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. .

SPE

SPE 14261

Induced Fracture Orientation Determination

in the Kuparuk Reservoir

by K.W Gri f f i n,ARCO Al aska I nc.

SPE Member

Copyrighi i 985, %Iefy of Peiroieum Engineers

This papar was prepsred for presentation at the 60th Annual Technical Conference and Exhibition of the Society of Petroleum Engineers held in Las

Vegaa, NV Septembsr 22-25, 1985.

This paper waa selected for presentation by an SPE Program Committee following review of information contained in an abatract aubmined by the

author(a). Contents of the paper, aa presented, have not been reviewed by the Sodety of Petroleum Engineers and are subject to correction by the

autho r(a). The m ateri al , as presen ted, does not necessari ly reflect any poai fi on of th e Society of Petrol eum Engineera, i ts office rs, or m em be rs . Pape ra

presented at SPE maetinga are subject to publication review by Editorial Commineea of the Society of Petroleum Engineers. Permission to copy ia

res tr ic ted to an abatrac t o f not more than 300 words. I llus trations may not be cop ied. The abetrac t should conta in consp icuous acknowledgment o fwhere

and by whom the paper is presented. Write Publication Manager, SPE, P.O. Box 833836, Richardson, TX 75083-3S36. Telex, 7S0989 SPEDAL.

SUMMARY:

The or i ent at i on of hydr aul i c f ract ur es I s

mni ng fracture or ientat i on. The methods whi ch

of ten a si gni f i cant factor i n the generat ion of an

. - . . .+d. , . . . -~. . l . . l dAdA-

. . ..-l—--& -1.- TL- .k*>a&.. &-

requi re rock property measurements to I nfer stress

UPL I I I I UI I I

ICIUWIUC ueveIupwIcIII,

p[arl.

Irre auttrcy LU

A ...44..4..&4- .. 1-s-.4+- ,. 4 . ..4....- 1.. .+4....

ur IeIILab IUII \uII->i I,e >Lralrl

A4 CC..s–

Iela Aa &lull, ulllel -

predl ct or determne fracture ori entati on al l ows

entl al strai n, and soni c vel ocl ty), requi re careful

eval uati on of the i mpact of fracturi ng on drai nage

ori entati on of the core sampl es, a homogeneous sand

patterns and on waterfl ood performance,

and

w th l ow”shal e content, and mul ti pl e sampl i ngs to

pl annl ng of further devel opment dri l l i ng.

In the

Kuparuk A Sand-- a medi um porosi ty, heavi l y mner-

ensure a cor rect i nterpretat ion of the resul t s.

Wel l bore el l i ptl ci ty measurements provi de fai r to

al i zed, shal y sandstone-- hydraul i c fractures are

good approxi mati ons of stress fi el d ori entati on.

requi red to achi eve the necessary i nj ecti on and The qual i t y of the data i ncreases w t h an l n-

producti on rates to sustai n waterf l ood and peri -

creasl ng degree of borehol e spal l l ng or eccentri -

pheral devel opment. ci ty. The openhol e techni ques, whi l e very useful

for veri f i cati on and di agnosti c purposes, are too

A program was devel oped to test the appl i ca-

expensi ve for general use as fracture ori entati on

bi l i ty of a vari ety of f racture ori entati on determnati on tool s.

determnati on techni ques, and

ai so to provi de

i nformati on on the ori entati on of Kuparuk hydraul i c

INTROWCTI(N:

f ractures.

Seven fracture or ientat ion deter -

mnati on and predi cti on techni ques were compared i n

Accordi ng t o curr ent r ock mechani cs and

a si ngl e wel l bore:

Cal cul at ion of wel l bore

hydraul i c fracturi ng theory, the ori entati on of the

el l i pt l ci t y f rom four - arm dipmeter cal i per s;

In- si tu st ress f iel d i s the domnant factor i nf l u-

on- si te measurement of core st rain relaxat ion; enci ng f racture or ientat ion.1 A hydraul i c f racture

laboratory measurement of di f f erent ial st rain on is created when bot tomhole i nj ect ion pressure

ori ented core sampl es (DSA) ; l aboratory measurement

overcomes the pore pressure and the mnimum i n- si tu

of soni c vel ocit i es through ori ented core sampl es;

compressi ve stress of the formati on. Rock materi al

anal ysl s of trl axl al borehol e sei smc data; w l l be di spl aced i n the di recti on of the m ni mum

eval uati on of expandabl e packer i mpressi ons and

compressi ve stress, and the fracture w l l extend

eval uati on of borehol e acousti c tel evi ewer resul ts.

i n a pl ane normal to thi s stress ( I . e. , I n the

Resul ts from thi s, and other, singl e-wel l bore tests

di recti ons of the maxi mum and i ntermedi ate com

were then compared w th f iel dw de DSA data, sonic pressi ve st resses) .

8ecause the overburden i s

vel oci ty data, wel l bore el l l pt i ci ty data, and faul t

general l y the maxi mum compressi ve stress at depths

and structure mappi ng. greater than approxi matel y 2000 f t (600m, hy-

draul i c fractures are near vert i cal In the Kuparuk

Al l of t he t echni ques examned provi ded

FormatI on (5700 - 6800 ft; 1740-2070M. Assumng

i ndi cati ons of fracture ori entati on. The downhol e the exi stence of hi gher compressi ve stresses i n the

t ri axl al sei smometer surveys proved to t@_ lmh

overl yi ng and underl yi ng barrier l ayers, frati ure

def ini t i ve and economcal as a method of deter - creat ion and extensi or t- .w l loccur pr imar i l y w thi n

~~e ?Gwer I / , , ”sw , , baf i ~?R tha A4.6 .++An A ~~e

RukJul urn .11= Uil=bbiwtl VI

References at end of paper.

maximum hori zontal str ess.

..

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.,

.

TN1’)lTCUT) URA(’ TITRT? OR TF.NTATTON DETEFWINATION IN THE KUPARUK RESERVOIR

S PE 14261

L

L..”uvM-

-.-. ---. — ------ .----—-- ———––———

The Kupar uk Ri ver Format I on ( Fi g. 1) I s am

I ndi rect Measurement

sequence of terrl genous cl astl c sedi ments deposi ted

- - -- - -- - - - -- - -- - - - -

on a shal l ow mar ine shel f dur ing the Lower Cre-

taceous Peri od.

The reservoi r I s an ant l cl lnal

Tri axi al Borehol e Sel smcs14-16

st ructure on the Prudhoe Upl i f t on the nor thern

edge of the Al askan North Sl ope. Oeposl ti onal l y,

Predi cti ve I nference

I t I s at the j unct ure between two maj or f aul t

- - -- - -- - -- - - -- - -- - -

systems; and ol der, northwesterl y- southeasterl y

faui t system and a younger , nor th- south faui t

system

a)

The formati on consi sts of two sand-si l t

wei i bore Ei l i pti ci ty measurem

ents f rom Four -arm Ipmeter

sequences whi ch are separated by an erosi onal

Cal i per Data5S 6*

17- 1~

. . - - - - z-—— . .

-rL.------ --------- ----4-*-

unccmTonnl Ly.

-z *b.-

n

tne Iuwer >equenue LunsI>L> WI LrIe m

_,A- .-k---- n->.....ba--?(’b~~

b)

Sands, a thi nl y l amnated ser ies of i nterbedded

Oi i - sl Le>Lral n

fwlaxabluri--

C)

Di f f erent i al St rai n Anal y-

sandstones, sl l tstones, and mudstones; overl ai n by

sI s23- 26

the 8 I I - i + a eab-{ae

n*4m.w.ilv ~f- in+nvhnrit+ad

Ultil,,

act ‘Ca Vf ‘V11U8 1 ‘J

,? ,=, “=””.=”

,41

C--{.- Ualnei+,,

anal vc{c27

sl l tstone and mudstone.

U1

.x/,,,u ,=,”Q,*J “..wrJ.7.-

The upper sequence

e)

Faul t and Structural Mappl ngg

consi sts of four mari ne sandstones, the C Sands;

over lain by a si l t stone, the D uni t . The Kuparuk

The di rect observati on techni ques use ori ented

reservoi r sands are i n the A and C uni t s. ” The

Kuparuk A Sands are more w despread than the C

downhol e tool s to observe the the i nduced fracture

Sands and provi de approxi matel y 60% of the re-

st the wel l bore.

The borehol e sei smometer detects

serves. The A Sands are quartozose, very f i ne to

and or ients sei smc si gnal s emanat ing f rom the

44. . A“m4. . n. . l

f reshl y created f racture f ace. The predi ct i ve

. . , / . 1e, -. . . 4’ aA

- , - I r . . . . l l , ,i - ?’ l +arl*m

1 l [ ICyralilcu, WCI I auf L.vu aIIU

4-.4.”

