the underlying Grandstand Formation and Killik 

Tongue in that they are mainly light gray, 

30 

very fine grained to fine-grained sandstones 

relatively poor in quartz and rich in chert 

and metamorphic rock fragments. Unlike those 

from the two lower units, however, they tend 

to be more poorly sorted, even bimodal; and 

they contain significantly more metamorphic 

rock fragments than chert fragments (figs. 15, 

16). Fragments of metaquartzite are especially 

common, and are more abundant than phyllite in 

the deeper samples. The Ninuluk samples 

contain less detrital quartz than samples from 

the Grandstand and Killik, and the shallower 

samples contain a considerable amount of 

carbonate (table 2). 

Grains in many of the samples are very 

tightly packed owing to the high content of 

metamorphic rock fragments (fig. 27). Sample 

No. 2110 contains laminae of fine sand and 

medium sand; and sample No. 2117, although 

unstratified, is bimodal fine and coarse sand. 

Detrital Grains 

With some exceptions the detrital 

components are petrographically identical to 

those of the underlying Grandstand Formation 

and Killik Tongue. Some phyllite fragments in 

sample Nos. 2080-2128 contain relatively large 

flakes of sericite (as large as 100 ~m in 

diameter); in addition, some contain biotite, 

and others contain clinozoisite(?). Free 

flakes of biotite in sample No. 2080 and in 

Figure 27.--Ninuluk Formation, 637.9 m 

(2093 ft). Very tightly packed 

phyllarenite. Note abundant phyllite 

grains wedged between noncompressible 

detrital grains and lack of pores. 

Matrix in lower left corner may 

represent highly deformed phyllite 

grain(s) (pseudomatrix). Ch, chert; 

Mx, matrix; Mp, phyllite; Mq, 

metaquartzite; M, muscovite. 

Photomicrograph, plane polarized 

light. 
stratigraphically higher samples are pleochroic 

pale yellow to dark reddish brown rather than 

light brown to dark brown. 

Matrix 

In thin section the matrix material in 

the Ninuluk is the same as that in the 

Grandstand and Killik. X-ray diffraction 

analysis, indicates the presence of illite, 

chlorite, and kaolinite, and the absence of 

smectite, in the fraction that is less than 

2 ~m. 

Authigenic Minerals 

Authigenic cement in sandstones studied 

consists of calcite, quartz, siderite, and, 

possibly, chlorite. Quartz overgrowths are 

notably less abundant in the Ninuluk Formation 

than in the Grandstand Formation and Killik 

Tongue. A colorless overgrowth on feldspar 

was noted in sample No. 2068. Sparse, green, 

finely crystalline aggregates of chlorite may 

be authigenic. 

As was the case in samples from the 

Grandstand and Killik, calcite in the Ninuluk 

Formation occurs mainly as anhedral to euhedral 

individuals that may be recrystallized detrital 

carbonate grains. These grains average 70-

150 ~m in diameter and are generally composed 

of several to many anhedral sparry crystals 

that have an average size of 30-50 ~m in 

diameter (some average only 3-5 ~min diameter). 

Many of the grains exhibit twinning. Much 

calcite, though, is definitely authigenic, 

especially in sample No. 2080. This calcite 

replaces detrital silicate and detrital calcite 

grains along grain boundaries. 

Siderite crystals in sample No. 2068 

occur in great numbers along the boundaries of 

detrital silicate grains and p~eferentially 

replace phyllite fragments. Locally they 

replace calcite. They do not occur on free 

surfaces of quartz overgrowths, but do occur 

along the contact between detrital quartz and 

quartz overgrowth. 

X-ray diffraction analysis indicates 

considerable amounts of calcite and dolomite, 

and in four samples (Nos. 2049, 2068, 2080, 

2093) a siderite reflection was tentatively 

identified. No mineral in thin section was 

positively identified as dolomite, even though 

the sections had been stained with alizarin 

red. Abundance of metamorphic rock fragments, 

chert, and detrital carbonate grains and the 

low content of quartz in the shallower samples 

suggest that the source rocks for these 

sandstones were dominantly limestone and lowgrade metamorphic rocks. These were most 

probably pre-Cretaceous rocks that are present 

in the Brooks Range to the south (Brosge and 

Tailleur, 1971; Grybeck and others, 1977; 

Bartsch-Winkler, in Ahlbrandt, 1979). 

31 

Porosity 

Porosity is mostly intergranular. Visible 

pores average about 35 ~m in size and are 

triangular, equant, or elongate intergranular 

spaces that have not been filled with matrix, 

deformed phyllite grains, or authigenic 

carbonate. 

Colville Group 

SEABEE FORMATION AND TULUVAK TONGUE OF THE 

PRINCE CREEK FORMATION 

Except for sample No. 1824 which is 

similar to samples from the Ninuluk Formation, 

the samples from the Seabee Formation and 

Tuluvak Tongue of the Prince Creek Formation 

are light-gray, very fine grained to finegrained sandstones characterized by an abundance 

of volcanic rock fragments, high content of 

detrital plagioclase feldspar, low content of 

detrital quartz, and generally abundant 

chloritic and smectitic matrix of authigenic 

origin (figs. 15, 16, 28). Calcite is abundant 

in some samples. 

Figure 28.--Seabee Formation, 409.3 m (1343 

ft). Tightly packed phyllarenite with 

authigenic chlorite matrix. Large 

volcanic rock fragment contains rather 

large plagioclase crystals and is 

somewhat atypical. Chlorite occurs as 

masses of intergrown flakes (lower 

center) and as radial growths that 

fill intergranular pores (upper right 

and in fig. 32). Note slightly deformed 

biotite flake at lower right. B, 

biotite; Cl, authigenic chlorite; P, 

plagioclase feldspar; H, hematite· 

stain; Mx, matrix of chlorite; Lv, 

volcanic rock fragment. Photomicrograph, 

plane polarized light. 
Detrital Grains 

Quartz, chert, phyllite, and metaquartzite 

all appear to be the same petrographically as 

in the Nanushuk Group. No grains of volcanic 

quartz were noted. Quartz is slightly more 

abundant and volcanic and metamorphic rock 

fragments are less abundant in the Tuluvak 

Tongue than in the Seabee Formation. 

The dominant volcanic rock type is a 

quartz-free intermediate rock that has an 

extremely high content of plagioclase (fig. 

29). Average composition of 20 randomly 

selected grains in sample No. 1343 is 94 

percent plagioclase microlites, 5 percent 

chloritic material, and 1 percent opaque 

mineral. Mean size of the grains is 240 ~m in 

diameter and maximum is 500 ~m; roundness of 

the grains is about equally divided between 

subangular, subrounded, and rounded. 

Plagioclase microlites are generally unaltered 

and have an average size of 16x60 ~m; many, 

though, have a much more acicular habit. 

Extinction angle of albite twins of the 

microlites is 0°. The microlites have a 

random orientation in about two thirds of the 

grains and a subparallel orientation in the 

remainder. Untwinned, compositionally zoned 

blocky microlites in some grains take a slight 

sodium cobaltinitrite stain and may be alkalic 

feldspar. Very finely crystalline chloritic 

material occurs in the triangular and linear 

Figure 29.--Seabee Formation, 409.3 m (1343 

ft). Typical volcanic rock fragment. 

At right edge of photograph, note 

authigenic chlorite matrix (masses of 

intergrown flakes) between volcanic 

rock fragment and other detrital 

grains. Surfaces of detrital grains 

are etched by chlorite. Cl, massive 

chlorite; E, etching; P, plagioclase 

feldspar; Mq, metaquartzite; Qm, 

monocrystalline quartz. 

Photomicrograph, crossed nicols. 

