reservoir stratigraphic heterogeneity within the lower ... · shale interval (shell creek shale;...

Rocky Mountain Geology, v. 49, no. 2, p. 167–190, 13 figs., 3 tables, November 2014 167

Reservoir stratigraphic heterogeneity within the Lower Cretaceous Muddy Sandstone in the Powder River Basin, northeast Wyoming, U.S.A.: Implications for carbon dioxide sequestration

Majie Fan*

Department of Earth and Environmental Sciences, University of Texas at Arlington, P.O. Box 19049, Arlington, Texas

76019, U.S.A.

*Correspondence should be addressed to: [email protected]

ABSTRACT

The Muddy Sandstone in the Powder River Basin (PRB), northeast Wyoming, is a promising reservoir for CO2 sequestration because: (1) existing wells for hydrocarbon production can be used for CO2 injection when a field is depleted; and (2) data are available to assess the ability and capacity to trap CO2. Here, I provide new data and compile published results to: (1) characterize four oil and gas fields (the Amos Draw, Kitty, Hilight, and Sand Dunes fields) in the PRB with respect to lithofacies, sedimentary environment, sandstone composition, sand-body geometry, and porosity and permeability; and (2) assess the controls on reservoir heterogeneity and the CO2 sequestration potential.

Five lithofacies are recognized based on core description and log responses. They are interpreted as offshore, lower–middle wave-dominated shoreface, weathering zone, fluvial incised-valley, and tide-influenced estuarine depositional environments. The Muddy Sandstone contains predominantly quartz, with total quartz higher than 70 percent of the total framework grains. The percentage of feldspar is generally less than 5 percent, except for the Rozet Member in the Amos Draw Field, which is up to 22 percent. Sandstone petrographic examination also shows that the Muddy Sandstone can be divided into four groups based on the relative abundance of pore space, carbonate cement, and matrix. Sandstone with high porosity up to 23 percent is found in the shoreface lithofacies in the Amos Draw and Hilight fields and is also found in the estuarine lithofacies in the Kitty Field. The incised-valley lithofacies is of particularly low porosity due to high matrix content and carbonate cementation. The measured porosity in the sandstone varies between 1 percent and 23 percent, and the permeability is generally less than 10 millidarcys (mD). The variation of porosity is consistent with the observation in thin sections. XRD results show that the pore-filling clay minerals include kaolinite, chlorite, illite, and smectite. Core and well log correlation show that sandstone formed in lower–middle shoreface environments is laterally extensive and of uniform thickness, whereas sandstone of fluvial and estuarine origins is more variable in lateral extent and thickness. Based on examination of lithofacies, sandstone geometry, and thin section petrography, I suggest that the best reservoir interval for CO2 sequestration in the Amos Draw Field is the lower Rozet Member, in the Sand Dunes and Hilight fields is the Springen Ranch Member, and in the Kitty Field is the Ute Member. Variables examined in this study provide important inputs for calculating CO2 capacity potential and predicting chemical reactivity after CO2 injection.

Reservoir quality of the Muddy Sandstone is highly heterogeneous, and the complexity may be attributed to a combination of depositional environment, history of relative sea-level change during deposition, and type and extent of diagenetic alteration. The Muddy Sandstone, along with the overlying Mowry Shale, represents one third-order depositional sequence. Diagenetic processes include feldspar and lithic dissolution, secondary clay formation, quartz overgrowth, and four stages of carbonate cementation, which are early dolomite overgrowth, secondary calcite filling, dolomite replacement, and spotty siderite cementation. Carbonate cementation is interpreted as early diagenetic products formed during marine transgressions.

KEY WORDS: CO2 sequestration, Cretaceous, diagenesis, Muddy Sandstone, Powder River Basin (PRB), reservoir heterogeneity, sequence stratigraphy.

168 Rocky Mountain Geology, v. 49, no. 2, p. 167–190, 13 figs., 3 tables, November 2014

INTRODUCTION

Carbon dioxide (CO2) sequestration potentially plays a significant role in mitigating release of CO2 increase into the atmosphere, which may contribute to global warming. Some geologic formations may have the capacity to store a large amount of CO2. Depleted hydrocarbon fields are attractive CO2 sequestration reservoirs because: (1) they have been extensively investigated during hydrocarbon exploration and production; (2) they have data available for simulation modeling to assess the ability and capacity to trap CO2; and (3) they have existing wells for injection. In addition, CO2 injection can be used to enhance oil recovery if the reservoir is in depletion stages. In recent years, CO2 storage in depleted hydrocarbon fields has been extensively studied including simulation of CO2 migration, geochemical modeling, long-term storage integrity, and risk assessment (e.g., Bachu, 2000; Oldenburg et al., 2001; Li et al., 2006; Mito et al., 2008; Tarkowski and Wdowin, 2011). Generally, the feasibility of sequestration in depleted oil and gas fields depends on the storage capacity of the reservoirs.

Sequestration capacity may vary significantly across geological formations as a result of reservoir heterogeneity. Both structural and stratigraphic factors control reservoir heterogeneity. Structural factors include the abundance, character, and architecture of fractures, faults, and folds. Important stratigraphic factors of the target intervals include sand-body continuity and connectivity, and porosity and permeability. These factors are controlled by depositional environment, sequence stratigraphic architecture, and post-depositional diagenesis. These factors may vary across a range of scales, from: (1) basin-scale changes in sedimentary environment and tectonics; to (2) reservoir-scale changes in lithofacies, sand-body geometry, and stacking patterns; to (3) microscopic-scale changes in porosity/permeability and mineral composition. These reservoir properties constrain the volume available in a subsurface field for CO2 injection (capacity). Reservoir capacity for CO2 sequestration may be modeled by computer simulations to enable prediction of flow properties, chemical reactions, and potential environmental impacts after CO2 injection. For example, a heterogeneous rock

body may result in flow paths that disperse and increase storage capacity by increasing the rock–CO2 contact, whereas a homogeneous rock body may reduce storage capacity by bypassing CO2 into other formations (Hovorka et al., 2004).

In this paper, the Lower Cretaceous Muddy Sandstone in the Powder River Basin (PRB), northeast Wyoming, is used as an example to demonstrate stratigraphic reservoir heterogeneity and its influence on CO2 storage capacity. I examined four oil and gas reservoirs in the PRB to delineate the lithofacies, sedimentary environment, sand-body geometry, sandstone composition, and porosity and permeability of the potential sequestration intervals. These data were obtained from published literature as well as my analyses. The data include: (1) core lithofacies analysis and interpretation of depositional environment; (2) petrographic examination of representative sandstone thin sections; and (3) log correlation of wells. All measured porosity and permeability are compiled from publicly available data at the U.S. Geological Survey (USGS) Core Research Center and the Wyoming Oil and Gas Conservation Commission. The four studied fields are the Amos Draw, Kitty, Hilight, and Sand Dunes (Fig. 1). The fields are then compared to determine how the various controlling factors influence stratigraphic heterogeneity of the reservoirs and to explore how stratigraphic heterogeneity affects CO2 sequestration. The cores and wells I studied are represented by their API numbers.

GEOLOGIC SETTING

The PRB in northeast Wyoming is one of the Rocky Mountain intermontane basins that developed during the latest Cretaceous–early Eocene Laramide Orogeny (Dickinson et al., 1988; Fig. 1). The PRB is bounded on the west and east by the Precambrian basement-involved Bighorn Mountains and Black Hills. It is bounded on the southwest and south by the Casper Arch, Laramie Mountains, and Hartville Uplift. During the Late Cretaceous, the region was located in the Western Interior Seaway (e.g., DeCelles, 2004). The Cretaceous deposits in the PRB are at least 2 km thick (Robinson Roberts and Kirschbaum, 1995), which represents significant basin subsidence caused by flexural loading of the Sevier fold-and-thrust belt, and dynamic process

M. FAN


induced by the f lat-subduction of the Farallon Plate (DeCelles, 2004; Liu and Nummedal, 2004; Jones et al., 2011). The displacement of the Bighorn Mountains caused f lexure subsidence of the basin during the latest Cretaceous–early Cenozoic, and Cenozoic basin fill is up to 2 km thick in western parts of the PRB (Curry, 1971). Outcrops of the Muddy Sandstone are present along the flanks of the Black Hills and Bighorn Mountains (Fig. 1).

PREVIOUS STRATIGRAPHIC STUDIES

In the PRB, the Muddy Sandstone is a major oil- and gas-producing interval and has yielded more than 1.5 billion barrels of oil-equivalent hydrocarbons (Dolson et al., 1991). The Muddy Formation and equivalent strata are underlain by the Lower Cretaceous Skull Creek and Thermopolis Shales and are overlain by the Upper Cretaceous Mowry Shale (Fig. 2A). The Muddy Sandstone is considered as the lower sandy interval of the Muddy Formation, and it includes the Rozet, Recluse, Cyclone, Ute, and Springen Ranch Members (Fig. 2B; Martinsen, 1994). The Muddy Formation also contains an upper

shale interval (Shell Creek Shale; Fig. 2B). The Shell Creek Shale and overlying Mowry Shale are the sealing lithofacies of the Muddy reservoir rock in the four studied fields.

The stratigraphic framework and sedimentary environment of the Muddy Sandstone have been assessed from outcrop and core examinations as well as well-log characteristics in the PRB (Baker, 1962; Eicher, 1962; Prescott, 1970; Gustason et al., 1988; Odland et al., 1988; Weimer, 1988; Dolson et al., 1991; Martinsen, 1994). Throughout Cretaceous time, marine to marginal-marine sandstone and shale accumulated during transgression and regression of the Western Interior Seaway (Weimer, 1988). The Muddy Sandstone is one of several sandy intervals that formed in a marginal-marine environment. By studying outcrop, Eicher (1962) suggested that the Muddy Sandstone along the west margin of the PRB was deposited in a shallow-marine environment during a marine transgression. Baker (1962) studied the Newcastle Sandstone, a Muddy Sandstone equivalent, along the east margin of the PRB and interpreted it as fluvial incised-valley deposits. More recent studies, which focused on well-log correlation with l imited core descript ion, demonstrate

Figure 1. General map of Powder River Basin (PRB) and nearby area in northeastern Wyoming showing distribution of outcrop of Muddy Sandstone and four oil and gas fields characterized in this study. Black line represents Belle Fourche Arch.