,“b~ , ,J L=,,-l,b=” ,,8

--...,,-,. ,,.w~.+tane in m-wb nwnnnr+inc

ahm]t

l,~>L> Inea>urc “a, ,Cll,,”,,a ,,, ,Vsm +/1”+/=, “,-- ““”w.-

part by ankerl te.

Shal i ness var ies w del y both

t he di amet er of t he core and requi r e proper

vert ical l y and aeral l y throughout the sand.

i n

cl eaner sect i ons porosi t i es ar e near 23% and

appl i cati on of rock mechani cal property theory to

i nf er I n- si t u st resses and

i nduced fracture

permeabi l i ti es are near 100 ml l i darcies.

ori entati ons fr om thi s data.

The A Sand has been f ound t o be ver y sus-

Two wel l known t echni ques f or f ract ure

cepti bl e to damage.

Hydraul i c fr acturi ng has been

found to be a conveni ent and effecti ve techni que

or ientat ion detect ion were not used In thi s work

for removi ng wel l bore damage and provi di ng some

due to pract i cal l i m tat i ons of the data. Lack of

st imul at ion of the reservoi r . Present ly, 100 f t

r esol ut i on of sur face t i l tmeter data due to the

(30m” fracture l engths are used, whi ch resul t In

depths i nvol ved and to the exl st l ng permafrost

l ayer r ender s thi s t echnique

i nappl i cabl e. 28

producti vi ty i mprovements of 3. 0. Thi s I mprovement

I nter ference or pul se pressure test i ng al so i s

i s eveni y di vi ded between damage removal and

l nappi i cabi e because the l ongest nyaraui l c Tracwre

. . _ * . . . .

sti mul ati on, and enhances the economcs on many

Kuparuk dr i l l si tes.

I n such a si tuati on, proper

hal f - l en ths are f ar l ess than one- hal f t he wel l

spacing,2$-32

pl acement of wel l s and proper di st ri but i on of

producer s and inj ector s can mnlmze unswept

L. W

Teufe14 has proposed the mcrocrack

reserves, overl appi ng fl ood patterns, and cycl i ng

of i nj ecti on f l ui ds.

model of st rai n rel axat i on w th whi ch t o rel at e

cor e pr opert i es t o t he i n- si t u st at e of st ress.

ARCO Al aska, Inc. devel oped an extensive

Core rel axati on w l l be the greatest I n the

dl rectl on of maxi mum hori zontal stress, due to the

program 1) to compare the accuracy and appl i ca-

bi l i ty of a vari ety of i nduced fracture ori entati on

formati on and openi ng- up of mcrocracks perpendi -

cul ar t o t hi s st ress.

Fracturi ng theory predi cts

detecti on and predi cti on techni ques, and 2) to use

these techni ques to map fracture ori entati ons i n

that hydraul i c fractures w l l propagate perpendi -

the Kuparuk A Sand.

cul ar to these cracks - - i n the di recti on of

maximum hori zontal stress.

Al l of the techniques used In thi s work have

been previ ousl y descri bed i n the l i terature. Much

OESCRI PTI UOF TECIMQUES:

of the past work was of a devel opment 1 nature or

 - 9 Thi s i s

I MPRESSION PACKERS:

The Impressi on packers

restr icted to a few test ing methods.

the most extensi ve compari son to date of fracture

are expandable- type product ion packers w th a

or ientat ion determnat ion and predi ct ion tech-

mal l eabl e rubber j acket over l eaf - type f l exi bl e

steel el ements.

They are run on tubi ng and are

nlques. ori ented by l andi ng a w rel l ne-conveyed gyroscope

The techni ques i nvesti gated i n thi s work can

i nto an ori enti ng prof i l e j ust above the packers.

be di vi ded i nto three categori es based on type of

Once a pl ug has been w rel l ne set In the bottomof

t he st ri ng t he packer s are i nf l at ed w th t ubi ng

measurement; di rect observati ons (at the wel l bore

pressure.

Several packers can be stacked to cover

sand face), i ndi rect measurements (f romformati on

a l ong i nterval .

The fl exi bl e steel l eaves cause

si gnal s) , and predi c ti ve I nf erence ( test i ng of

the packer s to ret ract when tubing pressure i s

rel ated propert i es).

The fol l ow ng techni ques were

used:

rel eased so that the tool s can be pul l ed out of the

hole.

Di rect Observati on

BOREHOLE ACOUSTI C TELEVI EWER: 10-13” The

- - -- - - - - -- - -- - -- -

borehol e acousti c tel evi ewer i s an ul trasoni c tool

a)

ImpressI on Packers

whi ch empl oys a hi gh resol uti on transducer rotati ng

b) Borehol e

through 360° to generate both a travel t ime and a

Acousti c

Tel e-

ref lectance “pic ture” of the borehole wal l . The

vi ewerl @13

.

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SPE 4 6

\

-%r--

\

‘/

E-5

LEGEND

WELLBORE ELLI PTI CI TY

— DATA

~–~ SONI C VELDCI TY DATA

DI FFERENTI AL STRAI N

‘ “-- ””- ANALYSI S DATA

KUPARUK RI VER UNI T

Fi cI .0—Comoarieon of predi ctedri anteti onf i nducedf racturaaromwal l boreel l i pt i ci ty,onic velocity, and dif-

ferential atrainknalyaia date.

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N

m

~

KUPARUK RIVER UNIT

Fig.

O-TOP of mwfure map of predkfcfl

orlenfation of Induced fracfuroa from 8cJnicveloclfv dam.

 ~’ ~

\XW L

Fig. S-TOP of 8frucfura map of pmdkfod orknfafloa of Induc.d fmcfums from dlffwenfhl strain

 

WV81Ddata.

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‘ s

‘5

Fig. 3—Rw6 dkgmms gm’mmmd from dngl~ and 2wo-ph66666ismicdat6-Well 2G07.

N

PACKER

ELEIIN7

626s, —

;

n

6276, —

‘1

PACKER

ELEhhNl

Fig. 4-Pm2fmc2u

m Inllambk packw lmpm8-

8ion6-Well 2(3-07.

s

Fig. 6-Ros6 d681gnfrom wellbore elliptklty dm6-Well 2G07.

..

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.

N

‘s

S

Fig. 6-Rose dnigps generated from tingle. and two-pha8eselsmlcdafa-Well 1L-o7.

&l

  w

750

23

-a

 

75Q Ai&_x v I m-n

1 \. / Wml U H

\

\ ----- -- ..-

KUPARUK RIVER UNI I

Fig. 7-ToP of structure map of pmdlcfcd otfentatlon of Induced fracfuma from wellbore.lIlptlclfv data

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.

TABLE V

TRIAx IAL BOREHOLE SEISMICATA

KUPARUK WELL 2F-01

NELL

------

US-15

S-P ARRIVAL

EVENT

SEISNIC

TIME SEPARATION

NW8ER CHARACTER

(Ine)

------ ------------ ---------------

 Inttl al 8s’eakdown**

1 SI ngl e-phase

2 s i ngie-phase

3

s1ngl e-phase

4

single-phase

SI n gl a -ph a se

: single-phase

s i n gl a -p ha se

:

s1ng l e-phase

9 single-phase

s1ng l e-phase

10   Inj t l al p~- in st . s9e* * * 1 o

11 two-pha se

12 two-pha se 20:5

13 two-phase

8.8

14 two-phase

15

two-phase 3:::

16 single-phase

17

s1ngl e-phase

18 s 1ngl e-phase

single-phase

;: single-phase

21 single-phase

22 s1ngle-phase

23 a i ngle-phase

24

single-phase

25 single-phase

26 single-phase

27 single-phase

28 two-phase

28.0

POLARIZATION

(DEGREES)

------------

150

45

43

1%

::

40

35

42

42

:

1::

1 1

62

33

E

43

70

51

58

40

59

52

TAB LE VI

FIELOWIOE NELLBORE ELLIPTICITY OATA

US-18

US-23

US-25

lE-05

lL-07

lQ-09

IV-14

2A-02

20-15

2F-01

2G-07

2W36

2U-07

3C-06

um

I mrmr

ORiH~~~iof4 *i[~~~~i~ ~~

“LLMWIIL

OEVIATION OATA

OF MAXIWN

H. 8 . ELLI PT .

OIR. INCLIN.

STRESS WOR AX.

(OE6 REES) ( OESREES) (OE6 REES)

(DE6REES)

---------

90

2

148

1::

270

8

-------- . . . .. . . . .. .

