additional geologic site characterization studies west hackberry salt dome

8/19/2019 Additional Geologic Site Characterization Studies West Hackberry Salt Dome

1/110

SANDIA REPORT

SAND90-0224 •

UC-126

Unlimited Release

Printed December 1991

DE92 9885

III

11/11111111111111 1111

Strategic Petroleum Reserve SPR

Additional

e o ~ o g i ite

Characterization Studies

est

Hackberry Salt Dome, Louisiana

, Thomas

R.

Magorian, James

T.

Neal, Stephen Perkins,

, Qiang

J.

Xiao, Kathleen

O.

Byrne

_ ~ : : ~ -

c _::_

- - ~ ~ ; ~ A

REPRODUCED BY

NTIS.],

u.s.

Department of Commerce

National

Technicallnronnation

Service

I

I Springfielcl Virginia 22161

.

l

~

SF290QO(B,Bl

Prepared by

- Sandia Nat ional Laboratories

Albuquerque,

New

Mexico

87185

and Livermore, California

94550

fo r the United States Department

of

Energy

under Contract DE-AC04-76DP00789


2/110

Issued by Sandia Kational Laboratories, operated for the United States

Department of

Energy by Sandia Corporation.

NOTI E

This report was prepared as an account of work sponsored by an

agency of the

enited States

Government. Neither the United States Govern

ment nor any agency thereof, nor any of the ir employees, nor any of thei r

contractors, subcontractors, or their employees, makes any warranty, express

or implied, or assumes any legal liability or responsibility for the accuracy,

completeness, or usefulness of any informat ion, apparatus , product , or

process disclosed, or represents

that

it s use would not infringe privately

owned rights. Reference herein to any specific commercial product, process, or

service by

trade

name, trademark, manufacturer, or otherwise, does

not

necessarily constitute or imply its endorsement, recommendation, or favoring

by the United States Government, any agency thereof or any of their

contractors or subcontractors.

The

views and opinions expressed herein do

not necessarily state

r

reflect those of

the

United States Government, any

agency thereof or any of their contractors.

Printed

in the United States of America.

This

report has been reproduced

directly from the best available copy.

Available to DOE -and DOE contractors from

Office of Scientific and Technical Informa:tion

PO

Box 62

Oak Ridge,

TN

37 31

Prices available from (615) 576-8401,

FTS

626-8401

Available to the public from

National Technical Information Service

US

Department

of Commerce

5285

Port

Royal Rd

Springfield, VA 22161

NTIS price codes

Printed copy:

A05

Microfiche copy:

A01


3/110

SAND90-0224

Unlimited Release

December 1991

Strategic Petroleum Reserve SPR

Additional

Geologic

Site

Characterization

Studies

West Hackberry

Sal t

Dome

Louisiana

Thomas R Magorian

Amherst New York

James T.

Neal

Sandia

National Laboratories

Albuquerque

New

Mexico

Stephen

Perkins Qiang

J Xiao Kathleen

O

Byrne

Acres International

Corporation

Amherst New York

Prepared by Sandia

National

Laboratories

Albuquerque 87185 and Livermore

CA

94550

for the U S. DOE

under

Contract DE-AC04-76DP00789

UC-126

ABSTRACT

This report is a revision

and

update of

th e original geologic

s i te

characterization

report

that

was published

in 1980 Many

of

the topics

addressed in

th e

earl ier

report were predictive in nature

and

i t

is now

possible

to

reexamine them some 12

years la te r using

the data from 17 new

caverns

and more than ten years

of SPR

storage

experience

Revised maps of the sa l t configuration show

an

overhang

and faults on

the n orth sid e

of

th e

dome, defining more

clear ly

th e

edge

relationships

with

respect

to th e SPR

caverns

Caprock faults may locally i nf luence the

p atte rn o f subsidence which is occurring primarily as

a

result

of

cavern

creep closure

The

greater subsidence

rate

occurring at

West

Hackberry

w ill lik ely

require

mitiga tive act ion

within

a few

years

Seismicity

of

low intensi ty recurs inf requently at West Hackberry but a

small

earthquake in

1983 caused dish rat t l ing

in th e

immediate

vicini ty

i i i


4/110


5/110

•

4.

•

i

q

~ ~ ~ - : ~ ~ r : c c ~ -- .c• ., : ~ ~ ; - ~ : : - - : ~ ; ; ~ - ; - ,

1

West Cove

1

_ .

. ::_ -

. . - l

l

:,t

l

- .

< .:

.

:

.

, .

.

.

I: ·

{BlackLakej

.

IC alcasieu Lake ~ ; ~

z::

._, .

,

F ront is pi ec e: H igh- al ti tu de view of West Hackberry SPR s i te

shoWing

th e -20 f t is land over th e

dome

surrounded by

coastal

mars hla nd s. G ulf

of

Mexico i s 5 mi from

to p

of photo, due

south

of West Cove.

.

.

C

0

a

e

CD

a.


6/110


7/110

TABLE

OF

CONTENTS

Strategic Petroleum Reserve SPR)

Additional Geologic

Site

Characterization Studies

West

Hackberry

Salt Dome Louisiana

INTRODUCTION

N

PURPOSE .

1

New

or Revised

I n f o rma t i o n

1

GEOLOGIC

ASPECTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Hydrology.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Caprock

. , .

. . . .

7

Salt ; .

. .

.

. .

21

Salt

on t o u r s

28

Struc tural In te rpre ta t ions 33

SPR

SYSTEM CONSIDERATIONS.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. .

.

33

Cavern Configurations 33

Subsidence 42

Hurricane Storm Surge Levels 48

Seismici

ty.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 48

Environmental Considerations 50

Summary o f S igni fi cant

Features Affecting

SPR 52

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53

References . . . . . . . . . . . . . . 54

Appendices

A Yest

Hackberry Regional Geologic History

A-1

B

Projected

Loss

of

Coastal

Marshlands B-1·

C Prediction

of

Subsidence Resulting from Creep Closure

of Solutioned-mined Caverns in Salt Domes C-1

D Yell Log Data D-1


8/110


9/110

LIST OF

TABLES

Table

1

Stratigraphic Correlation Chart

10

Table

2 West Hackberry

Cavern

Geotechnical Parameters 34

Table

3

Oxy

USA

Cavern Data.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Table 4 Projected Elevations for

Selected

West Hackberry

Stations

. . . . . . . . . . . . . . . . . . . . . . . . 47

LIST OF FIGURES

Front-

piece

Figure 1

Figure

2

Figure

3

Figure

4

Figure 5

Figure

6

Figure

7

Figure 8

Figure 9

High

Altitude

View

of

West Hackberry SPR Site

i i i iv

Depth to Anahuac Shale

3-4

Depth to Hackberry Shale

5-6

West Hackberry Brine

Disposal

Well 2-C 8,9

Depth

to Top of

Caprock 11-12

Base with Site Boundaries, Caverns, and Flood

Contours 5-16

North-South Cross Section 17-18

Depth to

Top

of Salt 19-20

East-West

Cross Section 25-26

Conceptual

Diagram West Hackberry Structural Features. 27

Figure

10

Westernmost

North-South Cross

Section

29-30

Figure

11 Easternmost North-South Cross

Section

. .

31-32

Figure 12 Composite of Generalized SPR Cavern Configurations. . . . . 35

Figure 13

Air Photo,

West

Hackberry SPR Site . ,

37-38

Figure 14 Olin Brine Caverns ; October 1989 Sonar Surveys . . . . . . . . . 41

Figure 15 Oxy

USA

Cavern Configurations.. . . 43

Figure 16 Isoseismal

Map

16 Oct 83 Lake Charles

Earthquake

. . .

. .

49

Figure

17 Earthquake

Acceleration

Probability Map... 51

vi


10/110


11/110

INTRODUCTION N PURPOSE

The

in i t i a l

geologic

s i te charac te r iza tion repor t

[Ref.

1]

was

completed

in

1980, when

only the five caverns that were acquired

from

th e

Olin

Corporation

s

6,7,8,9,

and 11) existed.