Figure 2. A, Stratigraphic column and succession intervals of Lower Cretaceous strata in PRB; and B, Generalized stratigraphic cross section of Muddy Sandstone in studied fields (modified from Martinsen, 1994). Not scaled.

RESERVOIR HETEROGENEITY WITHIN THE MUDDY SANDSTONE


that the Muddy Sandstone is stratigraphically complex, containing a variety of marine and nonmarine lithofacies and many intraformational unconformities (Gustason et al., 1988; Odland et al., 1988; Dolson et al., 1991; Martinsen, 1994).

The Muddy Sandstone, as described below, has been divided into three genetic packages based on lithofacies and stratigraphic architecture (Dolson et al., 1991; Martinsen, 1994). They include: (1) an older marine interval, (2) an incised-valley interval, and (3) a younger marine interval (Dolson et al., 1991; Martinsen, 1994). Based on Martinsen (1994), the older marine interval (Rozet Member) consists of one or more coarsening-upward, shale-to-sandstone sequences with normal, open-marine trace fossils. The lower part of each sequence displays planar laminations and hummocky cross-stratification, and the upper parts show hummocky to high-angle cross-stratified or massive bedding. The Rozet Member is dominantly quartzarenites, sublitharenites, and litharenites. The incised-valley interval (Recluse Member) consists of variable proportions of shale, siltstone, and sandstone and commonly contains thin coal and coaly beds. The sandstone is massive and commonly shows evidence of soft-sediment deformation. The sandstone is quartzarenite and sublitharenite. The younger marine interval (Cyclone, Ute, and Springen Ranch Members) is quartz-rich and consists of coarsening-upward, shale-to-siltstone or shale-to-sandstone sequences showing a variety of well-preserved sedimentary structures.

STUDIED FIELDS

The Muddy Sandstone in the Amos Draw Field is divided into the Rozet (sandstone), Ute (shale), and Springen Ranch (shaly sandstone) Members (Fig. 2B; Von Drehle, 1985; Odland et al., 1988; Martinsen, 1994). The producing interval in this field is mainly the Rozet Member. There are few published studies from the Sand Dunes Field, where the producing interval is mainly the Springen Ranch Member. The Kitty and Hilight fields are located in two large incised-valley systems that developed to the north and south of the Belle Fourche Arch in the PRB (Fig. 1; Byrd Larberg, 1980; Wheeler et al., 1988; Dolson et al., 1991; Martinsen, 1994). The two valleys cut into the Skull Creek Shale locally, and thus the lower Muddy Sandstone is completely eroded in many

places in the two fields. The Muddy Sandstone presented in the Kitty and Hilight fields is divided into the Recluse, Cyclone, Ute, and Springen Ranch Members, and the Rozet Member exists only at edges of the valleys. The main producing intervals are the Ute Member in the Kitty Field and the Springen Ranch Member in the Hilight Field.

LITHOFACIES AND SEDIMENTARY ENVIRONMENTS

Core Description and Interpretation

I examined 15 cores from the Amos Draw, Kitty, Hilight, and Sand Dunes fields to characterize the lithofacies, constrain the depositional environments, and guide field-scale well-log correlations. The core intervals were subdivided into f ive major lithofacies, interpreted as offshore, lower–middle wave-dominated shoreface, weathering zone, fluvial incised-valley, and tidal-influenced estuarine depositional environments (Table 1 and Figs. 3–5).

Gamma-ray Log Responses and Lithofacies

Gamma-ray logs are presented to ensure consistent and accurate representation and interpretation of lithofacies observed in cores, though resistivity and spontaneous potential logs are studied in many wells (Fig. 6). In the Amos Draw and Sand Dunes fields, lithofacies F has high gamma-ray values and irregular log response, suggesting that the lithofacies is clay rich and thinly bedded. Lithofacies S1 and S2 show funnel trend representing upward coarsening. Lithofacies S2, however, has low resistivity compared to S1. This is because lithofacies S2 has high kaolinite, and kaolinite does not contain potassium to have high gamma-ray response (Odland et al., 1988). Lithofacies S4 displays irregular log response representing interbedded siltstone and mudstone. In the Kitty and Hilight fields, lithofacies S3 is dominated by blocky log response representing well-amalgamated sandstone. Locally the lithofacies is serrated, representing interbedded sandstone and siltstone. Lithofacies S4 displays bell- and serrated-shaped responses in the lower half, and blocky and serrated-shaped responses in the upper half. The bell and serrated lower half represents upward fining, and the blocky and serrated upper half represents

M. FAN


Lith

ofac

ies

code

Li

thof

acie

s na

me

Out

crop

and

cor

e de

scrip

tion

Inte

rpre

tatio

nD

epos

ition

al

envi

ronm

ent

FBi

otur

bate

d sil

tston

e an

d m

udsto

ne

Dar

k gr

ay, t

hinl

y be

dded

, or m

assiv

e sil

tston

e an

d m

udsto

ne.

Silts

tone

bed

s sho

w p

lana

r- a

nd ri

pple

-lam

inat

ion

and

good

so

rtin

g, a

nd th

ey c

onta

in fo

ram

inife

ra, b

ival

ve fr

agm

ents,

and

py

rites

. Thi

n, v

ery

fine-

grai

ned

sand

stone

with

shar

p ba

ses a

nd

tops

occ

asio

nally

occ

ur. B

iotu

rbat

ed b

y C

hond

rites,

Pal

eoph

ycus

, Pl

anol

ites,

and

Tere

belli

na.

Biot

urba

ted,

mas

sive

siltst

one

and

mud

stone

are

offs

hore

dep

osits

fo

rmed

bel

ow st

orm

-wav

e ba

se (E

lliot

t, 19

86).

Thi

nly

bedd

ed

siltst

one

and

fine-

grai

ned

sand

stone

wer

e de

posit

ed w

here

oc

casio

nal s

torm

s affe

cted

dep

ositi

on b

etw

een

fair-

wea

ther

and

sto

rm-w

ave

base

s (El

liott,

198

6; W

alke

r and

Plin

t, 19

92).

Offs

hore

S1C

oars

enin

g-up

war

d sa

ndsto

ne

Ligh

t bro

wn

and

gray

, pla

nar-

lam

inat

ed, i

nter

laye

red

very

fine

-gr

aine

d sa

ndsto

ne a

nd si

ltsto

ne c

oars

en u

pwar

d to

trou

gh a

nd

hum

moc

ky c

ross

-lam

inat

ed o

r pla

nar-

lam

inat

ed, m

ediu

m-

grai

ned

sand

stone

. Silt

stone

bed

s are

bio

turb

ated

by

Skol

ithos

, Te

ichich

nus,

Cho

ndrit

es, a

nd P

aleo

phyc

us. M

ediu

m-g

rain

ed

sand

stone

is p

oorly

to w

ell s

orte

d an

d is

mas

sive

in K

itty

and

Hili

ght f

ield

s.

Inte

rlaye

red

sand

stone

and

silts

tone

wer

e de

posit

ed a

bove

stor

m-

wav

e ba

se (W

alke

r and

Plin

t, 19

92; K

amol

a an

d Va

n W

agon

er,

1995

). H

umm

ocky

and

trou

gh c

ross

-str

atifi

ed sa

ndsto

ne w

ere

depo

sited

abo

ve fa

ir-w

eath

er w

ave

base

, and

dep

ositi

on w

as

dom

inat

ed b

y sh

oalin

g of

fair-

wea

ther

wav

es (E

lliot

t, 19

86; W

alke

r an

d Pl

int,

1992

).

Low

er–m

iddl

e w

ave-

dom

inat

ed

shor

efac

e

S2M

assiv

e sa

ndsto

ne

Cre

amy

whi

te m

ediu

m-g

rain

ed sa

ndsto

ne, ~

1.5

m th

ick,

occ

urs

only

in th

e up

per R

ozet

Mem

ber i

n th

e Am

os D

raw

Fie

ld.

Con

tain

s hig

h ka

olin

ite c

onte

nt a

nd a

bund

ant r

oot t

race

s (O

dlan

d et

al.,

198

8).

Hig

h ka

olin

ite c

onte

nt w

as d

ue to

wea

ther

ing

of fe

ldsp

ar g

rain

s (O

dlan

d et

al.,

1988

). T

he su

baer

ial e

rosio

n of

the

top

of th

e Ro

zet

Sand

stone

repr

esen

ts lo

ng-te

rm st

abili

zatio

n of

floo

dpla

in (M

iall,

19

88).

Wea

ther

ing

zone

S3Fi

ning

-up

war

d sa

ndsto

ne

Gra

y-ye

llow,

mas

sive,

coa

rse-

grai

ned

sand

stone

fine

s upw

ard

to

plan

ar-la

min

ated

, fin

e-gr

aine

d sa

ndsto

ne o

r to

mas

sive,

m

ediu

m-g

rain

ed sa

ndsto

ne. S

ands

tone

is p

oorly

to m

oder

atel

y so

rted

and

con

tain

s gra

nule

- to

pebb

le-s

ized

intr

acla

sts a

t the

ba

se. O

verli

es li

thof

acie

s S1

and

F w

ith e

rosio

nal b

ase

and

only

oc

curs

in K

itty

and

Hili

ght f

ield

s. C

onta

ins a

bund

ant w

ood

debr

is an

d th

in c

oal b

eds.

Soft-

sedi

men

t def

orm

atio

n is

com

mon

.

Fluv

ial i

ncise

d-va

lley

depo

sits (

Van

Wag

oner

et a

l., 1

990)

that

tr

unca

te o

lder

shor

efac

e de

posit

s and

loca

lly in

cise

offs

hore

de

posit

s und

erly

ing

the

shor

efac

e de

posit

s. T

he o

ccur

renc

es o

f the

lit

hofa

cies

in th

e K

itty

and

Hig

hlig

ht fi

elds

sugg

est t

hat t

here

may

be

at l

east

two

inci

sed-

valle

y sy

stem

s in

the

easte

rn p

ortio

n of

the

Pow

der R

iver

Bas

in. T

he m

axim

um th

ickn

ess o

f the

inci

sed-

valle

y de

posit

s ind

icat

es th

at th

e m

axim

um in

cisio

n re

lief i

s ~8

m.