62+/. 5

;

73+/-10

68+/- 5

:

98+/.15

2 153+/- 5

8+/- 5

1

102+/- 5

1:

32+/- 5

30+/-15

47+ f- 5

:

17+/- 5

4

20+;-2:

:

158+/: 5

5 100+/- 5

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

152+/-5

163+/-10

158+/- 5

8+/.15

63+/- 5

98+/- 5

12+;- 5

122+/- 5

120+/-15

137+/- 5

107+/-

new;-y

68+ / 5

10+ /- 5

el’r.

”. n.

>IKIKL W

NEARBY

FAULTING

(OEGREES)

27

;:

15,118

122

4

10

12

135

;:

16

T AB LE V II

FI ELC4 11 0E DI FFERENTI AL STRAI N M TA, SWI C VELOCI TY M TA

ANO HELL8 0RE ELLI PTI CI TY OATA

ORIENTATION OF ORIENTATIW OF AZINUTH OF K4XIWI

M INI MUM SONI C KAxI MU4 DI FFERENTI AL HORI ZWTAL STRESS

OEPTH VELOCITY

STRAIN

F R. HELL 80 AE EL LIPT .

t (ELL ( FT-MO) (OESREES) (OE6REES)

(DEGREES)

----- ------ -------------- --------------------

.,.. . . .?.

Ws-i> Qlm

. . . ,

-,5

ml -a

, .. . ,

W/-

4

uS-23 6127 13$J-~

w{-, ;

~p~~ ~~g

. -. , ---

- - . ,- --

l L-07 ~

0+/- 5

lL-07 176+/- 5

188+/- 1

2A-02 6424

21+/- 5

21+;. 2

2F-01 6524 ;37+;-1:

125+/-’1

26-07 6349.5 -

129+/- 2

26-07 6360

44+/- 5 31+/- 4

2v-fM 6283

50+/-10

50+/-o

3C-06

6343

55+/-5

52+/.4

8+/- 5

8+/- 5

30+/-15

17+/. 5

20+/-20

20+/-20

5+/- 5

100+/- 5

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Fig. l--Kuparuk type log.

I?R.E-FRACTURE

POST

FRACTJJW. ..

Fig. 2—Pre- and ,pa)stfracture televiewer displays.

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S PE 14261

Kenneth W. G riffin

3

r eal advantage of thi s t ool I s that I t produces a

di rect record of the physi cal f eatures of the

borehol e wal l . The tool i s r un on el ect ri c l i ne at

a very sl ow speed ( 5 f t/ m n; . 03m s) across t he

openhol e i nterval and I s ori ented using a magnetfc

compass whi ch emts a si gnal each ti me the trans-

ducer rotates past magnet ic north. Other di rec-

4. 4 l m. -A +hn. 4. +, . . -. . . 1+. . As. . - . . .&. . - . . . -l . +— . i +&- . &

urufJ =arc I , I I =l I l vciuIa Lcu I

r cm brveae II II,9SIIIII LL9SIIL

si gnal s.

TRI AXI AL BOREHOLE SEI SMOMETER: 14- 16 The

trl axl al borehol e sei smometer, descri bed byT. L.

Dobecki 15, contatns three ”orthogonal l y mounted

sei smc detectors. I t i s l owered Into the borehol e

on a seven-conductor el ectrl c l i ne and i s hydraul -

i cal l y cl amped I nto pl ace I n the open hol e i nterval

or near the per forat i ons i n a cased wel l .

I t i s

ori ented usi ng a coaxi al l y mounted gyroscope.

Fracturi ng fl ui d i s pumped past the anchored tool ,

thus creati ng the fracture. The surface equi pment

i s t hen shut down and i sol at ed f rom the wel l .

Dur i ng the moni t or i ng per i od, sei smc signal s

generated from the fracture face are recei ved by

the sei smometer. The orthogonal confi gurati on of

t he det ect ors al l ows t he sei sm c si gnal s to be

sorted i nto compressi onal and shear events, and

t he compressi onal event s can be ori ented to

determ ne the di recti on of thei r source ( the

f racture face) w th respect to the tool .

HELLBORE ELLI PTICI TY MEASUREMENTS: 5*6S17-19

- rL- z- .... - . .— –_. . – - . .

.. . &L.

Ine Tour-arm cai lper on Lne gyroscopfc dipmeter

tool i s used to determ ne the maj or and m nor

measured axes of the borehol e on a foot-by-foot

basi s. Examnat ion of thi s data stat i st i cal l y for

an ent i re zone al lows est imat ion of the overal l

bor ehol e axes of el l i pt i ci t y. Al t hough dr i l l ed

w th a r ound bi t , i n t he pr esence of hor i zont al

st ress di f f erences the borehol e spans or wears

i nt o an el l i pt i cal shape. The maj or axi s of t hi s

el l l pse w l l be I n the dl rectl on of mni mum

hori zontal stress, and, therefore, perpendi cul ar to

t he di r ecti on of predi ct ed I nduced f ract ure

propagati on.

ON-SI TE STRAI N RELAXATI ON: 20- 22 Hori zontal

strai ns are measured on a pi ece of freshl y-pul l ed

or iented core using three pai r s of t ransducers

mounted on a si ngl e ri gi d ri ng and equal l y spaced

around the di ameter of the core.

Thi s core sampl e

shoul d be taken from the bottomof the core barrel

and i s gener al l y avai l abl e 4- 6 hours af ter i t I s

cut.

I t 1s w ped cl ean and I nmedl atel y mounted i n

the strai n rel axati on apparatus i n a temperature

stabl e envi ronment.

The st rai n response of the

core i s moni tored unt i l the next sample i s ready

for testi ng (6 to 8 hours) or unti l the strai n

response has ended.

The ef fects of mnor temp-

erature changes on the transducers are accounted

for , al though by the the the cores are recovered

they have cool ed to near roomtemperature and the

strai n rel axati on I s assumed to be i sothermal , The

effects of dehydrati on on the core are assumed to

be nondi recti onal and to have l i tt l e i mpact on the

f i nal resul ts.

From the strai n data, the i nter -

pol ated di recti ons of maxi mum and mni mum strai n

can be determned.

Based on the mcrocrack model , -

t he di r ect i on of maximum st rai n pr edi ct s t he

di recti on of maxi mum i n-situ stress, and, hence,

the di recti on of fr acture propagati on.

DI FFERENTIAL STRAI N ANALYSI S (DSA) : 23- 26 “DSA

requi res repressur ing a sampl e of or iented core

wel l above I ts ori gi nal pressure and then recordi ng

the ori ented strai n data as the pressure I s

gradual l y rel eased. Thi s techni que was i ntroduced

in the l i t er ature by St ri ckl and and Ren.23 The

ef fects of mcrocracks on rel axat ion data can be

. 3 -A,e. - J

l oenzl Tl ea, and the dt~e~ti ~n Of the Cwoi l fi dXiS Gf

maxi mum stratn, maxi mum i n-si tu stress, and

predi cted f racture propagati on determned.

SONIC

VELOCI TY ANALYSI S: 27 Soni c vel oclt y

anal ysi s Invol ves determni ng the soni c vel oci ty

across several di ameters of a sampl e of or iented

core. Soni c compressi onal waves w l l experi ence

maxi mum scatteri ng, attenuati on, and sl ow ng of the

si gnal perpendi cul ar to the predoi ni nant ori entati on

of mcr ocr acks i n t he core.

The l east amount of

di st ur bance I n t he si gnal w l l occur par al l el t o

the or ientat ion of mcrocracks. Thus, the or ien-

tati on of mnimum soni c compressl onal wave vel ocl ty

corresponds to the di rect ion of maxi mum i n-si tu

stress and predi cted i nduced fr acture ori entati on.

FAULT AND STRUCTURAL MAPPI NG: 9 Compari son of

faul t data w th fracture ori entati on data provi des

an esti mati on of the Impact of faul ti ng on fracture

ori entati on.

I t al so al l ows one to est imate the

amount of vari ati on I n the hori zontal stress fi el ds

between the ti me of faul t i ng and today. Overl ays

of f racture or ientat ion data w th f i el d maps hel p

correi ate structure

w th

current preferred

f r acture or i entat i ons. ( Fi gs. 7, 8, 9) .

KUPARUKUELL2G-07 TESTIN6:

Seven fracture ori entati on determnati on and

predi ct i on techni ques were compared i n testi ng

conducted In thi s wel l bore or on core sampl es or

l og data taken from thi s wel l . The procedure for

the wel l work fol l ows, whi l e the testi ng procedures

Inmost cases are onl y bri ef l y descri bed. In these

cases the testi ng fol l owed procedures outl i ned i n

the references.

Procedure:

Each of the above techniques was tested in

Kuparuk Wel l 2G- 07.