Since that

time 18

cavern

wells were

dril led

and

17 new caverns were leached

and

are now some

90

f i l led

with

crude

oi l

toward

the

currently

authorized

si te

c apac it y o f

219 million barrels MMB). The

construction

of

the

new

caverns ha s

significantly enhanced our confidence

in understanding

the

sa l t

dome

features.

I n add it io n

to

information that has become available during more

than

10

years

of

SPR

operation, new data are

also

available from numerous

commercial wel ls adj acen t

to the

s i te

This report

is a revision

and update of th e ear l ier

si te

characterization

r p o r ~ placing

t he geo logi c

understanding

in better

perspective. Several aspects a re

given

special attention in

the

report:

sa l t

contours

and structural interpretations

as

they relate to

cavern

integri ty;

subsidence

history

over

SPR

caverns;

and

potent ial

flooding

during future operations. In

numerous

cases, the original

maps

are

re

interpreted

in

l igh t of the

new

information,

and with reference

to

current

1991)

concepts

of Gulf Coas t geology.

New or

Revised

Information

The 18 new

cavern wells provided detailed information

on

th e character

of th e

sa l t mass

and

also the sa l t

contours

on top of

the

dome A new

sa l t map

is

presented, along with new interpretations of the structural

geological

configuration. These

have been

aided by o i l

company

interpretations and data, especially

on

th e north side adja cent to Black

Lake.

Configurations of the 22 caverns are discussed, along with the

.ten

year operating

history

a t th e s i te

Few

i f any , problems exis t although

Cavern I I I has

behaved

in

an

atypical manner.

The

3-dimensional

computer

model shows

that

Cavern

I I I

is

approximately

200

f t

further from th e

edge

of

the

sa l t than previously

estimated.

However a

faul t

and

shear zone

have been found in i t s

vicini ty.

Subsidence occurring over the cavern f ield

has

been resurveyed

annually for

some

eight years a t

more

than

eighty survey points, and

suff icient

data

exis t

to

make definitive

judgments

on

future direction.

The data show that West Hackberry is

subsiding

a t a greater rate than

the

other SPR

s i tes

and

that

th e

areas

on

the

s i te

with

low

elevation

will

eventually requ i re pro tec tion from permanent inundation. The adjacent

coastal marshlands are

also

subsiding and some 35 sq mi/yr of south

Louisiana is becoming open

water

and part of th e Gulf of Mexico Present

conditions and future

trends

suggest

that

the

higher por ti on s o f

the

West

Hackberry

s i te

are

effect ively an island in the

marsh

see frontispiece),

and

that eventually i t wil l

be a

small

island

in

open

water with direct

connections to

th e Gulf.

1


12/110

Hurricane

surge

heights have been rev ise d to a higher va lu e than

previous ly indica ted ;

current 100 yr

flood stage heights are about

10 f t

above

mean

sea level amsl a t the s i te

The

eye

of

Hurricane

Audrey

in

1957

passed

about 12 mi west of

th e

s i te and produced high

water

marks of

10 f t above mean sea level

a t

that location.

National

seismic

zonation

maps

have

been refined in

the past ten

years bu t

the

Gulf Coast

interpretat ion

is

l i t t l e changed,

th e area being

essentia l ly aseismic.

Nonetheless; new data and a

small ear thquake

1983

near the

s i te a re d is cuss ed .

GEOLOGI SPE TS

The geologic discussion presented in Appendix A complements

that given

in th e ear l ie r

report [Ref. 1]

and is

not intended to dup lic at e

i t

The

geologic information

base

is needed to help maintain

th e integri ty

of th e

o il

storage

caverns

and

in clude s th e

extent

and

cha ra ct er o f

the

sa l t

dome

in i t s regional set t ing.

The

sa l t

mass containing

th e o il is in

turn

held

and

s tabil ized by th e

regional

sediments

into

which th e

sa l t

dome is

intruded. The low-permeability muds,

part icularly those a t geopressure

forming the shale

sheath,

form add it io na l p ro te ct ion for any

o il

stored in

the dome

[Ref.

2].

Figures

1 and 2

are

s tructural contour maps showing

depth to

Anahuac

and Hackberry

shale

units ,

respectively.

Figure

2

also

shows

the

locat ion o f c ro ss -s ec tions used

in subsequent

figures. Table 1

explains th e

abbreviated

s tr a ti g raph ic un it s

shown

on

th e sections.

Hydrology

Fresh

water

is

found

on

th e

is land in

th e

upper

glacial-equivalent

sands of the

Chicot

aquifer. The Wisconsin is freshest and most potable,

although the I l l inoian

is

also

suitable

for industrial use. The lower

Wisconsin or

Alton

is referred to

as

the 200 f t aquifer.

The

water in the caprock may contain quantit ies

of

hydrogen sulfide.

At

th e

base

i t is saturated

brine

in equi libr ium with

th e

sa l t that i t is

dissolving.

Deeper waters in hydrocarbon-bearing

sands around the

dome

vary

from fully saturated brines

in the

more massive Miocene sands

mineralized

close

to

the sal t to

anomalously-fresh

carbonate-saturated

brines r ich in boron, vanadium and

other ocean-floor

concentrates in

isolated sands in

contact

with

geopressured

shales.

The

DOE

injection

well

f ield

is

located

on

the opposite south

side

of

th e

dome from

th e o il

storage caverns. Directionally

dr i l led

from a

central

pad on the

steep

southeast

flank of

th e dome, a l l th e wells

were

completed in

the

RL

zone

at th e top of

th e

lower Miocene see Table

1 .

This

well-sorted marine bar sand exhibits good permeability

a t the top

and dips 30 degrees south-southeast. All of

the

wells took brine at

relatively good rates

in i t i a l ly

2


13/110

-

o

o

o

o

Z 1t 8Sl lW III WZ O I


14/110


15/110

\

~ ; : : J ~

I

1MI I

1 1

i O

I :


16/110


17/110


18/110

~

' ,[

.

.

II

I 80 ..= ....

N:...

....

.

_

: . . -

••••••••

l I I

••

••• •••

•.• I .

,

• • •

I

.....

....... .

_

• ••

11.11.

• • •

WEST HACKBERRY

DOE BRINE DISPOSAL WELL

NO. 2-C

u

:E

>

0

>

:::

.....

a

0 gI =11

~

. lJ

0

.lJCI

l:lIE

a

:5

0

CI :

>0

ll

::J

iii

C1

. . . . .

25

Recent

MUCK

•

CLAY

••

••

71

••

III

II

·: :·: ::: : ::e

100 Wisconsin SANe •

: : :.: :.: :.:.: : GRAVEL

:8::::::6:

100 ppm

sooo

6000

ppm

8

1310 Kansan

SANe

•

GRAVEL

2

27: :

Figure 3

SHEET

1

OF

2


19/110

WEST HACKBERRY

DOE

BRINE DISPOS L

WELL

NO 2 C

5 30

1

In .

I

n

••

1

••••

noo

. .

to

..0

E

9

.

CL Y

~

: : :0: : : : 1660 Nebraskan/Lafayette

S ND

GR VEL

: :·0

·0:· ;;;

~

1 = = ~ 1

. . . . . . .

1860 Pliocene -

SILT

with

:

thin S ND

laye,..

TITr

IIII

Trn

TITr

IIII

TITr

TITr

TITr

TITr

IIII

IIII

TITr

Figure 3 cont.