32 

interstices (average 15 ~m in length) between 

plagioclase microlites and appears to be 

highly altered aphanitic groundmass. Minute 

yellow pinpoints of sodium cobaltinitrite 

stain in the groundmass of some grains may 

indicate the presence of groundmass alkalic 

feldspar or, instead, may represent stained 

alteration products. No unaltered 

ferromagnesian minerals were noted, but rare, 

small, equant masses of chloritic material may 

represent highly altered pyroxene or amphibole 

microlites. In sample No. 1331 many grains 

are partially replaced by calcite, and in 

sample No. 514 the altered groundmass in most 

volcanic rock fragments appears to be smectitic 

rather than chloritic. 

In addition to the volcanic rock fragments 

described above, grains of a somewhat different 

volcanic rock occur in trace amounts in sample 

Nos. 1328-1365. This rock (actually several 

different rock types may be represented) 

typically contains about 60 percent plagioclase 

microlites and 40 percent dark-yellow-brown to 

nearly opaque groundmass. The rock may only 

be a variant of the more abundant plagioclaserich volcanic rock. 

Most, if not all, of the plagioclase in 

the sandstones is of volcanic origin and may, 

in part, represent phenocrysts too large to 

appear in the sand-sized volcanic rock 

fragments. The plagioclase is generally 

unaltered, but some grains are highly 

sericitized, and in sample No. 1331 many 

grains are partially replaced by calcite. 

Most grains are angular to subangular and 

appear to be broken fragments. Albite twinning , 

is common, and some grains are compositionally 

zoned. Maximum extinction angles measured on 

albite twins suggest that the plagioclase is 

andesine to sadie labradorite. Rectangular 

inclusions (15-25 ~m) of unaltered brown glass 

were noted in a few grains. In samples rich 

in smectite, many of the plagioclase grains 

and some quartz grains are highly fractured 

and shattered (fig. 30). Rare grains have 

leached pores. 

The alkalic feldspar, likewise, may be 

largely volcanic in origin. An optic angle of 

15-30° was measured on one alkalic feldspar in 

sample No. 771, but this grain also contained 

irregular patches of plagioclase. Other 

alkalic feldspar grains are also perthitic. 

Most grains are blocky and untwinned, although 

a few grains that have grid twinning were 

noted. Some grains are slightly altered, but 

most are fresh. 

Biotite is pleochroic brown, but in some 

samples two varieties seem to be present: 

one, pleochroic pale yellow brown to very dark 

brown; and the other, medium orange brown to 

dark orange brown. In many samples biotite 

flakes (or possibly fragments of a biotite 

schist) are extremely altered and replaced by 

siderite and penninite. The siderite occurs 

as tiny (15 ~m) crystals that have grown in 
Figure 30.--Seabee Formation, 235.0 m (771 

ft). Phyllarenite with authigenic 

smectite matrix. Note intergranular 

pore and smectite coatings on surfaces 

of detrital grains. Plagioclase (two 

grains?) in lower left corner is 

highly fractured and shattered; smectite 

coats some fractures, but not others, 

in the plagioclase. Ch, chert; P, 

plagioclase feldspar; Mx, matrix; Mq, 

metaquartzite; Po, pore; S, smectite. 

Photomicrograph, plane polarized 

light. 

Figure 31.--Seabee Formation, 409.3 m (1343 

ft). Mass of intergrown flakes of 

authigenic phyllosilicate, presumably 

chlorite, filling an intergranular 

pore. Note clusters of smaller flakes 

attached to larger flakes, suggesting 

two stages of chlorite growth. Scanning 

electron micrograph. 

great profusion along biotite cleavage planes, 

completely shredding the biotite fragments. 

In samples rich in smectite, many biotite 

flakes exhibit kink folding. 

33 

Matrix and Authigenic Minerals 

As seen in thin section, an authigenic 

phyllosilicate that has the optical properties 

of prochlorite makes up over half of the 

matrix in sample Nos. 1343-1365 and about one 

fourth of the matrix in sample No. 1328. The 

remainder of the matrix material in these 

samples appears to be mainly detrital sericite 

with possibly some authigenic illite. The 

prochlorite occurs as masses as much as 250 vm 

across of intergrown flakes (as much as 30 vm 

long) that fill intergranular spaces (figs. 

28, 29, 31) and also as radial (fan-shaped) 

growths of flakes projecting from pore walls 

(fig. 32). Commonly, the chlorite etches 

adjacent detrital grains. 

Much of the matrix in sample Nos. 118-771 

is also authigenic, but the authigenic 

phyllosilicate in these samples has the optical 

properties of smectite rather than prochlorite 

and also occurs in a somewhat different 

manner. Much of the smectite, especially in 

the shallower samples, occurs as clumpy masses 

of intergrown flakes (flakes average 0.1-5 vm 

in length) that fill intergranular pores or 

merge to form a continuous matrix in which 

detrital grains "float" (figs. 33, 34). No 

volcanic glass shards or relicts of altered 

glass shards were noted in the matrix. The 

smectite is also present, especially in the 

Figure 32.--Seabee Formation, 409.3 m (1343 

ft). Chlorite-filled pore seen in 

figure 28. Note radial (fan-shaped) 

growths of flakes projecting into 

elongate intergranular pore. Flakes 

from opposite walls do not everywhere 

touch, leaving a long medial opening. 

At right edge chlorite occurs as a 

mass of intergrown flakes. Ch, 

hematite-stained chert; Clm, massive 

chlorite; Cl, chlorite; Qm, 

monocrystalline quartz; Lv, volcanic 

rock fragment. Photomicrograph, plane 

polarized light. 
Figure 33.--Tuluvak Tongue of Prince Creek 

Formation, 156.7 m (514ft). 

Phyllarenite with authigenic smectite 

matrix. Smectite occurs as clumpy 

masses that fill intergranular spaces 

and as continuous matrix between 

detrital grains. Note bifurcating and 

anastomosing fractures in matrix; also 

note variety of detrital grains. B, 

biotite; C, calcite; Ch, chert; F, 

feldspar; P, plagioclase feldspar; Mx, 

matrix; Mp, phyllite; Mq, metaquartzite; 

Qm, monocrystalline quartz; S, smectite 

matrix. Photomicrograph, plane 

polarized light. 

Figure 34.--Tuluvak Tongue of Prince Creek 

Formation, 156.7 m (514ft). Dense 

masses and coatings of smectite with 

bifurcating and anastomosing fractures. 

Scanning electron micrograph. 

deeper samples, as a discrete coating as much 

as 10 ~m thick of overlapping flakes (as much 

as 15 ~m long) on surfaces of detrital grains 

(figs. 30, 35) and, more rarely, as radial 

34 

Figure 35.--Seabee Formation, 229.8 m (754 

ft). Dense masses and coatings of 

smectite with bifurcating and 

anastomosing fractures. Note thick 

coating on rounded grain to left of 

center. Scanning electron micrograph. 

growths of flakes (as much as 12 ~m long) on 

intergranular pore walls (fig. 36). The 

coatings are present both on free surfaces of 

grains and on surfaces where grains are in 

contact. Etching of detrital silicate grains 

by the smectite is very common. Besides 

smectite, the matrix in sample Nos. 118-771 

also contains some detrital and (or) 

authigenic(?) sericite, chlorite, and illite. 

X-ray diffraction analysis indicates the 

presence of illite, chlorite, smectite, and 

kaolinite in the fraction that is less than 

2 ~m in size. Larger amounts of smectite are 

present in sample Nos. 118-771. Two samples 

in the Seabee Formation contain interstratified 

smectite-chlorite. 