The sequence of events i s as

fol l ows:

1. The wel l was dri l l ed through the l ower Kuparuk

Sand and casi ng was set at the top of the

l ower Kuparuk Sand.

2. A core was taken through the l ower Kuparuk A

Sand. Thi s core was or i ented at f i ve- f oot

Interval s usi ng a gyroscope. Onsi te st rai n

/ - - -

r el axat i on, di f f er ent i al st rai n, and soni c

vel oci ty measurements were taken on three

samples f r om the cores. As onl y one set of

onsl t e st rai n

rel axati on equi pment was

avai l abl e, onl y one sample per cor i ng run

coul d be tested.

3. Openhol e l ogs, i ncludl ng a four-armdi pmeter,

wer e r un across t he 140 f t ( 43m openhol e

i nterval f rom TD to the casi ng shoe. The

di pmeter cal i per data was processed to deter-

mne the axes of wel l bore el l i pt i ci ty.

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4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

Forty barrel s of 10. 3 ppg

(1.23

g/ cm3) NaC1-Br

bri ne were spotted over the openhol e i nterval

and the borehol e acousti c tel evl ewer was run

across the openhol e I nterval .

Fi ve expandi ng rubber seal i mpressi on packers

were run and set i n the openhol e sand. The

packer assembl y was ori ented usi ng a gyroscope

and sett i ng prof i l e. The packers were set w th

a di f ferenti al pressure of 1000 PSI (6.9 MPa)

for 30 mnutes. The packers were then

rel eased and pul l ed out of the hol e.

A f racture st ri ng was run In the hole and the

packer set near the casing shoe. The openhol e

sand I nterval was broken-down w th 3000 gal s

, . .

{11. 4 i i i ~j of 2% KCI water pl us f rtcti on

reduci ng agent.

The trl axl al borehol e sei smometer was run i n

the hol e on el ect r i c l ine and clamped to the

formati on face. The sei smometer was ori ented

usi ng a gyroscope.

Downhol e sel smcs were

then moni tored f or 30 mnutes. On each

sei smometer run, wei ghts attached to the tool

were requi red to start the sei smometer and

el ectri c l i ne fal l l ng downhol e.

An unpropped hydraul i c f racture was then

pumped I n three stages, each fol l owed by a 30

mnut e per i od I n whi ch f ormat i on sei smc

responses were moni tored. The pump schedul e

i s out l i ned in Tabi e i .

Aft er pul l i ng the sei smometer and the fr acture

str i ng out of the hol e, the borehol e acousti c

televlewer was rerun. The gel l ed f racture

f l ui d squel ched the si gnal such that no

useabl e data coul d be gathered.

Dri l l pi pe was rerun, and the openhol e

i nterval was reamed, washed, and condl tl oned,

A NaC1-Br pi l l was spot ted In the openhole

i nter val and the dr i l l pi pe pul l ed out of the

hol e.

The borehol e acousti c tel evi ewer was rerun but

squel chi ng of the soni c si gnal st i l l rendered

the data usel ess.

Dri l l pi pe was rerun and the openhol e I nterval

was agai n r eamed and condi t i oned, and a

NaC1- Br pi l l was spot ted i n t he openhol e

I nterval .

The borehol e acoust i c t el evl ewer was run

across the openhol e Interval usi ng both l ow

and hi gh frequency si gnal s.

The tool was

ori ented usi ng a magneti c compass.

Our expandi ng rubber seal I mpressi on packers

were run and set I n the openhol e sand. The

- - - 1- - - - - - -—L1. .. . - . . 4- L. J

. . . .—

paGKer- assemuly was orl en~ea usi ng a gyroscope

and sett i ng prof i l e. The packers were set w th

a di f ferent ial pressure of 500 PSI (3.5 MPa)

f or 15 mnut es.

The packer s were then

rel eased and pul l ed out of the hol e.

OTHERKUPAIW UELLTESTIN6:

I n f ur ther t est i ng,

seven on- si t e st rai n

rel axati on measurements were taken I n Kuparuk Wel l

l L-07 duri ng ori ented cori ng operati ons. DSA and

soni c vel ocl ty measurements were al so run on the

same sampl es, and wel l bore el l l pti cl ty measurements

were made fromf our- arm di pmeter cal l per data.

Kuparuk Wel l 2F-01 was dr i l l ed, cased, and

compl eted In the Kuparuk A Sand. The sand was

broken down w th sl l ck water, and borehol e sei smc

surveys were run pri or and subsequent to pumpi ng an

unpropped hydraul i c f racture.

Wel l bore el l l pti clt y

cal cul at i ons were al so made on cal l per data f rom

thi s wel l .

FTFllWI1’lF -F Iti AMl CJMWT MTA.

. .-—.”. —..,

.- m. B-L, -mm.

Fl el dw de data was generated from DSA and

soni c vel ocit y measurements on 13 Kuparuk A Sand

ori ented core sampl es, and fromwel l bore el l i ptl -

ci ty measurements of both the A and the C Sand from

15 Kuparuk four-armcal i per data tapes. Thi s data

was revi ewed and compared w th the above test data

and w th faul t and structural mappi ng.

OISCUS WM:

WELL 2G-07, PREFRACTURE DATA: The prefracture

A. ’ -

zel evfewer run provi ded basei l ne data about the

ori gi nal borehol e wal l condi t i ons ( Fi g. 2) .

Al though no ori entati on data was gathered due to a

m14, ,. . . . . +4. . . .f i

 

l . -

Vllal I UT (,L lull

Lrlt

------- . L _

cumpass,

- .--m . A

r. ne prerracrure

tel evi ewer run reveal ed a smooth, round borehol e

w th onl , ymnor vugs and rough spots. A natural

fracture zone was I denti f i ed j ust bel aw the casi ng

shoe and the t racks produced by the openhol e

i oggi ng runs were vi si bl e.

I t was possi bl e t o

ori ent thi s data vi sual l y w th respect to the

post f racture tel evl ewer data usi ng the l oggi ng

tool tracks vi si bl e In each.

The pref racture i mpressi on packer run provi ded

I mportant I nformati on about the perf ormance of the

packers under our condi t i ons.

The t op f our

I mpressI on packers were compl etel y torn up, w th

most of the rubber removed from the el ements. ARCO

personnel determned that the recmnnended setti ng

t ime and pressure di f ferent i al were too hi gh for

these tool s and deci ded to reduce both by one-hal f

when runni ng the post fr acture I mpressI on packers.

The

hntt,.wm I&4&4hI

4...- . . . ...-4--

Wvtibw:ll (1 Il&llj

---,--- ---- -.

IIIIpIe>SIUII pacawm was pl ugged

w th mud and f ormat i on sol i ds,

and dl d not

i nfl ate.

The sei smometer was run af ter the Ini t i al

formati on breakdown because expected Ini t i al

breakdown pressures were at the fai l ure l l mt of

the seal s In the tool .

The pref racture sei smometer

survey dl d not begi n unti l 4 hours af ter the

concl usi on

of the breakdown.

No sel smc si gnal s

were recei ved from the formati on, veri fyi ng that

the f r~~t~re h~~ alvaariw haalarl

-,, W“”J ,,SZU,=”.

WELL 2G-07, POST FRACTURE DATA: The post

fracture data al l produced rel ati vel y consi stent

resul ts.

The post fracture sei smometer survey

reveal ed a fracture extendi ng at an ori entati on of

28+/ - 7°.

The useful sei smc responses were al l

col l ected duri ng the fi rst post fracture moni tori ng

peri od. No useabl e data was col l ected af ter the

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5

second and thi rd stages apparentl y because erosi on

of the format ion around the sei smometer cl amp

l oosened the tool , squel chi ng the formati on sei smc

- . - - . 1 I - L. J . A.

si gnal .

m . –—&L. e, . - L

Ine aa~a Trom c.neTl rsL post f racture

moni t or i ng per i od ( Tabl e I I ) consi st ed of 125

event s. Of these, 37 were unusabl e because of

excessi ve noi se, weak si gnal , or poor cl ampl ng

ef fects (quest ionabl e tool or lentat lon) . Forty-

three si gnal s had i denti f i abl e compressl onal and

shear wave phase components, and 45 were of onl y a

si ngl e, unknown phase.

The or i entat i on of the

I nduced f r acture was cl ear l y I dent l f l ed by the

two-phase si gnal s as 28+/ -7”, and thi s ori entati on

was rei nforced by the si ngl e phase data as seen i n

the rose di agrams (Fi g. 3).