SHEET

2

OF

2


20/110

TABLE 1 - VEST

H CK ERRY

STRATIGRAPHIC CORRELATION

CH RT

Unit

Recent: Beaumont clay

Q

Pleistocene

U

Wisconsin

A

Alton Peorian:

Prairie

Fm

T Sangamon: Ifontgomery Fm

E I l l inoian

R

Yarmouthian: n ~ l y Fm

N Kansan

A

Aftonian:

Williana

Fm

R Nebraskan

Y Lafayette

Symbol

a

s

i

p

ka ks

ne

Lithology

peat muck

mud

sand

and

gravel

mud

sand and gravel

mud

sand and

gravel

mud

sand

and gravel

gravel

T

E

R

T

I

A

R

Y

Pliocene

Miocene

Upper

Bigenerina f loridana

Textularia

Bigenerina

nodosaria

Textularia

stapperi

PL

MI

L

2

s i l t

mud,

and

sa

mud

sand

sand and gravel

mud

sand and gravel

mud

marine

sand

delta ic

sand

mud

delta ic sand

mud

Middle

Bigenerina humblei H

Cristel laria

CI

Cibicides

carstensi

op m CO

Amphistegina

Lower

Robulus RL

Operculinoides OP

Cibicides

C

Ifarginulina ascensionensis M

Siphonina

davisi

- - - U NCO N F O R M I T Y .

Anahuac

Discorbis) R

Oligocene

Heterostegina

H

Harginulina howei

MH

Frio

F

Cibicides hazzardi

-

CH

U NCO N ORM IT Y -

Hackberry

facies

H

Vicksburg VX

:10

unconformity

shale

thin

sands

sand

shale

m arin e sand

bituminous l imest

sand

and shale

sand

shale

thin sand

shale

coral reef

sand

shale

sands

marine·sands

geopressured

sha

b la ck s ha le


21/110

LEGEND

COX: on

l

=

OLIN

CONST

OIA

1= O O E

OF CAVERN

W LL

NO

.

-

X S

• 20.016

CENTER OF L,..-J

CAVERN L-CAPROQ(

n

O O E_ PROPERTY

LINE

CAPRoa<

CONTOUR

-5000

CONTOURS

IN fEET

BELOW

£A N SEA

LEYUI

\

®

\

o

o

8

B LAC K

L A

KIE

IT

6

_ 5 3000 FEET

i

fiGURE 4

WEST

HACKBERR

CAPROCK

p lI U

\


22/110


23/110

I t

l ies

on

top of

f la t

sa l t

across

th e

dome as a resul t of the

leaching of

sa l t to a

f l a t surface by

groundwater

as

the

dome r ises

through t he ove rlying sediments.

The

relat ively

insoluble

anhydrite

accumulates as

a cap and,

in

the

presence of

methane gas

seeping

up

th e

face of the

dome

is part ly

converted to carbona te .

The

continued

upward

movement

of

the

sa l t with l each ing to

a

f l a t surface creates

a complexly

faulted

and

fractured

domal-

to flat-topped

cap

containing extensive

interconnected voids ranging

from

small

vugs

to

caves.

The

caprock a t

West Hackberry

is

relat ively

thin -400

f t and l imited

in aerial extent. I t does not

overdrape the

stee p s id es of

th e

dome as

occurring a t th e next dome north, Sulphur

Mines

--

a

small, round conical

dome.

Most

of

the

S caverns

are loc ated near

the

middle

of

th e

dome

where

caprock

condi ti on s a re relat ively uniform. However Cavern I I I

is

located

near the

steep

outer edge

of

the sal t a t th e feather edge of the caprock

Figures 5,

6 . The

subsurface

control near

Cavern

I I I

is

l imited. The

closest wells dri l led into th e solid sa l t

face

are

in

Section

19

to th e

west

and

Section

16

to

the

northeast.

The

in tervening contro l

includes

one well

that included salt-mineralized

sands a t a

depth

of

approximately

3000

f t indicating that i t is

close to the sal t

face, as

shown

on the

cross-section

Figure 6 . The resul tant

interpretat ion

as shown on th e

sa l t map Figure 7

is

suf fic ien tly s t ra ight , except for the radial

fault

bel ieved to be

related

to a possible

shear

zone, to make the cavern quite

secure despite th e evidence

for an

overhang.

The

se ismic su rv ey s, while

incomplete, support

this

interpretation, as does gravity

data.

I f

o i l leakage

from

th e storage caverns

were to

occur i t

would

migrate

into

the

caprock

and join

th e

much

larger

volume of o il which

has

migrated

up

the face

of

the sal t

dome. Although no

commercial wells

have

been

completed

in

th e

caprock

at

th is dome

due

to

i ts

relat ively

low

porosity,

the thin overlying sands are o il

productive

and adequately sealed from the

surface by more

than

200

f t of

mud. However

gas may

leak

through these

muds,The gas accumulation under the brine

pond

l iner i s apparently

biogenic, originating

possibly from

unscarified decaying grass

[Ref. 15],

but a t other

domes

is indicative

of

escaping hydrocarbons.

h l l o ~

domestic water

wells

nearby also

make

gas.

Thus,

the r isk of

environmental

contamination through migra ti on path s a lr eady naturally

f i l led with hydrocarbons may be

moot.

Lost circulat ion:

The

hydrology

of

caprock i s controlled by th e large

voids

crea te d in

the

solution process.

Although the

water

is

s at ur at ed i n

carbonate

throughout,

in sulfate

half-way down and is

saturated

brine at

the

base, th e

flow

is

suff icient

to

keep

the

top

of

the

sa l t

very

nearly

f la t Hydrologic calculations

of the

rate of

sa l t

solution

which must

be

close to

that

of

intrusion

inside the

dome

were

made

a t

Bayou Choctaw

and

found to be

in

agreement with the geologic data

of

upl i f t on th e

flanks.

Thus,

lost circulat ion is

to be expected while

dri l l ing caprock,

although th e

problem

is less in thin caprock here than, for example, a t

Big

Hill where

the

caprock i s

one

of

th e

thickest

known

in

the

Gulf Coast.

13-14


24/110


25/110

- ~ . \

,


26/110


27/110

II

108

lOS

101

03

115 109

••

•

I

.-

1m

_ _

.

_.

---

r

...

nl l l l_

Fl ••

Dr

•

..

.-

1 1141

•

.

.

..

.

.

.

..

..

·

.

·

·

.

·

·

.

. . .

.

·

·

•

·

·

·

I

·

· .

,

ir.

•

•

:

••

•

•

I

·

.-

•

•

...

...

• •

:t .

.r .

•

.

·

.

.

-

.,

. a

..

•

....

1 .

....

•

PI e

I

=>

1

\

SALT

•

•

NOTE:

REFER

TO

TABLE

I FOR

STRATIGRAPHIC

SYMBOlS

p.17.18

F IGURE

SECTIO

ON FIGU

WEST H

SECTIO

V:H

= I


28/110


29/110

31

>

.p.19 20

fiGURE

7

WEST

H CK ERR

SALT

oX OXY

= OL 1N

CONST 1

1=

o.o .

Of CAVERN

r

WELL

NO

OX S

crNT[R

Of

l r J

CAVERN L SALT a n

0.0 . [ .

PROPERTY _ ••_ _

LiNt

SALT

CONTOUR

5

CONTOURS

IN

r[[T

BELa. Io£AN SO

[V [U

LEGEND

o 1500 3000

FEET

SCALE i

17

K

18

®

.\


30/110


31/110

The most cost-effective method of pene trat ing

the

caprock

has

clearly been

demonstrated to

be

dri l l ing without returns.

By using

water

instead

of

mud to cool the bi t

hole

can

be

made in

this

br i t t l e rock without

cementing

every few feet , once casing is se t in the

hard

carbonate

caprock.

Hydrogen

Sulfide: ~ t Hackberry

may

have

signif icant

concentrations

of hydrogen sulfide. This

toxic

gas, commonly known in oi l f ie ld

terminology as sour gas; is formed in the re ac ti on o f hydrocarbons with

anhydrite to form carbonate caprock and sulphur.

Although

sulphur

exploration was not commercially

success fu l, t he re

are abundant shows of

sulphur

a t

the

top

of

the

anhydrite cap,

part icularly

in th e usual

location

near

th e

rim of

th e dome West

Hackberry

has

been

prospected

and

i s

close to

many domes that have produced commercial

sulphur,

including

High Island,

Fannett

and Spindletop [Ref. 4].

As

a result hydrogen

sulfide is

detectable

in most sal t-dome caprocks

[Ref.