Calcite in samples containing only small 

amounts of calcite appears to be the same as 

the possibly detrital variety occurring in 

samples from the Nanushuk Group. In samples 

with relatively large amounts of calcite (Nos. 

118, 545, 763, 1331), the calcite occurs 

mainly as irregular, optically continuous 

(poikilotopic) crystals (as large as 1 mm) 

that fill intergranular pores and replace 

detrital silicate grains along grain boundaries. 

Free surfaces of calcite crystals that partially 

fill pores are coated with smectite in some 

samples. X-ray diffraction analysis indicates 

small amounts of calcite and dolomite. 

Porosity 

Intergranular spaces in sample Nos. 1343-

1365 are completely plugged with the authigenic 

prochlorite, and no visible pores were noted 

in these samples; similarly, no visible pores 

are present in sample No. 1331 owing to complete 
Figure 36.--Seabee Formation, 229.8 m (754 

ft). Smectite coatings on detrital 

grains. To left of center, the sequence 

of coatings includes inner layered 

coating next to chert grain, outer 

radial coating, medial pore, outer 

radial coating, inner layered coating, 

and feldspar grain. At lower left a 

layered coating has pulled away from 

adjoining grains. Ch, chert; aF, 

altered feldspar; Po, pore; S, smectite; 

Sl, layered smectite. Photomicrograph, 

plane polarized light. 

cementation by calcite. Authigenic prochlorite 

is less abundant in sample No. 1328, and 

visible pores in this sample are the result of 

incomplete filling of intergranular spaces by 

prochlorite. Many visible pores in sample 

Nos. 118-771 are normal intergranular spaces 

incompletely filled by matrix material, but a 

large number of the open spaces seen in thin 

section are unusual bifurcating and anastomosing 

fractures as much as 30 ~m wide and 400 ~m 

long that cut through and split the clumpy 

smectitic matrix (figs. 33-35). These fractures 

appear to have been caused by a swelling or a 

"pulling apart" of the rock. The fracturing 

was probably caused by swelling and shrinking 

of the smectite due to wetting and drying, but 

freeze and thaw of ice crystals may have been 

a contributing factor, also. The questions of 

when the fracturing occurred and whether or 

not the fracturing actually exists in the 

subsurface are moot ones. It is conceivable 

that the swelling and shrinking of the smectite 

were not caused by natural processes, but 

rather were caused by man-related processes 

such as drilling or sample preparation. The 

shattered plagioclase grains and kink-folded 

biotite flakes common in the smectite-rich 

samples suggest that expansion (and presumably 

contraction) has occurred at least once under 

conditions of considerable confining pressure, 

but whether or not the cracks in the smectite 

35 

matrix occurred during the same episode is not 

known. 

FACTORS AFFECTING POROSITY AND PERMEABILITY 

Several factors were identified 

petrographically as having effects on porosity 

and permeability. First of all there seems to 

be no discernible relationship between 

compaction, as influenced by depth of burial, 

and porosity and permeability. In fact, 

deeper samples from Umiat test well 11 are 

just as porous and actually more permeable 

tha:n shallower samples owing to abundant 

intergranular porosity in the deeper samples 

and abundant matrix in the shallower samples 

(figs. 37, 38). Modal grain size appears to 

be a minor factor in its effect on porosity 

and permeability. In all formations, porosity 

and permeability tend to increase with 

increasing modal grain size (figs. 39, 40). 

In general, a minimum grain size of about 175 

~m appears to be necessary for good (>50 md) 

permeability. 

Composition of the rock has a major 

EXPLANATION 

+ Tuluvak Tongue of Prince Creek Formation 

• Seabee Formation 

A Ninuluk Formation 

o Killik Tongue of Chandler Formation 

!:::. Grandstand Formation 

I 

Volcanic and smectite-rich 

sandstone 

(Colville Group) 

I Quartz, chert and 

lphyllite-rich sandstone 

: (Nanushuk Group) 

1-

z 

UJ 

(.) 

a: 

UJ 

a. 

z 

>--

1-

ii5 

0 

a: 

0 

a. 

UJ 

> f= 

(.) 

UJ 

LL tt 5 

• 

+ • • 

+ 

• + 

• 

y=bx+a 

a=13.177 

b= 0.001 r= 0.09 

• 

. . 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

•I 

I 

I 

I 

I 

I 

I 

I 

oa!:::. 

~ ~0 6. 

• !:::. 

A 

I o~----~~~--~~~--~5~4~8~6~--~~~--~~. 

(1200) (1800) (2400) 

DEPTH, IN METERS (FEET) 

Figure 37.--Effective porosity versus 

depth. The solid line is the line 

defined by linear-regression analysis 

on all the data points. The equation 

of the solid line and the values of a, 

b, and r (correlation coefficient) are 

shown on the graph. 
(/) 

w 

C3 

a: 

<( 

0 

:J 

_J 

~ 

~ 

> 1-

:J 

05 

<( 

w 

~ 

a: 

w 

a. 

a: 

< 

EXPLANATION 

+ Tuluvak Tongue of Prince 

Creek Formation 

• Seabee Formation 

.& Ninuluk Formation 

o Killik Tongue of Chandler 

Formation 

6 Grandstand Formation 

y=a(x)b 

a=-31.455 

b= 0.045 

r= 0.33 

0~-+~~~~--~ ~-= 4~8~ ~~--~~ll 

(1200) (1800) (2400) 

DEPTH, IN METERS (FEET) 

Figure 38.--Air permeability versus depth. 

1-

z 

w 

(.) 

a: 

w 

a. 

~ 

> 1-

iii 

0 

a: 

0 

a. 

w 

> 

f= 

(.) 

w 

u. 

u. 

w 

0 

0 

The solid line is the least-squares 

fit to a power equation for all the 

data points. The least-squares program 

was modified to calculate data points 

equal to zero. The equation of the 

solid line and the values of a, b, and 

r (correlation coefficient) are shown 

on the graph. 

EXPLANATION 

+ Tuluvak Tongue of Prince Creek Formation 

Seabee Formation 

A Ninuluk Formation 

o Killik Tongue of Chandler Formation 

e:, Grandstand Formation 

0 

0 + 

. . 

0 0 

y=bx+ a 

a=10.335 

b= 0.024 

r= 0.33 

MODAL GRAIN SIZE, IN MICROMETERS 

Figure 39.--Effective porosity versus modal 

grain size. The solid line is the 

line defined by linear-regression 

analysis on a ll the data points. The 

equation of the solid line and the 

values of a, b, and r (correlation 

coefficient) are shown on the graph. 

36 

en 

w 

G 

a: 

<( 

0 

::::; 

..J 

~ 

~ 

> 300 1-

::::; 

iii 

<( 

w 

:::!; 

a: 

w 

a. 

a: 

;;: 

EXPLANATION 

+ Tuluvak Tongue of Prince Creek Formation 

• Seabee Formation 

A Ninuluk Formation 

o Killik Tongue of Chandler Formation 

e:, Grandstand Formation 

Y=a(x)b 

a=120.269 

b= 0.088 

r= 0.50 

0 

o~-----f.~--~~100~~ ~~----~~----~ 

MODAL GRAIN SIZE, IN MICROMETERS 

Figure 40.--Air permeability versus modal 

grain size. The solid line is the 

least-squares fit to a power equation 

for all the data points. The leastsquares program was modified to 

calcul ate data points equal to zero. 

The equation of the solid line and the 

values of a, b, and r (correlation 

coefficient) are shown on the graph. 

effect on porosity and permeability. The 

relationship between permeability and 

composition is shown on figures 41 and 42. 

Samples classed as sedimentary litharenite 

generally have greater permeability than those 

classed as volcanic litharenite or phyllarenite. 

