SPE 13858 MS_Fracturing Without Proppant

8/20/2019 SPE 13858 MS_Fracturing Without Proppant

1/12

SPE/DOE

ociety

of

U.S. Dopartmtnt

Petrolwm Engineers

of Energy

SPE/DOE 13858

Fracturing Without Proppant

by T.R. Harper,* J,T. Hagan, and J.P. Martins, British

Petrdeurn Co.

SPE Member

Copyright1985, Sooietyof PetroleumEn9inaars

This paperwas presentedet theSPE/DOE 1965 LowPermeebiMyGee l+aaewoi~ held inDenver,ColoreUo,Mey 19-22, 19S5.The Material iasubjectto

mrraohn by the author. Permissionto copy is restrictedto an abstractOfnot more then S00 wds. Write SPE, P.O. SoxS2SS2S,Richardson,Texas

750sMSS6. Telex 7S0S8SSPE DAL.

MS ERACT

The recordsrefer to productionoperationsconducted

in ‘E@ami, mostly before 1W.

The resultsof fracturestimulation

.—------- .--1 -.---b A . ..4+h .mA w+

+hfi,, + m.nmn+ ~Z

Possiblereaaonswhy fracturingsrithout

Treamw3uw3

MIIPLCUU-IA4 W. . . . -U.. .& . .. . . . =.. rr--=

pmpparit may give rxse

~Q ~ ~Q~&J~ ~ ~v~ ~~~~el

agents in two reservoirain England are compared.

The‘effectupon the conductivity of proppant-fee

includeshear displacementbetweenopposingfracture

faces ao that a mismatchresultswhen the fracture

e-..+,,-..O* e

m~~~~ denarture

of the wellboreaxis

..e”.-.””“.

--=——-—.

=ttempts tQ clwee

In naturallyfractured

from a principalstress plane ia asseased.

reservoirs,large a ale block slidingand dilation

3

f jointsmay occu .

This investigationis

restrictedto reservoirswhich are not naturally

IREoDueTIoE

fracturedto any substantialdegree,and therefQre

does not considerthe block slidingmechanism.

In 1960 it was reportedthat wells in the

Los Angelesbasin had been

Yucc:eyr:ez;;u:;

AVAILABLEREPOETSOF PROPPAHT-FREBFRACTOIW

stimulatedwithout proppant.

sTIm3LATxon


2/12

2

FRACTURINGWITHOUTPROPPANT

SPE

13888

,ecoveryattributableto proppedfracturetreatments

schedulesand proppant-freetreatments,both using

xceeded that achievedby proppant-freetreatments.

crude oil as the fracturingfluidand all conducted

.,-..+4,.-1 w,l.1 1.S

L.grnbert and Trevits2and Mahoney et a13

i~ v=. .AtimA .-A.*-.

eported proppant-freestimulationof the 2.2 feet

0.76m) thick Mary Lee coal bed at a depth of

Fracture stimulationtreatmentsin the

Egmantonand Eathemealloil fields were carried out

,pproximetely200 feet (366m). Mhoney et al

beportedthat the coal was brokan down with water

primarilyin the CarboniferouaNo.1 sandstoneGroup,

comprisingthe Crawshawand Sub-Altonsandstones.

,ndthen stimulatedat 2-6 bbl/minwith foam

In the Egmantonfield these formstionaare a series

incorporatingfluorescentpaint.

The magnitudeof

be nnmt-nt.imulnkinn rlmilvproduction was described

of channelsandstonesinterbeddedwith shales;up to

=... .---— ----- .---4

=--——-.—_—

v l.m.lA.+,...a.m+. .-- mmasam+ the +fi+.1hit-lrnanm

IS

acceptable. Minebackrevealedthat both vertical

f ====-UV=-~..- =.- Y---”-”

.“... ...-”..-”--

md horizontalsurfaceawere paint-stained

of the interbeddedsandstone-shalesequencebeing

;hroughoutan ellipticalarea and in part the

approximately20-25m.