5].

The

presence

of hydrogen

sulfide complicates

dri l l ing

through

th e

hard

caprock because

everything

in

th e

hole, including

th e

dr i l l

str ing, t urn s b la ck and corrodes. Any pipe harder than API American

Petroleum Ins t i tu te) Class E is

subject

to brl t t le fai lure under

normal

fatigue loads,

part icularly when corrosive saturated

brine must also be

used to

dr i l l

into sal t . Nickel

and

manganese, used to harden the

steel are more subject to sulfide corrosion

and

c rack ing than even

iron.

Faults: Caprock

is characterist ical ly fau lted in

most of

the cores

that are recovered,

so much so

as to

be

a

permeable jumble of

broken

blocks

with

secondary

calcite

cementation. Some of these faults

extend to

th e

surface, and

may

control

subsidence as

well as

localize small,

natural

shallow

o il

accumulations.

The

faults

are

further

suggested by th e shape

of

the tr iangular subsidence trough [Ref.

18], and by

the producing

wells

on

higher

blocks

across

the

top

of

th e

dome

The active shallow faults origina ti ng in th e caprock or sa l t

shear

zones have

only displaced th e

Recent

sediments a few

feet .

They do not

pose

any

apparent r isk to th e storage caverns by themselves, but

subsidence

along them

could

conceivably damage surface faci l i t ies or well

casing, as has occurred at

other

domes used

for

storage o f LPG) products,

e. go ,

Stratton

Ridge, [Ref.

]

Salt

The general shape of

the

combined

East

and West Hackberry domes a

flat-topped and

sl ight ly- t i l ted el l ipsoidal

cylinder,

is

similar to that

of

most

elongated

sa l t

domes

In

the

case

of

Hackberry,

th e

t i l t

is

northward.

The

west

end

is relat ively

blunt and

the

east end,

a t

th e

saddle to

East Hackberry, sharply

poin ted F ig .

7).

This disagrees

signif icant ly

with

the ear l ie r interpretations [Ref. I ]

which

included a

deep

valley

on the no rth side and an

elongate

conical dome As a result ,

several

signif icant

revisions

in the

external geometry of

the

sal t stock

were required in revising the dome contours.


32/110

Commercial

exploratory dr i l l ing

was

very

l imited in

the

area f rom 1986

to

1991

because of the decline in o il prices so l i t t l e

new data

has been

available although

a few

old

wells

have been twinned to keep

up

production.

The

steep

southeast face

along

with

the sharp

east end

suggests

that a transform

or

wrench fault

separates the

domes.

Study

Method:

Sediment

structure

around

th e

dome

is

used

in

this

study to he lp de fin e

the

sa l t face. Methods of

determining th e

sa l t

face

include

dip and convergence or thinning

of the

beds

uplif ted

by

the sa l t

intrusion.

Asymptotic Dip: . From f la t beds

in the

bottom

of th e

rim

syncline the

dips

of

the sediments

around

the

sa l t

increase

65

degrees in

many places

against the near-vertical face. This

asymptote

allows the horizontal

posit ion of the sa l t face

to

be calculated

from

the observed

change

in

dip.

Convergence: In

addition to

structure as discussed below

s tr a tig raph ic vari a tion

is

used

in

this

study

to

help

define

the

edge

of

the sa l t That i s th e intersection

point

a t which

projected beds meet

is

a good

estimate of th e sa l t face. There is extreme

convergence

in th e

Oligocene with i t s thick shales but very l i t t l e convergence

in

th e

overlying Miocene Sands. The resul tant thinning is

part icularly

apparent

in th e oil-productive

Frio

sands.

Rate

Of

Uplift :

The

overal l average intrusive r ise of the dome

as

a

whole

can be calculated

from

the upl i f t

of dated marker

beds

that are

asymptotic to

th e face

of th e sa l t

The

deepest penetrated

Hackberry

shale

sheath

HB , some 40

million years old

my ,

has been uplif ted

some

7000

f t the top of the Oligocene DR,

30

my

6000

f t

middle Miocene

AB,

15

my

3000

f t

Miocene

10 my

2000

f t Pliocene 2

my

500

f t and

Peorian

p

0.5

my

100

f t

These

value s a re

a ll

very

close to

a

rate

of

0.1

mm/yr,

which is the

same

as that observed a t

Bayou Choctaw

and Big

Hill .

This

rate

is exceeded only

by

th e Five Island Chain including

Weeks

Island which has an apparent

upl i f t

rate

as

high as

4 mm/yr.

Spines:

The

spine theo ry

of

sa l t intrusion

and i t s

validation

in

mines

is reviewed in the

Weeks Island

SPR Geological

Characterization

Report

[Ref.

7].

The

well log data and

their

correlation a t

Weeks shows

two

spines separa ted by

a

shear zone in the south half of the dome used by

SPR. The

spines

are

interpreted as anticl inal

features or.domes

in the

anhydrite correlation data

a t

Big Hill

[Ref. 8].

In

east-west domes

l ike

West

Hackberry th e sa l t

flow

l ikely occurs in

widely-separated spines .

However,

there is·

insufficient

control within

the

sa l t

to define

the se spine s by their shear

zones

i

e areas of

more

anhydrite which

separate them. The

holes that were dr i l led to

leach

th e

new DOE caverns were

only

part ia l ly logged and a few cores cut. Only one

hole per cavern was dr i l led except 117

which has

two and logged through

the

sa l t so tha t i t was not possible to use th e methodology developed a t

Big Hill

for mapping anhydrite bands and

th ereby th e in ternal structure of

the

sa l t

intrusion. Consequently

any

additional cavern development should

22


33/110

requi re exploratory dri l l ing

and

logging

to

delineate such features within

the sa l t

mass, even

though

speci fi c e ff ec ts on cavern construction

may

be

speculative.

Core samples show that

the sa l t is relat ively

dark

with considerable

disseminated anhydrite, even in the middle

of

apparent spines. The sa l t

crystals

are

t ightly

interlocked,

as

a result

of

the

compaction

due

to

the

weight of th e caprock. This dark sa l t beli ev ed t o be

l es s r ec ry s ta ll iz ed

since

upl i f t i s typical

of slower-moving domes

Shear

Zones: All sa l t domes

that

have

been

studied have their shear

zones

centered

on

and

paral le l to the

underlying sa l t ridges. The

shear

zones are a lways between th e spines. They are observed

as

a

high

concentration

of near-vert ical anhydrite

and

o th er i nc lu si on

bands,

usually

ref lected as

a

sharp

trough

or

low on the surface of the sal t

Sediment trapped between the spines

in an

overhang could

be

incorporated

into

the sa l t dome

by

continued

int ru sion , c reat ing

potent ial

prryblems i f

cavern leaching is attempted

acro ss s hear z o s ~

The

postulated

nor theast -southwest shear zone correlates very closely

with the faul t running

into

th e overhang Figures

8,

9 . A secondary shear

zone

normal to

this appears to cross i t

over the

center of th e

dome

somewhat l ike Weeks Island. This

complication

may be related to the

apparent

steep

dips

in

Miocene sediments near

the nor thwest corner

where a

radial

faul t

t ies

in with the

apparent

shear. This shear zone also

represents th e axis of th e sa l t ridge upon which th e dome s i t s

The par t ia l near-vert ical overhang on th e north side adjacent to the

s i te is a

much-less

complete seal, requiring la te ra l

sealing

along

th e

shear zone which has acted as a fault beyond the edge of the sa l t stock.

I t is

unlikely,

however, that a l l

th e

o i l and gas trapped against this

sa l t

dome

have

been

found.

Well Control

Significant dri l l ing has

been

done

close

to

th e sa l t face

around the

dome

since the

original geologic

characterization.

moco

has dr i l led two

additional wells downdip in the product ive

sa l ien t a t th e

southwest

corner

of the

dome which

do not

change

the

interpretat ion

of

th e sa l t

face. All

of

the available well data are included in th e appended Well Tables

Appendix

D . A long

overhang may l imit the depth

and extent of

caverns

in a broad arc

across

the north s id e of the OE property. This overhang

is very nearly ver t ica l l ike the

north

side of Weeks

Island and

the West

side of

Bayou Choctaw and

unlike

the 60

degree

overhang on the south side

of

Big

Hill .