As can be seen in figures 43 and 44, rocks 

that have a high content of compressible 

grains (phyllite, schist, mica, and, rarely, 

chert and micaceous metaquartzite) generally 

have low porosity and permeability values. 

Similarly, rocks that have a high matrix 

content or carbonate cement also generally 

have low porosity and permeability values 

(figs. 45, 46). It is also apparent in figures 

43-46 that an increase in the amount of 

compressible grains or matrix has a much 

greater effect on permeability than on porosity. 

Other factors specifically affecting 

permeability, as pointed out by Krynine and 

Ferm (1952), include the modal size of visible 

pores and the percent of pore wall coated by 

phyllosilicate. A decrease in the former or 

an increase in the latter will cause a decrease 

in permeability. Estimated values for these 

parameters are given in table 2 for each 

sample. 

Some of the specifJc petrographic factors 
QUARTZ 

EXPLANATION 

o <1 md 

6 1·50 md 

• 50·100 md 

x >100 md 

0 

6 

0 0 

0 

0 6 

ROCK FELDSPARL-----------'---------- C...% ________ .....l.. ________ ~FRAGMENTS 

(including chert) 

Figure 41.--Air permeability of samples listed in table 2 plotted on primary arenite trian?le 

(Folk and others, 1970). 

affecting porosity and permeability in the 

formations penetrated in Umiat test well 11 

are described in the following paragraphs. 

Grandstand Formation and Killik Tongue of 

the Chandler Formation.--In the Grandstand 

Formation, effective porosity decreases with 

increasing content of compressible grains 

(mainly phyllite and mica), matrix, and 

carbonate (figs. 43, 45). Except for matrix, 

a similar relationship exists in the Killik 

Tongue. 

The principal factor affecting permeability 

in the Grandstand Formation and Killik Tongue 

is partial to complete filling of intergranular 

spaces by (1) deformed compressible grains 

such as phyllite and mica, (2) matrix material 

(much of which is probably derived from the 

abrasion and disintegration of metamorphic 

rock fragments), and (3) authigenic carbonate 

minerals (figs. 44, 46). Those samples that 

have the best porosity and permeability, such 

as sample Nos. 2298, 2532, 2832, and 2849, 

have very low amounts of phyllite, matrix, and 

authigenic carbonate. In general the rocks 

with the best permeability are chert arenites 

and those with the poorest permeability are 

37 

phyllarenites (table 2, fig. 42). The factors 

controlling phyllite and matrix abundance .:.re 

unknown, but may be related to environment of 

deposition. Permeable sandstones containing 

sparse phyllite and matrix may have been 

deposited in high-energy environments that 

disintegrated the phyllite fragments and 

winnowed away the fine debris. Other textural 

attributes and sedimentary structures observed 

in the Umiat 11 cores, however, do not 

conclusively support this interpretation. The 

occurrence of petrographically identical 

phyllite fragments in both high- and lowphyllite sandstones and changes from high to 

low phyllite content over relatively short 

vertical distances (2-3 m) suggest that cha~ges 

in provenance is not a major factor controlling 

variations in phyllite abundance in the 

Grandstand and Killik at Umiat test well 11. 

If reservoir quality in these units is primarily 

related to environment of deposition, then the 

search for promising reservoirs can be dire~ted 

to those areas where high-energy environments 

may have existed. Promising reservoirs in the 

Grandstand and Killik should also exist in 

those parts of the basin which, for one 
METAMORPHIC 

ROCK FRAGMENTS 

EXPLANATION 

o <1 md 

6 1-50 md 

'\ • 50-100 md 0 

0 X >100 md 0 

\ 

0 \ 

\ 6 6 6 o'b 

PHYLLARENITE ~ 

0 

0 

0 

0 

VOLCANIC LITHARENITE SEDIMENTARY LITHARENITE 

X 

IGNEOUS SEDIMENTARY 

ROCK L-------------------------------------L-----------------------------------__J ROCK 

FRAGMENTS 50% FRAGMENTS 

Figure 42.--Air permeability of samples listed in table 2 plotted on litharenite triangle (Folk 

and others, 1970). 

paleogeographic reason or another, received 

only sparse amounts of metamorphic rock debris. 

Ninuluk Formation.--Porosity and 

permeability in the deeper samples from the 

Ninuluk Formation decrease with increasing 

content of matrix and compressible grains. 

The low porosity and permeability values in 

the shallower samples of the Ninuluk are due 

to plugging of intergranular spaces by carbonate 

minerals. 

Seabee Formation and Tuluvak Tongue of 

the Prince Creek Formation.--In the Seabee 

Formation and Tuluvak Tongue, the amount of 

matrix has little effect on effective porosity 

(fig. 45). The higher porosity values in 

sample Nos. 118-771 are apparently due to the 

larger number of intergranular pores, and, 

possibly, fractured smectitic matrix. The 

great abundance of authigenic matrix in these 

units does, on the other hand, have a major 

effect on permeability (fig. 46). Permeability 

decreases with increasing matrix content. As 

seen in figures 43 and 44, porosity and 

permeability in the Seabee Formation appear to 

increase with increasing content of phyllite 

plus schist, but a comparison with table 2 

shows that several samples with low phyllite 

content have high calcite content a~d that the 

pore-plugging effect of the calcite is 

responsible for the low porosity an-" 

permeability values. As in the cas~ of 

porosity, the slightly higher permeability 

values in sample Nos. 118-771 are apparently 

due to the larger number of intergranular 

pores and, possibly, fractured smectitic 

matrix. 

38 

CORE AND WELL~LOG ANALYSES 

Core and well-log analyses of Umiat test 

well 11 were made to determine the average 

porosity and permeability of the sandstone 

units of each formation. Results of this 

analysis will be useful in future study of 

regional porosity and permeability distribution 

in the NPRA. 

Core-analysis data were obtain~d from 

Collins (1958). These included porosity and 
EXPLANATION 

+ Tuluvak Tongue of Prince Creek Formation 

• Seabee Formation 

.. Ninuluk Formation 

0 Killik Tongue of Chandler Formation 

6 Grandstand Formation 

1-

z • w 0 6 0 () 

a: 

w D. + • • • a.. 6 

~ D. 

~ •D. 1-

Ci5 

0 0 

a: 

0 

a.. +• .. w 

> i= y=bx+a 

() .. w • • a=16.673 LL 

LL b=-0.253 w r=-0.33 

o~-------5~--~--~1~0~----~1~5------~2~0 ______ _J 

PHYLLITE PLUS SCHIST, IN PERCENT 

Figure 43.--Effective porosity versus 

percent phyllite plus schist. The 

solid line is the line defined by 

linear-regression analysis on all the 

data points. The equation of the 

solid line and the values of a, b, and 

r (correlation coefficient) are shown 

on the graph. 

air permeability of most sandstone units of 

each formation (table 3). 

Well logs available for the analysis 

included spontaneous potential (SP); 16-in. 

short normal (SN); 64-in. long normal (LN) 

(from 33-1003 m); Microlog (ML) (2-in. normal 

and 1~-in. inverse, from 33-1003 m); Lateral 

(from 52-448 m); and temperature survey (from 

0-104 m). Except for the SP log in the 

permafrost zone (0-229 m), the log quality was 

fairly good. 

The porosity of sandstone beds in the 

Grandstand Formation was estimated from the 

well-log-analysis methods using combinations 

of SN and SP, and ML and SP. Both gave rather 

inconsistent results compared to previously 

reported core-analysis values (Collins, 1958). 