These sandstoneunits are

largelycontinuousacroas the field. Any natural

‘ractureconaiatedof numeroueparallalsurfaces

fracturingwhich may be present is not obvious from

rithinthe naturallyfracturedcoal.

The authora

‘eportedthat fractureawere not propagatedinto the

cores but wells are verticaland bedding essentially

horizontal.

In the Bothamsallfield, the Sub-Alton

ltrataoverlyingthe coal bed.

Tnusp the desired

and Crawshawaandatoneato which stimulation

~eightgrowth controlwas achieved.

However,a

treatmentswere appliedtypicallyhave a

:omparableproppedfracturestimulationof smaller

permeabilityof less than lmd. Locationsof the

rolumer sul.tedin a greaterwell productivity

2

Bothameallwells, and the petrologyand diagenetic

.ncrease.

history of the N . 1 sandstoneGroup are shown in a

8

Freeman et a14 describeda seriesof

paper by Hawkins .

Litrogenstimulati=eatmants of shaly

Depthe of completedintervalavaried

Egmantonsthalation treatments

ormstions.

from2436 ft (742m)to 4470 ft (1362m). The shale

Initialatimulationein 1956 were

is reportedlynaturallyfracturedand production

Lncreaseawere achieved. No comparisonwaa made

performedby pumpingcrude oil direct to the

caaing.

IXI1957 and 1958,25 hydraulicfracture

rithsand-proppedfracturea.

Laboratoryteatsof

flowthroughfracturedsamplearevealedthat losses

treatment using 20-40 sand aa proppantand fluid

loss additivewere performed. Crude oil without

>f permeabilitywith change of confiningpressure

acrerepresentedby a higher gradientof

sand, but with fluid loss additive,waa again used

in 1958. All treatmentswere pumpedat

permeability/pressureor saw cut samplesthan for

approximately5-7bbl/min.

Intervalstreatedwere

~tural fractures. The authora relatedthis to the

typicallyin the range of 20-45ft (6-14m). Table 1

Zreatersize of asperitiesassociatedwith natural

Fractures.

Bloreover,ased on the shape of the

auzmarisesthe resultsof some

of

these

treatment. The resultsshouldnot be taken as

permeabilityv. confiningpressurerelationships,

theauthorsconcludedthat much of

the production

directlycomparablebecause of the variationof

near-wellboreconditions. Nevertheless,the results

Lossesassociatedwith drawdownof a well stimulated

by no-proppantfracturingwould occur early in the

in Table 1 indicatethat proppant-freefracturing

W=S g~n~~~~~v aucceesful

—-------— ;

antipLl~tiCUlar successwas


3/12

SPE 1385S

T.R. Harper,J.?. iiagaiinti2.F. ii~=tirls

~

we of fluid loss additive. The crude oil smPle

Yom this well contained19$ by weight wax and a

meflush of wax diaperaantwas includedin the

subsequentfracturetreatmentwith proppant.

Fluid

.OSSadditiveand aand with a concentrationof

~pProxtitely 1.51bs/gallwere incorporated,and an

Lfterfluahof hot water.

The treatmentwas very

—s.-

,--------- -.--a..”+

... s..,.”l

mcceasxu~, ~ncrwae~u~

PL UUUCUAUU ..vIM ac

kmignificantamount to 500 gallonsper day of oil

;nd300 gallons per day of water.

However,the

?umpingrate in the treatmentwith sand was a factor

)f 1.3-2greaterthan the previoustreatment,and

khevolume of fluid twice as great.

It is

?easonableto asaume that the largertreatment

zonductedat a higher pump rate createda more

3xtensivefracture.

These resulte,therefore,do

lot demonstratethat the presenceof the aand acting

isa proppingagent was a criticalfactorin the

........ -e tbbe.nA +mam+man+.

.Wuu=-- “.

“-u- . ..-—.-..