Fluv

ial i

ncise

d-va

lley

S4

Inte

rbed

ded

sand

stone

, sil

tston

e,

mud

stone

, an

d co

al

Thi

nly

inte

rbed

ded

gray

-yel

low,

ver

y fin

e-to

med

ium

-gra

ined

, pl

anar

-and

ripp

le-la

min

ated

sand

stone

, silt

stone

, dar

k gr

ay

mud

stone

, and

coa

l ofte

n sta

ck a

s fin

ing-

upw

ard

sequ

ence

s w

ith e

rosio

nal b

ases

, and

to a

less

ext

ent a

s coa

rsen

ing-

upw

ard

sequ

ence

s. H

umm

ocky

cro

ss-la

min

atio

n on

ly sh

ows i

n th

e co

arse

ning

-upw

ard

sequ

ence

s. Sa

ndsto

ne is

poo

rly–w

ell s

orte

d an

d co

ntai

ns m

ud c

lasts

at t

he b

ase.

Cla

y dr

apes

and

sand

stone

-m

udsto

ne c

oupl

ets a

re c

omm

on. C

onta

ins a

bund

ant w

ood

debr

is an

d so

me

bent

onite

bed

s. G

lossi

fung

ites b

urro

ws a

re

com

mon

.

Fini

ng-u

pwar

d se

quen

ces w

ith e

rosio

nal b

ases

wer

e de

posit

ed a

s ba

yhea

d de

lta o

r dist

ribut

ary

chan

nels

deve

lope

d in

a w

ave-

dom

inat

ed e

stuar

y, an

d th

e m

udsto

ne a

nd c

oal w

ere

depo

sited

as

estu

arin

e ce

ntra

l-bas

in d

epos

its (D

alry

mpl

e et

al.,

199

2). C

lay

drap

es su

gges

t tha

t the

bay

head

del

ta w

as in

fluen

ced

by ti

des

(Fen

ies e

t al.,

199

9). C

oars

enin

g-up

war

d se

quen

ces a

re m

arin

e sh

oref

ace

depo

sits (

Wal

ker a

nd P

lint,

1992

), su

gges

ting

the

conn

ectio

n of

estu

ary

to o

pen

mar

ine

envi

ronm

ent i

n th

e es

tuar

y m

outh

, whe

re w

ave

ener

gy is

hig

h du

ring

storm

s (Ro

y et

al.,

198

0). Ti

de-in

fluen

ced

estu

arin

e

Tabl

e 1.

Lith

ofac

ies a

nd in

terp

reta

tions

use

d in

this

study

.Ta

ble

1. L

itho

faci

es a

nd in

terp

reta

tion

s use

d in

this

stud

y.RESERVOIR HETEROGENEITY WITHIN THE MUDDY SANDSTONE


variation of lithology from well-amalgamated sandstones to interbedded sandstone, siltstone, mudstone, and coal.

Correlation and Distribution of Lithofacies

In both the Amos Draw and Sand Dunes fields, the studied intervals are characterized by two

coarsening-upward sandstone bodies of lithofacies S1 sandwiching interbedded siltstone and mudstone of lithofacies S4 (Figs. 3–6). The lower coarsening-upward sandstone is the Rozet Member, deposited in shoreface environments, consistent with the interpretation by Odland et al. (1988), Dolson et al. (1991), and Martinsen (1994). The upper Rozet Member changes to lithofacies S2, which

Figure 3. Core descriptions and correlations in Amos Draw and Sand Dunes fields. Cores are denoted by well API numbers. Datum in Amos Draw Field is top of Rozet Member. Note: this study suggests best interval for CO2 sequestration is lower Rozet Member in Amos Draw Field and Springen Ranch Member in Sand Dunes Field.

M. FAN


Figure 4. Core descriptions and correlations in Hilight Field. Datum is top of Cyclone Member. Note: this study suggests best interval for CO2 sequestration is Springen Ranch Member.



Figure 5. Core descriptions and correlations in the Kitty Field. Datum is top of Cyclone Member. Note: this study suggests best interval for CO2 sequestration is Ute Member.

Figure 6, facing page. Well log correlation along N–S cross sections in studied field. A, Amos Draw Field; B, Sand Dunes Field; C, Hilight Field; and D, Kitty Field. Black log lines are gamma-ray logs with sandstone in gray. Sections are marked as black lines in Figure 12. Sandstone beds of Rozet Member in Amos Draw and Sand Dunes fields and Springen Ranch Member in all fields are laterally consistent and display upward coarsening. Sandstone beds of Recluse, Cyclone, and Ute Members have complex stacking patterns and geometry.

M. FAN


4900528511 4900527938 4900527490 4900527251 4900527539 4900526958 4900526970 4900526955GRMD GR

1800MD GR

1800MD GR

1800MD GR

1800MD GR

1800MD

1800MD GR

1800MD GR

18009900

9960

9940

9920

9980

9860

9920

9900

9880

9940

9820

9880

9860

9840

9900

9920

9980

9960

9940

10000

9830

9890

9870

9850

9910

10000

10060

10040

10020

10080

10100

10160

10140

10120

10180

10120

10180

10160

10140

10200

4900922716 4900922633 4900922700 49009227554900922615 4900922764MD GR

1800MD GR

1800MD GR

1800MD GR

1800MD GR

1800MD

1800GR

12570

12630

12610

12590

12650

12620

12680

12660

12640

12700

12570

12630

12610

12590

12650

12890

12950

12930

12910

12970

12620

12680

12660

12640

12700

12690

12750

12730

12710

12770

4900522168MD GR

1800MD GR

1800MD GR

1800MD GR

1800MD GR

1800MD

1800MD GR

1800MD GR

1800

4900522028 49005218484900521473 4900521467 49005220824900521659 4900521741 490052271349005212105MD GR

1800MD GR

1800

8720

8780

8760

8740

8800

8850

8910

8890

8930

8820

9340

9400

9380

9360

9420

8870

9480

9540

9520

9500

9560

9080

9140

9120

9100

9160

9280 9580

9730

9790

9770

9750

9810

9730

9810

9790

9750

9830

9820

9880

9860

9840

9900

9650

9710

9690

9670

9730

9760

9820

9800

9780

9840

GR

4900521785MD GR

1800

49005205634900520664490052260749005210764900521860 4900520705 49005202084900520519 4900520719MD GR

1800MD GR

1800MD GR

1800MD GR

1800MD GR

1800MD

1800MD GR

1800MD GR

1800GR MD

1800GR

7860

7920

7900

7880

7940

8770

8830

8810

8790

8850

8510

8560

8540

8520

8580

8420

8480

8460

8440

8500

8190

8250

8230

8210

8270

8820

8820

8880

8860

8840

8900

8920

8950

9110

8990

8970

9130

8590

8650

8630

8610

8670

9170

9230

9210

9190

9250

8870

8930

8910

8890

8950

897092708690

Springen Ranch

Springen Ranch

Springen Ranch

Springen Ranch

Ute

Ute

Ute

Ute

Rozet

Cyclone

Cyclone

Recluse

Recluse

Rozet

A

B

C

D



is a weathering zone formed during a regional erosion event (Odland et al., 1988; Martinsen, 1994). The sandwiched interval of lithofacies S4 is the Ute Member, which represents brackish water or estuarine central-basin deposits. The upper coarsening-upward sandstone is the Springen Ranch Member, which is open-marine, shoreface deposits. In the Sand Dunes Field, the Ute Member contains more sandstone beds. The laterally most extensive and sandy lithofacies are the lower Rozet Member in the Amos Draw Field and the Springen Ranch Member in the Sand Dunes Field.

In the Kitty and Hilight fields, the studied intervals are in the order of lithofacies F changing to S3 with sharp contact, then to S4, and finally to S1 (Fig. 6). In some of the studied wells, a lower coarsening-upward sequence of lithofacies S1 overlies lithofacies F. Lithofacies S1 is the Rozet Member, which is completely eroded in the other wells. Lithofacies S3 is a blocky sandstone body, which is the Recluse Member of incised-valley deposits. Lithofacies S4 is mainly characterized by a fining-upward sequence overlain by a sandstone-dominated upper interval. In some wells, the upper interval consists of interbedded sandstone and shale. One layer of bentonite occurs in lithofacies S4 and is easily recognized as an interval of high gamma-ray and low resistivity. I correlate the bentonite with the top of the fining-upward sequence, defining the surface as the top of the Cyclone Member, and defining the upper lithofacies S4 as the Ute Member. The thickness of lithofacies S3 and S4 laterally varies. The coarsening-upward S1 at the top of the studied intervals is the Springen Ranch Member. Compared to the Kitty Field, the Recluse, Cyclone, and Ute Members are shale prone in the Hilight Field, and the Springen Ranch Member is sand prone and thick in the Hilight Field.

SANDSTONE PETROGRAPHY AND CLAY MINERALOGY

Thin sections from nine cores in the Amos Draw, Kitty, and Hilight fields were examined. These sandstone samples were selected from all the members in the Kitty Field to aid in recognizing relationships between sandstone composition and lithofacies. Samples from the Amos Draw and Hilight fields also were selected to characterize sandstone

composition. Forty-five fine- to medium-grained sandstone samples were point-counted following the modified Gazzi-Dickinson method (Ingersoll et al., 1984). Sandstone composition was determined by identification of 400 grains per slide. Matrix, cement, and pore space features also were counted. Sandstone petrography results are summarized in Table 2 and Figure 7. Matrix of four samples from the Hilight Field was examined for clay-mineral composition. Matrix (<63 mm) was separated by dry sieving and prepared for XRD analysis by hand grinding in a mortar and pestle. Oriented smears on glass slides were x-rayed with a Scintag XDS 2000 automated powder diffraction system equipped with a solid state X-ray detector at 2° per minute scanning speed. Relative abundance of clay minerals was determined based on peak height. These results (Fig. 8) combined with other clay-mineral compositional data made public by the USGS Core Research Center are presented in Table 3.

XRD results from this study show that clay matrix from the Muddy Sandstone in the Hilight Field is mainly kaolinite and chlorite (Fig. 8). Results compiled from the public data show that the clay matrix in the Kitty and Hilight fields is dominated by kaolinite and illite, with lesser amounts of smectite and chlorite (Table 3). Petrographic study show that total quartz grains, including monocrystalline and polycrystalline quartz, make up more than 70 percent of the total framework grains while feldspar and total lithic grains comprise at most 30 percent (Table 2, Fig. 7). Lithic fragments consist primarily of shale grains and to a lesser extent carbonate, biotite, glauconite, and wood fragments. Feldspar grains include potassium feldspar and plagioclase. Petrographic results show that the sandstone samples from the Ute, Recluse, Cyclone, and Springen Ranch Members in the Kitty and Hilight fields contain abundant monocrystalline quartz (>75 percent), but a lesser amount of polycrystalline quartz (Table 2). The abundance of feldspar and lithic fragments are generally low, with the sum less than 10 percent (Table 2). Samples from the Rozet Member in the Amos Draw Field, however, have feldspar abundance up to 22 percent. They also have slightly higher abundance of polycrystalline quartz and lithic fragments compared to samples from the Kitty and Hilight fields (Fig. 7).