Seismic Data

The

original

seismic data from 1983 was obtained under contract by

Woodward

Clyde Consu lt an ts , Inc.

However th e

l ines

were

not extended

out

into Black Lake

far

enough

to

get good

ref lect ions

from th e steep

sa l t

3 4


34/110


35/110

-

-

--

.

SALT

-

-

-

-

-

:

:

:

-

--

:

:

•

·

.

:::

.

.

.. :,

.

.

I

•

,

CAPROCIC

1

I

, I

D

D 7

8

U

V

U

114

107

1011

•

.-

--

m

:

NOTE: R EFER TO

TABLE I FOR

SmA TI

GRAPH

IC S n8OlS

FIGURE

SECTIO

ON

FIGU

p.

25 26

l T H

SECTIO

V,H =


36/110


37/110

22

27

LEGEND

SAL

T

CONTOUR 5

D O Eo PROPERTY _ ••

LINE

PROBABLE

SP IHE CENTER

21

20

H

..

o. s o. J

l _

I

PROBABLE

SPINE

CENTER

2 500

1


38/110

face

and i t s flanking sediments. The only data

is

from the top of the

cap

and

sa l t

Amoco data is available, possibly

indicating

an

overhang. The

cr i t i ca l

l ine ,

closest to

Cavern 111, was to have been

reprocessed

in

early

1991

to help resolve the

overhang uncer ta in ty , but

with

lower

o il

prices

apparently

has been delayed

indefini tely.

Amoco g ravi ty d ata was

examined to

improve

the

interpretation of

shallow

faults , sal t spines, and possibly

subsidence.

The

data

support

th e overal l i n te rpret a ti ons reported

on

here.

Sal t

Contours

The sa l t contours

Figure

7 were f i t ted to the digitized database

using

more

than

50

cross-sections, smoothed both horizontally and

ver t ica l ly between

the

faults found

in well

cuts in th e

oil-bearing

and

overlying sediments near the sa l t The most

important

changes in th e

shape

of

the

dome

from

previous

maps

are

th e overhang and

faults

on the

north side, next to the SPR storage s i te

Most

of

the

shape of the

rest of

the

dome

connecting to

East

Hackberry in a neck

protected

by shale, is smoother than previously mapped

since

we have shown that

the shallow

solution topography

on th e top

of

the

dome

is

unrelated

to

th e s t ~

flanks which

have never been systematically

contoured via

computer

graphics with

a

digi ta l database.

An

east-west and th ree north-south cross-sections Figures 6, 8, 10,

and

11 ;

located

on Fig.

2

have

been prepared from the

digi t ized

database

for this report . The two westernmost north-south

sections

show clearly

the

overhang

jus t

north of

the

SPR

s i te

The

westernmost section Figure

10 shows

th e northwest corner of th e

dome

where the

complex

near-ver t ical

Frio sands have been dragged up to

a lmos t cover

th e shou lder of th e

dome. The

o i l has leaked

up

into th e

basal Miocene sand, and

probably

from here into

the

sands above the

caprock.

A

similar

complex area is found

in the

same posit ion a t Weeks

Island where the n e r ~ v e r t i l sands are basal Miocene age.

The middle north-south section

Figure

6 through

th e

SPR

caverns

shows the normal 60 degree dips

extending

nearly

a

mile

out from the sa l t

overhang,

providing

most of

th e o il production.

The

easternmost

section

Figure

11

shows a

wide

band

of

geopressured

Hackberry

sha le t runcat ed by the unconformity a t the top of the Oligocene

which

protects

the sa l t face,

suggesting

a

large

area

of

undeveloped

storage potentia l .

The eas t-west sec tion

Figure 8 runs

th e length of

the

dome crossing

the

SPR

s to rage a re a

and

showing

one

of th e faults believed poss ib ly


39/110

NORTH

SOUTH

1_1

_

....

6 :

•

41

•

41

•

81 11ft

1

. .

.

.

.

.

.

.

.

.

.

. .

·

.

1 0

IGOD

•

1- llIOII

2lIOII

PRO K

l IOII

«lOG

O

0

«lOG

........

........

-l OOO

•

•

•

SALT

7000

J

1

\

.

1 7000

/

-lIOOO

laaa I

ICIXII

nn

nn

NOTE: REFER TO TABLE I FOR

STRATIGRAPHIC SYMBOLS

p 29 3O

FIGURE 10

SECTION LO

ON

FIGURE 2

WEST H CK

SECTION C

V:H

=

I


40/110


41/110

SALT

-

-

I

-

-

...

..

....

- -

...

-

,

..

-

.IF

V

r

I

.

.

.

.

. .

. .

.

·

.

.

.

.

.

.

.

.

.

.

I

,

I

·

.

•

•

11

.....

CAPROCK

NOTE: REfER

TO

TABLE I

fOR

STRATIGRAPHIC

SYMBOLS

fiGURE

SECTION

L

O

fiGURE

p.31·31

WEST H C

SECTION

V:H = :


42/110


43/110

activated by cavern

creep

and bounding the tr iangle of greatest surface

subsidence. This faul t is th e sur face expression

of

a probable shear zone

separating active spines. I t shows on

both

sa l t and caprock maps. e have

no

evidence

that any

of

these faults intersect the caverns,or the well

casings.

Structural Interpretation

Dome-Related Fault iD : The

shear

zone observed

in the

new

wells

continues

outside

the

sa l t

as the single

radial

faul t on the dome Figures

1, 2)

that is

o il

productive, having been substantiated at th e northwest

corner

of

the

dome and

discussed

earl ier under the section on shear zones.

The West and

East

Hackberry Salt Domes, along

with

the Big Lake

structure to th e east,

form an east-west

ridge in the

middle of

the

Hackberry embayment, the most

prominent

Frio

feature

of the Gulf Coast.

I t

is

a large

depression

that was f il led in Oligocene middle Frio

time

with deep-water shale.

Big

Hill , a preViously

characterized

SPR dome,

l ies on

the

west edge of

th e

embayment [Ref. 8].

The rim syncline surrounding

the

sa l t

r idge represents

the

equilibrium

in the intrusive

sa l t

between the sands being deposited from the northwest

and

the

Hackberry Embayment.

SPR SYSTEM

CONSIDER TIONS

The

effects

of regional and local geology may

affect th e

SPR

operations in a variety

of

ways. These aspects

are

discussed in the

fol lowing pages.

Cavern

Configuration

The

five caverns

which were purchased from

the Olin Corp.,

6, 7,

8,

9, and

l l ex i s t ed

at the time of th e 1980

si te

characterization. The

geometry of

these caverns is

unchanged, but refinements in some of

the

technical

data

have been made; these

changes are

indicated in

Table

2,

along

with the

data from

the

17 new caverns,

101-117.

Caverns 101-

116 are single-well

caverns,

whereas 117 a two-well cavern, similar

to

the Phase

III

caverns

at Big

Hill .

Table 2 was compiled by Boeing

Petroleum Services

and Usts

the

most

relevant parameters

associated

with cavern integrity. All depths

are

given

in

feet below the bradeDbead

flange

(which

varies

from 4 to 19 f t

emsl),

but

cavern-induced subsidence

gradually lowering th e

mean

sea

level

values.

A

brief

description

of

the

data

follows:

·Cavern number

i s

shown on Figures 5

base

map), and 13

a ir photo)

-Date constructed indicates

time of

leaching,

but does not

include

workovers, etc performed subsequently.