However, plots of core porosity vs. the 

resistivity of 16-in. short normal (Rl6") or 

the resistivity of 64-in. long normal (R64 .. ) 

and plots of log air permeability (Ka) vs. 

core porosity showed rather consistent linear 

relationships. Thus, such correlations were 

used to determine the porosity of sand members 

when core data were not available. 

Formation-water resistivity was estimated 

from formation-water analysis and well-log 

analysis. This formation-water resistivity 

C/) 

w 

0 

a: 

<( 

0 

::J 

....J 

~ 

~ 

>--

1-

::J 

iii 

<( 

w 

~ 

a: 

w 

a.. 

a: 

< 

EXPLANATION 

+ Tuluvak Tongue of Prince Creek For11ation 

0 • Seabee Formation 

A Ninuluk Formation 

o Killik Tongue of Chandler Formation 

!:::. Grandstand Formation 

£::,0 

6 0 

y=a(x)b 

a=2365.116 

b= -2.518 

r= -Q.6.ct. 

• 1 o-!t~ • 1 I +---t--~+~.-2LQ_...,. .. ~-...,j .. ~25 

PHYLLITE PLUS SCHIST, IN PERCENT 

Figure 44.--Air permeability versus percent 

phyllite plus schist. The solid line 

is the least-squares fit to a power 

equation for all the data points. The 

equation of the solid line and the 

values of a, b, and r (correlation 

coefficient) are shown on the graph. 

39 

was used in the estimation of water saturation 

in the Grandstand Formation. 

Average Porosity of Each Formation 

Correlation between core porosity and 

normal-log resistivities.--Plots of core 

porosity and normal-log resistivities were 

made to determine any consistent relationships 

between them for the purpose of estimating 

porosity of the sand intervals for which core 

data were not available. 

Only the better developed sands (less 

shaly) that were greater than 3 m in thickness 

were selected. Two intervals were analyzed 

separately: 0-235 m (within the permafrost 

zone) and 610-917 m. 

Figures 47 through 50 show the correlation 

between core porosity and normal-log 

resistivity. A roughly linear relationshiP 

exists between the core porosity and the 

normal-log resistivity: 

1. The R64 .. ranges from 10 to 90 ohn-m 

in the permafrost zone and from 40 

to 80 ohm-m in the deeper zone. The 

slope of the correlation is much 

lower in the permafrost zone. 
1-

z 

w 0 

0 

a: 

w 

a.. 

~ 

>=" 1-

Ci5 

0 

a: 

0 

a.. 

w 

> 

i= 

0 

w 

u. 

u. 

w 

0 

0 

EXPLANATION 

+ Tuluvak Tongue of Prince Creek Formation 

• Seabee Formation 

0 

Ninuluk Formation 

Killik Tongue of Chandler Formation 

Grandstand Formation 

• 

• 

0 

• !:::, 

• + 0 

+ 

+ • 

• • 

y=bx+ a 

a=14.586 

b= -0.039 

r= -0.11 

+ 

Figure 45.--Effective porosity versus 

percent matrix. The solid line is the 

line defined by linear-regression 

analysis on all the data points. The 

equation of the solid line and the 

values of a, b, and r (correlation 

coefficient) are shown on the graph. 

2. The R16" ranges from 15 to 45 ohm-m 

in the permafrost zone and from 40 

to 60 ohm-m in the deeper zone. 

Again the slope of the correlation 

is much lower in the permafrost 

zone. 

Lines shown on figures 47 through 50 are 

fit to the data using the least-squares method. 

The correlations were used to estimate the 

porosity of the uncored intervals (table 4). 

The significance of the linear relationships 

and the lower slope of correlation for the 

permafrost zone have not been investigated. 

Average porosity of each formation.--The 

weighted average porosity of the formations 

penetrated by Umiat test well 11 are tabulated 

in table 4; they are averages of core porosity 

and porosity obtained from the aforementioned 

correlation method. Only the better developed 

sandstone beds (thickness greater than 3 m 

picked from SP and ML) are included in computing 

the average porosity. The weighted average 

porosity is 14.6 percent for the Tuluvak 

Tongue, 11.5 percent for the Seabee Formation, 

12.6 percent for the Ninuluk Formation, 16.4 

percent for the Killik Tongue, 15.6 percent 

for the upper part of the Grandstand Formation, 

and 15.1 percent for the lower part of the 

Grandstand Formation. 

40 

Cl) 

w 

u 

a: 

<( 

0 

:J 

_J 

~ 

~ 

>=" 1-

:J 

1Ii 

<( 

w 

~ 

a: 

w 

a.. 

a: 

< 

EXPLANATION 

+ Tuluvak Tongue of Prince Creek Formation 

• Seabee Formation 

Ninuluk Formation 

Killik Tongue of Chandler Formation 

Grandstand Formation 

• 

y=a(x)b 

a=88.341 

b= -1.079 

r= -0.44 

• L--4~~~~~~+L+--.-+·~~~------~'-===~~+wl 12 24 36 48 60 

MATRIX, IN PERCENT 

Figure 46.--Air permeability versus percent 

matrix. The solid line is the leastsquares fit to a power equatio, for 

all the data points. The equation of 

the solid line and the values of a, b, 

and r (correlation coefficient) are 

shown on the graph. 

Porosity from well-log analysis.--The 

porosity of Grandstand Formation sandstone was 

estimated by w·ell-log analysis. The porosity 

was obtained by two analysis methods: one 

using SN and SP, and the other using ML and 

SP. The porosity obtained from SN and SP is 

consistently higher than the core-analysis 

porosity. The porosity obtained from ML and 

SP does fall in the range of core porosity, 

however (fig. 51). The unsatisfactory 

scattering of the comparison data indicates 

inconsistency in either the well-log-analysis 

porosity or the core-analysis porosity. 

If core-analysis porosity is a9sumed to 

be accurate, the average porosity of the 

formation can be obtained from core-analysis 

data and, where cores are not avail.:ble, from 

the correlation of core porosity anc R6411 . 

Average Permeability of Each Formation 

Correlation between core porosity and air 

permeability.--Espach (1951) showed that, for 

Umiat test wells 2 and 3, a log Ka vs. core 

porosity plot results in a linear relationship. 

A similar core permeability and porosity plot 

was made for Umiat test well 11. Data used in 

this plot are shown in table 5 and the resulting 

plot, in figure 52. In figure 52, sqmples A, 
Table 3.--Core-analysis and well-log data 

[Leaders (---) 1ndicates no data~ R , 11 , resistivity of 64-in. long normal; 

R

16.,, res1stivity nf lb-in. short 6riormal]. 

Depth 

(meter~) 

Jn. o 

39.0 

42.7 

71.0 

74.1 

100. q 

156. ~ 

151:1.2 

lbll. 3 

lbb.l 

227.4 

229.8 

232.6 

235.0 

404.8 

407.7 

40Q.4 

413.9 

4lb.l 

556.0 

624.5 

627.9 

632.5 

638.0 

643.1 

646.2 

652.0 

670.6 

700.4 

702.6 

724.8 

727.3 

745.2 

746.8 

749.8 

771. b 

857.4 

860.8 

863.2 

865.9 

868.4 

911.4 

913.5 

915.9 

Air 

permeabilitv 

lmdl 

Effective 

porosity 

I percent) 

Average 

effe-Ltive 

porosity 1 R6411 (percent) (ohm-m) 