M. FAN


Sample† Member Qm(%)# Qp(%) C(%) K(%) P(%) Lsh(%) Oil(%) O(%)* Grain (%) Cement (%) Matrix (%) Pore (%) Group

Amos Draw Field

524520-9862 Rozet 54.0 12.5 8.4 0.2 1.1 17.3 0.0 6.4 56.1 0.8 41.9 1.2 4

524520-9868 Rozet 82.3 3.0 2.5 2.5 3.0 5.5 0.3 0.8 77.3 0.4 20.6 1.7 4

524520-9871 Rozet 74.2 12.0 0.0 1.3 8.3 2.5 0.0 1.8 81.3 1.2 15.9 1.6 4

524520-9873 Rozet 64.2 7.5 0.3 1.3 17.0 8.8 0.0 1.0 72.5 2.4 24.5 0.5 4

524520-9877 Rozet 74.6 3.5 0.0 4.5 12.4 4.2 0.0 0.7 86.6 3.4 6.7 3.2 4

524520-9880 Rozet 60.2 12.5 3.7 8.6 13.0 0.0 0.0 2.0 77.1 7.0 9.1 6.8 4

524520-9882 Rozet 65.8 5.0 0.0 2.3 18.0 8.5 0.0 0.5 73.1 3.8 22.3 0.7 4

Kitty Field

520750-8941 Ute 91.8 1.0 1.0 0.2 0.0 0.0 0.5 5.5 97.3 0.0 1.9 0.7 2

520750-8950.25 Recluse 75.4 10.1 14.1 0.4 0.0 0.0 0.0 0.0 70.3 20.3 8.8 0.6 3

520750-8953 Recluse 87.3 5.5 7.2 0.0 0.0 0.0 0.0 0.0 58.5 0.3 40.8 0.4 4

520750-8957 Recluse 72.0 5.0 16.1 0.2 0.0 6.0 0.0 0.7 71.2 21.6 7.2 0.0 3

520750-8958 Recluse 78.8 7.8 6.6 2.2 1.9 0.0 2.7 0.0 42.2 2.2 54.6 1.1 4

520750-8951.5 Recluse 89.4 6.9 1.4 0.0 0.0 0.0 0.0 2.3 86.3 0.0 13.7 0.0 4

521076-8438 Cyclone 90.8 7.2 0.0 0.0 0.0 1.0 1.0 0.0 62.0 38.0 0.0 0.0 3

521076-8439.5 Cyclone 83.2 5.9 2.4 0.0 0.0 8.6 0.0 0.0 100.0 0.0 0.0 0.0 2

521076-8448.4 Recluse 88.2 7.4 1.2 0.2 1.0 2.0 0.0 0.0 98.1 0.0 1.9 0.0 2

521076-8465.5 Recluse 83.8 1.9 5.9 0.0 3.0 5.4 0.0 0.0 82.3 0.0 17.7 0.0 4

521076-8467.6 Recluse 90.4 0.0 8.4 0.0 0.0 1.2 0.0 0.0 64.1 29.3 6.6 0.0 3

520429-9426 Ute 93.5 2.9 0.0 1.2 0.0 1.0 0.0 1.4 87.4 0.0 0.0 12.6 1

520429-9448 Recluse 87.1 2.0 10.6 0.0 0.0 0.0 0.3 0.0 66.4 0.0 31.9 1.7 4

520429-9451 Recluse 94.6 1.3 2.2 0.0 0.0 0.8 1.1 0.0 43.3 2.3 52.5 1.9 4

520429-9454 Recluse 98.8 0.0 0.0 0.0 0.3 0.0 0.9 0.0 56.3 0.0 43.7 0.0 4

520429-9456 Recluse 89.0 6.3 3.5 0.0 0.3 0.8 0.0 0.3 78.4 3.9 16.5 1.2 4

520429-9457 Recluse 87.3 4.5 6.2 0.0 0.3 0.3 0.0 1.4 71.7 0.7 27.0 0.5 4

520429-9465.1 Rozet 96.7 0.6 1.5 0.0 0.9 0.0 0.0 0.3 75.1 0.0 24.9 0.0 4

520664-8839 Ute 83.8 1.8 6.4 0.5 0.7 4.6 0.0 2.3 95.0 0.0 0.9 4.1 1

520664-8847 Ute 80.7 7.0 4.6 0.0 0.9 4.4 2.4 0.0 96.0 0.0 4.0 0.0 2

520664-8852 Ute 95.1 1.5 1.9 0.0 0.5 0.2 0.7 0.0 98.8 0.2 0.7 0.2 2

520664-8870 Recluse 93.9 2.3 0.3 0.0 1.2 0.3 0.0 2.0 99.7 0.0 0.3 0.0 2

520664-8883 Recluse 98.8 0.0 0.3 0.5 0.0 0.3 0.3 0.0 98.0 0.0 2.0 0.0 2

520664-8884 Recluse 95.3 2.0 0.8 0.0 0.0 0.3 0.0 1.8 93.7 0.0 0.2 6.1 1

521107-9194.5 Ute 94.6 0.2 0.0 0.5 0.2 0.7 2.7 1.0 89.7 0.0 0.0 10.3 1

521107-9196.5 Ute 96.2 0.5 0.0 0.0 0.0 0.0 0.0 3.3 85.1 0.0 1.5 13.4 1

521107-9208 Ute 95.2 4.8 0.0 0.0 0.0 0.0 0.0 0.0 86.7 0.0 0.7 12.6 1

521107-9212.2 Ute 98.0 0.0 0.2 0.0 0.0 0.0 0.7 1.0 97.1 0.0 0.0 2.9 2

521107-9233 Cyclone 85.1 1.3 2.6 0.5 0.8 5.7 3.4 0.8 68.9 5.3 13.9 11.9 3

Hilight Field

522168-8716.5 Springen Ranch 84.2 7.1 3.0 1.6 0.7 0.7 2.7 0.0 67.8 0.0 26.7 5.6 4

522168-8717 Springen Ranch 90.3 6.4 2.2 0.0 0.0 0.0 1.0 0.0 63.6 0.0 36.4 0.0 4

521742-9677.5 Cyclone 84.1 0.0 4.4 0.8 0.0 0.0 4.4 6.3 81.3 0.0 18.7 0.0 4

521474-9333 Springen Ranch 95.3 1.7 0.2 0.5 1.2 1.0 0.0 0.0 89.5 0.9 3.1 6.5 1

521474-9339 Springen Ranch 95.7 1.7 0.9 0.0 0.0 0.9 0.9 0.0 75.5 0.7 0.7 23.2 1

521474-9345 Springen Ranch 98.8 0.2 0.0 0.5 0.0 0.0 0.5 0.0 83.6 0.0 3.1 13.3 1

521474-9355 Springen Ranch 97.4 1.3 1.3 0.0 0.0 0.0 0.0 0.0 79.3 1.3 2.6 16.8 1

521474-9362 Ute 96.8 2.0 0.7 0.0 0.0 0.0 0.5 0.0 84.8 0.0 14.6 0.6 4

521474-9398 Rozet 95.7 1.7 1.7 0.0 0.2 0.5 0.0 0.2 71.2 0.0 19.6 9.2 4

Table 2. Modal petrographic data.

#Qm: monocrystalline quartz; Qp: polycrystalline quartz; C: chert; K: potassium feldspar; P: plagioclase; Lsh: shale lithic fragments; O: other.

*Other includes biotite, glauconite, zircon, wood fragment.

†Numbers beside last six digits of core APL represent stratigraphic depths of the samples below KB in feet.

Table 2. Modal petrographic data.



Sandstone petrography results from this study show that matrix content is generally less than 50 percent while the percentages of pore space and cement are low for most samples (Table 2). Sandstone in the Muddy Sandstone can be classified into four types based on percentage of pore space, carbonate cement, and matrix. Group 1 sandstone is tightly compacted and possesses pore space higher than 10 percent of the volume. This group contains more than 95 percent of monocrystalline quartz, but very small amounts of carbonate cement and clay matrix; sometimes, quartz overgrowth is observed. Microscopic inspection shows that some of the pore spaces were generated by dissolution of feldspars (Fig. 9A). Group 1 is found in the Ute Member in the Kitty Field and Springen Ranch Member in the Hilight Field (Table 2). Group 2 sandstone displays minimum pore space and common quartz overgrowths. Quartz overgrowths are recognized by the presence of a dusty rim that

separates overgrowth from host quartz grains or by a clay coating on the original quartz grain (Fig. 9B). Group 2 has more than 90 percent quartz, and some samples have up to 9 percent of shale and carbonate lithic fragments. This group is common in both the Ute and Recluse Members in the Kitty Field (Table 2). Group 3 sandstone displays minimal pore space, but contains 5–40 percent by volume of carbonate cement, including calcite, dolomite, and siderite. Calcite and dolomite cements are interpreted to have formed during three stages. An early stage of dolomite overgrowth on quartz grains is overprinted by a second stage of calcite filling the pore space between grains. A third stage of dolomite replaces calcite cement (Fig. 9C ). Siderite cement occurs within the calcite cement and displays radial fibrous texture with light brown color under polarized light (Fig. 9D). This group is found in both the Cyclone and Recluse Members in the Kitty Field (Table 2). Group 4 sandstone contains 6–55 percent

Table 3. Types of clays in representative core samples.