44/110

WEST HACKBERRY CAVERN GEOTECHNICAL PARAMETERS

DataCurrent to 6105191

Cavern

Date

Constructed

Cavern

Volume,

MMB

Top

Caprock

Top

Salt

Casing

Seat

Top

Cavern

BottomCavern,

Dale

Cavern

Height

H

Diameter

D

HID

Nearest

Cavern

Pillar

Thlckness P PID

Rool

Thickness

B

Distance

toDome

BID Edge E

EID

Distance

To Property

Line

BH

Eleva

198

6

1946 8.8

1598

1949 2582 3249 3390 01191

141

662

0.21

9 331 0.50

1300 1.96 480 0.73

350

5.2

7

1946

13.1

1551

1992 2393 2552 3494 01191

942 315

2.99

6 609 1.93

560 1.78 1650 5.24

189 4.3

8 1946 10.3

1515

2035

2337 2450

3449 12190 999

272 3.67

9

149 0.55

415 1.53 1700 6.25

239

13

9 1947

9.8

1550

2100 2525 .,.3213

-3555,02191

342 454

0.75

8

149 0.33

1113

2.45

1200

2.64

744

11.

11

1962 8.6

1529 2085 2790 -2951

3756

2 9

804

276

2.92 108 567 2.05

866 3.13 2500 9.06

349

10.

101

05181-1 2 83

11.2

1609 2050

2434

2555

4440

03191

1885

206

9.15 103 397 1.93

505 2.45 2600 12.62

735 18.

102

02182-11184

11.1 1621

2063

2440

2628

4498 03191

1870 206

9.08 103

448 2.17

565

2.74

2210 10.73

122

15

103 05181-01184

10.4 1558

2038 2432

2667

4423 01191

1756 205

8.57 101 397

1.94

629

3.07 1900 9.27 746 16.

104

05181-02184

11.5 1561

2076

2450 2625

4546 2 9 1921 206 9.33 102 450

2.18

549

2.67

3000

14.56

101

17

105

01181-01184 11. 5

1647

2058 2458 2640

4609

2 9 1969

204

9.65

104

492

2.41

582

2.85

3000

14.71

641

17

106

01184-08187

11.3

1660

2065 2402 2556 4346 2 9 1790 212

8.44

104 492 2.32 491 2.32 1560

7.36 154 16.

107

07181-07184

11.5

1608

2058 2473 2585

4556 12190

1971

204

9.66

103 470 2.30 527 2.58 1510

7.40 149 14.

108

02182-12184 11.5 1664

2053 2420 2596

-4440,01191 1844

212 8.70 112 513 2.42

543 2.56

1700

8.02

144 7.5

109

03184-11185 12. 0 1606

2057

2469

2563 4644 12190

2061 204.

10.10

9

386 1.89 526 2.58 1000

4.90

820

9.3

110

02182-03185 11. 2 1683

2072 2430 2567

4568

03191

2001 200

10,01

111 520 2.60

495

2.48

400 2.00 206

6.7

111

01182-04188 10.6 1980

2180 2534 2622

-4596,01191 1974 196

10.07 110 520

2.65

442 2.26

500

1.53 100

6.9

112

09183-01187

11.4

1650

2050 2437 2562

4532 2 9

1970

203

9.70 108 513 2.53 512

2.52 1800 8.87 157

7.9

113

07182-06185 12. 2

1920

2113

2772

2827

4692 12190

1865

216

8.63

114 518

2.40 714 3.31 500

2.31

106

6.2

114

09182-09185

11.3

1668

2073 2380 2520

4549 2 9 2029 200

10.15 113 518 2.59 447 2.24

1000 5.00

213

6.1

115

02184-06187

11.8 1713

2073 2450 2540

4634 2 9

2094

201

10.42 107 478 2.38 467 2.32

900

4.48

636

7.7

118

07182-09185

11.5

1773

2088 2520 2840

4718 12190

2078

199

10.44

114 542 2.72 552 2.77

1100 5.53

180 6.9

117

06185-09188 12.7 1594

2051

2412 2560

4609 06190

2049

211

9.71 108

421

2.00

509

2.41

2100 9.95

241 13.


45/110

FIGURE 12 GENERALIZED CAVERN CONFIGURATIONS WEST HACKBERRY SPR SITE

0»

I

6 z

NI

9 11

101

~

103

104

105

~

..

sw

500

a

11III

N.llL

S

2500

3000

I

I

=I 3000

I

8.6 9.8

X 3500

3346

FT

.-

=I

3500

ti

01/91),

3450

FT

3420

FT

01/91)

12190

3540

FT

W

02191

0

I LEGEND

I

3724 FT

02191

4000

8.6 • Csvsm volums million bsrrels

=I 4000

3363 • OlllbrtneInlerfsC8deplhsnd dsle

0

200 400 600 800 1000 1200

4500

I

CAVERN WIDTH

I

4181 FT 03191). 4368;; ;;3/91

4356

FT

01191

4500

4518

FT

02191

4700

4700

\:.I,

CIt

2300 E

1

2300

106 107 108 109 110 111 112 113

11

4

115 116 117

2500

.

2500

4500

3500

4000

3000

4036 FT 02191

4224FT

12190

3761 FT 12190 4339 FT 02191

4179

FT

02191

4424

FT

12190 3928

FT

03/91)

FT

01191

3821

FT

01/91)

4528

FT 12190

3950 FT 02191

4554 FT 12190 1 4900

4900 [

4500

3000

t-

I i l l 2. 111 51

.11 5 .

112.0. 1i1O:9.

110.6

X 3500

t-

Il

W

0

4000

TA01l1601 ZJ


46/110

• ... _

_.

_

••

_ _ ~ , •• •

__

._ , .

__

._

••• __

__ ..

__

••

_ __ . __ __

•• •

. _ ••

• ••

_

_ • _ ......

_ ,

Cavern

volume

, in millions

of barrels,

i s usually

about

10 larger

than the volume

of

stored material, allowing for brine in th e cavern

bottom.

·Top

of

caprock

and

sal t

respectively, are

the

uppermost

surfaces of

those

units .

·Casing

seat · and ·cavern

top

(or bottom)

is

e l f ~ e x p l a n a t o r y

·Cavern

Height H)

i s the distance

from

cavern top to bottom.

·Diameter D) is the cons truc ted diameter, Which is an idealized

(average) cylinder diameter that

would

correspond to the f inal

cavern

volume

with

the

given height.

H/O is

the rat io of the cavern heigh t to the constructed diameter,

providing

a measure

of

th e

cavern

shape.

·Pi l lar thickness (P)· is t he thi ckness of

the

pi l lar

of

sal t between

a cavern

and

i ts nearest neighbor.

P/O is the

rat io

of the

pi l lar

thickness and the const ructed

diameter,

providing

a relative measure of mechanical integrity.

Roof thickness B) i s

th e distance between th e top of the

cavern and

the

top of sal t .

B/O is the rat io

of

the roof thickness to the const ructed

diameter,

providing a

measure

of mechanical integrity.

Distance

to

dome

edge

(E)

is

the est imated

distance

between

the

cavern and the

outside

edge of dome sal t .

·E/O is the

rat io

of

the distance

to

th e

edge of dome to

th e

constructed diameter , providing

a measure of

mechanical integrity.

·Distance to

property

l ine is the closest

distance between

the

cavern

edge

and the SPR property l ine.

BHF Elevation

is

the

bradenhead

flange

elevation

in

1988,

rounded

to

0.1 f t .

The values shown in Table 2

ref lec t

the very

conservative design

approach used throughout the SPR system, espec ia ll y for

Caverns

W 101

117. The

preexisting

caverns (W 6-11) do not follow those same

guidelines, of course,

but

there have

been no s tabi l i ty

or safety issues

with them.

Cavern

Shapes

Figure 12 s w ~ current cavern shapes by best estimates.

Caverns

6-11 are

quite

well

mapped, having

been sonar

surveyed when

fi l led only

6


47/110

V e r t i c a l ai r phot o

cavern locations.

a1 s ur f ace features

showing

p r n ~ 1 12 000.