The t el evi ewer run I ndi cated an errat i c

f r acture extending f r om the casi ng shoe to the

bottom of the hol e,

extendi ng through both si des

of t he bor ehol e ( Fi g. 2) . The crack dl d not pass

through the center of the borehole, but rather

I ntersected the borehol e wal l roughl yat NOE and

S30W The overal l fracture azimuth I s 15+/ -10°. The

tel evl ewer al so reveal ed that the faul t i ndi cated

i n the prefr acture data had undergone considerabl e

erosi on. The st ri ke of t hi s f aul t i s 16” at a di p

angl e of 25° f rom vert i cal . The post f ract ure

travei t i me dl spi ay al so i ndi cates sl i ght wel l bore

el l i pt i ci t y w th t he mnor axi s, whi ch t heoret i -

cal l y corresponds to predi cted f racture or ient -

ati on, ori ented at 14+/ -15°. Substanti al spal l i ng

of the formati on I s apparent i n the deeper openhol e

i nterval s. I t probabl y i s due to the two per iods of

ci rcul ati on before the data was taken, and shoul d

occur pri mari l y i n the di recti on of mni mum

hori zontal stress,

perpendi cul ar to the i nduced

f racture.

The or i entat i on of the spal l l ng i s 82

+/ -25°, whi ch suggests an ori entati on of 172 +/ -25°

for the maj or hor izontal stress. The two per iods

of ci rcul ati on were necessary to cl ear the wel l bore

of t he gel used i n t he f ract ur i ng f l ui d. Thi s gel

absorbed the soni c si gnal and rendered the tel e-

vi ewer usel ess unti l the bottomof the wel l bore was

cl eaned out and gel l ed f l ui ds had stopped l eaki ng

f rom the f ract ur e .

Af ter a cl ean br ine pi l l was

spotted and the fl ow fromthe fr acture had stopped,

the avai l abl e post f racture tel evi ewer data was

obtai ned.

The tel evi ewer compass worked properl y

and good ori entati on data was obtai ned al ong w th

the soni c di spl ay.

The post f ract ur e Impr essi on packer run

produced i mpressi ons of the fracture on the bottom

two packers.

The i mpression produced when the

rubber seal i nf l at ed i nt o t he l i p of one or both

edges ~f the ~r~~k {c u4cihla

illt,e4-a+&4 4.,

the l i ne draw ngs (~g~’ ~~’ ”\~~s~s~~p~~~CYo~~

general l y match the correspondi ng tel evi ewer data,

al though defl ati on of the packers made the match

di f f i cul t t o do.

No equi pment was avai l abl e w th

whi ch to rei nf l at e the packer s.

The fracture

i mpressions run general l y al ong an azi muth of

8+/ - 20°.

On-si te strai n rel axat i on data col l ected on

three core sampl es predi cted fracture azimuths of

36+/ -4°$ 22+/ -2° , and

115+/ -~0 (Tabl e ). The

f i rst two sampl es match the other data col l ected,

both w th respect to the st ress f iel d or ientat ion

and w t h respect to the verti cal vari abi l i t y i n

t hi s f i el d t hrough t he sand i nt erval . The t hi r d

sample, t he shal i est of the three, predi ct ed an

azimuth al most perpendi cul ar to the actual ori en-

tati on of fracturi ng.

The cal i per data i n thi s wel l i ndi cated very

l i t tl e wel l bore el l i pt i ci t y. At no poi nt di d t he

recorded val ues exceed . 1 i nch - - the l i m t of

resol uti on for the cal i per tool . Neverthel ess, the

stat i st i cal l y di str ibuted data (Fi g. 5) i ndi cated

a pref er red axi s of el l i pt i ci t y at an azimuth of

110 ./-20°.

The maxi mum hori zontal stress, and

prefer red or ientat ion of i nduced f ractur ing,

theref ore i s predi ct ed to l i e at an azimuth of 20

+/ - 20” .

Whi l e of poor qual i t y, t hi s dat a rei n-

f orces the resul t s of t he other t est i ng on thi s

wel l . The mni mal wel l bore el l i pt i ci ty recorded by

the cal i per data probabl y i s due to the f act that

the wel l was not dr i l l ed past the base of the sand.

I n al l other cases at l east 200 to400 addi t i onal

feet of hol e were dri l l ed.

WELL l L-07; ON-SI TE STRAI N RELAXATI ON DATA:

Three ori ented A Sand core sampl es were tested for

strai n rel axat ion (Tabl e IV). Al l of the sampl es

are thi n, very shal y sands i nterbedded w th shal e

stri ngers. On-si te strai n rel axati on data predi cts

st ress f i el d or i entat i ons i n the A Sand roughl y

perpendi cul ar to those predi cted by wel l bore

el l i pti ci ty, DSA, and soni c vel oci ty measurements;

and al so perpendicular to st ress or ientat ions

predi cted by faul t mappi ng.

WELL 2F-O1; TRI AXI AL BOREHOLE SEI SMC DATA:

Sei smc responses provi ded ori entabl e data duri ng

two moni t ori ng peri ods; the f i rst, af ter the

i ni ti al breakdown of the formati on before the tool

was run i n the hol e and cl amped near the perfora-

t ions; and the second,

af ter the f i r st pump- i n

peri od (Tabl e V). Duri ng subsequent moni tori ng

peri ods the sei smc tool came uncl amped fromthe

casi ng wal l and rotated f reel y. No meaningful

ori entati on data was gathered duri ng these peri ods.

Ten si ngl e-phase events were recorded after the

i ni ti al breakdown.

Fi ve two- phase events, f ol l owed

by 15 si ngl e-phase events and a f i nal two-phase

event, were recorded after the fi rst pump-i n stage.

TL- r. . - –A

tne TracLure azimuth was determned to be 44. / -8°

(Fi g. 6) whi ch compares wel l w th that determned

from the sei smometer survey i n Wel l 2G-07 (offset

wel l s, 1. 5 m l es (2. 4 km apart) , and w th that

determned fr om wel l bore el l i pti ci ty measurements

i n Wel l 2F-01.

Thi s ori entati on i s perpendi cul ar

t o that predi ct ed f rom DSA and soni c vel oci t y

measurements.

Al l of the anomol ous sei smc si gnal s

i n the wel l 2F-Oi data were ori ented essenti al l y

perpendi cul ar to thi s ori entati ~n.

FIELDWIDERATACOLLECTI(MM EVALUATION:

Dat a f rom 12 Kupar uk wel l s, i n whi ch t he wel l

devi ati on i s j udged not to have al t ered- the

wel l bore el l i pti ci ty, was eval uated (Tabl es VI and

... . . - . - -

Vl l ).

ul t terenti ai st rai n and soni c vel oci t y

analyses were per formed on 12 Kuparuk A Sand

sampl es from ei ght Kuparuk wel l s (Tabl e VI I) . Al l

of thi s data was eval uated and compared w th the

resul ts of the si ngl e-wel l bore tests and w th faul t

mappi ng.

Resul ts fromeach of the f i el dw de tests

are mapped on a Kuparuk structure and faul t map i n

Fi gs. 7, 8, and 9.

Overal l , t he dat a poi nt s i n

each wel l bore compare wel l w t h each ot her,

al though some di screpancies do exi st parti cul arl y

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between the wel l bore el l i ptl cl ty data and the core

sample measurements.

These seemo be primari l y

due to weak stress fi el d ori entati ons I n some areas

of the f i el d whi ch resul t I n varyi ng test r esul t s

depending on the par ti cul ar proper ti es of the

sampl e and the actual property measured by each

test , upon the aval l abl l l ty of a nonshal y sect ion

i n the core on whi ch to run the test, and upon

whether the test measures data fr cma singl e sampl e

or data averaged across the i nterval .

General l y,

the fracture ori entati ons run i n northeasterl y-

southwesterl y di recti ons, al though the i nfl uence of

nearby faul t i ng i s apparent i n several cases. In

wel l s WS-15 and WS-18, whi ch l i e al ong the per i -

phery of the fi el d, the predi cted I nduced fracture

ori entati ons are perpendi cul ar to the contours of

the structure.

EVALUATION OF TESTING TECHNIQUE PERFORMANCEMI

RELM61LITY:

1.

2.

The borehol e acoustic tel evi ewer produces

very cl ear , detai l ed representat ions of the

borehol e wal l s.

I t not onl y i dent i f i es t he

presence and ori entati on of fractures, vugs,

and other features;

but al so reveal s the

i r regul ari t y of t he f ract ure f ace where i t

i ntersects the borehol e. The tel evi ewer can

al so be used to i nfer fracture ori entati on by

determni ng the major axi s of el l i pt i ci ty as

wel l as the main axi s of wel l bore spal l i ng.

The wel l bore spal l i ng features, especi al l y,

provi de a consi stent f racture or ientat ion

i nterpretati on whi ch coi nci des w th actual

fracture ori entati on determned i n thi s wel l .