J?othameallell No. 3 was drilledwith a

bentonite/watermud and completedin the Sub-Alton

3andstonewith perforationsfrom 3236-3248ft B.R.T.

(986-9901z) and 3254-3284ftB.R.T. (992-10C)lm);the

permeabilityof the upper zone was determinedto be

less than O.lmd, of the lower zone 10-25md.

Four stimulationtreatmentswhich can be

asmznedto have involvedfracturingwere conducted

overa period of some 10 years (Figure

4).

Treatment1 was curtailedfor operationalreasons

and only 18 bbls of

~rude oil were pumpedto the

formationthrough2 /8 inch drill pipe at a WHTP of

3800 psi (26 MPa).

Despite the smallvolume of

fluid pumped, the effectof this was to increase

productionfrom 1833 gallons,ofoi&?:r $aY (g.p.d.)

(6.9 m’/day) to 5375 8.p.d. (2-.3 m’ldaY),reducing

9

to a steady 1250 g.p.d. (4.7 m /day) of crude oil.

Well P.I. declinedby a factorof

successfullyarresteda productiondecline in the

first instance. Whether or not the pre-existing

fracturewae re-openedhas not been determined;the

major effectof the treatmentmay have been a result

of the chemicalsused in the vicinityof the sand

face. The final (proppant-free)fracture

stimulationemployedinjectionrates four times

L Lb-— L-_ ,---.

..* A---& ..- 4n ----“ A..1


4/12

4

FRACTURINGWITHOUT PROPPANT

SPE 13858

Blockswere hydraulicallyfracturedwith

Fracturedasmpleaof Hopeman Sendstoneand

oil and 1.48 inch (37.5mm)plugs were cored through BirchoverGritstone(Table2) were tested in the

the fracturewith the long axie of the core lying

laboratoryat a range of ahear dieplacementa

withinor close to the plane of fracture. A

extendingfrom zero to 0.5 mm.

This was achievedby

confiningstreea differenceof not less than 1000

pai wae imposedduring fracturing. Sampleswere

placingone piece of approximatelysemi-circular

then cleanedby a toluene-methanolsequenceusing

perforatedsh~ materialof known thicknessat each

end of a sample,but on opposingsides of the

soxhletextractiontechnique.

The sampleewere

fracture. By this arrangement,the ahear

confinedin a Hock triaxialcell and simulated

formationbrine flowed to determineasmple

displacementia achievedat the outeet of the

permeability. The simple assumptionthat flow

experimentwithoutfrictionalslidingbetweenthe

opposingfractureaurfacea.

This is repreeentative

occurredindependentlyin the fractureand the rock

of the growth of a hydraulicfractureout of a

matrix (flow parallel to fractureplane), with a

principalplane.

Initially,when the fractureis

linearpressuredrop, was usetito calculatevalues

for fractureconductivity. Thus, the permeability

ellipticaland one axis is short,shear diaplace-

mente are small. As the fracturegrows, the ahear

of intact samplesof each material (withoutany

fracture)were teatedat a range of confining

displacementoccure in an open (negativeeffective

stress)condition.

pressures. These values for intactmaterial,Ko,

were subtractedfrom the Darcy permeability

The higher shear displacementswhich were

calculatedfor the fracturedeample,K, with the

includedin the teat programmeare appropriateto

appropriategeometricalfactorapplied to give a

value for fractureconductivity:

greater deptha,where stressdifferencesare

greater. For example,at 10,000feet (3050m), a

maximum atresadifferenceof 4000 psi - 5000 pai

& (K - Ko)

(27-34MPa) may be more common. This ie approx-

eK. =

J

(1)

imatelythree times greater than that used in the

above example,and for the same,geometryand

materialpropertiesa ahear displacementof 0.3 mm

where e K. = fractureconductivity(red.cm.), D =

$“

would be predicted.

Where wellboresare

cross-seclonal width of fracture (equivalentto

piug diameter).

intentionallydeviated,the value of shear

displacementcould be significantlygreater.