Core Percent of clay Dominant clay minerals Other Source

9200520750 (8920–8973

feet†, 13 analyses) 6-52 kaolinite illite, chlorite, smectite USGS9200521076 (8438–8489 feet, 5 analyses) 7-63 illite chlorite, smectite, kaolinite USGS9200520918 (8786–8836 feet, 9 analyses) 7-65 kaolinite illite, chlorite, smectite USGS9200520664 (8853–8885 feet, 6 analyses) 4-37 illite, kaolinite chlorite, smectite USGS9200520107 (9176–9235 feet, 10 analyses) 4-38 illite, kaolinite chlorite, smectite USGS

9200521742 (9652–9688 feet, 5 analyses) 23-59 illite chlorite, smectite, kaolinite USGS9200524953 (9374–9403 feet, 13 analyses) 5-60 illite, kaolinite chlorite, smectite USGS9200521742 (9651 feet, 1 analysis) Small amount chlorite, kaolinite smectite This study9200521742 (9658 feet, 1 analysis) Small amount chlorite, kaolinite smectite This study9200522310 (8722 feet, 1 analysis) Small amount chlorite, kaolinite smectite This study9200522310 (8698 feet, 1 analysis) Small amount chlorite, kaolinite smectite This study

Table 3. Types of clays in representative core samples.

Kitty Field

Hilight Field

†The stratigraphic depths of the samples are measured below KB.

M. FAN


by volume of clay matrix and up to 10 percent pore space. This group is distributed in the Rozet Member in the Amos Draw Field, Recluse Member in the Kitty Field, and Springen Ranch Member in the Hilight Field (Table 2). Dissolution of feldspars and lithics are commonly observed in Group 4. In the Amos Draw Field, such sandstone also contains up to 27 percent of lithic fragments, consistent with observations by Odland et al. (1988) and Martinsen (1994).

Four types of post-depositional alteration are summarized from petrographic examination of the sandstone samples. They include: (1) mechanical compaction, which is common in all members; (2) dissolution of grains, particularly feldspars and lithic fragments (found only in Group 1 and 4 sandstone); (3) formation, dissolution, and recrystallization of pore-filling cements, including calcite, dolomite, and smectite, and development of quartz overgrowth (carbonate cements of different stages are common in Group 3 sandstone; quartz overgrowth is found in all sandstone, but is common in Group 1 sandstone); and (4) formation of grain-replacing and pore-filling kaolinite (this is

common only in Group 4 sandstone in the Rozet Member in the Amos Draw Field).

POROSITY AND PERMEABILITY

Petrographic study shows that Group 1 sandstone has high porosity (6–23 percent), Group 4 sandstone has porosity varying between 0 and 9 percent, and Group 2 and 3 have porosity generally less than 1 percent (Table 2). The measured porosity of the lower Rozet Member in the Amos Draw Field ranges from 5 to 13 percent, whereas the upper Rozet Member is <5 percent, which results from the high content of kaolinite formed during subaerial weathering of the strata (Martinsen, 1994). This agrees generally with my point-count data, which shows that sandstone of the upper Rozet Member in well 4900524520 has lower porosity than the lower Rozet Member (Table 2). The horizontal permeability of the lower Rozet Member ranges from 0.01 to 0.3 mD, and the upper Rozet is less than 0.01 mD. The porosity of five cores in the Sand Dunes Field varies between 1 percent and 23 percent, with the highest of 5–23 percent in the Springen Ranch Member (Fig. 10). The horizontal

Figure 7. Ternary QtFL diagram showing compositional variation of framework grains in Muddy Sandstone. See Table 2 for data. Qt includes monocrystalline and polycrystalline quartz. F includes potassium feldspar and plagioclase. L includes shale fragments, chert, and other grains.

Figure 8. X-ray diffractogram of four representative samples from Hilight Field. Gray is air-dried; black is glycolated. Minerals include: c-chlorite, ca-calcite, k-kaolinite, q-quartz, s-smectite.



permeability is up to 150 mD, and the highest values are in upper parts of the Springen Ranch Member. The porosity of five cores in the Hilight Field varies between 1 percent and 23 percent, with the highest in the Springen Ranch Member (Fig. 10). This is consistent with my observation that the porosity of studied sandstone samples of the Springen Ranch Member in the Hilight Field is up to 23 percent. The horizontal permeability of Springen Ranch Member is up to 15 mD (Fig. 10). There are no measured porosity and permeability data available for cores from the Kitty Field. My thin section study of the Kitty Field shows that many sandstone intervals in the Recluse and Cyclone Members are extensively cemented and

contain high amounts of clay matrix, whereas the Ute Member has high porosity up to ~13 percent (Table 2).

ISOPACH PATTERNS

Introduction

Isopach maps of the Muddy Sandstone and structural maps of the top of the Muddy Sandstone were constructed based on lithofacies and log responses. Twelve wells in the Sand Dunes Field, 173 wells in the Amos Draw Field, 12 wells in the Kitty Field, and 60 wells in the Hilight Field were correlated (Figs. 6, 11, and 12).

A

D C

B

100 µm

100 µm 100 µm

100 µm

F Q

Q

Q

Q

Q

R

R R

L

K

F

S

Figure 9. Photographs of representative thin sections of Muddy Sandstone in the Kitty Field. A, Secondary pore space (shown in blue) generated by dissolution of feldspars (F), well 4900520107. Thin section from 9,208 ft; B, No pore space due to quartz overgrowth, well 4900521076. Thin section from 8,439.5 ft; C, Dolomite overgrowth on quartz grains followed by calcite (stained to red) filling pore space, and subsequent dolomite veins invading calcite, well 4900520750. Thin section from 8,950 ft; and D, Secondary (post-depositional) light-brown siderite cement showing radial fibrous texture in sandstone of high clay matrix, well 4900520429. Thin section from 9,456 ft. All are in cross-polarized light. Q = monocrystalline quartz, F = feldspar, R = quartz overgrowth with a clay rim, K = kaolinite matrix, L = lithics, and S = siderite.

M. FAN


Amos Draw Field

In the Amos Draw Field, the thickness of the Rozet Member is 15–35 ft (5–12 m) and increases to the west (Figs. 6A and 11A). Although the Springen Ranch Member is also regionally continuous, it is 5–10 ft (2–3 m) thick, significantly thinner than the Rozet Member (Fig. 6A). The measured depth of the top of the Muddy Sandstone varies between 9,500 ft (2,896 m) and 10,500 ft (3,200 m) below the kelly bushing (KB; Fig. 12A), and KB is at 4,200–4,700 ft (1,280–1,433 m) above sea level. The thickness of the Rozet Member is high in the east side of the field and low in the west (Fig. 11A).

Sand Dunes Field

In the Sand Dunes Field, the Rozet Member is shale prone in some wells, whereas the Springen Ranch Member is sandier and more laterally persistent (Figs. 6B and 11B). The Springen Ranch sandstone is 12–32 ft (4–10 m) thick across the field and thickens toward the south and southeast of the field (Fig. 11B). The measured depth of the top of the Muddy Sandstone varies between 12,400 ft (3,780 m) and 13,100 ft (3,993 m) below KB (Fig. 12B), and KB is at 5,600–6,000 ft (1,707–1,829 m) above sea level. The top of the Muddy Sandstone in the Sand Dunes Field is the lowest of the four studied fields; it is ~1500 ft (~457 m) lower compared to the top in the Amos Draw Field.

Hilight Field

The Recluse, Cyclone, and Ute Members are not laterally continuous in the Hilight Field, and they generally thin toward the south and north (Fig. 6C). This interpretation is consistent with that of Martinsen (1994), which documented that the three members progressively onlap the Skull Creek Shale from northwest to southeast within an incised-valley. The Ute Member is 4–22 ft (1–7 m) thick and is laterally continuous (Figs. 6C and 11C). The measured depth of the top of the Muddy Sandstone varies between 8,000 ft (2,438 m) and 10,000 ft (3,048 m) below KB (Fig. 12C), and KB is at 4,600–5,000 ft (1,402–1,524 m) above sea level. The top of the Muddy Sandstone, which deepens toward the southwest, is the highest in the four studied fields. It is ~2,300 ft (~701 m) higher compared to the top in the Amos Draw Field.

Kitty Field

The thickness of the Recluse, Cyclone, and Ute Members varies across the Kitty Field (Figs. 6D and 11D). In general, the Recluse Member contains quartz-dominated sandstone, and the thickness ranges from 5 to 30 ft (2 to 9 m). The overlying Cyclone Member is more silty and shaly and varies in thickness. The Ute Member is dominated by quartz-rich sandstone, of 18–28 ft (5–9 m) thick, and it thickens toward the south (Fig. 11D). The Springen Ranch Member is thin, but laterally extensive. The measured depth of the top of the Muddy Sandstone in the Kitty Field varies between 7,900 ft (2,408 m) and 9,200 ft (2,804 m) below KB (Fig. 12D), and KB is at 4,100–4,700 ft (1,250–1,433 m) above sea level. The top of the Muddy Sandstone deepens toward the southwest in the Kitty Field, and it is ~1,500 ft (~457 m) higher compared to the top in the Amos Draw Field.

The top of the Muddy Sandstone generally deepens toward the west in the four studied fields. The top is higher in the Hilight and Kitty fields compared to the top in the Amos Draw and Sand Dunes fields. This trend suggests that the basin limb was tilted down to the west after deposition, most likely caused by f lexural loading by growth of the Bighorn Mountains during the Laramide Orogeny (e.g., Flores and Ethridge, 1985).

Figure 10. Cross plot of permeability vs. porosity for core samples from Hilight, Amos Draw, and Sand Dunes fields in PRB. Springen Ranch Member has highest porosity and permeability.



DISCUSSION

Reservoir Heterogeneity of Muddy Sandstone

Characteristics of high-quality subsurface reservoirs for CO2 sequestration include high porosity, high permeability, high abundance of reactive Ca-, Mg-, and Fe-bearing non-carbonate minerals, great thickness, and good continuity of sandstone intervals (e.g., Holloway, 2001; Kharaka et al., 2006). These characteristics vary for the Muddy Sandstone within each of the reservoir intervals, resulting in reservoir heterogeneity. The most favorable interval for sequestration within the Muddy Sandstone varies in the four studied fields. The primary reservoir in the Amos Draw Field is the lower Rozet Member because of its high thickness, high porosity and permeability, high feldspar abundance, and high sand/mud ratio compared to the Springen Ranch Member. The primary reservoir in the Kitty Field is the Ute

Member, resulting from its high porosity (up to ~30 percent). Both the valley-fill deposits of the Recluse Member and estuarine deposits of the Cyclone Member in this field are thick and sandy. They have low porosity and permeability, however, because of extensive cementation, high matrix content, and large vertical and lateral variations of lithofacies. These variations result in reduced CO2 sequestration capacity and ability. The primary reservoir in the Hilight Field is the Springen Ranch Member. The stratigraphic complexity in the Hilight Field is similar to the Kitty Field, and the valley-fill deposits in the Hilight are more shale prone in comparison to the Kitty. The Springen Ranch Member is laterally thick and consistent, with high porosity and high permeability, and thus it is the best interval for sequestration. The primary reservoir in the Sand Dunes Field is the Springen Ranch Member because of its greater thickness, high porosity and permeability, and high sand/mud ratio compared to the Rozet Member.