I t s use i s l i mted to uncased i nterval s and i t

requi res a cl ear , sol i ds- f ree f l ui d,

such as

a heavy br i ne, as

the borehol e medi um i n

order to produce a cl ear soni c pi cture.

The tr iaxl al borehol e sei smometer . whi ch

di rectl y measures the sei smc di sturbances

emanati ng from the fracture face, produces

the most rel i abl e and precise measurement of

I nduced f racture ori entati on.

The tool may be

ori ented usi ng ei ther an attached gyroscope or

an ori ented surface di sturbance.

Whi l e

proppant cannot be safel y pumped w th the tool

and el ect ri c l i ne i n t he hol e, t hi s t ool can

be run as part of an expanded pre-fracturi ng

breakdown and pump- i n sequence at a reasonabl e

cost. Onl y smal l vol umes of f l ui d of ungel l ed

f l ui d are requi red to produce substant ial

sei smc responses i n medi um porosi t sand-

stones.

In thi s work, vol umes of .75 bbl / f t

(. 39 m3/ m of openhol e i nterval were adequate

to produce clear, frequent, ori entabl e sei smc

di sturbances for a 20 to 30 mnute peri od, The

sl i mhol e tool whi ch was used i n thi s work due

to tubi ng restr ict ions i mposed some severe

pressure l i mtati ons on our operati on. Al so,

the sl l mhol e tool coul d not generate enough

force i n the cl ampi ng armto securel y anchor

the wei ghted tool str ing to the casi ng wal l s

i n the 2F-1 test. Whether used i n openhol e or

casi ng, car e shoul d be t aken t o r eset and

ensure a good cl amp before each pump- i n. I t

was unnecessary to use gel i n the fracturi ng–

f l ui d; i n f act , t he gel ser ved to squel ch the

sei smc si gnal s rather than extend the acti ve

peri od.

3.

4.

5.

, /

The onsi te strai n rel axati on measurements

seemed to produce defi ni te ori ented stress-

strai n responses. The techni que works best i n

cl eaner, homogeneous sand sampl es.

I n Wel l

2G-07 the resul ts compared favorabl y w th

other techni ques.

In Wel l l L-07, the onsl te

strai n rel axati on measurements were 60° to 90°

di f ferent from those predi cted by wel l bore

el l i pt ic i ty, soni c vel oci ty and di f ferent ial

~tr aj ~

rn~~stlrtamentc. ~n~ by fault

manning,-, . .... .. . . .

. .-rr

The sands in thi s wel l are heavi l y lamnated

and shal y.

The wde var i at i on i n data f rom

thi s wel l suggest s t hat t he st ress f i el d i n

thi s wel l i s rather weak, and that rock

heterogenei ti es domnated or i nfl uenced many

of the measurements.

Impressi on packers can be used to obtai n an

est imate of f racture or ientat ion and var i -

abi l i ty.

Equi pment shoul d be avai l abl e w th

which to reinf late the packers to borehole

di ameter bef ore taki ng photographs and

measurements.

Even w th a ser ies of packers

stacked together , si gni f i cant i nterval s of

i nf ormati on are l ost at each coupl i ng.

Tai l pi pe shoul d be run bel ow the bottompacker

to mni mze pl uggi ng of the bottompacker w th

bott omhol e sedi ments.

The prefracture

i mpressi on packer run was i mportant as a basi s

f rom whi ch to j udge the proper packer i n-

fl ati on parameters i n the post fracture run.

ARCO determned that under our condi ti ons (Pr

= 3000 psig; 20.7 MPa, Tr=160”F; 71”C) , a

15 mnut e i nf l at i on peri od at 500 psi ( 3. 45

MPa) pressure di f ferenti al was adequate to

obtai n cl ear i mpressi ons w thout damagi ng the

packer rubber. Al so we found that i t i s

i mportant to ensure that the packers are not

i nf l at ed across l arge vugs or washout s,

because the steel l eaves w l l l ock i n the

over inf lated posi t ion resul t i ng in a badly

damaged packer when the stri ng I s pul l ed out

of the hol e.

Wel l bore el l i pti ci ty measurements provi de very

useful predi ct ions of In si tu stress f i el d and

I nduced fracture ori entati ons.

The maj or

f actor s af f ect i ng the qual i t y of wel l bore

el l i pt i ci ty measurements are the wel l bore

I ncl i nati on through the zone of Interest and

the degree of spa?l i ng seen.

Wel l bore

el l i pt i ci t i es ar e i nf l uenced by wel l bor e

devi ati ons of 10° or more fromvertical i n the

: : : a; : ; i ; ; %r ; : ; : ; ; : : r~: ;h: :~: :~;

t i ons much l ess than thi s i nf l uence wel l bore

el l i pti ci t i es i n shal l ower zones, and no

i mpact of l i mted devi ati ons has been seen i n

some deeper, harder zones.

Spal l i ng whi ch resul t s i n el l i pt i ci t i es of

l ess than . 2 i n. ( . 5 mm i s of ten due to

factors other than st ress f ield or ientat ion

and shoul d be negl ected i f possi bl e, part i -

cul ar l y I f i t di sagrees w th data f rom l arger

scal e spal l i ng i n the same i nterval .

I f data

f rom smal l - scal e spal l i ng i s used to predi ct

fracture ori entati on, i t shoul d be compared

careful l y w th structure and faul t mappi ng and

any other avai l abl e data to determne whether

the i nterpretati on of the wel l bore el l i pti ci ty

8/9/2019 29. SPE-14261-MS

13/16

S P E 14261

Kenneth W. G riffin

7

6.

data I s reasonabl e. The mnor eccentr lc l t l es

i n many cases seem t o ref l ect the stress

ori entati on of the formati on and coi nci de w th

the or i ent at i on of t he l ar ge- scal e el l l pt l -

cltl es.

In other

cases they seemo resul t

fr om the I nhomogenei tl es I n the rock materi al

I t sel f and are or i ented at obl l que angl es to

the large- scal e el l l pt i cl t l es. They seemto

r ef l ect t he mnor st ress axi s I n many cases

and are ori ented perpendi cul ar to the l arger-

scal e el l l pti c lty val ues.

I n every case where

smal l -scal e wel l bore eccentr i ci ty does not

coi nci de w th the l arge-scal e spal l i ng, data

generated

rom t he l arge- scal e spal l l ng

matches other stress f i el d or l entatton data

f rom the wel lbore or nearby wel l s .

It iS

evi dent that several factors coul d control the

or i entat i on of mnor wel l bore el l l pt l cl t i es

i ncl udl ng; the stress f i el d i tsel f , rock

I nhomogenel tl es, and a mnor stress axi s.

Foot-by-f oot data for the Interval shoul d be

sorted by magni tude of the eccentr lc l ty, and

the smal l er eccent ri ci t y values deleted to

determne the maj or wel l bore el l i pti ci ty axi s.

The l ower cutoff for useabl e wel l bore el l l pti -

cl t y dat a i s general l y about . 2 f n. ( . 5 i nn) ,

al though I t I s dependent on the actual

,

A- - - - - - 1- - I . . - - A. . .4..*1l4m”

erosi onal stresses ImJUUW w w I I I Irly as we?]

as upon the formati on rock properti es, and i s

best determned f or each set of data by

I nspectI on.