The range of shear displacementsof 0.1 -

THE EFFECTOF WEAR D18PLAC=03-FEACI’ORE

0.5mm wae chosen to be primarilyrepresentativeof

CONDUCTIVITY

subverticalwellboree. Referringto Table 2, it may

be noted that these values are of the order of one

It is highly improbablethat a wellbore

grain diameterfor the Hopeman sandstone. The

EirchoverGritstonegrain size range ia greater,and

,..

w1ll be driiied preciaeiyin a principaletrees

the range of shear displacementsimposedis of the

plane. Even where wells are intendedto be

order of the lower end of the grain size range.


5/12

SPE 13858

T.R. Harper,J.T. Hagan and J.P. Martins 5

McGuire-Sikoratype of relationshipscan be used to

asseas the influenceon well productivityof such

~;;~~~a?~nductivit

y: formationpermeability

The laboratorydeterminationsyield a

fractureconductivity(darcyft.): formation

permeability(red)ratio of 0.01 - 0.1 for a 1 md

reservoir,or 0.1

- 1.0 for a 0.1 md formation.

The significanceof samplesize upon

observedpermeability,must how ver, be taken into

%

EscoiiGt.TaaEg SE* F;therspecllCc=clcd$tithst

large-scaleundulation(wavineaa),rather than the

small scale roughnesswhich is superimposedon the

waviness,controlsthe mechanicaland hydraulic

propertiesof fractures.

In the expertients

reportedhere, the maximum cross-sectionalwidth of

fractureavailablefor flow was only 37.5 mm.

If we

can ignore the possibilityof long term embedment,

or of pluggingby fines,a higher conductivityfor

fractureageneratedin the field than that observed

in the small samples in the laboratorymust be

assumed.

Unfortunatelyno definitionof the size

effectis ava lable. Based upon recognised

+

relationships, an order of magnitudeincreasein

fractureconductivitybetween laboratoryse=p:escf

sandstoneand field-scalefracturee

in

the East

Midlandawould representan approximateincreaseof

well productivityby a factorof 2-3 attributableto

no-proppantfracturing.

Therefore,if the outcrop

sandstone which were testedare assumed to be

approximatelyrepreaentativeof the Egm.sntonnd

Bothamsallreservoirrocks, it may not be necessary

to invokefracturingthroughskin damageor

“perforationbreakdown”as the reasonfor the

auccesaof the proppant-freetreatments. In cases

where increasesof well productivityapproachedan

order of magnitude,however, it is concludedthat

fracturingthroughdamage or into a more permeabie

fracturesinitiatein the plane of the wellboreare

conduciveto high shear displacements,but

subsequenteffectivenormal streaaesacting on the

fracturesare higher.

COECLUSIOMS

i.

2*

=---4 ---- -----4.” -s s..--+....: . . . .. +h ,. .. + . ,” ,, ,. .. .m+

rL-WVLUU~ &-CpUL-kZ5 WA LA~tibULLU6 “AWL”IA” pLWYp~AA.

are confined to naturallyfracturedreservoirs

and a reservoirhaving abrupt lateral facies

changee. The Egmantonand Bothameallfields are

not notably naturallyfractured,and at least in

the Egmantonfield the sandstonehorizonsare

largely continuousacross the field. A

comparisonof fracturingwithoutproppantand

fracturingwith proppantat low sand

concentrations,using crude oil as fracturing

fluid, demonstratesthe following:

a)

fracturingwithoutproppantwas effectively

used to increasewell productivity;

b) no evidencefor a more rapid decline in

well productivityafter fracturingwitinout

proppantrelativeto proppedtreatment

could be observedin the productiondecline

curves;

c)

the fracturetreatmentswith proppant(and

usually fluid leas additive)were more

effectivethan those without proppant.