10 y 90 sca e

37-38

~

eproduced f rom

best

available copy


48/110


49/110

with

b rin e . However

data

used

to compile cavern

shapes

for W 101-117

were derived

from

s on ar r ec or ds

obtained

d ur in g c av er n

development,

an d

from o il f i l l an d in te rfa c e

records

obtained

during

leach an d

f i l l

operations. Because sonar

recordings

could

not

be obtained through oi l

the o il f i l l vs

volume

data r e s u l t in axisymmetric cavern

shapes

on the

drawings,whereas

in

fact

they

are N on et he le ss , t he

data

an d sonar

r ec o rd s o bt ai ne d

d ur in g c av er n

development

show

v er y s ym me tr ic al c av er n

shapes

fo r the

new

caverns W

101-117),

suggesting there is

a

general

absence

o f s ig n if ic a nt

mineralogical or s t ru c tu r al e f fe c ts

t h a t

have

re s ulte d in

p r e f e r e n t i a l l y

oriented

caverns. Cavern

W 111

is

a

notable

exception, with pronounced

assymetry

in

the

to p 2 f t .

Cavern

6.is

somewhat

s au ce r- sh ap ed , w i th

a

diameter

o f nearly 12

f t an d a height of about 14

f t .

The

aspect

r a t i o o f 0.21 using

the

constructed diameter) is the lowest in the SPR system an d there has been

c on ce rn o ve r possible

collapse o f

th e cavern roof.

However

the

twelve

plus

year h is to ry o f SPR

operations

combined

with the former 32-year

hi st ory

o f O l i n s brine

feedstock

e x tra c tio n at tests to i t s

long-term

s tabi l i ty . The September 1978 blowout and f ire

a t

t h i s cavern was

unrelated to the

low

aspect rat.io [Ref. 9].

Cavern

9

ha s

two lobes separated by a 6 0 f t neck at

about

337

f t

depth.

The

sa l t ledges

here

are

a

pot ent i al source for sa l t fal ls which

could

damage hanging

s t r i n g s

but

t h i s

has

not occurred.

Caverns

101-117 are for the most p a r t

unremarkable,

an d

s i g n i f i c a n t

deviations from

design

shapes

have

not

occurred. Caverns W

101, 102, and 1 3 have s l i g h t l y

wider

tops

than

an

id e a l

tapered cylinder,

a nd Ca ve rn

W 111

has

a

small ledge, o r s ho ul de rs , near

the

top.

The

s ma ll d ia me te r

above

t he s ho ul de rs

was

d e lib e ra te ly

caused

by

f i l l ing

with

o il d ur in g the las t

l ea ch in g s ta ge

to prevent

fu rth e r growth.

T he se m in or

departures

have

no

bearing

on

cavern

operation

an d

present

no

sa fe ty

or

i n t e g r i t y concerns.

Cavern

113 was constructed

with

the las t

cemented

casing s e t 27 f t deeper than the other Phase II wells. This re su lte d

in

a

s l i g h t l y deeper cavern top

and

th e cavern height

was reduced somewhat

so t hat the

nominal

to p an d

bottom

are

at 28 and 47

f t

re sp e c tiv e ly

[Ref. 10].

Cavern

112

ori gi nal l y

was

to have

been

constructed j us t west o f Cavern

113 b ut e xp lo ra ti on

revealed

a re -e n tra n t

an d f a u l t st ruct ure in the sa l t

face

along

the

north side of the dome resul t i ng in i n s u f f i c i e n t distance

to the edge of

sa l t

an d requiring t hat th e cavern be re -lo c a te d

south

of

Cavern

11

F igure 13 ).

Additional

Cavern

Space

In

the event

i t would become

n ec es sa ry t o abandon

one

or

more o f

the

exi st i ng

caverns,

or

to t ransfer o il

for some

reason,

there

is

probably

room for another cavern jus t

outside the DOE property

n o rth e a st

of Cavern

11 an d s ou th ea st o f abandoned

Olin

Caverns 3- 4

coal esced) .

To v e rify

t h a t s u f f i c i e n t pi l lar

space

e x i s t s

at this

location,

the

former Olin

caverns

would

need to be ope ned an d sonar

surveyed.

Space fo r

two other

caverns also

e x i s t s

immediately

south

of

Cavern W

106,

an d

southwest of


50/110

Caverns

WH 108 and

117,

but neither

of

these l ocat ions a re

presently

on

O property.

Similarly, off

of O property,

j us t

west

of

Caverns 104, 102,

and 107

(Fig. 13), there are p ossib le locations where storage caverns

could

be

constructed,

with

cavern

roofs

at

-2500

f t

or

deeper.

These

depths

have

. already

led to

greater creep/subsidence rates a t West Hackberry. and th is

fact

combined with the already low elevation would have to be reconciled.

With th e exist ing cavern volume

to ta l

exceeding 275

million

b arre ls in

36 exist ing and five abandoned

caverns,

the

dome is approaching the

reasonable upper

l imit f or s to ra ge . All

of the

above

considerations

would

require

study

prior to

serious thought of expansion.

New

Olin Caverns 12., 13. 14

The Olin Chemicals Group completed th re e b ri ne wells in 1977 to

provide feedstock for i ts ch1or-a1kal i operat ions a t Lake Charles.

SPR

Cavern

116

is

th e

closest

adjacent

cavern

to

th is

group,

750

f t

northeast

of Olin 12 (Figs. 5. 13). Figure 14 shows

the

pi l la r thickness between

the two

caverns

to be more

than

500 f t

All

three

Olin well s were

ident ical

in

design, but

minor

var ia ti on s i n

tubing and cavern depths occur. The three wells produce brine which

consumes sa l t a t a rate of

about

one million barrels volume) annually.

Total cavern volume was

12.72

MM

(from

sonar) in

O c t o b ~ r

1989 and 1991

year-end estimates are 15.5

MM

1989 sona r r ecords show th e caverns

as elongated

cylinders

approximating

baseball

b ~ ~ ~ · .in shape,

with

th e large dimension a t the

bottom. The

highly

s Y m m e ~ i c a shapes are somewhat questionable because

the sonar survey was performed through two

hanging

str ings. At that time

the to ta l volume was 12.7

million barrels ,

with maximum diameters

of 188,

178,

and

173 f t

for Caverns

12 ,

13, and

14 , respectively.

All three wells

had

operated

in

the

bottom

injection

- top

recovery

mode, which produces

th e observed-shape

caverns.

A December 1989 Olin

l e t te r to

th e

Louisiana

Office of

Conservation,

Injection and.Mining Division, indicated that i ts

1989 sonar logging showed the

inter-cavern

distance between two caverns

was 205 f t So

as

to not exceed

the

200 f t separation s pe cif ie d in

Statewide

Order 29-M, Olin requested a change in

i t s

leach extraction

procedure for two of i t s wells, with the

apparent

intent of al ter ing the

shapes

to more regular cylindrical forms.

Because

the

wells

are

spaced

390

f t

apart,

and

because the

maximum

diameters

are already

being

approached

in two of

th e

three caverns there

is a l imit to

how

much more extraction ,of brine

is

,possible, perhaps as

much as twice the current

to ta l

or

roughly twelve

years.

a t current rates.

Olin management

personnel

indicated

they

had no

immediate plans

for

expansion to o.ther·

locations.

40


51/110

· 5

Figure 14

O in Brine Caverns;

October 1989

Sonar Surveys

Cavern locations are

shown on Fig. 7

SPR

Cavern 116 shown

In two dimensions on

this cross section

5 08 =Volume, In

Million Barrels

-2860

•

-3036

5 08

3 59

4 05

1 4275

1 4560

-4660

I

4500

·4

t ·3

LL

C

J

-

C 3500

5000

o

200

... ...

so

150 250

FEEi

41


52/110

x USA

Caverns 1-11

Oxy

USA

I nc . ope ra te s

11 storage caverns

containing

a

variety

of LPG

products Figs. 5, 15 ; Table 3 . Total storage volume in

m i d ~

was

sl ightly

more than 16 million barrels ,

with individual

caverns ranging

from

0.86 to

2.77 MMB.

Useable

storage volume is approximately 14 MMB.