Figure 11. Isopach map of: A, Rozet Member in Amos Draw Field; B, Springen Ranch Member in Sand Dunes Field; C, Ute Member in Hilight Field; and D, Springen Ranch Member in Kitty Field. Squares represent well data used in study. Units are in feet.

M. FAN


New Sequence Stratigraphic Framework

Sequence stratigraphy provides a useful way to interpret the large-scale architecture of reservoir development in the four fields studied in the PRB. Previous studies discussed the significance of major unconformities (Gustason, 1988; Gustason et al., 1988; Weimer, 1988; Ryer et al., 1990; Martinsen, 1994) in the Muddy Sandstone in the PRB. Sequence stratigraphic evolution of the Muddy Sandstone in the Hilight Field was also discussed previously (Donovan, 1995). In this paper, I use the sequence stratigraphic concepts of Van Wagoner et al. (1990) to explain the reservoir distribution within the Muddy Sandstone in each of the fields studied (Fig. 9). The sequence stratigraphic interpretation from this study is based on the work of authors listed in this section (‘New Sequence Stratigraphic Framework’) as well as my interpreted depositional environment (Table 1).

The underlying Skull Creek Shale and equivalent Thermopolis Shale were deposited during the first

incursion of the Cretaceous seaway into Wyoming during Albian time and are interpreted to represent an early highstand systems tract. Onset of Muddy deposition took place as a shoreface environment prograded from northwest to southeast across the PRB when sea level started to fall (Gustason, 1988; Gustason et al., 1988). This marine regression formed the lower-shoreface deposits of the Rozet Member in the Amos Draw and Sand Dunes fields and possibly in the Kitty and Hilight fields. The Rozet Member in the Sand Dunes Field to the south of the other fields is finer in grain size and is inferred to have been deposited farther offshore. The Rozet is interpreted as a late highstand systems tract. Subsequent sea level fall resulted in incision into the older shoreface deposits. The incision is evident as NW–SE trending paleovalleys in the Kitty and Hilight fields, whereas the upper Rozet Member in the Amos Draw Field and interfluve in the Kitty Field experienced erosion as the region remained as a paleohigh (Martinsen, 1994). This unconformity is described as lowstand

Figure 12. Structural contour map of top of Muddy Sandstone: A, Amos Draw Field; B, Sand Dunes Field; C, Hilight Field; and D, Kitty Field. Squares represent well data used in study. Black lines represent cross sections in Figure 6. Units are in feet.



surface of erosion in previous studies (Weimer, 1988; Martinsen, 1994) and is interpreted herein as a sequence boundary (Fig. 13).

Subsequent infilling of the valleys consists of fluvial and estuarine Recluse and Cyclone Members in the Hilight and Kitty valleys and the Ute Member in all the fields. The depositional environment and thickness of the Ute Member vary laterally, depending on the degree to which the valleys were filled by the end of Cyclone deposition. The Ute Member in the Amos Draw and Sand Dunes fields was deposited in a restricted, brackish-water environment. As a result, the Ute Member in the two fields contains abundant shale. In contrast, the Ute Member in the Kitty and Hilight fields represents shallow-water environments including estuaries or barrier islands; as a result, it is locally very sandy (Martinsen, 1994; Fig. 13). This study interprets the Recluse, Cyclone, and Ute Members as a lowstand systems

tract and the depositional surface at the top of the Ute Member as a transgressive surface. Subsequent marine transgression toward the northwest resulted in a change from the estuarine environment to an open-marine environment. I interpret the lower-shoreface deposits of the Springen Ranch Member and open-marine deposits of the Skull Creek Member as a transgressive systems tract. The maximum flooding surface is situated within the overlying Mowry Shale (Bohacs et al., 2005). The Muddy Sandstone and the overlying Mowry Shale represent one depositional sequence. Because the depositional span of the Muddy Sandstone is at most five million years, my research suggests that the depositional sequence is a third-order depositional sequence (Van Wagoner et al., 1995).

Diagenesis

The distribution of diagenetic alterations observed in this study can be explained by the changes in relative sea level and rates of sediment supply during deposition. Late highstand systems tracts a re characterized by aggradation and progradation of shoreline in response to high sedimentation rate and decrease of relative sea level rise (Van Wagoner et al., 1990). Lowstand systems tracts are characterized by high sedimentation rate associated with decreased rate of relative sea level fall (Van Wagoner et al., 1990). Sediments formed in late highstand and early lowstand systems tracts, particularly in wet climatic conditions, may be subjected to pedogenic processes when the sea level drops, resulting in substantial silicate dissolution and kaolinization (Nedkvitne and Bjørlykke, 1992; Morad et al., 2000; Ketzer et al., 2003; Morad et al., 2010). The high kaolinite concentration in the upper Rozet Member in the Amos Draw Field is interpreted to have formed under these conditions (Odland et al., 1988). This also explains why sandstone in the fluvial Recluse Member in the Kitty and Hilight fields experienced substantial silicate grain dissolution. Silicate dissolution forms clay minerals and secondary silica, and it probably caused quartz overgrowth and high matrix content in some sandstone bodies in the two members.

Transgressive systems tracts are characterized by sediment starvation during rapid relative sea level rise (Van Wagoner et al., 1990). Carbonate cementation

Figure 13. A, Chronostratigraphic diagram of Muddy Sandstone. B, Sequence stratigraphic interpretation of A. Striped area in A = depositional lacuna. HST = highstand systems tract, in gray. TST = transgressive systems tract, in green. LST = lowstand systems tract in red. MFS = maximum flooding surface, in green. SB = sequence boundary, in red. TS = transgressive surface, in blue. Muddy Sandstone is shown in yellow. Sandstone bodies in HST and TST are dominantly shoreface deposits, and in LST are dominantly f luvial, and estuarine channels. Black triangle represents period of marine regression, and white triangle represents period of marine transgression.

M. FAN


is a common feature of transgressive systems tracts. That is particularly the case on f looding surfaces, because of the abundance of carbonate bioclasts, organic matter, bioturbation, and prolonged settling time of the sediments (e.g., Al-Ramadan et al., 2005; Morad et al., 2000, 2010). Carbonate cementation is through diffusion of dissolved Ca2+, Mg2+, and HCO3

- from the overlying seawater. Diffusion is enhanced by the presence of abundant carbonate bioclasts, which act as nuclei for the precipitation of calcite (e.g., Taylor et al., 2000; Al-Ramadan et al., 2005). Therefore, the first stage of carbonate cement in the Recluse and Cyclone Members in the Kitty Field may be an early diagenetic product precipitated during the marine transgression of the Springen Ranch and Skull Creek Members. Subsequent sea level fall promotes migration of meteoric water and subsurface f luids, which facilitates dissolution of carbonate cement, thereby producing secondary pore space. The secondary pore space may be filled by carbonate cement during other transgressive systems tracts during the Late Cretaceous. Thus, I suggest that the second and third stages of carbonate cementation observed in the Recluse and Cyclone Members in the Kitty Field may have happened during subsequent transgression of the Western Interior Seaway.

Implications for CO2 Sequestration

Reservoir stratigraphic heterogeneity does not only impact CO2 sequestration capacity by controlling reservoir porosity, thickness, and lateral continuity. It may also impact ability for CO2 sequestration by influencing f luid-flow pathways, post-injection chemical reactions, and types and amounts of micro-porosity.

Reservoir heterogeneity affects the lateral and vertical continuity of permeable compartments and thus impacts patterns of f luid f low and potential CO2 migration (Meyer and Krause, 2006). Lower-shoreface sandstone of the Rozet and Springen Ranch Members are relatively homogeneous and laterally continuous. Permeability values tend to increase up-section in coarsening-upward sandstone sequences, as is typical for shoreface deposits. Simulation models demonstrate that CO2 injected into lower-shoreface sandstone tends to migrate upward to the top of the sandstone sequences and

then spread laterally as a thin plume (Hovorka et al., 2004). In addition, the subaerial erosion on the top of the Rozet Member in the Amos Draw Field represents long-term stabilization of f loodplain (Miall, 1988). The fine-grained sandstone of the Ute Member in the Amos Draw Field and the Shell Creek Shale in the Sand Dunes Field have good lateral continuity along with low porosity and permeability, and thus are an ideal seal for CO2 storage in this unit. Therefore, the Rozet Member in the Amos Draw Field and the Springen Ranch Member in the Sand Dunes Field have the greatest potential for CO2 sequestration. Fluvial and estuarine sandstone in the Kitty and Hilight fields are heterogeneous and discontinuous, which limit the volume for CO2 storage. These isolated mudstone, siltstone, sandstone, and coal beds are local in scale and would not be strong inhibitors to horizontal flow. They may act as a baffle to vertical flow, however, slowing the rise of buoyant fluids to the seal (Bryant et al., 2008).

Understanding the potential for dissolution of minerals in the reservoir is significant because the possibility for eventual precipitation of carbonate minerals capable of trapping CO2 over geologic time scales depends on the availability of cations that would be provided by dissolution of these mineral precursors (Xu et al., 2004; Peters, 2009). The Muddy Sandstone contains both detrital and authigenic minerals that could potentially be reactive when CO2 is injected. Mineral dissolution rates are several orders of magnitude higher at low pH (pH of ~3 or 4), which would be expected when CO2 is injected and which would cause the formation of brines to become undersaturated (Kharaka et al., 2006). Geochemical modeling also shows that the pH of formation brines can drop significantly (Parry et al., 2007). The pH drop related to CO2 injection could cause dissolution of Fe-bearing clay minerals, potentially mobilizing associated trace metals that are commonly adsorbed onto iron oxides or organic compounds (Kharaka et al., 2006). Carbonate minerals would be highly reactive in CO2-generated acid brine. Carbonate cements of four stages are found in the fluvial incised-valley lithofacies in the Kitty Field, and they are expected in the f luvial incised-valley lithofacies in the Hilight Field. The dissolution of carbonate cement potentially provides important ions for the formation of long-term carbon-sequestering mineral phases. Zones with



abundant clay matrix are also found in the Recluse and Cyclone Members in the Kitty and Hilight fields. Clay matrix, particularly illite and chlorite, contains iron. These iron-rich silicate minerals may react with CO2 and increase the sequestration capacity. Remnants of dissolved feldspars are found in the Rozet Member in the Amos Draw Field, providing mineral surfaces for potential reaction with CO2 filling the pores.