‘theoreticalnd laboratorystudiessuggestthat

the conductivityof unproppedhydraulic

fractureais increasedas a resultof shear

displacementof a magnitudecomparableto a


6/12

l?QArViTIRTNt? WTTHnIIT PRfIPP&NT

6

. .-- .”..-..- “------- ------ ----

SPE 13858

mlIEwLATmtE

K-

K“

D

e

v

u

x

c

al, U2

B

permeability

permeabilityof fracturedsample .

diameterof core plug

fractureaperture

Poi8son’sratio

shear displacement

distancefrom centre of fracturein plane

of fracture

fracturehalf-length

principal.9tresses,pproxhately vertical

and horizontal

inclinationof principalplane to plane of

fracture

A XUOULEDGEHEMTS

The authorswish to acknowledgethe

interpretationsand qualityof the recordsprepared

by Messrs. C.M. Adcock and J.H. Edwardsduring the

developmentof the Egmentonand Wthameall

oilfields,and the assistanceduring the

investigationof Mr. IL Milton-Taylerand also

Mr. p.

King. The

authorswish to thank the management

of the BritishPetroleumCompanyPLC for permissionL

publish this paper.

.—-”-

M6s.suGm

1.

2.

Ghauri,il.K.

Results

of

well stimulationby

hydraulicfracturingand high rate oil

backflushing,J. Pet. Tech., June 1980.

Lambert,S.W., Trevits,M.A. The feasibilityof

no-proppantstimulationto enhanceremoval

of methane from the Mary Lee @albed, U.S.

Dept. of EnergyReport of Investigation,

April, 1980.

APPEHDIX

A

F)TSPFACmEEIPS AT TEE -AI= (M’ A-——-—

?LAT

ELLIPTIC CRACK

The displacementsat the surface of an

elliptichole (FigureAl) in an infiniteelastic

medium are given by Jaegerend Cook . Using theirl

nomenclature,the displacementsare given by the

real and imagina~ parts of ths followingexpression

2G(UC + iUn)

“

[xdz -z7GT

-m [mT/w’ c l”2

Conaidera flat crack of length 2C (givenby 50 = O)

in which case $, $’,$ reduce to:

1

P C{cos 2

4’=72

+ i (1-COS~g’

---—-

‘ ” ‘

“TP2

4J=+P2

Cos 2 13- sin 2 S cot n-i(l-coa211)ot rI}

c {- sin 2 (rI-6)+ i (1-cos26)}cosec n


7/12

NUMSER

OF TYPE OF FRACTURE

PRODUCTIONDURING

FACTOR

WELLS

STIMULATION “

ONE YEAR PERIOD

OF

(TONS)

INCREASE

IN

PRODUCTION

WITNOUT

GAIN AS

FRACTURE A RESULT

STIMULATION OF FRACTURE

STIMULATION

5

Crude oil without proppsnt

2348

1800

1.76

pumped direct to casing

15

Crude oil with proppant 5075 15968

4.15

pumped through drill pipe

4 Crude oil without proppant 414 2520

7.09

pumped through drill pipe

with fluid loss additive

TABLE 1. RESULTS OF SONE FRACTURE STIMULATION TREATMENTS CONDUCTED IN EGNANTON FIELD IN 1956 AND 1958


8/12

./ \

Q

y-$=’

BOTHAMSALL

L

m

EGMANTON

—

SCALE

: 2040

eowml

F@. l- lace tion of Egmanton and 2othemeel l oi l f ie lds.


9/12

a

a

g

c

(-J

-1000

-1

5

z

“’’”~

.—————————_-——_—_____

500

1 ------ ~. I--WQ-——

o

I

D

wELL7— __

———— ———__ —______

<

——— —____

——— ——_—J__

—————— ———— ___

JiFIMIAIMIJ1 JIAIS1OINIOJ lFIMr AI MIJIJ lAls 10 INlo

*

1958

1959

Fig. 3-Oecline cu vea before and ah propped fracture sfimulatbn in 1S5S inwelle in the Egmanton f ield previously

fracture.etimulefed without pmppant,

N


10/12

,1 1

1 1 I I II

_.–’ .-,---- )’. -~, l.-l 1,1,

I I I I

I I

I

Ii Ill

I>, ’J. J ”)”.,--,. ,’1

1- I

,, /,----

,-., ,J

->

‘-, ,

, ,’. ” .