Cavern

12

has been

permitted, and once constructed will

produce

brine

for

several years prior to product

storage; i ts location

is

north of

and

centered between caverns 1

and

3.

TABLE 3

OXY

USA

CAVERN DATA:

WEST IlACKBERRY

LA

Cavern

Volume,

Product

Casing

Tota l

Diameter ,

Diameter .

Las t

MMB

Seat

Depth

Maximum

Constructed

Sonar

ox-

1

1 . 61

Raw

-2252

-2855

249

138

17 May 91

ox-

2

0.98

Citco

nC-4

-:2254

-2891

244

105

19 Fe b

90

Ox-

3 0.86

Ci tco

nC-4

-2287

-2873

261

102

14

Dec

88

ox-

4

Ci tco

iC-4/BB

-2343

-3030

258

108

27

Mar

90

ox-

5

2.77

Propane

-2366

-3361

248

148

31 Mar

89

Ox-

6 1 .

66

Ethane

-2352

-3101

181

126

16

Apr 88

ox-

7

0.89

Propylene

-2328

-3175

115

87

08 Mar

90

ox-

8

1 . 53

fg B utane

-2347

-3106

176

120

30

Aug

89

ox-

9

2.00

Butane

-2345

-3091

273

139

09

Apr

90

Ox-l0

1.

35

fg Butane

-2561

-3583

144

97

03

Aug

90

Ox-l l .

1. 40

Propane -2566

-3383

145 110 15 Apr

88

Cavern shapes as revealed on

sonar

.records are a l l very symmetrical

Fig.

15 , at test ing to th e uniformity and purity of sal t and the general

lack

o f non -hal it e const it uent s

that

lead. to assymetry.

Oxy

Cavern

5

is

closest to

SPR

Cavern 112; the

web

thickness between them

is

700

f t a t

th e

closest

approach a t -3150 f t . Using constructed

diameter

values

average cylinders , the average pi l lar thickness increases to 780

f t .

Subsidence over. the

Oxy cavern f ield

has

been

monitored by way of

repet i t ive leveling on some six

occasions

in

the las t

seven years. The

data,

while

not

subjected

to

de ta i led sc ru t iny ,

show

very l i t t l e i f

any,

lowering

.of surface elevations. In view

of

th e

subst an t ia ll y l es s

storage

volume 6.6 of

the

SPR

to tal spread

out over 140 acres, combined

with

substantial ly

more sha llow cave rns average depth - 3132 f t a negligible

amount of subsidence is not unreasonable to expec t. The effect of cavern

depth on subsidence

is explained further

in Appendix

C

42


53/110

Ox-1

Ox 2

Ox-3

Ox 4 Ox 5

Ox-6

Ox 7 Ox 8

Ox-g

Ox 1 Ox

-2000 .

=-----=r/--

Caprock

-2200

I

E Nis E

NIS E IW

NIS

E IW NIS EIW

NIS

-2400

-2600

-

I

\

\

\

\

\

\

0 89

Q

Q

-2800

l

LL

w

I

[

1

-

111 \

/ \ J 1 1

I

1

I 1.53

:

s:

-

o

-3000

Q

I

/

U l

1 1

11.40

C

. I

Legend

-3200

I

=

Cavern Volume,

I

I

r

/1.35

Million Barrels

-3400

l

I

0

100

200

300

. -. 1

150

250

FEET

-3600 l

I

Cavern Locations are

.shown on Fig. 7

-3800

Figure 15 Oxy USA Cavern Dep ths and Configurations;

Composite

section not a

cross

section.


54/110

Subsidence

Subsidence p o t e n t i a l was d i s c u s s e d .i n the 1980

s i te

c h a r a c t e r i z a t i o n

r e p o r t an d

acknowledged to be

a

concern.

The

p r i n c i p a l

causes

o f

subsidence were

i dent i f i ed as f l ui d

withdrawal o f

water, gas,

an d oi l ,

cavern c o l l a p s e , an d cavern creep closure.

Ten

years o f

experience an d numerous

observations

can.now put these

an d o t h e r subsidence sources into accurate perspective, an d provide

numerical bounds on

each.

The

p r i n c i p a l

sources and.

average values,

in

order

o f importance,

are:

Subsidence

Category

UY :

a) cavern creep

closure

-0.20

b)

f l ui d withdrawal,

Black Lake)

-0.08

?

c)

regi onal

subsidence

0.010

d)

sea

level

r i s e 0.0075

e) other

subsidence/collapse

minor

f) cavern collapse none

a t

W

H

Understanding these

sources makes

i t

possible tO,estimate future

elevation

trends, an d to enable

remedial measures

to be planned, where

appropriate. Examinatior th e values

shows t h a t

s u bs id en c e i nd uc ed by

c av er n c re ep cl osure OVE the overall n um eric al b ud ge t, a lm os t to

the p o i n t

o f negating th, sources.

However, each

is

discussed

b r i e f l y ,

in

reverse

o rdE . impor t ance ,

to

show

how i t af f ect s

th e

SPR

si te :

Cavern

collapse

f)

h as o cc ur re d over numerous s o lu t io n -m i ne d c av er ns

in Texas and Louisiana,

generally

r esul t i ng from uncontrolled

brining

an d

e ro sio n i nt o the overlying caprock

and/or

overburden

[

Refs. I I ,

12].

Hindsight

in

each case u su al ly r ev ea ls t h e c ir cu m st an ce s t hat le d to

f a i l u r e .

.

Even though

today s solution

m1n1ng

t ec hn ol og y c an

avoid the

problems

t h a t previously

plagued

the

industry,

West

Hackberry ha s

some

older

caverns adjacent

to

the

SPR

property

about

which l i t t l e is known,

an d

some

p o t e n t i a l fo r

ins tabi l i ty

may e x i s t . Abandoned Olin Caverns

I ,

2, 3, 4,

an d

5

have

not

been sonar-logged

an d

the

i nt er nal

dimensions

are

u n c e r t a i n .

1989 volume

estimates [Ref.

1 3]

based

on

O li n p r od u ct io n

s ta t i s t i cs

showed t he fo ll ow in g

values:

Olin

1 & 2 -

147.7

dia x

600

h t;

1.83 MM vol. each)

Olin

3 4 -

179.8

dia x

600

h t;

2.71 MM vol. each)

Olin

5 -

80.2 dia

x

600 h t; 0.54 MM vol.

44


55/110

These dimensions are the cylindrical forms

of known

cavern heights

constructed d iamet er s , u si ng the

assumed

maximum volumes based on

conservative

estimates

of

production

obtained

from

Olin Corporation

[Ref.

14]. The maximum

cavern diameters are assumed

to

be

wider; i t is known for

example,

that Caverns 1,2 and 3,4 ar e coalesced

[Ref.

1].

One

conclusion

based on

th e above estimates was

that the map Fig. 6.12

in the 198 report probably showed th e cavern extents to be somewhat larger

in maximum d iame te r t han

actual ly

exists . No doubt

th e

early

estimates

were

conservative intentionally and probably based on history,

as revealed

in the

ultrawide former

Olin Caverns

6

and 9.

Although

Olin Caverns 1-5

have

apparently

been stable for some 4 yrs, uncertainty re.mains.

Other

subsidence/collapse e

result ing

from

mining of sa l t

or

sulphur

has

occurred

a t numerous other domes in Texas

and Louisiana, but

mining is

absent a t

West Hackberry.

o w e ~ e r cracking

of

the

SPR

brine pond

l iner

in

1987-1988 may be related to

local

subsidence caused

by cation

exchange

reactions in the

underlying c layey

soils , upon

interact ion with

the

brine

in

ground

water

[Ref.

15].

This

l a t te r

aspect

is

discussed

further

under

Environmental Considerations.

Sea

Level Rise d is

occuring

in

the

Gulf of. Mexico a t a rate nearly

double th e g lob al rate.

The mean

r ise

in

the Gulf

is 0.23

cm/yr

0.0075

f t /yr an a lmost

ins ignif icant

amou

additional geologic site characterization studies west hackberry salt dome

Documents