Stratigraphic heterogeneity also affects the amount, types, and geometry of micropores within the sandstone. Clay authigenesis promotes an increase in specific surface area and the creation of microporosity (Eslinger and Pevear, 1988). Clay rims, especially illite, on quartz grains inhibit quartz overgrowth and maintain the sandstone porosity. The large surface area generated by authigenic clays can deteriorate the effectiveness of surfactant and polymer solutions in CO2 storage because of the tendency of these chemicals to adsorb on clay surfaces and be lost from circulation (Kalpakci, 1981). Diagenetic clay minerals can also control the retention rate of CO2. An example is that smectitic clays would favor a higher retention of CO2, especially in acidic environments (Venaruzzo et al., 2002). This aspect may particularly influence the CO2 capacity in the lower Rozet Member in the Amos Draw Field as well as the fluvial incised-valley lithofacies in the Kitty Field because of high matrix content.

Future Work

This study provides a background framework for identifying and evaluating reservoir heterogeneity on CO2 sequestration in the Muddy Sandstone of the PRB, northeastern Wyoming. Though this study identified four potential intervals for CO2 sequestration, realization of the maximum possible storage capacity requires more detailed understanding of the textural and mineralogical variability that will inf luence the fate of injected CO2. Additionally, simulation of CO2 injection in these fields is still lacking, which requires more data related to variables such as hydraulic pressure, temperature, structural setting, and brine chemistry. This study recommends that future work include: (1) more detailed studies of mineralogy focused on specific authigenic phases and pore characteristics; and (2) experimental evaluation of the effects of exposure to CO2-charged brines under conditions of elevated pressure and

temperature. Such studies should provide important parameters for reactive transport modeling, f luid-f low modeling, and f luid-pressure modeling, and they will improve understanding of CO2 injection into depleted oil and gas fields.

CONCLUSIONS

Sedimentologic, petrographic, and mineralogical analyses of the Muddy Sandstone in four oil and gas fields in the PRB, northeast Wyoming, demonstrate the reservoir heterogeneity that occurs throughout the formation. The heterogeneity is a result of spatially variable depositional environment, relative sea level change, and type and extent of diagenetic alteration.

The Muddy Sandstone contains f ive major lithofacies, representing offshore, lower–middle wave-dominated shoreface, weathering zone, fluvial incised-valley, and tidal-influenced estuarine depositional environments. The Muddy Sandstone in the Amos Draw and Sand Dunes fields includes the Rozet Member, deposited in wave-dominated shoreface, and Ute Member deposited in an estuarine central-basin environment, and the Springen Ranch Member of wave-dominated shoreface deposits. In the Kitty and Hilight fields, the incised-valley deposits of the Recluse Member eroded the Rozet Member locally, and the overlying Cyclone and Ute Members, deposited in estuarine environments, contain thick sandstone bodies. The Springen Ranch Member of lower-shoreface deposits occurs in both the Kitty and Hilight f ields. Sandstone bodies formed in wave-dominated shorefaces are laterally extensive and of equivalent thickness in each field. The ones formed in incised-valley and estuarine environments, in contrast, have variable thicknesses and lateral extents.

Sandstone petrographic analysis shows that quartz makes up more than 70 percent of the total framework grains, and the percentage of feldspar is generally less than 5 percent, except for the Rozet Member in the Amos Draw Field, which is up to 22 percent. Muddy Sandstone can be divided into four groups based on the relative abundance of pore space, carbonate cement, and matrix, and the sandstone types are closely related to depositional environment. Dissolution of feldspar and lithic fragments is commonly observed, enhancing the porosity. XRD

M. FAN


results show that the pore-filling clay minerals include kaolinite, chlorite, illite, and smectite, which destroy porosity. Four stages of carbonate cementation are observed, including early dolomite overgrowth, secondary calcite filling, dolomite replacement, and spotty siderite cementation. Both the secondary porosity generated by feldspar dissolution and diagenetic carbonate cementation may enhance potential for CO2 sequestration by providing reactive mineral surfaces and calcium ions for the formation of long-term carbon-sequestering mineral phases.

A sequence stratigraphic model is proposed to explain reservoir development of the Muddy Sandstone in which it, along with the overlying Mowry Shale, represent one third-order depositional sequence. The Rozet Member represents an older, late highstand systems tract. The unconformity at the top of the Rozet Member is a sequence boundary. The Recluse, Cyclone, and Ute Members are components of a lowstand systems tract, and the depositional surface at the top of the Ute Member is a transgressive surface. The Springen Ranch Member and the overlying Skull Creek Member are components of a transgressive systems tract.

Re ser voi r cha rac ter i z at ion in the four fields suggest that the best reservoir interval for sequestration in the Amos Draw Field is the lower Rozet Member, in the Sand Dunes and Hilight fields is the Springen Ranch Member, and in the Kitty Field is the Ute Member. Reservoir heterogeneity is controlled by depositional environment, sea level changes, and post-depositional diagenesis. I suggest that realization of the maximum possible CO2 storage capacity in the Muddy Sandstone in the PRB requires detailed understanding of the textural and mineralogical variability that will influence the fate of injected CO2. This study recommends that computer simulations be conducted to improve understanding of injections in depleted oil and gas fields.

ACKNOWLEDGMENTS

The Wyoming State Legislature provided funding for this research. I am deeply indebted to the helpful comments and suggestions from an anonymous reviewer, Professor Mary Kraus, Dr. Gus Gustason, Dr. Brenda Bowen, and RMG editors Robert Waggener and Jay Lillegraven.

REFERENCES CITED

Al-Ramadan, K., Morad, S., Proust, J. N., and Al-Aasm, I., 2005, Distribution of diagenetic a lterations in si l iciclast ic shoreface deposits within a sequence stratigraphic framework: Evidence from the Upper Jurassic, Boulonnais, NW France: Journal of Sedimentary Research, v. 75, p. 943–959.

Bachu, S., 2000, Sequestration of CO2 in geological media: Criteria and approach for site selection in response to climate change: Energy Conversion and Management, v. 41, p. 953–970.

Baker, D. R., 1962, The Newcastle Formation in Weston County, Wyoming: A non-marine (alluvial) plain deposit, in Diedrich, R. P., Dyka, M. A. K., and Miller, W. R., eds., Eastern Powder River Basin—Black Hills: Casper, Wyoming Geological Association, 17th Annual Field Conference Guidebook, p. 148–162.

Bohacs, K. M., Grabowski, G. J., Jr., Carroll, A. R., and five others, 2005, Production, destruction, and dilution: The many paths to source-rock development, in Harris, N., ed., The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences: Tulsa , Oklahoma, Society for Sedimentary Geology Special Publication 82, p. 61–101.

Bryant, S. L., Lakshminarasimhan, S., and Pope, G. A., 2008, Buoyancy-dominated multiphase flow and its impact on geological sequestration of CO2: Society of Petroleum Engineers Journal, v. 13, p. 447–454.

Byrd Larberg, G. M., 1980, Depositional environments and sand-body morphologies of the Muddy Sandstone at Kitty Field, Powder River Basin, Wyoming, in Enyert, R. L., and Curry, W. H., III, eds., Symposium on Early Cretaceous rocks of Wyoming: Casper, Wyoming Geological Association, 31st Annual Field Conference Guidebook, p. 117–135.

Curry, W. H., III, 1971, Laramide structural history of the Powder River Basin, Wyoming, in Renfro, A. R., ed., Symposium on Wyoming tectonics and their economic significance: Casper, Wyoming Geological Association, 23rd Annual Field Conference Guidebook, p. 49–60.

Dalrymple, R. W., Zaitlin, B. A., and Boyd, R., 1992, E stua r ine facie s model s: Conceptua l ba si s and stratigraphic implications: Journal of Sedimentary Research, v. 62, p. 1130–1146.

DeCelles, P. G., 2004, Late Jurassic to Eocene evolution of the Cordilleran thrust belt and foreland basin system, western U.S.A.: American Journal of Science, v. 304, p. 105–168.

Dickinson, W. R., Klute, M. A., Hayes, M. J., and four others, 1988, Paleogeographic and paleotectonic setting of Laramide sedimentary basins in the central Rocky Mountain region: Geological Society of America Bulletin,



v. 100, p. 1023–1039.Dolson, J. C., Muller, D. S., Evetts, M. J., and Stein, J. A.,

1991, Regional paleotopographic trends and production, Muddy Sandstone (Lower Cretaceous), central and northern Rocky Mountains: American Association of Petroleum Geologists Bulletin, v. 75, p. 409–435.

Donovan, A. D., 1995, Sequence stratigraphy of Hilight Field, Powder River Basin, Wyoming, U.S.A.: Unconformity control on Muddy thickness and distributions, in Van Wagoner, J. C., and Bertram, G. T., eds., Sequence stratigraphy of foreland basin deposits: Outcrop and subsurface examples from the Cretaceous of North America: American Association of Petroleum Geologists Memoir 64, p. 395–428.

Eicher, D. L., 1962, Biostratigraphy of the Thermopolis, Muddy, and Shell Creek Formations, in Enyert, R. L., and Curry, W. H., III, eds., Symposium on Early Cretaceous rocks of Wyoming and adjacent areas: Casper, Wyoming Geological Association, 17th Annual Field Conference Guidebook, p. 72–93.

Elliott, T., 1986, Siliciclastic shorelines, in Reading, H. G., ed., Sedimentary environments and facies (second edition): Oxford, United Kingdom, Blackwell Scientific Publications, p. 155–188.

Eslinger, E., and Pevear, D., 1988, Clay minerals for petroleum geologists and engineers: Tulsa, Oklahoma, Society of Economic Paleontologists and Mineralogists Short Course Notes 22, ix + 412 p.

Fenies, H., Resseguier, A. D., and Tastet, J.-P., 1999, Intertidal clay-drape couplets (Gironde Estuary, France): Sedimentology, v. 46, p. 1–15.