‘- ).-l-~ .

,-

,

,),’, -’ZJ, “-- -f~,

\-

0 ; :-,’ --’,-:,-_

- .

-, ’,-,;.,

,. .

)

,- A’-’,, }J’ -,-J\ ,,

,-

,. ~>,.,- \

-,1

,-.

:m’ +’:,-:)’ J“;

-e .).,., ?

.-

-J

l) -’.)

>----- ,\-

1 1 I I

il’ ‘1“ ‘

I

I

I

‘

‘

‘ I I

111’ l, l:\’.’--”.’ J- JJI’11’IIIL.C

lll l~l ~]l’,,’l.’-:) .’. )’, \’.’. ”,(li Iillll l


11/12

F@. 8-:711- d ImcturssilledwithO OXYin inBhchowrgrilstomunderMV stress-Wins 8fww

acwnmlsof0.1 and0.5 mmwereimpmd onlmcwo8- (a) 81 w dlsplvxmeti on I rwtura 0.? mm. CZ51W

f imng WE88WW 1JIM Pi axial pressufu l ,,WO WC (b) a imaf d@@acemem onImcluw 0.1 mm. Umf in ing

PfeCSUrn5,? Pd. a id Pmwm,:5,500 w (c)ahaaf t isc4awnwnt cmImclurw 0.5 mm. canning v-w

1,~ p i, amd PIWWrn 1,Wl P9Kand(d)sheafduF+Icament onf racture 0.5 mm, confiningpmswm 5,LW2

W, W pmwurw5 ,540ps i.


12/12

woo

*------4 .-

. .

----

.

‘..

-,,,

,

,

I , “= 0.25mm

,

,

I

;

I

,

I

t

“’.,,

‘.

‘,

‘0. ‘.

“~.s’j,,

Q.>,

..*

--o-----

*

-a.. - \

b

- .’\

‘.

,.

‘.

8*’.

‘.

‘.

‘.

‘8* ‘.

. .

* %.

. . .

,.

,. . .

. . .

.-h ‘-.

--e...

-O----- *..

y.. ‘------*--- -’-

-.. . . .- ----

‘.

‘.

‘.

‘.

‘.

‘.

,, -’-[: “’’’’..”;0”5’

.

9.

‘.

‘.

. ‘.

.

8

-.

*

‘.

‘b,

‘.

a

‘..

‘.

‘.

/’

. u= .Imm

‘.

.

t ‘

“’..,.

...

U=o

“-..

-...

*.

-..

-.

“*

I

1

I

1

I

I I t

1000 2000

20

40

MPO

EFFECTIVE NORMAL STRESS ON FRACTURE

~.

B-VWIINIWI 01

fKIIXIM CC+NIIXHVW wnheffedva normalstressonfradu*Bim~ g~~.

5000

1000

*

--s..

-.

.

‘.

‘b.

i

\\

\8

“./”u=

25mm

‘a

.

..-

---

-------- .*-

8,

88

‘9

‘.

‘.

%.

/

U=o

..

.,

.-.

-----

--------- --

)

)

=

d

E

01

1

I

t

I

1

moo 2000 &

4000

P r;

EFFECTIVE NORMAL ‘STRESS ON FRACTURE

* . g -va riauon d

fCSCIUreCOWJUCt”~ with efkotwa nonnaI stress on

lracIur6-HoPmm sandxw.

~. A1-ElllPtk hole

ln Sm63pz

al

infinity.

SPE 13858 MS_Fracturing Without Proppant

Documents

Transcript of SPE 13858 MS_Fracturing Without Proppant