Tuluvak Tongue of the Prinu:.- Creek Formation 

10. ~ 11.7 90 

<1 U.l 11.7 90 

6. ~ 15.4 15.4 45 

cl 17. q 14.8 35 

11.1:1 14.8 35 

u. 9 13.9 86 

15.9 16.4 35 

16.8 lb. 4 35 

26 HLO lb.4 35 

Seabee F'ormat 1on 

< 1 14.9 lb.4 35 

5. 1 18. 3 18.0 23 

7. 0 17.7 18.0 ~3 

0 12.7 lb. 7 15 

48 20.6 16.7 15 

27 18.4 8.5 35 

0 .6 8. 5 35 

0 6. 5 l:i. 5 35 

0 7. 0 8. 6 36 

10.1 8. b 36 

9. 7 9. 7 50 

Ninuluk Formation 

10. b 11. 3 75 

11.8 11.3 75 

13.1 11.3 75 

10.4 11.3 75 

29 14.5 14.5 55 

28 13.4 14.5 55 

51 15.5 15.5 55 

Killik Tongue of the Chandler Formation 

0 1~. 4 12.4 80 

550 19.8 18.0 55 

13 lb. 2 18.0 55 

102 19.6 18.2 53 

10 16.8 18.2 53 

Grandstand Formation (upper part l 

120 17.6 lb. 5 60 

81 16.5 16.5 60 

27 15.0 16.5 60 

235 19.0 19.0 40 

Grandstand Formation {lower part) 

100 16.4 16.9 45 

158 17.4 16.9 45 

280 17.1 17.1 35 

14.7 17.0 40 

400 19.3 17.0 40 

1 13.5 12.2 50 

2. 3 12.9 12.2 56 

0 10.2 12.2 56 

Rl6" (ohm-m) 

35 

35 

17 

18 

18 

45 

30 

30 

30 

30 

16 

16 

10 

10 

30 

30 

30 

33 

33 

35 

bO 

60 

60 

60 

50 

50 

50 

55 

46 

46 

46 

44 

50 

50 

50 

40 

50 

50 

40 

42 

42 

53 

55 

55 

1T\..Io or more consecutive equal values are the average effective porosity of 

the interval. 

B, and C are excluded owing to their abnormally 

low permeabilities in contrast to their high 

porosities (depth between 702-730 m). 

The correlation indicates a linear 

relationship between the permeability and the 

porosity for (1) rocks having depths less than 

405 m, and (2) rocks having depths greater 

than 644 m, excluding data points A, B, and C 

on figure 52 (lower sandstones in Killik 

Tongue). 

41 

1-

z 

w 

u 

0:::: 

w 

a.. 

z 

>- Iv; 

0 

0:::: 

0 

a.. 

w 

0:::: 

0 

u 

R64IN OHM-METERS 

Figure 47.--Correlation of core porosity 

1-

z 

w 

u 

0:::: 

w 

a.. 

z 

>- 1-

v; 

0 

0:::: 

0 

a.. 

w 

0:::: 

0 

u 

and R64" for beds stratigraphically 

above 610 m {2000 ft) (in the permafrost 

zone). 

R64 1N OHM-METERS 

Figure 48.--Correlation of core porosity 

and R64" for beds stratigraphically 

below 610 m (2000 ft) {below the 

permafrost zone). 

These plots also indicate that permeability 

at depths less than 405 m will be less than 1 

Qd if the porosity is less than 11.5 percent 

and that the permeability at depths greater 

than 644 m will be less than 1 md if the 

porosity is less than 9 percent. 

On the basis of these correlations, it 

appears that an average permeability can be 
1-

z 

w 

u 

0:: 

w 

0... 

~ 

> 1-

v; 

0 

0:: 

0 

0... 

w 

0:: 

0 

u 

0 

10 20 30 40 

R 161N OHM-METERS 

Figure 49.--Correlation of core porosity 

1-

z 

w 

u 

0:: 

w 

ll.. 

z 

> 1-

v; 

0 

0:: 

0 

ll.. 

w 

0:: 

0 

u 

and R16" for beds stratigraphically 

above 610 m (2000 ft) (in the permafrost 

zone). 

50 

QL-------L-------~-------L-------L------~ 

35 40 45 50 55 

R 16 IN OHM-METERS 

Figure 50.--Correlation of core porosity 

and R16" for beds stratigraphically 

below 610 m (2000 ft) (below the 

permafrost zone). 

estimated with reasonable accuracy for the 

Tuluvak Tongue, the Seabee Formation, the 

Killik Tongue, and the Grandstand Formation. 

60 

Average permeability of each formation.--

The average permeability of each sandstone is 

obtained from the permeability vs. core porosity 

correlations. The weighted average permeability 

is calculated for each formation and tabulated 

in table 6. The weighted average permeability 

for the Tuluvak is 3.9 md; Seabee, 3.1 md; 

Ninuluk, 10.7 md; Killik 96.2 md; upper part 

42 

1-

z 

w 

u 

0:: 

w 

ll.. 

~ 

> 1-

c;; 

0 

0:: 

0 

ll.. 

w 

0:: 

0 

u 

10 

MICROLOG POROSITY IN PERCENT 

Figure 51.--Correlation of core and microlog 

porosities. 

(/) 

w 

0100 

0:: 

<( 

c 

:::; 60 ...... 

~ 40 

z 

> 1- 20 :::; 

iii 

<( 

w 

:E 

0:: 

w 

ll.. 

2 

0 

o Permafrost zone 

• Below permafrost zone 

• 

20 

POROSITY IN PERC::NT 

Figure 52.--Correlation of core permeability 

and porosity. 

20 

30 
Interval 

m 

30.5-44.2 

67.1-76.2 

97.5-103.6 

123.4-128.0 

155.5-166.1 

176.8-179.8 

224.0-236.2 

400.8-417.6 

551.7-562.4 

623.3-638.6 

641.6-652. 3 

669.0-675.1 

698.0-704.1 

722.4-730.0 

743.7-749.8 

751.3-757.4 

768.1-775.7 

855. 0-861.1 

862.6-876.3 

876.3-883.9 

905.3-917.5 

923.5-938.8 

Thickness h 

m (ft) 

13.7 

9.1 

6.1 

4.6 

10.6 

3.0 

12.2 

16.8 

10.7 

15.2 

10.7 

6.1 

6.1 

7.6 

6.1 

6.1 

7.6 

6.1 

13.7 

7.6 

12.2 

15.3 

(45) 

(30) 

(20) 

(15) 

(35) 

(10) 

(40) 

(55) 

(35) 

(50) 

(35) 

(20) 

(20) 

(25) 

(20) 

(20) 

(25) 

(20). 

(45) 

(25) 

(40) 

(50) 

Table 4.--Weighted average porosity, Undat test well 11 

[Leaders (---) indicate no value] 

Arithmetic 

average porosity ¢ 

(percent) 

Cumulative 

thickness l:h 

m (ft) 

Storage 

capacity 

h(ft) X ¢ 

Tuluvak Tongue of the Prince Creek Formation 

12.9 

14.8 

13.9 

114.2 

16.4 

117.0 

17.3 

8.5 

9.7 

11.3 

14.5 

13.7 

22.9 

29.0 

33.5 

44.2 

47.2 

(45) 

(75) 

(85) 

(110) 

(145) 

(155) 

Seabee Formation 

12.2 

29.0 

39.6 

(40) 

(95) 

(130) 

Ninuluk Formation 

15.2 (50) 

25.9 (85) 

580.5 

444.0 

278.0 

213.0 

574.0 

170.0 

692.0 

467.5 

339.5 

565.0 

507.5 

Killik Tongue of the Chandler Formation 

12.5 6.1 (20) 250.0 

18.0 12.2 (40) 360.0 

18.2 19.8 (65) 455.0 

Grandstand Formation (upper part) 

16.0 6.1 (20) 320.0 

11.0 12.2 (40) 220.0 

19.0 19.8 (65) 475.0 

Grandstand Formation (lower part) 

16.9 6.1 (20) 338.0 

17.0 19.8 (65) 765.0 114.6 27.4 (90) 365.0 

12.2 45.7 (150) 732.0 116.5 61.0 (200) 825.0 

Cumulative 

storage capacity 

l:h(ft) X ¢ 

580.5 

1,024.5 

1,302.5 

1,515.5 

2,089.5 

2,259.5 

692.0 

1,159.5 

1,499.0 

565.0 

1,072.5 

250.0 

610.0 

1,065.0 

320.0 

540.0 

1,015.0 

338.0 

1,103.0 

1,468.0 

2,200.0 

3,025.0 

Formation 

average _ ~ 

porosity - l:h 

14.6 

11.5 

12.6 

16.4 

15.6 

1obtained from core-analysis porosity vs. R64, correlation. 

of the Grandstand, 167.0 md; and lower part of 

the Grandstand, 58.6 md. 