Fact or s such as bi t wei ght ,

ci rcul ati on

vel oci t i es and vi scosi t i es,

ci r cul at i on t imes, and l engt h of t ime t he

i nterval I s open dur ing subsequent dr i l l i ng

operati ons I mpact the degree of spal l i ng seen,

and affect the el l l pt i cl ty cutoff used on each

~~~ of ~~~~:

I n Wel l 2G-07, because t he

f ormat i on was cored and no rathol e was

dr i l l ed, the borehol e wal l was rel at i vel y un-

di st ur bed and onl y smal l - scal e wel l bor e

eccentri ci t i es were created.

In

thi s case,

the smal l -scal e wel l bore eccentri ci ty val ues

do predi ct the ori entati on of the maj or stress

as evi denced by compari son of the resul ts from

these measurements w th those from other

techni ques, especi al l y the wel l bore spal l l ng

data detect ed by the borehol e acousti c

tel evi ewer.

Each of the predi c ti ve test s (on-si t e st rai n

r el axat i on, wel l bor e el l l pt l cl t y, di f f er -

ent i al st rai n anal ysi s, and soni c vel oci t y

measurements) at tempt to Infer the i n-si tu

stress fi el d ori entati on from rock mechani cal

propert i es. For t hi s reason t hey ar e sus-

cept i bl e t o er ror s I nduced by r ock anl so-

tropl es, i ncl udi ng vugs, i ncl usi ons, secondary

f ractur ing and crumbl i ng, l amnat ions and

shal e vol umes. Thi s woul d be especi al l y true

i n areas w thout a strong stress ‘ fi el d

or ientat i on. One advantage of DSA and soni c

vel oci ty measurements over on-si te st rai n

rel axat i on i s that the techni ci an has a better

opportuni ty to sel ect a rel at ivel y nonshal y

sampl e f or t est i ng. I n wel l s such as l L- 07,

thi s sel ecti on coul d resul t i n superi or

or i ent at i on r esul t s usi ng t he l abor at or y

techni ques.

The qual i ty of wel l bore el l l pt l -

ci ty data seems to be pr i mar i l y dependent on

the degree of spal l i ng whi ch has occurred and

hol e angl e, r at her t han format i on anl so-

tropi cs.

7. On-si te st rai n rel axat ion, di f ferent ial st rai n

anal ysl s, and soni c vel oci t ies are l i mted by

the fact that the measurements are taken on

di screte sampl es.

Varl at l ons of st ress

ori entati on throughout the i nterval are thus

m ssed and can l ead to l arge errors I n the

overal l or ientat i on est i mates. Thi s probl em

I s probabl y si gni fi cant parti cul arl y I n shal y,

I nhomogenous and/ or faul ted i nterval s i n whi ch

the st ress f i eld or i entat i on I s fai r l y weak.

These measurements must be taken i n cl ean,

homogeneous sampl es to be representatl ve.

8. Al l of t he t echni ques whi ch depend on

 or

anal yses have a maj or l i mtati on i n the

Kuparuk Ri ver Reservoi r.

I t i s of ten very

dl f f fcul t to cut an unbroken core. The bi t

of ten j ams and breaks the core repeatedl y

duri ng a si ngl e run.

Thi s seems to be more of

a problem In the heavi l y l amnated areas of

t he f i el d and pr obabl y I s due t o t he di f f er -

ences between mechani cal propert ies In the

shal e and in the sand lamnae.

The spi nni ng

of t he cor e bar rel , whi ch r esul t s, makes i t

~~=~+f i l l l +f i f tf i n+n palate ~~fl~~~~~~on ~~~v~y~

u I 1 ILU I L. v e=} *V r =.” .-

to scr i be l l nes on a sampl e taken several feet

f rom the survey. Thus the or ientat ion of the

core sampl e for many sections of the core may

be unknown or i n questi on. Care must be taken

when sel ecti ng sampl es I n the f i el d f or

test ing, that good or ientat ion data for that

core sampl e w l l be avai l abl e.

COMCLUSI.14S:

1:

2.

Local st ress f i el d or ientat ions and Induced

fracture ori entati on vary across the Kuparuk

Ri ver Fi el d, al t hough the gener al t rend i s

north-south.

These var i at i ons appear to be

largel y due to the Inf l uence of two di s ti nct

st ress f i el ds and thei r r el at ed f aul t l ng. I n

some areas (Wel l s WS- 15 and WS-18) al ong the

peri phery of the sand, the preferred fracture

or i ent at i on seems al so t o be normal t o t he

contours of the structure.

The st ress f i el d In the Kuparuk Ri ver Reser -

voi r does not seemto be strongl y or iented i n

many areas, probabl y due to the stress rel l ef

provi ded by the extensi ve faul tl ng whi ch has

occurred, and al so to the shal y nature of many

areas of the reservoi r .

Thi s i s evi denced by

the extremel y uneven tel evl ewer traces of the

fracture In Hel l 2G-07, by thew ci el y varyi ng

resul ts of on-si te st ress rel axat ion test ing

I n Wel l l L- 07, and by t he w de vari ati on i n

stress ori entati ons determned from fl el dw de

wel l bore el l l ptl cl ti es, DSA measurements, and

soni c vel ocl ty measurements. I t i s obvi ous

that such factors as nearby faul t l ng and rock

I nhomogenel tl es easi l y al ter l ocal stress and

f ract ure ori ent at i ons. Because of t he i n-

el asti c nature of shal e, the hi gh shal e vol ume

and hi gh degree of shal e l amnat ion found i n

many areas l i kel y served to rel l eve much of

the di recti onal stress whi ch may have exi sted

at one t ime.

I n such cases, reservoi r

8/9/2019 29. SPE-14261-MS

14/16

R

TNTIU(WJI

FRACTURE ORIENTATION DETERMINATION IN THE KUPARUK RESERVOIR

SPE 1426

-..-.-—-

_-—-_——-—

Inhomogenei t l es woul d l i kel y domnate and

al t er the resul t s of wel l bore f ace or core

sampl e measurements.

3. Any of the di scussed techni ques can be used to

aetermne fracture cm~fi tst cm i ii nai l yasca.

. . . . a...-,.

The borehol e sei smometer I s the most versati l e

and def i ni t i ve of the techni ques used. A tool

must be used whi ch can be run through dr i l l

pi pe or tubi ng, can w thstand the frac@rin9

pressures used, and whi ch can anchor i tsel f

fiwmlv to ~h~ racina or wel l bore wal l . The

, , . . . , <

- -- . . . =

on- si t e st rai n rel axat i on, DSA, and soni c

vel oci ty measurements requi re non-shal y

homogeneous sampl es and mul ti pl e sampl i ng to

ensure qual i ty resul ts.

I n addi ti on the core

- . . - + I . -

----S..1 1./ aw+-n+.d wham it ic txiknn

Illu>l. Ue Gal c1 u I ly VI IClll,=u Wl,=rl I* l-. .?”.. -...

Wel l bore el . l i pt i ci ty measurements, when

rel ati vel y l arge-scal e spal l i ng occurs, al so

can provi de good esti mates of i nduced fr acture

ori entati on. Whi l e the borehol e tel evi ewer

provi des a detai l ed di spl ay of the borehol e

wal l , bot h i t and t he impressi on packer s

requi re an openhol e envi ronment. The expense

of thi s type of work i s general l y prohi bi t i ve.

REFERENCES:

1.

2.

3.

4.

5.

6.

7.

Hubert, M K. and Wl l i s, O. , Mechani cs of

Hydraul i c Fracturi ng, Trans. AIML, 20,

153- 168, 1957.

Warpi nskl , N. R. , Branagan, P. and Whner, R. , -

I n Si tu Stress Measurements atDOE’ s Mul ti -

wel l Experi ment Si te, Mesaverde Group,

Ri fl eL

Col orado, SPE 12142, presented at the 58th

Annual SPE Meeti ng, San Franci sco, CA, Oct.

5-8, 1983.

Hardw ck, P. and Carmas, G. R. Geol ogy

of the

Kuparuk Ri ver Oi l Fi el d, Al aska. Annual

AAPG-SEPMEMO-OPA Conventi on, Cal gary, Canada,

J une 27-30, 1982.

Teufel , L. W Predi cti on of Hydraul i c Fracture

Azi muth fromAnel asti c Str ai n Recover Measure-

ments of Ori ented Core, “Proceedi ng of 23rd

Symposi um on Rock Mechani cs:

Issues

i n Rock

Mechani cs”, Ed. by R. E. Goodman and F. F.

Hughs, p. 239, Soci ety of Mni ng Eng. of AIME,

New York, 1982.

Gough, O. I . and Bel l , J . S. , St ress Ori ent -

at i on f rom Borehol e Wal l Fractures w t h

Exampl es f rom Col orado, and Northern Canada,

“Can. J .

of Ear th Sciences (19) ,”

D.

1358,

1982. . . - .

~ro~, ~v. O., Forgotson, J . M and Forgotson,

b.

Drori+t-t+na ~h~ Q~j~n~~~l~n of

. . ““ . - “ . ..=

Hydr~~l i cal l y Created Fractures i n the Cotton

Val l ey Formati on of East Texas, 55th Annual

~

Dal l as,

exas, September

21-24, 1980. SPE 9269.

Sm th, M B. , t tohnan,G. B. , Fast , C. R. , and

Coul in, R. J .

The Azimuth of Oeep Penetrati ng

Fractures i n the Wattenburg F

i el d,

“J . of Pet .

~at.h

1 a7n

1--”’” {~~)”$ P. ~w~9 --J-.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

Teufel , L. W, Hart, C. M , Sattler, A. R.,

and Clark, J . A. Determnat ion of Hydraul i c

Fracture Azimuth by Geophysi cal , Geol ogi cal

and Ori ented Core Methods at the MWX Experi -

ment Si te,

Ri f l e, CO, 59th Annual SPL Tech-

nl ~al Conference, Houston, TX, September

16-19, 1984. SPE 13226.

Cl ark, J . A. The Predi ct i on of Hydraul i c

Fracture Azi muth through Geol ogi cal ,

Core, and

Analyti cal

Studi es, SPE

11611, SPE/ DOE

$ymposi um on Low Permeabi l i ty Gas Reservoi rs,

Oenver, CO, March, iS183.

Wley, Ralph, 1980, Borehole Tel eviewer -

Revi sited, Transactions, SPWLA 21st Annual

Loggi ng Symposium paPer HH.

Zemanek, J . , g& Q. , 1969, The Borehol e

Tel evi ewer: A New Logqi ng Concept f or

Fracture Locati on and Other Types of Borehol e

I nspecti on, J ournal of Petrol eumTechnol ogy,

Vol . 21, pp. 762-774.

Tayl or, T. J . I nterpretati on and Appl i cati on

of Borehol e Tel evi ewer Surveys, 24th Annual

sPi Ai Asyl l posi i i i n,une 27=30, 19830

Pasternak, E. S. ,

and Goodw l l ~ w“ p“ w

cat i ons of Oi qi t al Borehol e Tel evi ewer

24th Annual SPWLA Symposium J une

W

8/9/2019 29. SPE-14261-MS

15/16

.’

SPE 14261

Kenneth W. G riffin

9

21.

22.

23.

24.

25.

26.

27.

28.

Bl ant on. T. L. and Teuf el , L. W A Fi el d Test

of the- St rai n Recovery

Method of Stress

Oetermnatl on i n DevonI an Shai es, WE 12304,

nresented at the Eastern Regi onal SPE Meeti ng,

~h~pi on, PA, November 9- 11; 1983.

Teuf el , L. W

Determnati on of In Situ Stress

f romAnel astl c Str ai n Recovery Measurements of

Ori ented Core, SPE/ DOE 11649, SPE/ DOE Sym

posi umon Low Permeabl l l ty Reservoi rs, Denver,

CO, March, 1983.

St r i ckl and, F. and Ren, N. Predi ct ing the In

Si tu Stress for Deep Wel l s Usi ng the Dl f fer -

entl al Strai n Curve Anal ysi s, SPE 8954, 1980.

cs— - - Ca- - C. . , 4. . . A

>l l mnuns, G. , ait ylr Ieu, R.

u .*A

I=nwfic

n., Ullu I=V-a, .9

1974.

Ol f f erent lal St rain Analysl s : A New

Met hod f or Examni ng Cracks I n Rocks, J .

Geophys. Res. , Vol . 79, 4383-4385.

Seigf rl ed, R. , and s~~ns, G.> 1978” &C

acter lzat ion of Or iented Cracks w th Di f fer -

ent ial Strai n Anal ysi s, J . Geophys. Res. 83,

pp. 1269- 1278.

Ren, N. K. ,

and Rol egers, J . C. Di f ferent i al

Strai n Curve Anal ysi s - A New Method of

Determni ng

In-Si tu Stress State f rom Rock

Core Measurement s, I n Proc. 5th I nt . Sot .

Rock Mech. Congress, Mel bourne, Apri l , 1983.

, ----

LdLY, ~. ~.

P---.,4.,.m .-.4rwSe+i,wa nm4mmt-

bumpar ISull ul I I aebur= VI I II –

atl on Techni ques, 59th Annual SPE Techni cal

Conference and Exhl bl tl on, Houston, Texas,

September 16- 19, 1984. SPE 13225

Evans, K. On t he Devel opment of Shal l ow

Hydraul l c Fractures as Vi ewed through the

Surf ace Deformati on Fi el d: Part I - Pri nci pl es,

J . Pet . Tech. , p. 406 (Feb. 21, 1983) .

29.

30.

31.

99

ac.

33.

34.

Evans, K.

and Hol zhauser, G.

On the Devel op-

ment of Shal l ow Hydraul i c Fractures as Vi ewed

AL-- . . *L &k. -.

C.,v. ...e

a+nnnat lnn F~~i~~ Part

vnruuyn I, It C aur I uec &=IV . . . . ..-...o.

II-Case Hi stori es, J .

Pet. Tech., P. 411

(Feb. , 1983).

Ci nco- Ley, H. , and Samanl e90~ V“ ‘“ -

mnatl on of the Ori entati on of a Fl nl te

Conductl vl ty Verti cal Fracture by Transi ent

Pressure Anal ysi s, SPE 6750 presented at the

J a- - . . -

52m ~nnudl F~ii “--+’m”

13fi.”av. f’nlnradn.

I-lccullly, U=IIV=J * v-.”, --->

1977.

Ekl es, S. , Hadlnoto, N. , and Raghavan, R.

Pul se-Testi ng of Verti cal l y Fractured Wel l s,

SPE 6751 presented at the 52nd Annual Fal l

Meetlna. Denver. CO,1977.

--- - ..=, ---- - ,

Ila

D ”h . ...*

ura eb, A. , mJyIIaVaIIS

R.,