Flores, R. M., and Ethridge, F. G., 1985, Evolution of intermontane f luvial systems of Tertiary Powder River Basin, Montana and Wyoming, in Flores, R. M., and Kaplan, S. S., eds., Cenozoic paleogeography of the west-central United States: Denver, Colorado, Society of Economic Paleontologists and Mineralogists, Rocky Mountain Section, Third Annual Rocky Mountain Paleogeography Symposium, p. 107–126.

Gustason, E. R., 1988, Depositional and tectonic history of the Lower Cretaceous Muddy Sandstone, Lazy B Field, Powder River Basin, Wyoming, in Diedrich, R. P., Dyka, M. A. K., and Miller, W. R., eds., Eastern Powder River Basin—Black Hills: Casper, Wyoming Geological Association, 39th Annual Field Conference Guidebook, p. 129–146.

Gustason, E. R., Ryer, T. A., and Odland, S. K., 1988, Stratigraphy and depositional environments of the Muddy Sandstone, northwestern Black Hills, Wyoming: Wyoming Geological Association Earth Science Bulletin, v. 20, p. 49–60.

Holloway, S., 2001, Storage of fossil fuel-derived carbon dioxide beneath the surface of the Earth: Annual Review

of Energy and the Environment, v. 26, p. 145–166.Hovorka, S. D., Doughty, C., Benson, S. M., and two

others, 2004, The impact of geological heterogeneity on CO2 storage in brine formations: A case study from the Texas Gulf Coast, in Baines, S. J., and Worden, R. H., eds., Geological storage of carbon dioxide: Bath, United Kingdom, Geological Society of London Special Publication 233, p.147–163.

Ingersoll, R. V., Bullard, T. F., Ford, R. L., and three others, 1984, The effect of grain size on detrital modes: A test of the Gazzi-Dickinson point-counting method: Journal of Sedimentary Petrology, v. 54, p. 103–116.

Jones, C. H., Farmer, G. L., Sageman, B., and Zhong, S., 2011, Hydrodynamic mechanism for the Laramide Orogeny: Geosphere, v. 7, p. 183–201.

Kalpakci, B., 1981, Flow properties of surfactant solutions in porous media and polymer-surfactant interactions [Master’s thesis]: University Park, Pennsylvania State University, 238 p.

Kamola, D. L., and Van Wagoner, J. C., 1995, Stratigraphy and facies architecture of parasequences with examples from the Spring Canyon Member, Blackhawk Formation, Utah, in Van Wagoner, J. C., and Bertram, G. T., eds., Sequence stratigraphy of foreland basin deposits: Outcrop and subsurface examples from the Cretaceous of North America: Tulsa, Oklahoma, American Association of Petroleum Geologists Memoir 64, p. 27–54.

Ketzer, J. M., Holz, M., Morad, S., and Al-Aasm, I., 2003, Sequence stratigraphic distribution of diagenetic altera-tions in coal-bearing, paralic sandstones: Evidence from the Rio Bonito Formation (early Permian), southern Brazil: Sedimentology, v. 50, p. 855–877.

Kharaka, Y. K., Cole, D. R., Hovorka, S. D., and three others, 2006, Gas-water-rock interactions in Frio Formation following CO2 injection: Implications for the storage of green-house gases in sedimentary basins: Geology, v. 34, p. 577–580.

Li, Z., Dong, M., Li, S., and Huang, S., 2006, CO2 sequestration in depleted oil and gas reservoirs: Caprock characterization and storage capacity: Energy Conversion and Management, v. 47, p. 1372–1382.

Liu, S., and Nummedal, D., 2004, Late Cretaceous subsidence in Wyoming: Quantifying the dynamic component: Geology, v. 32, p. 397–400.

Martinsen, R. S., 1994, Stratigraphic compartmentation of reservoir sandstone: Examples from the Muddy Sandstone, Powder River Basin, Wyoming, in Ortoleva, P. J., ed., Basin compartments and seals: Tulsa, Oklahoma, American Association of Petroleum Geologists Memoir 61, p. 273–296.

Meyer, R., and Krause, F. F., 2006, Permeability anisotropy and heterogeneity of a sandstone reservoir analogue: An

M. FAN


estuarine to shoreface depositional system in the Virgelle Member, Milk River Formation, Writing-on-Stone Provincial Park, southern Alberta: Bulletin of Canadian Petroleum Geology, v. 54, p. 301–318.

Miall, A. D., 1988, Reservoir heterogeneities in f luvial sandstones: Lessons from outcrop studies: American Association of Petroleum Geologists Bulletin, v. 72, p. 682–697.

Mito, S., Xue, Z., and Ohsumi, T., 2008, Case study of geochemical reactions at the Nagaoka CO2 injection site, Japan: International Journal of Greenhouse Gas Controls, v. 2, p. 309–318.

Morad, S., Ketzer, J. M., and De Ros, L. F., 2000, Spatial and temporal distribution of diagenetic alterations in siliciclastic rocks: Implications for mass transfer in sedimentary basins: Sedimentology, v. 47, p. 95–120.

Morad, S., Al-Ramadan, K., Kezer, J. M., and De Ros, L. F., 2010, The impact of diagenesis on the heterogeneity of sandstone reservoirs: A review of the role of depositional facies and sequence stratigraphy: American Association of Petroleum Geologists Bulletin, v. 94, p. 1267–1309.

Nedkvitne, T., and Bjørlykke, K., 1992, Secondary porosity in the Brent Group (Middle Jurassic) Huldra Field, North Sea: Implication for predicting lateral continuity of sandstones?: Journal of Sedimentary Research, v. 62, p. 23–34.

Odland, S. K., Patterson, P. E., Gustason, E. R., 1988, Amos Draw Field: A diagenetic trap related to an intraformational unconformity in the Muddy Sandstone, Powder River Basin, Wyoming, in Diedrich, R. P., Dyka, M. A. K., and Miller, W. R., eds., Eastern Powder River Basin—Black Hills: Casper, Wyoming Geological Association 39th Annual Field Conference Guidebook, p. 147–160.

Oldenburg, C. M., Pruess, K., and Benson, S. M., 2001, Process modeling of CO2 injection into natural gas reservoirs for carbon sequestration and enhanced gas recovery: Energy and Fuels, v. 15, p. 293–298.

Parry, W. T., Forster, C. B., Evans, J. P., and two others, 2007, Geochemistry of CO2 sequestration in the Jurassic Navajo Sandstone, Colorado Plateau, Utah: Environmental Geosciences, v. 14, p. 91–109.

Peters, C. A., 2009, Accessibilities of reactive minerals in consolidated sedimentary rock: An imaging study of three sandstones: Chemical Geology, v. 265, p. 198–208.

Prescott, M. W., 1970, Hilight Field, Campbell County, Wyoming, in Enyert, R. L., ed., Symposium on Wyoming sandstones: Their economic importance—past, present, and future: Casper, Wyoming Geological Association, 22nd Annual Field Conference Guidebook, p. 89–106.

Robinson Roberts, L. N., and Kirschbaum, M. A., 1995, Paleogeography of the Late Cretaceous of the western

interior of middle North America: Coal distribution and sediment accumulation: U.S. Geological Survey Professional Paper 1561, 115 p.

Roy, P. S., Thom, B. G., and Wright, L. D., 1980, Holocene sequences on an embayed high-energy coast: An evolutionary model: Sedimentary Geology, v. 26, p. 1–19.

Ryer, T. A., Gustason, E. R., and Odland, S. K., 1990, Depositional history and sea-level f luctuations, Lower Cretaceous Muddy Sandstone, Powder River Basin, Wyoming, in Ryer, T. A., ed., Stratigraphic concepts and methods for exploration in clastic facies: A core workshop: Denver, Colorado, Rocky Mountain Association Geologists Short Course Notes.

Tarkowski, R., and Wdowin, M., 2011, Petrophysical and mineralogical research on the influence of CO2 injection on Mesozoic reservoir and caprocks from the Polish Lowlands: Oil and Gas Science and Technology, v. 66, p. 137–150.

Taylor, K. G., Gawthorpe, R. L., Curtis, C. D., and two others, 2000, Carbonate cementation in a sequence-stratigraphic framework: Upper Cretaceous sandstones, Book Cliffs, Utah-Colorado: Journal of Sedimentary Research, v. 70, p. 360–372.

Van Wagoner, J. C., Mitchum, R. M., Campion, K. M., and Rahmanian, V. D., 1990, Siliciclastic sequence stratigraphy in well logs, cores, and outcrops: Concepts for high-resolution correlation of time and facies: American Association of Petroleum Geologists Methods in Exploration Series 7, 55 p.

Venaruzzo, J. L., Volzone, C., Rueda, M. L., and Ortiga, J., 2002, Modified bentonitic clay minerals as adsorbents of CO, CO2, and SO2 gases: Microporous and Mesoporous Materials, v. 56, p. 73–80.

Von Drehle, W. F., 1985, Amos Draw Field, Campbell County, Wyoming, in Nelson, G. E., The Cretaceous geology of Wyoming: Casper, Wyoming Geological Association, 36th Annual Field Conference Guidebook, p. 11–31.

Walker, R. G., and Plint, A. G., 1992, Wave- and storm-dominated shallow-marine systems, in Walker, R. G., and James, N. P., eds., Facies models: Response to sea-level change: St. John’s, Newfoundland, Canada, Geological Association of Canada, p. 219–238.

Weimer, R. J., 1988, Record of relative sea-level changes, Cretaceous of Western Interior, U.S.A., in Wilgus, C. K., Hastings, B. S., Posamentier, H., and three others, eds., Sea-level changes: An integrated approach: Tulsa, Oklahoma, Society of Economic Paleontologists and Mineralogists Special Publication 42, p. 285–288.

Wheeler, D. M., Gustason, E. R., and Furst, M. J., 1988, The distribution of reservoir sandstone in the Lower Cretaceous Muddy Sandstone, Hilight Field, Powder River Basin, Wyoming, in Lomando, A., and Harris, P.,



eds., Giant oil and gas fields: Tulsa, Oklahoma, Society of Economic Paleontologists and Mineralogists Core Workshop 12, p. 179–228.

Xu, T., Apps, J. A., and Pruess, K., 2004, Numerical simulation of CO2 disposal by mineral trapping in deep aquifers: Applied Geochemistry, v. 19, p. 917–936.

Manuscript Received September 12, 2013

Revised Manuscript Submitted November 11, 2013

Manuscript Accepted March 31, 2014

M. FAN

reservoir stratigraphic heterogeneity within the lower ... · shale interval (shell creek shale;...

Documents