Formation-Water Resistivity 

From formation-water analysis.--

Formation-water analysis is available for 

water samples taken from Formation Test No. 8 

(724-735 m), No. 9 (746-751 m), and No. 11 

43 

(864-869 m). The total equivalent sodium 

chloride concentration of these waters was 

cal~ulated to determine the formation-water 

resistivities (tables 7-9). The formationwater resistivity ranges from 1.6 to 1.8 ohm-m 

at temperatures from 13 to l7°C. 

From well-log analysis.--Three well-log 

analysis methods were used to estimate the 

formation-water resistivity. These methods 
Table 5.--Core permeability and porosity data 

Depth 

(meters) 

42.7 

160.3 

227.4 

229.8 

235.0 

404.8 

640.1 

645.3 

646.2 

648.6 

652.0 

681.2 

700.4 

702.6 

n4.8 

727.3 

745.2 

746.8 

747.7 

749.8 

771.6 

857.4 

860.8 

863.2 

868.4 

913.5 

Air permeability Core porostty 

(md) (percent) 

Tuluvak Tongue of the Prince Creek Formation 

6. 2 

26.0 

5.1 

7.0 

48.0 

Seabee Formation 

27.0 

Ninuluk Formation 

29.0 

14.0 

28.0 

56.0 

51.0 

Killik Tongue of the Chandler Formation 

125.0 

550.0 

13.0 

102.0 

10.0 

Grandstand Formation (upper part) 

120.0 

81.0 

18.0 

27.0 

235.0 

Grandstand Formation (lower part) 

100.0 

158.0 

280.0 

400.0 

2. 3 

15.4 

18.0 

18.3 

17.7 

20.6 

18.4 

14.5 

13.5 

13.4 

15.7 

15.5 

16.7 

19.8 

16.2 

19.6 

16.8 

17.6 

16.5 

14.8 

15.0 

19.0 

16.4 

17.4 

17.1 

19.3 

12.9 

include (1) using SP and Rl6"' (2) using R

16 .. 

and R64 .. , and (3) using core porosity and 

R64"' 

Results of these analyses are shown in 

tables 10-12. As shown, the formation-water 

resistivity ranges from 0.65 to 0.90 ohm-m for 

method (1), is 2.3 ohm-m for method (2), and 

is 1.03 ohm-m for method (3). The average 

formation-water resistivity as determined from 

these three methods is 1.33 ohm-m. 

Water saturation by Ri and Tixier 

methods.--Both Ri and Tixier methods were used 

to evaluate the water saturation in the 

sandstones deeper than 723 m (lower part of 

the Killik Tongue and Grandstand Formation). 

The Ri method gives 100 percent water saturation 

(SW) for all the zones analyzed and the 

Tixier method gives SW ranging from 65 to 80 

percent. All of these saturation values 

indicate nonproductive water-bearing zones at 

Umiat test well 11. 

Results of Porosity and Permeability Analyses 

The weighted average porosity for the 

Tuluvak Tongue is 14.6 percent; Seabee 

Formation, 11.5 percent; Ninuluk Formation, 

12.6 percent; Killik Tongue, 16.4 percent; 

upper part of the Grandstand Formation, 15.6 

44 

Table 6.--Weighted average permeability 

[Leaders (---) indicate .no value; av. perrr.., average permeability] 

Depth 

~ 

Thickness 

Average 

porosity (<j>) 

(percent) 

Formation 

Average weighted 

permeability av. perm. 

(md) (md) 

Tuluvak Tongue of the Prince Creek Fornation 

30.5- 44.2 

67.1- 76.2 

97.5-103.6 

123.4-128.0 

155.5-166.1 

176.8-179.8 

224.0-236.2 

400. 8-417. 6 

551.7-562.4 

623. 3-636. 2 

641. 6-652. 3 

669.0-675.1 

698. 0-704.1 

722.4-730.0 

748.7-749.8 

751.3-757.4 

768.1-775.7 

855. 0-861.1 

862.6-876.3 

786.3-883.9 

905.3-917.5 

923. 5-938. 8 

13.7 (45) 12.9 1.7 

9.1 (30) 14.8 3. 2 

6.1 (20) 113.9 2. 5 

4. 6 (15) 14.2 3. 0 

10.6 (35) 16.4 7.1 

3.0 (10) 117.0 9.0 

Seabee Formation 

12.2 (40) 17.3 10.0 

16.8 (55) 8.5 0 

10.7 (35) 9. 7 

Ninuluk Formation 

15.3 (50) 11.3 2.8 

10.7 (35) 14.5 22.0 

Killik Tongue of the Chandler Formation 

6.1 (20) 

6.1 (20) 

7. 6 (25) 

12.5 

18.0 

18.2 

5. 0 

210.0 

2 41.7 

Grandstand Formation (upper part) 

6.1 

6.1 

7. 6 

6.1 

13.7 

7. 6 

12.2 

15.3 

(20) 

(20) 

(25) 

16.0 

1n.o 

19.0 

59.0 

2. 5 

385.0 

Grandstand Formation (lower part) 

(20) 16.9 70.0 

(45) 17.0 180.0 

(25) 114.6 23.0 

(40) 12.2 5. 2 

(50) 116.5 70.0 

~From core porosity vs. R6411 correlation. 

LAverage of core permeabilities. 

3.1 

96.2 

58.6 

Table 7.--Water analysis and formation-water 

resistivity from 724-725 meters 

Ionic Concentration Conversion Equivalent 

constituents (ppm) factor NaCl cone. 

(ppm) 

+ Ca+ 30 0. 95 28.5 

Mg+ 9 2.00 18.0 

Na 2,190 1.00 2,190.0 

co 3 96 1.26 120.9 

HCO.L 2, 960 .27 799.2 

so4 21 .50 10.5 

Cl 1,600 1.00 1,600.0 

Total 1 4,767.1 

1The formation-water resistivity for 4, 767.1 ppm NaCl equivalent solution 

is 1.6 ohm-mat an estimated formation temperature of l3°C. 
Table B.--water analysis and formation-water 

resistivity from 746-751 meters 

Ionic Concentration Conversion Equivalent 

constituents (ppm) factor NaCl cone. 

fppm) 

c + 8 o. 95 7.6 a+ 

Mg+ 3 2. 00 6.0 

Na 2,030 1. 00 2,030.0 

co 3 390 1.26 491.4 

HC03 3,120 . 27 842.2 

so<:.- 28 .so 14.0 

Cl 865 1. 00 865.0 

Total 1 4,256.4 

1The formation-water resistivity for 4, 256.4 ppm NaCl equivalent solution 

is 1.8 ohm-mat an estimated formation temperature of l3°C. 

Table 9.--water analysis and formation-water 

resistivity from 864-869 meters 

Ionic Concentration Conversion Equivalent 

constituents (ppm) factor NaCl cone. 