~~~ Thcwnne C U

,I,u ,lua, “. “.

Determnati on of the Ori entati on of a Verti cal

Fracture by I nterference Tests, J. Pet.

Tech.

(J an, 1977) 73- 80.

Kamal , M M

I nterf erence and Pul se Testi ng -

A Revi ew I nternati onal Petrol eumExhl bl tl on

~nl cal Synposl umof SPE, Bej l ng, Chi na,

March 18- 26, 1982, SPE 10042.

Dur fee, B. A.

Borehol e Geometr y of the West

Sak Sands -

A Method of Fracture Orl entatl on

Predl ctl on, ARCO Al aska I nternal Report, J ul y,

1984.

TABLE I

OPENHOLE FRACTURE PUMP SCHEDULE

... . . - - - --

WtLLL Zb-Ul

PUMPED ADDI TI VES

STAGE

VOLUME

TO WATER-BASE

(gal s)

FRAC. FLUI D

- . - - -

- - - - - -

- - - - - - - - - - -

1

4800

2%KC1 +

fl ui d l oss agent

2

1000O

2%gel l ed KC1+

f l ui d l oss agent

3

20000

2 KC1 +

fr i cti on reducer

SURFACE

I NSTANT.

TUBING SHUT- I N

RATE

PRESSURE

PRESSURE

(BPM

(P$i 9)

(PS19)

- - - - - - - - - - - - -

- - - - - - - -

14

2050

1600

13

2150

1500

16

2200

.

8/9/2019 29. SPE-14261-MS

16/16

.,

TABLE II

TRIAXIALEOREHOLESEISMIC DATA

KOPARUK WELL2G-07

TNO-PHASE SEISMIC SIGNALS

-------------------------

ORIENTATION

S-P ARRIVAL

OF

SIGNAL

TINE SEPARATION

(degrees )

(ins)

----------- ---------------

148

2.5

60

43.4

140

3.5

170

8.0

120

3.5

120 1.8

115

4s

3.9

5.3

40 6.0

30 6.3

45

7.0

38

4.6

29

2.8

32

4.2

35

34

3.1

2.8

23

37 :::

30 8.4

32

5.3

25

6.0

30

6.0

157

1.1

35

1.4

30

5.3

26

7.4

1.8

:

3.5

50 2.1

130

2.1

50

6.3

30

17.5

32

10.5

32

6.0

50

3.9

42 6.7

30 4.9

110

7.0

29 7.0

40 4.6

41 4.2

40 4.2

33

3.9

ORIENTATION OF SINGLE-

PHASE SEISMIC SIGNALS

 degrees

--------------------

16

138

172

27

25

165

35

45

145

140

130

12

140

39

18

16S

165

25

0

150

8

150

175

150

155

30

50

45

120

28

35

33

8:

40

45

46

140

25

30

128

45

27

TABLE 111

ON-SITE STRAINRELAXATIONDATA

KUPARUKHELL 26-07

CORE

ORI ENTATI ONOF

TEMPERATURE

SAMPLE

OEPTH LITHOLOGIC CORE

MXIPUBI STRAIN CHANGEOURING

NI FIBER (FT-MO)

UNI T DESCRI PTION

(OE6REES)

TEST (“F)

- - - - - - - - - - -

- - . - - . -- . - - - - -- - - - -- -

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

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

TABLE IV

ON-SITE STRAIN RELAXATION DATA

INJPARUK NELL lL-07

CORE ORI ENTATATION

TEMPERATURE

SAMPLE

--- —.. ---- -- .......... ------- —----- ----..-

DEFTH CORE or HAxlmum STSALN UIANtia uuKLNb

NDMBER (FT-TVDGL)

DESCRIPTION

(degrees )

TEST (deg.

F)

------ ----- -----------

--------—- ------------

1

6405

Ssnd/shale

99+1- 4

3

2 6411

laminae

S a nd l s ha le

90+ f-25

3

elm lLI.L1

iwc

1-F LCJ.L

Mminse

3 6462

Sand-some 119+ /- 4 3

a ha le la mina e