(ppm) 

+ Ca+ 14 0.95 13.3 

Mg+ 4 2.00 8.0 

Na 2,190 l.OO 2,190.0 

co3 126 l. 26 158.8 

HCO]_ 2,240 . 27 604.8 

504 19 .so 9.5 - Cl 1, 950 l. 00 1,950.0 

Total 1 4, 934.4 

1The formation-water resistivity for 4, 934.4 ppm NaCl equivalent solution 

is 1. 6 ohm-m at an estimated formation temperature of 17 °C. 

Table 10.--Formation-water resistivity from 

well-log analyses using SP and R16 , 

Interval SP Rl6" Tf Rm Rmf Rw 

(in meters) (-mv) (ohm-m) percent (ohm-m) (ohm-m) (ohm-m) 

723-730 40 45 55 3. 6 2.6 0. 90 

744-750 45 so 56 3. 6 2.6 .65 

863-877 48 43 62 3. 6 2.8 .68 

Table 11.--Formation-water resistivity from 

well-log analyses using R1 and R 6" 64" 

Interval 1

Rxo (meters) Rxo=R16., (ohm-m) Rt =R64" (ohm-m) Rt 

723-730 45 52 0.87 

744-750 50 58 .83 

752-758 68 90 . 75 

856-862 50 45 1.11 

863-877 45 40 1.13 

924-932 43 40 1.08 

1

Maximum ~~O = 1.13 = :f; Rw = ~:~ 3 = 2.3 ohm-m. 

Table 12.--Formation-water resistivity from 

well-log analyses using core porosity and 

Rt method 

Interval Core porosity 

(meters) (percent) 

723-730 18.2 

744-750 16.0 

7 52-7 59 11.0 

856-862 16.9 

863-877 17. Q 

924-932 16.0 

1Minimum Rwa = Rw = 1. 03 ohm-m. 

F = ~-2 

30 

39 

83 

36 

35 

39 

Rwa 1 = ~ 

1. 73 

1.49 

1. 08 

1. 25 

1. 60 

1. 03 

percent; and lower part of the Grandstand 

Formation, 15.1 percent. The weighted average 

permeability (air) for the Tuluvak Tongue is 

3.9 md; Seabee Formation, 3.1 md; Ninuluk 

Formation, 10.7 md; Killik Tongue, 96.2 md; 

upper part of the Grandstand Formation, 167.0 

md; and lower part of the Grandstand Formation, 

58.6 md. The formation water is rather fresh, 

about 5,000 ppm dissolved solids, with 

formation-water resistivity of 1.6 ohm-mat 

l3°C, At Umiat test well 11, the sandstones 

in the Killik Tongue and Grandstand Formation 

are non productive water-bearing rocks. 

SUMMARY 

Cretaceous sandstones in the Umiat 

Anticline contain the largest volume of oil 

discovered to date in NPRA. Umiat test well 

11, although dry and abandoned, penetrated the 

most complete sequence of Cretaceous rocks in 

the Umiat area. Each of the formations 

penetrated by the well was studied to identify 

the factors influencing porosity and 

permeability. Selected cores and core samples 

were studied to determine environments of 

deposition and sedimentary petrology, and 

electric logs were examined to determine 

porosity and permeability of uncored zones and 

to determine whether water saturation could be 

estimated. 

The Grandstand Formation and Killik 

Tongue of the Chandler Formation at Umiat 

contain numerous sandstone beds deposited in 

45 

a shallow, near-shore-marine prograding 

environment (delta-front sediments deposited 

northeast of delta-plain facies). The source 

terrane was southwest of Umiat and consisted 

of low-grade metamorphic rocks and possibl~· 

sandstone and cherty limestone. Sandstone 

samples studied petrographically are lightgray, well-sorted, very fine grained to finegrained chert arenites and phyllarenites 

relatively poor in quartz and rich in lithic 

fragments such as chert, phyllite, and 

metaquartzite. Samples with the best 

permeability have relatively low content of 

phyllite and matrix, probably due to deposition 

in high-energy nearshore environments. Highenergy nearshore environments (foreshoreshoreface) predominate throughout the Grandstand 

Formation, Killik Tongue, and Ninuluk 

Formations, as determined from sedimentologic 

core analyses. 

A roughly linear relationship was 

established between core porosity and normallog resistivity, and this relationship was 

used to estimate the porosity of uncored 

intervals. The weighted average porosity for 

the lower part of the Grandstand Formation is 

15.1 percent and for the upper part is 15.6 

percent. A linear relationship was also 

established between permeability and porosity 

for rocks at depths less than 404.8 m and for 

rocks at depths greater than 643.1 m. The 

weighted average permeability for sandstones 
of the lower part of the Grandstand is 58.6 md 

and for the upper part is 167.0 md. Weighted 

average porosity for sandstones of the Killik 

Tongue is 16.4 percent and the weighted average 

permeability is 96.2 md. 

The Ninuluk Formation was deposited, in 

large part, in a transgressive, shallow-marine 

foreshore environment which lay to the east of 

a delta-plain environment. Sandstone samples 

studied petrographically are similar to those 

of the Grandstand Formation and Killik Tongue, 

but are more poorly sorted and contain 

significantly more metamorphic rock fragments. 

A change in source area between the time of 

deposition of the Killik Tongue and that of 

the Ninuluk Formation may have occurred, or a 

reduction in degree of destruction and winnowing 

of metamorphic fragments relative to underlying 

sediments may have taken place. Samples from 

the upper part of the Ninuluk contain 

considerable detrital and authigenic calcite. 

Well-log analysis indicates that the weighted 

average porosity for the sandstone beds in the 

Ninuluk Formation is 12.6 percent and the 

weighted average permeability is 10.7 md. 

At Umiat test well 11 the Seabee Formation 

consists largely of shale and was deposited in 

an open-marine environment. Like those from 

the Nanushuk Group, sandstone samples studied 

petrographically contain fragments of lowgrade metamorphic rocks and chert but, in 

addition, contain abundant fragments of 

intermediate volcanic rocks. This dramatic 

change in composition may be the result of a 

change in paleodrainage from a nonvolcanic to 

a volcanic area, or may represent the initiation 

of volcanic activity in the original source 

terrane. Although core analyses of 

sedimentologic characteristics are not 

conclusive, the position of a sandstone unit 

with mudstone clasts at the base, graded 

bedding, and occassional ripple laminations in 

a black marine-shale sequence suggests 

deposition as a marine-basin (turbidite) 

sandstone. The presence of abundant authigenic 

chlorite and smectite in sandstones of the 

Seabee Formation reduces permeability and 

makes these sandstones inadequate reservoir 

rocks. Well-log analysis indicates that the 

weighted average porosity for sandstone beds 

in the Seabee Formation is 11.5 percent and 

the weighted average permeability is 3.1 md. 

The Tuluvak Tongue of the Prince Creek 

Formation consists of sandstone, siltstone, 

shale, bentonite, and coal deposited in a 

delta-plain, delta-front environment. The 

source terrane was to the west-southwest of 

the Umiat area. Sandstone samples studied 

petrographically are similar to those of the 

Seabee Formation, except that they contain 

slightly more quartz and less volcanic and 

metamorphic rock fragments, suggesting a 

slight change in source area and (or) a 

waning of volcanic activity. Abundant 

46 

authigenic smectite in these sandstones reduces 

permeability to very low values. Well-log 

analysis indicates that the weighte1 average 

porosity for sandPtone beds in the Tuluvak 

Tongue is 14.6 percent and the weighted average 

permeability is 3.9 md. 

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f< U.S. GOVERNMENT PRINTING OFFICE: 1979-677-129/25